Technology of plastics from wood press masses. Technological process, equipment and tools for the manufacture of profile parts from wood-polymer composition (WPC) by extrusion

Hi all!

We have a lot of interesting plastics for sale for decorative 3D printing. Today we will tell you about a new product – Wood from FiberForce. The price of the reel is 0.5 kg. - 3500 rubles.

FiberForce was founded in 2013 in Italy. In addition to ABS and PLA, FiberForce produces several types of special plastics, in particular FiberForce Carbon , which we have been supplying to Russia for quite some time and which has proven itself to be excellent
From the name FiberWood it is clear that plastic imitates wood products. Today we will try to figure out what makes it different from other similar plastics?
Decorative plastics can be divided into 2 types:

1. Imitating only the color of the product due to added pigments.
For example, ESUN Wood or ESUN Bronze.
The undeniable advantage of these plastics is that they do not cause problems during printing, and you immediately receive a finished product that imitates the color of metal or wood.

2. They contain “filling” in the form of a material that is imitated.
For example ESUN eAfill or eCopper.With these plastics, you need to be more careful about setting the printing parameters. Incorrect settings may cause the nozzle to become clogged. To “open” the filler, additional processing of the product after printing may sometimes be required.
Wood from FiberForce belongs to the second type of decorative plastics. The plastic is based on regular PLA filled with wood dust.

The rod is rough to the touch, with an interesting matte color of light wood.

The recommended nozzle temperature for printing is about 200 degrees, the table temperature is 50-60 degrees. Although plastic sticks well to printing platforms that are not heated. The main thing is not to forget to turn on the fan to blow the model =)
When printing, the plastic smells very pleasantly of fresh sawdust.
Unlike similar plastic LAYWOO-D3, Fiber Wood does not change its color when printing temperature changes, does not clog the nozzle and is very stable when printing.
LAYWOO-D3 – it was possible to print stably only using nozzles large diameter(from 0.8).

After 40 minutes of printing we get this nice machine)
The surface of the products looks very beautiful. Due to the matte nature of the material, the layers are almost invisible.

Surprisingly, our jar still smells like wood inside =)

Products made from FiberWood are excellent in sanding and processing.

Results

The most important advantage of FiberWood from Fiber Force is that, unlike other similar materials we have printed with, the risk of nozzle clogging is minimized. And all thanks to the optimal (small) content of wood dust. This decorative plastic did not cause us any trouble and performed well during printing. Despite the fact that the basis of Fiber Wood is PLA plastic, it is excellent for sanding, cutting and processing. This turned out to be a pleasant plus.

It is great for creating decorative elements, artistic objects or everyday objects with a wood look.

480 rub. | 150 UAH | $7.5 ", MOUSEOFF, FGCOLOR, "#FFFFCC",BGCOLOR, "#393939");" onMouseOut="return nd();"> Dissertation - 480 RUR, delivery 10 minutes, around the clock, seven days a week and holidays

Savinovskikh Andrey Viktorovich. Obtaining plastics from wood and plant waste in closed molds: dissertation... Candidate of Technical Sciences: 05.21.03 / Savinovskikh Andrey Viktorovich; [Place of defense: Ural State Forestry University]. - Ekaterinburg, 2016. - 107 p.

Introduction

CHAPTER 1. Analytical review 6

1.1 Wood composite materials with synthetic binders 6

1.2 Lignocarbohydrate and piezothermoplastics 11

1.3 Methods for modifying wood particles 14

1.4 Lignin and lignocarbohydrate complex 19

1.5 Cavitation. Cavitation processing of plant raw materials 27

1.6 Bioactivation of wood and plant particles with enzymes.. 33

1.7 Selection and justification of the direction of research 35

CHAPTER 2. Methodological part 36

2.1 Characteristics of starting substances 36

2.2 Measurement techniques 41

2.3 Preparation of bioactivated press raw materials 41

2.4 Production of DP-BS 41 samples

2.5 Preparation of a sample of press raw materials for plastic 42

CHAPTER 3. Obtaining and studying the properties of wood plastics without a binder using modifiers 43

CHAPTER 4. The influence of chemical modification of wheat husk on the properties of RP-BS 57

CHAPTER 5. Preparation and study of the properties of wood plastics without a binder using bioactivated press raw materials 73

CHAPTER 6. Technology for producing DP-BS 89

6.1 Calculation of extruder performance 89

6.2 Description of the production process 93

6.3 Estimation of the cost of finished products 95

Conclusion 97

Bibliography

Introduction to the work

Relevance of the research topic. The volume of production of processed wood and plant raw materials is constantly increasing. At the same time, the amount of various waste from wood processing (sawdust, shavings, lignin) and agricultural plants (straw and cereal seed shells) also increases.

In many countries, there is production of wood composite materials using synthetic thermosetting and thermoplastic organic and mineral binders as a polymer matrix, and crushed plant waste as fillers.

It is known that it is possible to produce wood composite materials by flat hot pressing from wood processing waste without the addition of synthetic binders, which are called piezothermoplastics (PTP), lignocarbohydrate wood plastics (LUDP). It is noted that the initial press compositions have low plastic-viscosity properties, and the resulting composites have low physical and mechanical properties, especially water resistance. And this requires finding new ways to activate the lignin-carbohydrate complex.

Thus, work aimed at using wood and plant waste without the use of synthetic binders to create products is relevant.

The work was carried out on the instructions of the Ministry of Education and Science of the Russian Federation, project No. 2830 “Obtaining wood plastics from wood and agricultural plant biomass waste” for 2013-2016.

The purpose and objectives of the work. The goal of the work is to obtain plastics from wood (DP-BS) and agricultural waste (RP-BS) without adding synthetic binders with high performance properties.

To achieve this goal, it is necessary to solve the following tasks:

To study the process of formation of DP-BS and RP-BS based on wood (pine sawdust) and plant (wheat husk) waste.

To study the influence of chemical modifiers, as well as technological parameters (temperature, humidity) on the physical and mechanical properties of DP-BS and RP-BS.

Determine rational conditions for obtaining DP-BS and RP-BS from wood and plant waste.

To establish the effect of bioactivation of press raw materials with activated sludge on the physical

co-mechanical properties of DP-BS.

The degree of development of the research topic. Analysis of scientific, technical and patent literature has shown a very low degree of development of issues related to the patterns of formation of the structure and properties of wood plastic without a synthetic binder.

Scientific novelty

The kinetic laws of the process of formation of DP-BS and RP-BS (activation energy, pre-exponential factor, reaction order) were established using the DSC method.

The influence of chemical modifiers (hydrogen peroxide, urotropine, isomethyltetrahydrophthalic anhydride, cavitation lignin, hydrolytic lignin) on the rate of formation of DP-BS and RP-BS has been established.

The kinetic patterns for the production of DP-BS using bioactivated wood waste were obtained.

Theoretical significance The work is to establish the patterns of influence of a number of modifiers and the humidity of press raw materials from wood and agricultural waste on the physical and mechanical properties of DP-BS and RP-BS.

Practical significance work consists of using waste renewable raw materials and experimentally proving the possibility of obtaining DP-BS and RP-BS with increased physical mechanical properties. A recipe for producing DP-BS and RP-BS has been proposed. Products made from DP-BS have low formaldehyde emissions.

Methodology and research methods. The work used traditional methodology scientific research And modern methods research (differential scanning calorimetry, IR Fourier spectroscopy, PMR 1 N).

Submitted for defense

Results of a study of the thermokinetics of the formation of DP-BS, RP-BS and the influence of modifiers and humidity on this process.

Patterns of formation of the properties of DP-BS and RP-BS in closed molds under the influence of temperature, humidity of press raw materials and its chemical modification.

Degree of reliability of research results is ensured by repeated repetition of experiments and the use of methods for statistical processing of the obtained measurement results.

Approbation of work. The results of the work were reported and discussed at the VIII International Scientific and Technical Conference “Scientific Creativity of Youth for the Forestry Complex” (Ekaterinburg, 2012), IX International Scientific and Technical Conference “Scientific Creativity of Youth for the Forestry Complex” (Ekaterinburg, 2013), International Conference “Compositional materials based on wood and other fillers" (Mytishchi, 2014).

Publications. Based on the dissertation materials, 12 articles were published, including 4 articles in publications recommended by the Higher Attestation Commission.

Workload

The dissertation is presented on 107 pages of typewritten text, contains 40 tables and 51 figures. The work consists of an introduction, 6 chapters, a conclusion, and a list of references, including 91 references to domestic and foreign works.

Lignocarbohydrate and piezothermoplastics

Lignocarbohydrate and piezothermoplastics. These materials are made from sawdust or other plant materials by high-temperature processing of the press mass without the introduction of special synthetic binders. Technological process the production of lignocarbohydrate wood plastics consists of the following operations: preparation, drying and dosing of wood particles; carpet formation, cold pressing, hot pressing and cooling without releasing pressure. When preparing the press mass, wood particles are sorted, then the fraction with a particle size of more than 0.5 mm is further crushed, the quality sawdust goes into the dryer, and then into the spreading machine. The carpet is formed on pallets coated with a layer of talc or anti-adhesive liquid. First, the finished carpet is fed into a press for cold pressing, which lasts for 1.5 minutes at a pressure of 1-1.5 MPa, after which it is sent for hot pressing at a pressure of 1.5-5 MPa and a temperature of 160-180 C. Pressing the boards 10 mm thick lasts 40 minutes.

Under the influence of temperature, partial hydrolysis of wood polysaccharides and the formation of organic acids occur, which are catalysts that contribute to the destruction of the lignocarbohydrate complex. The resulting chemically active products (lignin and carbohydrates) interact with each other during pressing. As a result, a more dense and durable material than wood.

Raw materials for the production of lignocarbohydrate wood plastic are obtained by processing coniferous and deciduous wood. Along with sawdust, machine shavings, crushed wood, bark mixed with wood, crushed logging waste and some lignified agricultural waste can be used to produce plastic. Impurities in the raw materials of partially rotten wood improve the physical and mechanical properties of lignocarbohydrate plastics.

Compared to particle boards, lignocarbohydrate plastics have a number of advantages: they are not subject to aging due to the destruction of the organic binder and their strength indicators do not decrease over time; There are no toxic emissions during operation environment. Significant disadvantages of the production of lignocarbohydrate plastics are the need for powerful pressing equipment and the duration of the pressing cycle.

It is noted that under the influence of pressure and temperature, crushed plant materials acquire the ability to form a durable and hard material of a dark color that can be molded. This material is called piezothermoplastic (PTP).

The starting raw materials, along with sawdust, can be crushed coniferous and deciduous wood, flax and hemp fire, reeds, hydrolyzed lignin, and odubin.

There are several methods for obtaining PTP, which have been thoroughly studied and introduced into production, but have not found further application due to high energy costs: 1) a one-stage method for obtaining PTP (A.N. Minin. Belarusian Institute of Technology); 2) a two-stage method for producing plastics from hydrolyzed sawdust (N.Ya. Solechnik, Leningrad LTA); 3) technology for the production of lignocarbohydrate wood plastics (LUDP) (VN. Petri, Ural LTI); 4) steam explosion technology (J.A. Gravitis, Institute of Wood Chemistry, Latvian Academy of Sciences). Piezothermoplastics are divided into insulating, semi-solid, hard and super-hard.

At medium density 700-1100 kg/m3 piezothermic plastics made from birch sawdust have a static bending strength of 8-11 MPa. When the average density increases to 1350-1430 kg/m3, the tensile strength during static bending reaches 25-40 MPa.

The high physical and mechanical properties of piezothermoplastics allow them to be used for the manufacture of floors, doors, and also as a finishing material. A type of wood plastic is vibrolite, the technological features of which are partial grinding of sawdust and small shavings in a vibrating mill, mixing the finely ground mass with water and then obtaining sludge. From a mixture of sludge with particles 0.5-2 mm in size, a carpet is formed in a casting machine, which is dewatered by a vacuum pump. The resulting press mass is supplied for cold and hot pressing. The finished slabs are transported to a hardening chamber, where they are subjected to heat treatment, as a result of which their water absorption is reduced by almost 3 times and swelling by more than 2 times.

Vibrolite is used for laying subfloors, installing partitions, cladding wall panels in public buildings, manufacturing of built-in furniture and panel doors.

Since the 30s in the USSR, many researchers have been involved in the production of slab materials by piezothermal processing of plant raw materials without the use of traditional binders. The work was carried out in the following directions: 1) pressing natural, untreated sawdust; 2) pressing of sawdust pre-autoclaved with water steam (pre-hydrolysis) or steam with a catalyst (mineral acid); 3) pressing of sawdust pre-treated with chemical reagents: a) gelatinization of the press mass (chlorine, ammonia, sulfuric acid and other substances) for its partial hydrolysis and enrichment with substances with binding properties; b) chemical polycondensation of the press mass with the participation of other chemicals (furfural, phenol, formaldehyde, acetone, alkaline and hydrolytic lignins, etc.).

Preparation of bioactivated press raw materials

The endothermic minimum corresponds to the process of hydrolysis of lignin - a carbohydrate complex and the easily hydrolyzed part of cellulose (polysaccharides).

The exothermic maximum corresponds to polycondensation processes, which determine the process of formation of DP-BS. Since the process is catalyzed by acids that are formed during the pyrolysis of wood, as well as due to the presence of resin acids contained in extractive substances, this is an n-order reaction with autocatalysis.

For wood waste with modifying additives (hydrogen peroxide, urotropine, IMTHF), the peak maxima on the DSC curves shift to the left, which indicates that these compounds act as catalysts for the above processes (T1 100-120 0C, T2 180-220 0C), accelerating the process of hydrolysis of wood polysaccharides, as well as the lignin-carbohydrate complex.

From Table 3.2 it is clear that at the first stage, with increasing humidity of the press raw material, the effective activation energy increases (from 66.7 to 147.3 kJ/mol), which indicates a greater degree of hydrolytic destruction of wood. The use of modifiers leads to a decrease in the effective activation energy, which indicates their catalytic effect.

The values ​​of the effective activation energy at the second stage of the process for modified press raw materials change slightly with increasing humidity.

The use of modifiers leads to a decrease in the effective activation energy at the second stage of the process. Analysis of kinetic equations showed that the best model at the first stage of the process it is an n-order reaction, at the second stage it is an n-order reaction with auto-acceleration: A 1 B 2 C.

Using the kinetic parameters of the process, t50 and t90 (the time required to achieve a conversion degree of 50 and 90%) were calculated for unmodified and modified press raw materials (Table 3.3), and conversion curves were also presented (Fig. 3.4-3.6) .

Dependence of the degree of conversion on time at different temperatures(pine, initial humidity of press raw materials - 8%) Figure 3.5 - Dependence of the degree of conversion on time at different temperatures (pine, modifier - urotropine, initial humidity of press raw materials - 12%)

Dependence of the degree of conversion on time at different temperatures (pine, modifier - hydrogen peroxide, initial humidity of press raw materials - 12%) Table 3.3 - Time values ​​​​for reaching the degree of conversion of 50% and 90% at different temperatures No. Degree of conversion Press raw materials with a humidity of 8% Press raw materials with a moisture content of 12% (modifier - 1.8% H2O2, %) Press raw materials with a moisture content of 12% (modifier - 4% C6H12N4, %)

The use of hydrogen peroxide speeds up the process at the first stage by more than 4 times than when modifying press raw materials with hexamine. A similar pattern is observed at the second stage of the process. Based on the total time of formation of DP-BS, the activity of the press raw materials can be arranged in the following row: (unmodified press raw materials) (press raw materials modified with urotropine) (press raw materials modified with hydrogen peroxide). In order to establish the influence of humidity and the content of the amount of modifier in the press raw materials on the operational properties of DP-BS, mathematical planning of the experiment was carried out. A preliminary study was carried out on the influence of the humidity of the initial press raw materials on the physical and mechanical properties of DP-BS. The results are shown in table. 3.4. It has been established that the higher the initial moisture content of the press raw materials, the lower the physical and mechanical properties, such as bending strength, hardness, and bending modulus of elasticity. In our opinion, this is due to a greater degree of thermohydrolytic destruction of the lignocarbohydrate complex. Table 3.4 - Physical and mechanical properties of DP-BS obtained at different humidity levels of the press material

Thus, the physical and mechanical properties of DP-BS depend on the formulation and conditions of its preparation. So, for plastic with high physical and mechanical properties, the following composition should be used: lignin content 3%, IMTHF content 4%, initial moisture content of press raw materials 6% and hot pressing temperature 1800C. For plastic with low values ​​of water absorption and swelling, it is necessary to use the following composition: lignin content 68%, IMTHFA content 2%, initial moisture content of press raw materials 17% and hot pressing temperature 195 C0.

The influence of chemical modification of wheat husk on the properties of RP-BS

The depth of thermohydrolytic destruction of lignin in wood and plant materials depends on the type of chemical modifier used.

Our studies of the formal kinetics of plastic production show that lignin coniferous species(pine) has greater reactivity than lignin annual plants(wheat husk). These results are consistent with the oxidation results of model lignin compounds from softwood, hardwood, and plant-derived lignin. Analysis of the literature showed that theoretical research The peculiarities of the transformation of wood under enzymatic influences made it possible to develop the biotechnology of wood plastics based on the partial biodegradation of the lignocarbohydrate complex.

It is known that biotransformed wood particles significantly change their plasticity. Also, the species composition of wood raw materials has a significant impact on the physical and mechanical properties of plastic.

Bioactivated processing of wood waste various types ligno-degrading fungi, bacteria, in our case activated sludge, is promising for the production of press raw materials for DP-BS(Au).

Initially, the laws of the process of obtaining DP-BS(Au) based on wood waste using activated sludge (Figure 5.1) with different bioactivation periods were studied. 0.5 7 days 14 days

A study of the formation process of DP-BS(Au) by the DSC method showed that there are two exothermic maxima on the w = f(T) curves (Fig. 5.2). This indicates that the process can be represented as two parallel reactions, corresponding to bioactivated and non-activated press raw materials, i.e. A 1 B and C 2 D. In this case, reactions 1 and 2 are n-order reactions).

The kinetic parameters of the formation process of DP-BS(Au) were determined. The results are shown in table. 5.1. Table 5.1 - Kinetic parameters of the formation process of DP-BS(Au)

At the second stage of the process of obtaining DP-BS(Au), the values ​​of the effective activation energy are of the same order as for wood press raw materials (see Chapter 3). This indicates that this exothermic peak corresponds to non-bioactivated wood pulp. Using the kinetic parameters of the process, t50 and t90 (the time required to achieve the degree of conversion of 50 and 90%) of the modified press raw materials were calculated (Fig. 5.3, 5.4).

Figure 5.3 - Values ​​for the conversion time of DP-BS(Au) at different temperatures (bioactivation time 7 days) Figure 5.4 - Values ​​for the transformation time of DP-BS(Au) at different temperatures (bioactivation time 14 days)

In order to establish the influence of activated sludge and cavitation lignin on the physical and mechanical properties of DP-BS(Au), an experiment planning matrix was compiled based on regression fractional mathematical planning of type 25-1 (see Table 5.2).

The following independent factors were used: Z 1 – content of cavitation lignin, %, Z 2 – hot pressing temperature, C, Z 3 – activated sludge consumption, %, Z 4 – duration of exposure (bioactivation), days; Z 5 – initial humidity of press raw materials, %.

The following output parameters were taken: density (P, kg/m3), bending strength (P, MPa), hardness (T, MPa), water absorption (B), swelling (L, %), flexural modulus of elasticity (Ei, MPa ), impact strength (A, kJ/m2).

According to the experimental plan, samples in the form of disks were made and their physical and mechanical properties were determined. The experimental data were processed and a regression equation was obtained in the form of a linear, polynomial of 1st and 2nd degree with an assessment of the significance of the factors and the adequacy of the equations, which are presented in Tables 5.2-5.4. Table 5.2 - Planning matrix and experimental results (three-level five-factor mathematical plan) a) hot pressing temperature and cavitation lignin content; b) consumption of sludge mixture and pressing temperature; c) humidity of press raw materials and duration of bioactivation; d) duration of bioactivation and content of cavitation lignin.

It has been established that the density of DP-BS(Au) with an increase in the content of cavitation lignin in the press raw material is extreme: the minimum density of 1250 kg/m3 is achieved with a CL content of 42%. The dependence of the density of DP-BS(Au) on the duration of bioactivation of press raw materials is also extreme and the maximum value is achieved at 14 days of bioactivation (Figure 5.5c).

Estimation of the cost of finished products

Conducted studies on the production of DP-BS, DP-BS(Au) and RP-BS (see Chapters 3,4,5) show that the physical and mechanical properties of plastic depend on the formulation of press raw materials, the type of chemical modifier and the conditions of its production .

In table Table 6.1 shows the physical and mechanical properties of plastics (DP-BS, DP-BS(Au) and RP-BS) obtained under rational conditions.

From the analysis of the results obtained (Table 6.1) it is clear that for the manufacture of products with high physical and mechanical properties, a press composition of the following composition is recommended: wood waste (pine sawdust), modifier - hydrogen peroxide (consumption - 1.8%) initial humidity - 12%.

To increase productivity, an extrusion method is proposed, which allows the production of molded products.

The dissertation examines the production of plinths. To comply with the conditions determined during hot pressing in closed molds, the extrusion head consists of two parts (a heated part of the head and the second - without heating). In this case, the residence time of the press composition in the heated part of the extrusion head is 10 minutes.

To determine the annual production volume, the extruder productivity was calculated.

For a single-screw extruder with variable (decreasing) depth cutting of a spiral channel, the volumetric productivity (Q, cm3/min) can be calculated as follows:

Here A1, B1, C1 are the constants of the forward and two reverse flows, respectively, at a variable screw cutting depth, cm3; Table 6.1 – Physical and mechanical properties of DP-BS, DP-BS(Au) and RP-BS (summary table) No. item 1245 6 Indicator Humidity of press raw materials,% Modifier DP-BS(Au) DP-BS RP-BS 12 % (4%-C6H12N4) 12% (1.8%-H202) CL - 3% Consumption AI-37% Humidity - 10% GL - 3% IMTHFA-4% Humidity - 6% GL - 68% IMTHFFA-2, 5% Humidity - 17.9% Humidity - 12% GL - 3% Hydrogen Peroxide - 0.06% Humidity - 12% GL - 35% Hydrogen Peroxide - 5% Humidity - 12%

Bending strength, MPa 8 12.8 10.3 9.6 12.0 - 8 9.7 Hardness, MPa 29 29.9 27.7 59 69 20 19 34 Flexural modulus of elasticity, MPa 1038 2909.9 1038, 6 732.6 2154 1402 1526 1915 Water absorption, % 59.1 148 121.7 43 59 34 143 139 Swelling, % 6.0 12 8 3 5.0 1.0 7 7.0 1 K – coefficient of the geometric shape of the head, K=0.00165 cm3; n – screw rotation speed, n=40 rpm. where t is the cutting pitch, cm, assumed to be t = 0.8D; - number of auger cutting passes, =1; e – width of the auger ridge, cm; e = 0.08D; - coefficient geometric parameters auger:

Coefficients a, b depend on the geometric dimensions of the screw. They are easy to calculate if you have a drawing of the auger, from which the following values ​​are taken: h1 – depth of the spiral channel at the beginning of the feeding zone, cm; h2 – depth of the spiral channel at the beginning of the compression zone, cm; h3 – depth of the spiral channel in the dosing zone, cm; If the screw dimensions are unknown (with the exception of D and L, which are known from the extruder brand), then take h1 = 0.13D. After this, the remaining parameters are calculated: where L is the length of the screw, cm; L0 – length of the screw to the compression zone, cm; where Lн is the length of the pressure part of the auger, cm; Ln=0.5L. where i is the degree of compression of the material; i=2.1. The obtained calculation results using the above formulas make it possible to calculate some other parameters of the screw.

Wood waste is sorted on vibrating screens (item 1) from large particles, then the wood particles pass through a metal detector (item 3). The coarse fraction enters the hammer crusher (item 2) and then returns to the vibrating sieve (item 1). From the vibrating sieve, small particles are fed by pneumatic transport into a cyclone (item 4), and then into a hopper (item 5), from where they are fed into a drum-type dryer (item 6) using a portioned screw conveyor, and the wood particles are dried to a moisture content of 6%. Shredded wood waste enters the cyclone (item 7), then into the dry crushed waste hopper (item 8) with a screw conveyor, through which it is fed to a belt scale (item 9).

The hydrogen peroxide solution is prepared in a tank (item 10) for mixing with water. Hydrogen peroxide is dosed using a scale (item 11). The supply of the required amount of water is regulated by a flow meter. The hydrogen peroxide concentration should be 1.8%. Belt scales feed required amount crushed wood particles into a continuous mixer (item 12), which also receives a certain amount of modifier solution. The components are thoroughly mixed in the mixer; the moisture content of the press raw materials should be 12%.

Then the press raw materials enter the distribution funnel (pos. 13), from where they enter the hopper (pos. 14) of the finished press raw materials. The bunker is the main buffer storage to ensure uninterrupted operation of the plants. The hopper (pos. 14) is equipped with a screw dispenser (pos. 15), with the help of which the finished composition is loaded into the hopper of the extrusion plant (pos. 16), with the help of which the finished composition is fed into the extrusion head.

The channel of the extrusion installation (item 17) is heated to a temperature of 1800C, the residence time in the heated part is 10 minutes, in the unheated part it is also 10 minutes.

The pressed product (item 18) is sent to the stage of trimming, culling and sorting, then enters the stage machining. After the control stage, finished goods sent to the finished goods warehouse. Figure 6.1 Technological flow diagram for the production of a product in the form of a DP-BS plinth from wood waste without adding binders using the extrusion method

Table 6.2 shows the calculation of the annual requirement for raw materials for the production of skirting boards. The estimated annual productivity of the production line for this type of product is 1 ton. Table 6.3 – Calculation of the need for raw materials and supplies Type of raw materials Consumption rate (1 t), Cost of 1 kg of raw materials, rub. Amount of costs for 1 ton of products, thousand rubles. Pine sawdust 0.945 8 7.56 Process water 0.048 7 0.33 Hydrogen peroxide 0.007 80 0.56 Total: 8.45 The amount of costs for the purchase of raw materials per ton of finished production products will be 8.456 thousand rubles. Compared to the production of this type of product from DPKT, which amounted to 47.65 thousand rubles. Thus, the production of plinths from DP-BS is economically feasible. With production of 50 t/year, savings on raw materials will amount to 1.96 million rubles.

Plastic is universal material It has found wide application in the manufacture of various components and parts in both industrial and household appliances. Products made from it are used in interior design of residential premises and offices.

A type of material called liquid plastic allows you to create crafts of a wide variety of shapes and sizes. This makes it possible to bring original design solutions. How to make liquid plastic at home?

Materials for production

To make liquid plastic with your own hands, you need to prepare the following:

• container made of glass or metal;
• acetone;
• Styrofoam.

In this case, the amount of acetone used depends on the desired volume of the finished product.

If you want to make liquid plastic with your own hands, the recipe for its preparation will be based on dissolving polystyrene foam in acetone. For this purpose they use It is a packaging container for various household and electronic equipment.

How to make liquid plastic with your own hands

Step by step recipe The preparation of the named material looks like this:

1. Open the container with acetone and pour the liquid into the glass container so that its level from the bottom is approximately 1 cm.
2. Polystyrene foam must be broken into many small pieces, each of which will be easily placed under the thickness of the solvent.
3. You can make liquid plastic with your own hands by dropping each piece into a container and waiting for it to completely dissolve.
4. Polystyrene foam should be added to the container until it stops melting. Then you need to wait 5-10 minutes for the unused acetone to evaporate.
5. After this, a viscous mass is formed at the bottom of the container, which can be used to produce a variety of products.

Knowing how to make liquid plastic, remember that complete hardening of the mass lasts 20-30 hours. Consequently, the part being manufactured cannot be removed from the mold within this period of time.

The substance should be applied rubber spatula small size. Movements should be smooth. Liquid plastic must be stretched over the surface to be treated. If you use it to fill cracks, it is better to use brushes with hard bristles. They need to “push” the mixture into the gaps. After the plastic has hardened, it is recommended to apply another layer of the substance.

The described product has long been sold in finished form. It only needs to be heated in a water bath or in special equipment. A hair dryer is also often used for this.

As a rule, liquid plastic is produced in dense packaging. Its terms and storage conditions are strict. The temperature in the room where it is located should not fall below 15 degrees. Otherwise, the product will lose its performance characteristics:

• viscosity;
• elasticity;
• hardness after hardening;
• practicality;
• durability.

The cost of liquid plastic is quite high. That's why it's better to do it yourself.

Precautionary measures

Acetone is a very dangerous liquid that has an extremely negative effect on the human body. Therefore, it is allowed to make liquid plastic with your own hands only if the following precautions are strictly observed:

1. Before working with acetone, you must carefully study the instructions for its use. It is indicated on the container label.
2. Special sealed safety glasses should be used. They will protect your eyes in case of liquid drops and vapors. Working without them can cause serious eye injury.
3. Acetone is toxic, so it should only be used in a well-ventilated area. In this case, it is necessary to use respiratory protection.
4. This is a highly flammable product. Therefore, do-it-yourself liquid plastic is made far from sources open fire. Smoking is strictly prohibited when performing work.
5. Residues of acetone must not be poured into the sewer system.
6. At the end of the process, as well as after pouring the finished plastic into molds, you must thoroughly wash your hands.

Applications of liquid plastic in finishing

The product has been used for finishing for a long time. After its application, an elastic film appears on the treated surface. It is highly waterproof and UV resistant. The material protected by such a film is not afraid of exposure to aggressive detergents. The smooth surface has a pleasant shine and retains its characteristics for many years.

Liquid plastic in window work

Most newly installed plastic windows have gaps in the joint area. To exclude such a phenomenon, all details window design, which are connected to each other, are treated with the described substance. After drying, it creates an elastic, sealed film on the surface. Applying liquid plastic to windows with your own hands is possible after making the material according to the above method.

Anti-corrosion agent

Liquid plastic is also characterized by a high degree of adhesion with the processed material. metal surface. This property of the substance began to be used in anti-corrosion treatment of steel. Liquid plastic is applied to the surface without prior priming. It dries out in a few hours. After this, a film is formed on the surface that will protect the material from rust.

The task of the technology for manufacturing products from thermoplastic wood-polymer composite materials is fundamentally simple - to combine all the ingredients of the future composite into a homogeneous material and form it into a product of the desired shape. However, its implementation requires a certain set of rather complex technological equipment.

1. General principles of technology.

The starting raw material for the production of WPC is wood flour (or fiber), base resin in the form of a suspension or granules and up to 6-7 types of necessary additives.

There are two fundamentally different schemes for producing extrusion products from thermoplastic WPC:

• two-stage process (compounding + extrusion),
• one-step process (direct extrusion).

In a two-step process, a wood-polymer compound is first made from the original ingredients. Resin and flour are kept in two silos. Flour, dried in a special installation, and resin are sent to a weighing dispenser and enter the mixer, where they are thoroughly mixed while hot with the addition of the necessary additives. The resulting mixture is then formed into small granules (pellets), which are then cooled in a special device (cooler).

Rice. 1. Scheme for obtaining granulated wood-polymer compound

Then, this compound is used for extrusion of profile products, see diagram of the extrusion section, Fig. 2.

Rice. 2. Diagram of the extrusion section

The granulate is fed into the extruder, heated to a plastic state and pressed through a die. The extruded profile is calibrated, sawed across (and, if necessary, lengthwise) and placed on the receiving table.

Wood polymer compound is also used for casting or pressing products from thermoplastic WPC.

In the case of direct extrusion, the ingredients are sent directly to the extruder; see, for example, one of the diagrams for organizing the process of direct WPC extrusion in Fig. 3.

Rice. 3. Scheme of direct extrusion of wood-polymer composites.

In this case, wood flour is supplied from the hopper to the drying unit, dried to a moisture content of less than 1% and entered into the storage hopper. Then the flour and additives go into the dispenser, and from it into the mixer (mixer). The mixture (compound) prepared in the mixer is fed into the storage tank of the extruder using a transport system. Resin, pigment and lubricant are fed from appropriate containers into the extruder, where they are finally mixed, heated and extruded through a die. Next comes cooling (and, if necessary), calibration of the resulting profile, and then cutting to the required length. This scheme is called direct extrusion.

Currently, both schemes are widely used in industry, although many consider direct extrusion to be more progressive.

There are enterprises abroad that specialize only in the production of granules for WPC, i.e. for sale. For example, at WTL International the capacity of installations of this type is up to 4500-9000 kg/hour.

For an approximate location of the equipment of the extrusion section (line) for direct extrusion of profile parts, see the following diagram.

Depending on the purpose of the project, the production of extrusion WPC can be implemented in the form of a compact site in one installation, or in the form of a workshop (a plant with a larger or smaller number of production lines.

Large enterprises may have dozens of extrusion plants.

The limiting temperatures of the extrusion process for different types of base resins are shown in the diagram in Fig. 6.

Fig.6. Limit temperatures of the working mixture (line 228 degrees - ignition temperature of wood)

Note. Most natural and synthetic polymers at temperatures above 100 degrees. C is prone to degradation. This is due to the fact that the energy of individual molecules becomes sufficient to destroy intermolecular bonds. The higher the temperature, the more such molecules become. As a result, the length of the polymer molecular chains is reduced, the polymer is oxidized, and the physical and mechanical properties of the polymer are significantly deteriorated. When extreme temperatures are reached, degradation of polymer molecules occurs in en masse. Therefore, during hot compounding and extrusion, it is necessary to carefully control the temperature of the mixture and strive to reduce it and reduce operating time. Polymer degradation also occurs during natural aging composite when exposed to ultraviolet radiation. Not only plastic is subject to degradation, but also the polymer molecules that make up the structure of the wood component of the composite.

The pressure of the molten mixture in the extruder barrel is usually between 50 and 300 bar. It depends on the composition of the mixture, the design of the extruder, the shape of the extruded profile and the flow rate of the melt. Modern powerful extruders are designed for operating pressures of up to 700 bar.

The WPC extrusion speed (i.e., the melt flow rate from the die) ranges from 1 to 5 meters per minute.

The main part of this technological process is the extruder. Therefore, below we will look at some types of extruders.

2. Types of extruders

In Russian literature, extruders are often referred to as worm presses. The operating principle of the extruder is the “meat grinder principle”, well known to everyone. A rotating auger (worm) grabs material from the receiving hole, compacts it in the working cylinder and pushes it under pressure into the die. In addition, the final mixing and compaction of the material occurs in the extruder.

The movement of material in the extruder when the screw rotates occurs due to the difference in the coefficients of friction of the material against the screw and the cylinder. As one foreign specialist figuratively put it: “the polymer sticks to the cylinder and slides along the screw.”

The main heat in the working cylinder is released due to compression of the working mixture and the work of significant frictional forces of its particles on the surface of the extruder and on each other. For processing thermoplastics, extruders are equipped with additional devices for heating the working mixture, measuring the temperature and maintaining it (heaters and coolers).

In the plastic industry, the most common, due to their relative simplicity and relatively low price, are single-cylinder (single-screw) extruders, see diagram and photo, fig. 7.

Rice. 7. Standard diagram and appearance of a single-cylinder extruder: 1- hopper; 2- auger; 3-cylinder; 4- cavity for water circulation; 5- heater; 6- grate; 7-forming head. Process phases (I - material supply, II - heating, III - compression)

The main characteristics of the extruder are:

• cylinder diameter, mm
• ratio of the length of the cylinder to its diameter, L/D
• screw rotation speed, rpm
• motor and heater power, kW
• productivity, kg/hour

Note. The nominal performance of an extruder is a relative value. The actual performance of an extruder may differ significantly from the nameplate in a particular technological process, depending on the material being processed, the design of the dies, post-extrusion equipment, etc. Indicators of the efficiency of a particular extrusion process are the ratio of productivity to power consumption, equipment cost, number of personnel, etc.

The following diagram shows the differences in performance of TEM series extruders from the English company NFM Iddon Ltd when producing granules and profiles using different WPC compositions.

The next type is conical screw extruder. Structurally, it is similar to a cylindrical extruder, but the screw and working cavity are made in the shape of a cone. This makes it possible to more energetically capture and push loose material into the working area, compact it and quickly raise the pressure in the die area to the required level.

Note. Cylindrical and conical single screw extruders can be used to produce thermoplastic WPC profiles in a two-stage process, i.e. when processing finished WPC compound.

Extruders with two cylindrical or conical screws are more productive, see fig. 8. In addition, they have significantly better mixing properties. Extruder screws can rotate in one direction or in opposite directions.

Rice. 8. Diagrams of screws of double-cylinder and double-cone extruders: feeding zone, compression zone, ventilation zone, dosing zone

The design of a twin-screw machine is much more complicated and more expensive.

The screws of modern extruders are complex design, see Fig. 6.9.a. and rice 6.9.b.

Fig.1.9. Window for real
monitoring the process in the extruder.

Various mechanical, hydraulic and chemical processes occur in the working cavity of the extruder, the observation and precise description of which is difficult. In Fig. 9 shows special armored glass window for direct observation of the extrusion process (FTI)

Due to their high productivity and good mixing properties, twin-screw machines are used to implement the direct extrusion of thermoplastic WPC. Those. they mix the components and feed the prepared working mixture into the die. In addition, twin screw extruders are often used in a two-stage process as compounders to produce WPC granules.

The screws of twin-screw machines do not necessarily have only helical surfaces. To improve their mixing properties, special mixing sections with other types of surfaces can be made on the screws, which provide significant change the direction and nature of the movement of the working mixture, thereby ensuring better mixing.

Recently, the Japanese company Creative Technology & Extruder Co. Ltd, for the processing of wood-polymer compositions, a combined extruder design was proposed, in which twin-screw and single-screw extruders are combined in one cylinder body.

The basic mechanisms of the phenomena occurring during extrusion of thermoplastic materials are well studied. IN general outline see for example the appendix "Introduction to extrusion"

Note. The installation for the production of wood-plastic sheets at Rostkhimmash uses a disk extruder. In some cases, in the production of DPCT, piston extrusion can be used instead of screw extrusion.

Exist special methods mathematical computer modeling of extrusion processes used for the calculation and design of extruders and dies, see Fig. 10. and in computer control systems for extruders.

Rice. 10. Computer modeling system for extrusion processes.

Extruders used in WPC production must be equipped with effective device degassing to remove vapors and gases and have wear-resistant working surfaces, for example, a cylinder with deep nitriding and a screw reinforced with molybdenum.

Traditionally, wood flour with a moisture content of less than 1% is used in WPC production technology. However, new modern extruders, designed specifically for the production of WPC, are capable of processing flour with a moisture content of up to 8%, as they are equipped with a powerful degassing system. Some believe that the water vapor generated in the extruder helps to facilitate the extrusion process to some extent, although this is controversial. For example, the Cincinnati Extrusion company indicates that the extruder produced by the company is mod. Fiberex A135 at a flour moisture content of 1-4% will have a productivity of 700-1250 kg/hour, and at 5-8% only 500-700 kg/hour. Thus, a standard extruder, even equipped with a degassing system, is still not a dryer, but is simply capable of more or less effectively removing a small amount of moisture from the working mixture. However, there are exceptions to this situation, for example, the Finnish Conex extruder described below, which can also work on wet materials.

In general, water must be completely removed from the material during extrusion to ensure a dense and durable composite structure. However, if the product is used indoors, it may be more porous and, accordingly, less dense.

One extruder designed specifically for the production of wood-polymer composites is shown in Fig. eleven.

Rice. 11. Extruder model DS 13.27 from Hans Weber Gmbh, Fiberex technology

Extruders used in a two-stage process for preliminary granulation of WPC, instead of a profile die, are equipped with a special granulating head. In the granulating head, the flow of the working mixture leaving the extruder is divided into several streams of small diameter (strands) and cut into short pieces with a knife.

After cooling they turn into granules. The granules are cooled in air or water. The wet granules are dried. Granular WPC is suitable for storage, transportation and further processing into parts at the next stage of the technological process or at another plant by extrusion, injection molding or compression molding.

Previously, extruders had one loading zone. New models of extruders developed for processing composite materials may have two or more loading zones - separately for resin, separately for fillers and additives. In order to better adapt to work on different compositions, extruders and compounders are often made collapsible sectional design, which allows you to change the L/D ratio

3. Dies (heads) of extruders

The die (the so-called “extruder head”) is a replaceable extruder tool that gives the melt leaving the working cavity of the extruder the required shape. Structurally, the die is a slot through which the melt is pressed (outflows).

Rice. 12. Die, profile, calibrator.

The final formation of the material structure occurs in the die. It largely determines the accuracy cross section profile, the quality of its surface, mechanical properties, etc. The die is the most important integral part dynamic extruder-die system and actually determines the performance of the extruder. Those. with different dies, the same extruder is capable of producing different amounts of profile in kilograms or linear meters (even for the same profile). This depends on the degree of perfection of the rheological and thermotechnical calculation systems (extrusion speed, extrudate swelling coefficient, viscoelastic deformation, balance of individual extrudate flows, etc.) In the photograph, Fig. 6.13. shows a die (on the left) from which a hot profile emerges (in the center) and is sent to the calibrator (on the right).

To produce products with complex profiles, dies are used that have a relatively high resistance to the movement of the melt. The main task that must be solved inside the die during the extrusion process, and especially for a complex profile part, is equalizing the volumetric velocity of various melt flows in the die over the entire section of the profile. Therefore, the extrusion speed of complex profiles is lower than that of simple ones. This circumstance must be taken into account already at the stage of designing the profile itself, i.e. products (symmetry, thickness, location of ribs, transition radii, etc.).

Fig. 13. Prefabricated two-strand die for the production of window profiles.

The extrusion process allows one extruder to simultaneously produce two or more, usually identical, profiles, which makes it possible to make maximum use of the extruder's performance when producing small profiles. For this purpose, double-strand or multi-strand dies are used. The photograph shows the appearance of a two-strand die, see Fig. 13

The dies are made of strong and wear-resistant steel. The cost of one die can range from several thousand to several tens of thousands of dollars (depending on the size, complexity of the design and accuracy and materials used).

It seems that the technical complexity of powerful modern extruders and dies for them (in terms of accuracy, production technologies and materials used) is approaching the complexity of aircraft engines, and not every machine-building plant can handle this. However, it is quite possible to consider the possibility of organizing the production of domestic extrusion equipment - if you use ready-made components of imported production (working cylinders, screws, gearboxes, etc.). There are companies abroad that specialize in the manufacture of just such products.

4. Dispensers and mixers.

In the production of structural materials, issues of homogeneity (uniformity of structure) and constancy of composition are, as is known, of primary importance. The importance of this for wood-polymer composites does not even require special explanation. Therefore, in WPC technology, much attention is paid to means of dosing, mixing and supplying materials. In the production of WPC, various technological methods and schemes for solving these processes are implemented.

Dosing of materials is carried out in 5 ways:

• Simple volumetric dosing, when the material is poured into a container of a certain size (measuring bucket, barrel or mixer container)
• Simple weighing dosing, when the material is poured into a container located on the scales.
• Continuous volumetric dosing, for example using a dosing screw. Regulation is carried out by changing the feed speed of the device.
• Continuous gravimetric dosing using special electronic devices.
• Combined dosing, when some components are dosed in one way, and others in another.

Volumetric dosing means are cheaper, weight dosing means are more accurate. Continuous dosing means are easier to organize into an automated system.

Mixing the components can be done using cold or hot methods. The hot compound is sent directly to the extruder for profile formation or to the granulator and cooler to produce granules. A special extruder-granulator can act as a hot mixer.

Notes:

1. Granular materials usually have a stable bulk mass and can be dosed fairly accurately using volumetric methods. With powders, and especially with wood flour, the situation is the opposite.
2. Organic liquid and dusty materials are prone to fire and explosion. In our case, this applies especially to wood flour.

Mixing the components can be done in various ways. For this purpose, there are hundreds of different devices, both simple mixers and automatic mixing units, see, for example, paddle-type mixers for cold and hot mixing.

Rice. 14. Computerized mixing and dosing station from Colortonic

In Fig. 14. shows a gravimetric system for automatic dosing and mixing of components, developed specifically for the production of wood-polymer composites. The modular design allows you to create a system for mixing any components in any sequence.

5. Feeders

The peculiarity of wood flour is that it is very small bulk density and not very good flowability.

Rice. 15. Feeder design diagram

No matter how quickly the extruder screw rotates, it is not always able to capture a sufficient amount (by weight) of the loose mixture. Therefore, forced feeding systems for extruders have been developed for light mixtures and flour. The feeder supplies flour to the extruder loading zone under some pressure and thereby ensures sufficient density of the material. The design diagram of such a feeder is shown in Fig. 15.

Typically, forced feeders are supplied by the manufacturer along with the extruder as a special order for a specific mixture, see for example the direct extrusion process diagram offered by Coperion, Fig. 16.

Rice. 16. Scheme of direct extrusion of WPC with forced feeding, Coperion.

The scheme involves loading individual components of the composite into different zones extruder. Appearance similar installation from Milacron, see Fig. 1.17.a.

Rice. 17.a. TimberEx TC92 twin-screw conical extruder with a forced-feed system with a capacity of 680 kg/hour.

6. Cooler.

In the simplest cases, the WPC extrusion process can be completed by cooling the profile. For this, a simple water cooler is used, for example, a trough with a shower head. The hot profile falls under jets of water, cools and takes on its final shape and size. The length of the trough is determined from the condition of sufficient cooling of the profile to the glass transition temperature of the resin. This technology is recommended, for example, by Strandex and TechWood. It is used where the requirements for surface quality and profile shape accuracy are not too high ( building construction, some decking products, etc.) or subsequent processing is expected, for example, sanding, veneering, etc.

For products with increased requirements for product dimensional accuracy (prefabricated structures, interior elements, windows, doors, furniture, etc.), it is recommended to use calibration devices (calibrators).

An intermediate position in terms of dimensional accuracy of the resulting products is occupied by the technology of natural air cooling of the profile on a roller table, used, for example, by the German company Pro-Poly-Tec (and it seems to be one of the Korean companies).

7. Calibrators.

The profile emerging from the die has a temperature of up to 200 degrees. When cooled, thermal shrinkage of the material occurs and the profile necessarily changes its size and shape. The calibrator's task is to ensure forced stabilization of the profile during the cooling process.

Calibrators are available in air and water cooling. There are combined water-air calibrators that provide better pressing of the extrudate to the forming surfaces of the calibrator. Vacuum calibrators are considered the most accurate, in which the moving surfaces of the profile being formed are sucked by vacuum to the surfaces of the forming tool.

The Austrian company Technoplast has recently developed special system water calibration and cooling of wood-polymer profiles, called Lignum, see fig. 18.

Rice. 18. Lignum calibration system from Technoplast, Austria

In this system, profile calibration occurs using a special attachment to the die, in which water vortex cooling of the profile surface occurs.

8. Pulling device and cutting saw.

When leaving the extruder, the hot composite has low strength and can be easily deformed. Therefore, to facilitate its movement through the calibrator, a pulling device, usually of the track type, is often used.

Rice. 19. Pulling device with cutting saw from Greiner

The profile is delicately captured by the caterpillar tracks and removed from the calibrator at a predetermined, stable speed. In some cases, roller machines can also be used.

To divide the profile into segments of the required length, movable disks are used pendulum saws, which during the sawing process move along with the profile and then return to their original position. The sawing device, if necessary, can be equipped with a ripping saw. The pulling device can be made in one machine with a cutting saw, see photo in Fig. 19.

9. Reception table

It can have a different design and degree of mechanization. The simplest gravitational ejector is most often used. For appearance, see, for example, Fig. 20.

Rice. 20. Automated unloading table.

All these devices mounted together, equipped with a common control system, form an extrusion line, see Fig. 21.

Rice. 21. Extrusion line for the production of WPC (receiving table, saw, pulling device, calibrator, extruder)

To move profiles around the enterprise, various carts, conveyors and loaders are used.

10. Finishing work.

In many cases, a profile made from WPC does not require additional processing. But there are many applications in which, for aesthetic reasons Finishing work necessary.

11. Packaging

The finished profiles are collected in transport bags and tied with polypropylene or metal tape. Critical parts can be additionally covered, for example, with plastic film or cardboard pads to protect them from damage.

Small profiles may require rigid packaging to prevent breakage ( cardboard boxes, lathing).

Domestic analogues.

During information research in the field of WPC extrusion, a search for domestic technologies was also carried out. The only line for the production of wood-plastic sheets is offered by the Rostkhimmash plant, website http://ggg13.narod.ru

Technical characteristics of the line:

Type of product - sheet 1000 x 800 mm, thickness 2 - 5 mm

Productivity 125 - 150 kg per hour

Line composition:

• twin screw extruder
• disk extruder
• head and gauge
• vacuum calibration bath
• pulling device
• cutting device, for trimming edges and cutting to length
• automatic storage device

Overall dimensions, mm, no more (dimensions are indicated without the thermal station and a set of control devices - to be specified when arranging the equipment at the customer’s place)

• length, 22500 mm
• width, 6000 mm
• height, 3040 mm

Weight - 30,620 kg

Installed power of electrical equipment is about 200 kW

This installation can be assessed as follows:

• has low productivity
• not suitable for the production of profile parts
• extremely low accuracy (+/- 10% in thickness)
• high specific material consumption and energy consumption

You can cut the parts and sharpen each of them manually, but this technique is very imperfect: it takes a lot of effort, and it is impossible to get two absolutely identical products. Therefore in this material you will learn how to perform plastic injection molding at home.

What we might need

To cast plastic with our own hands, we do not need any special tools or materials. We can make a template model, a kind of matrix, from almost anything - metal, cardboard or wood. But regardless of which option you choose, in any case it must be soaked with a special solution before starting work. This is especially true for wood and paper, because they actively absorb moisture and to prevent this process we need to fill the pores, preferably with liquid wax.

Silicone.

If we settled on this option, then we should buy it with the lowest viscosity - this will contribute to better streamlining of the part. Of course, the results will be more accurate. There are a great many varieties of it on the modern market, and it makes no sense to compare them with each other: we have neither the time nor the opportunity for this. We can only say with confidence that car sealant, preferably red, is ideal for coating. It will make pouring plastic at home much easier.

Deciding on the casting material

To be honest, there are even more molding materials than there are silicone varieties. Among them there are liquid plastic, and ordinary gypsum mixed with PVA glue, and even polyester resin. Substances for cold welding, low-melting metals and so on. But in our case we will be based on some other characteristics of casting substances:

• The duration of their work.
• Viscosity.

Regarding the first point, it indicates the time during which we can manipulate the material that has not yet hardened. Of course, if the production of plastic products takes place in a factory, then two minutes will be more than enough. Well, we, who do this at home, need at least five minutes. And if it happened that suitable materials If you couldn’t get them, then they can be easily replaced with simple epoxy resin. Where to look for it? In car dealerships or in stores for fans of aircraft modeling. In addition, such resin is often found in ordinary hardware stores.

Making a cut shape

This one is ideal for pouring plastic with your own hands, because you can pour unusual types of resins into it. A little trick of this technique is that at the preliminary stage the entire surface of the model needs to be treated with silicone, and then, after the material has completely hardened, the matrix can be cut off. After this, we extract its “insides,” which will be useful to us for further casting. In order for the shape to suit us, we need to apply a three-millimeter layer of sealant, after which we simply wait for the material to harden - this usually takes two hours. It is advisable to apply it with a brush. When applying the first layer, we must try to fill any unevenness or voids with the material so that air bubbles do not form later.

How does the casting process work?

First step.

We take the casting mold and clean it thoroughly - it should be dry and clean. All remnants of material remaining after preliminary procedures must be removed.

Second step.

If the need arises, we can slightly change the color of our composition: to do this, you just need to add one drop of paint to it, but in no case water-based (liquid plastics have a personal dislike for them).

Third step.

There is no need to degas our casting mixture. This can be explained by the fact that plastic molding at home initially provides for a relatively short “life”. At the same time, in order to remove air bubbles from small-sized products, you just need to remove them with your own hands after pouring.

Fourth step.

Mix all the necessary ingredients thoroughly and pour it into the template mold slowly, in a thin stream. This should be done until the mixture fills the entire volume and some more of the casting channel. And soon, when the degassing procedure takes place, the volume of this material will decrease significantly and become what we need.

And the last piece of advice: in order for the quality of the model to be high, the template needs to be cooled gradually, slowly. So, follow all the instructions and everything will work out for you!

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