Overview of polyurethane products

Material properties and specifications

The most common material today is polyurethane. What it is, what advantages it has, you already know. Now let's figure out the technical characteristics of this substance.

So, the presented material can work quietly in an aggressive environment, while its quality properties practically do not change. In addition, the substance is perfectly exploited in a fairly wide temperature range: from -60 to +80 degrees. Sometimes it can be heated up to 120 °, but this process should not last long, otherwise the material will simply collapse.

The polymer is able to withstand heavy loads and is less susceptible to aging than other substances. It is resistant to wear, moisture, temperature extremes, sunlight, salt, organic solvents. Polyurethane (what it is, you already know) is considered a very durable material. Moreover, its elasticity can be programmed in the production process. This material can have different characteristics, on which the scope of its application depends. It should be noted that polyurethane can be composed of one or more components.

How to use?

Polyurethane elastomer belongs to the category of materials that can be processed without much effort. Polyurethanes do not have the same qualities, and this is intensively practiced in many areas of the national economy. So, some matter can be elastic, the second - rigid and semi-rigid. The processing of polyurethanes is carried out using such methods.

1. Extrusion is a method for the production of polymer products, in which the melted material that has received the necessary preparation is pressed through a specialized device - an extruder.
2. Casting - here the melted mass is injected into the casting matrix by means of pressure and cooled. In this way, polyurethane moldings are made.
3. Pressing is a technology for the production of products from thermosetting plastics. In this case, solid materials are converted into a liquid viscous state. Then the mass is poured into the mold and by means of pressure they make it more dense. This product, while cooling down, gradually acquires the characteristics of a high-strength solid, for example, a polyurethane beam.
4. Pouring method on standard equipment.

Also, polyurethane blanks are machined on turning equipment. The part is created by acting on a rotating workpiece with various cutters.

By means of such solutions, it is possible to manufacture reinforced sheets, laminated, porous products. And this is a variety of blocks, building profiles, plastic wrap, plates, fiber and so on. PU can be the basis for both colored and transparent products.

Creating polyurethane matrices on your own

Strong and elastic PU is a material popular among folk craftsmen, from which matrices are created for casting a variety of products: decorative stone, pavement tiles, paving stones, gypsum figurines and other products. Injection molding PU is the main material due to its unique characteristics and availability.

Specificity of the material

The creation of polyurethane matrices at home involves the use of liquid 2-component compositions of different types, and which PU to use depends on the purpose of casting:

• to create matrices for lightweight products (for example, toys);
• to create finishing stone, tiles;
• for forms for heavy large objects.

Preparation

Before starting work, you need to purchase polyurethane for filling matrices. Two-component formulations are sold in 2 buckets and must be fluid and liquid when opened.

You also need to buy:

• originals of products from which the cast will be released;
• trimming MDF or laminated chipboard and self-tapping screws for formwork;
• specialized lubricating anti-adhesive mixtures;
• a clean container for mixing ingredients;
• compounding device (electric drill attachment, mixer);
• silicone based sealant.

Then the formwork is assembled - a box in the form of a rectangle with a size sufficient to accommodate the required number of models.

Form making

Primary models are laid on the bottom of the formwork at a distance of at least 1 cm between themselves

To prevent the samples from slipping, carefully fix them with a sealant. Right before casting, the skeleton is set to the building level.

Inside, the formwork and models are covered with an anti-adhesive mixture, and while it is absorbed, a working composition is made. The components are poured into a clean container in the required ratio (based on the preferred material) and thoroughly mixed until a homogeneous mass is created.

To create the molds, polyurethane is poured carefully into one place, allowing the material itself to expel excess air. Models must be covered with a polymerization mass by 2-2.5 centimeters

You can learn about what can be made from liquid polyurethane in the video below.

DIY polyurethane mold production technology

We purchase packaging of artificial stone that is ideal for your interior. Usually packages are designed for 1 square meter. On the edge of the chipboard furniture board, you need to spread out half a square of stone.

Important: we leave gaps between the stones, about 1-1.5 cm.Then, using silicone, you need to glue the stone tiles to the chipboard sheet

Then, using silicone, you need to glue the stone tiles to the chipboard sheet.

Use a slab trim to make a support 2 cm above the edge of the stone. Further, with the help of sanitary silicone, insulate all joints, this is necessary in order to prevent the leakage of liquid polyurethane. To obtain the most even shape, level the surface with the formwork installed on it. For more convenient work, you can put the formwork on the table.

Only after the silicone has hardened can the support and stone be covered with a separator. We give the separator time to crystallize and start working with injection molded polyurethane.

Next, we move on to making the mold. To do this, it is necessary to connect two pieces of liquid polyurethane. One part is orange and liquid, while the other is colorless and thicker. We measure the same amount of liquid with a scale and use a mixer to mix them thoroughly until smooth. Next, pour it into the formwork.

Important: be sure to make sure that the liquid from the canisters is mixed in equal proportions. Pour the form to the brim and leave to harden for about 24 hours.

Ideal for working with polymers above zero ambient temperature. Polyurethane does not have a special smell, but it is still not recommended to work with it indoors

Pour the form to the brim and leave to harden for about 24 hours. Ideal for working with polymers above zero ambient temperature. Polyurethane does not have a special smell, but it is still not recommended to work with it indoors.

After about 24 hours from a jelly-like mass, the polyurethane will turn into a stable form for casting artificial stone.

Next, you need to disassemble the formwork itself, with the help of a clerical knife we ​​cut off the places of strong sticking of silicone and polyurethane. After removing the formwork, detach the mold from the table. Allow the mold to dry out, the surface that has not been in contact with air may be slightly damp. Wipe the mold and leave for a few hours until the surface is completely dry. Then you can start casting the stone.

Types of liquid polyurethane for making molds

Polyurethane types:

• chilled casting;
• hot casting.

Cold-cast polyurethane is the most popular because it does not require special skills and non-budget equipment. All manipulations with such polyurethane can be carried out within a small production or at home.

Hot-cast polyurethane is commonly used to make ready-to-use end-use products. It is also widely used for surface and joint treatment. Unlike cold-cast polyurethane, special equipment is required to work with its analogue.

The main analogues of liquid injection molded polyurethane are silicone and formoplast.

Production stages

1. Creation of the project of the future matrix. It is necessary to accurately recreate the location of the sections;
2. Creates a casting structure with walls around the model. Plywood is perfect for these purposes;
3. Mix the molding material according to the manufacturer's instructions;
4. Pouring material. The material is carefully poured into the corner of the mold to allow the solution to flow through the prototype to reduce blistering.

Mechanical finishing of polyurethanes

Mechanical finishing of polyurethanes includes:

• turning. Cutters designed for polyurethane must have carefully sharpened and sharp barriers. When turning large parts, the depth of the cutter should be 2-3 mm at feed and 0.8-1 mm per revolution. It is necessary to ensure the largest possible gap between the polyurethane and the tool, the chips should come off as a continuous thread.
• grinding. Use a slow feed to make the sanding surface smoother. The large thickness of the removed layer can lead to melting of the surface of the part. The rotation speed of the grinding wheel should be 2255-3255 rpm. Sometimes sanding requires a coolant, water will do the job just fine. A dust pump manifold must be present at the workplace.
• drilling. Using slow speed twist drills will be the best solution. Use a hard backing material to avoid tearing the polyurethane at the drill exit. Feed rate approx. 0.5 mm per revolution.

Foamed polyurethane production technology

Polyurethane foam production is nothing more than
mixing
liquid isocyanate and polyol. In this case, it is necessary to observe the proportion.
The result of mixing is a foamy, airy mixture that
forms polyurethane foam when solidified. For the production of products from
PPU are required:

1. Equipment.
2. Raw materials.
3. Spray gun.
4. Lubrication.

In the production of polyurethane foam, it must be remembered that compliance with all
technological standards gives a high-quality product, and their violation leads
to marriage. The technological standards include:

1. Indoor air temperature.
2. Raw material temperature.
3. Compliance with the normative ratio of raw materials components.
4. High-quality mixing of components with each other.

In this case, the temperature regime plays one of the key roles,
because at low temperature indicators, the consumption of raw materials increases and
the very quality in polyurethane foam. It can also be reflected in different ways.
on finished products.
The finished mixture (foam) is filled in the forms. Fill them with the fill method.
Using the pouring method, thermal insulation boards can be made,
shell for pipe insulation. Also by pouring polyurethane foam into
molds can produce various decorative elements. Since liquid
polyurethane foam is quite "sticky", for this the form must be lubricated
special oil or silicone greases.

Polyurethane foam production by casting

For this method, it is important to have the necessary equipment, the availability of components for the production of polyurethane foam.Just like in the spraying method, the mechanism provides continuous feeding and intensive mixing of the mixture.

The only feature is that the reaction mass is not supplied under pressure, but is poured into molds or cavities. In order to obtain a good product at the output, mixtures with a slow foaming time are used. Most often, the filling of elements takes place in several stages, in portions. Because it is not always possible to accurately calculate the filling volume.

Filling PPU

Peculiarities

In the 40s of the last century in Europe, after lengthy experiments, a German chemical technologist named Bayer synthesized a material that had amazing properties. The polymer found widespread use after as many as 20 years. It began to be used in many branches of human activity.

The product also contains other components: reagents, emulsifiers, polyesters. And additives of catalysts and blowing agents completely change the structure of the final product. In terms of the number of variations, polyurethane overtakes such polymers as PVC, polystyrene and polyethylene.

Polyurethane can be presented in several possible states: in liquid with a high degree of viscosity, as soft rubber, it can be soft (foam rubber) and hard (foam plastic). It can also have both high and low elasticity, and can be foamed as a polyurethane foam.

The initial color of the polyurethane is yellow-brown. It is chemically inert, resistant to oils, ultraviolet light, as well as aggressive environmental influences, fungi and bacteria. The material has low toxicity.

Polyurethane in any of its manifestations does not lose its characteristics even with temperature fluctuations (in the range from -60 to +80 degrees), therefore such products serve people in the Far North and in the desert. By the way, in comparison with the same rubber, polyurethane is not destroyed by ozone.

Its amazing elasticity parameters are impressive - polyurethane stretch reaches 650% without significant damage. It also weighs quite a bit.

And although rubber, plastic and metal are considered its main competitors, they are inferior to polyurethane in some characteristics.

• Polyurethane is characterized by high coefficients of elasticity, wear resistance, ages more slowly than rubber. It tolerates mechanical stress better, moreover, after any deformation, it quickly returns to its original shape.
• In comparison with different metals, polyurethane is lightweight, resistant to abrasives. And most importantly, polymer production is much cheaper. Machine parts made of polyurethane create much less noise.
• Polyurethane is superior to plastic when used in hot or cold weather; it does not crack when subjected to impact.

In fairness, it is necessary to say a few words about the weaknesses of polyurethane. The polymer is airtight, and the foam parts shrink. And there is also an increase in fragility and hardness with prolonged exposure of products in the cold. But the biggest disadvantage is the difficulty of recycling polymer products.

Production

Polyurethane is derived from polyol and isocyanate, which are products of the petrochemical industry. To achieve certain technical properties, various additives are added to them, that is, in the production of polyurethane as a raw material, it is necessary to take into account its further field of application. Today it is the world's most sought-after polymer in all major industrial segments. Both foreign and domestic materials are presented on the synthetic polymer market.

In the manufacture of products, such technological methods as casting, extrusion, pressing, pouring are used.

Application of injection molded polyurethane

Two-component injection molded polyurethanes They are used for a variety of purposes: from casting gears of mechanisms to making jewelry.

The good performance properties of parts made of such materials allow them to be used in rather harsh conditions. These parts are chemically resistant, have good hardness and toughness. They can be:

• various shafts, gears, pulleys - due to good strength characteristics and high wear resistance, these parts serve for a long time and with high quality;
• wheels for loaders and trolleys: such wheels are stronger than rubber ones and can work even with serious tread damage;
• rollers - for example, guide and support rollers for conveyors and conveyor belts;
• toothed transmission belts, tracks and tracks - they are stronger than rubber and last longer;
• sealing elements, shock absorbers, etc. - due to the higher strength and wear resistance, replacing rubber parts with polyurethane is quite expedient. In this case, the elasticity of the part remains at the same level;
• couplings, bushings, bearing parts;
• various protective coatings;
• pipelines - excellent chemical resistance together with mechanical strength allows the manufacture of both one-piece pipeline elements and protection of pipelines from the outside or from the inside.

The properties of two-component polyurethanes allow them to be used for the manufacture of paints and varnishes and adhesives. Such varnishes, paints and adhesives are resistant to weathering, hold for a long time and firmly.

Also popular is liquid elastic two-component polyurethane for making molds for further castings, for example, for casting from plaster, wax, polyester resins, concrete, etc.

Polyurethanes are also used in medicine - they are used to make removable dentures. You can also make various jewelry from polyurethanes.

Even self-leveling floors can be made of polyurethane - such floors are highly wear-resistant and durable.

In some areas, parts made of polyurethane are even superior to steel in a number of parameters.

At the same time, the ease of manufacturing such parts makes it possible to manufacture both miniature complex parts weighing up to a gram and massive castings of 500 or more kilograms.

In general, four areas of application of two-component polyurethane mixtures can be distinguished:

• tough and durable parts, where polyurethanes replace steel and other metals;
• elastic parts - high elasticity of polymers and their elasticity are in demand here;
• parts resistant to aggressive influences - high resistance of polyurethanes to aggressive substances or to abrasive influences;
• parts that absorb mechanical energy due to high internal friction.

In practice, a complex of directions is often used, since several valuable qualities are required from many parts at the same time.

Applications

Two-component injection molding polyurethanes are practiced for a wide variety of applications, from casting gears to making jewelry.

Particularly significant areas of use for this material are as follows:

1. refrigeration equipment (cold and thermal insulation of commercial refrigeration equipment and household refrigerators, freezers, warehouses and food storage facilities);
2. transport refrigeration equipment (cold and thermal insulation of automobile refrigeration units, isothermal railway cars);
3. construction of quickly erected civil and industrial facilities (thermal insulation properties and the ability to withstand the load of rigid polyurethanes in the structure of sandwich panels);
4. construction and overhaul of residential buildings, private houses, mansions (insulation of external walls, insulation of elements of roofing structures, openings of windows, doors, and so on);
5. industrial civil construction (external insulation and protection of the roof from moisture by a rigid polyurethane spray method);
6. pipelines (thermal insulation of oil pipelines, heat insulation of pipes of a low-temperature environment at chemical enterprises by pouring under a casing installed in advance);
7. heating networks of cities, villages and so on (thermal insulation by means of rigid polyurethane hot water pipes during new installation or during overhaul using various technological methods: spraying and pouring);
8. electrical radio engineering (imparting wind resistance to various electrical devices, waterproofing contacts with good dielectric characteristics of rigid structural polyurethanes);
9. automotive industry (molded interior design elements of a car based on thermoplastic, semi-rigid, elastic, integral polyurethanes);
10. furniture production (creation of upholstered furniture using foam rubber (elastic polyurethane foam), decorative and body components made of hard PU, varnishes, coatings, adhesives, etc.);
11. textile industry (production of leatherette, polyurethane foam composite fabrics, etc.);
12. the aviation industry and the construction of wagons (products from flexible polyurethane foam with high fire resistance, made by molding, noise and heat insulation based on specialized types of PU);
13. machine-building industry (products from thermoplastic and specialized brands of polyurethane foams).

The properties of 2-component PU make it possible to use them for the production of varnishes, paints, adhesives. Such paints and varnishes and adhesives are stable to atmospheric influences, hold tightly and for a long time.

Liquid elastic 2-component polyurethane is also in demand for creating molds for castings, for example, for casting from concrete, polyester resins, wax, gypsum, and so on.

Polyurethanes are also used in medicine - they are used to make removable dentures. In addition, you can create all kinds of jewelry from PU.

In some areas, products made from PU are superior in a number of characteristics even over steel.

At the same time, the simplicity of creating these products makes it possible to create both miniature components weighing no more than a gram and bulky castings of 500 kilograms or more.

In total, 4 directions of using 2-component PU mixtures can be distinguished:

• strong and rigid products, where PU replaces steel and other alloys;
• elastic products - high plasticity of polymers and their flexibility are required here;
• products resistant to aggression - high stability of PU to aggressive substances or to abrasive influences;
• products that absorb mechanical energy through high viscosity.

Technical equipment for PPU spraying

For spraying, use equipment
which automatically
dosages two components. Moreover, such equipment
equipped with a mixing chamber in which it is intensively mixed
raw materials. In spray equipment, polyurethane foam in spray
the gun is supplied under pressure

Also, it is not unimportant that the equipment
for spraying polyurethane foam was equipped with a speed control function. So
so you can adjust the intensity of the application
heat-insulating material on the surface to be insulated

To
work on external insulation was carried out year-round, by spraying
the unit must be equipped with automatic heating tanks
components. And also a function of flow heating of raw materials is required. For
spraying equipment is characterized by low productivity
(1-3 kg / min).

The main difference between the two
types of equipment (for spraying and pouring)
is that the filling equipment has great performance
productivity (from 10 kg / min). Such installations are equipped with a timer,
which are automatically turned off when you finish filling a certain
quantity. This feature will help you use raw materials rationally and
avoid manufacturing defects. According to some reports, the installation
equipped with a timer allows you to save up to 40% of consumed raw materials.

The production of polyurethane foam requires compliance with all safety rules

The PU foam manufacturing process is a dangerous kind
works. After all, raw materials for production can cause skin irritation and
mucous membranes. When sprayed in air, a precipitate is formed with
components that settle on clothing and nearby vehicles
or other items can only be removed mechanically. Exactly
therefore, a person who directly works with spraying or
pouring polyurethane foam must be in a protective suit, respiratory
mask and glasses. There are several rules when working with spraying:

• it is forbidden to spray with polyurethane foam in
  closed premises, provided that people are in it in unprotected
  costumes, as well as in the presence of animals;
• when spraying PPU, it is necessary to make sure that there is no
  open fire centers;
• it is forbidden to burn the remains of components and mixtures;
• working personnel must be protected by special clothing,
  mask and goggles.

Pour the remnants of the mixed components down the drain
forbidden. All non-recycled polyurethane foam components
must be sent for disposal to specialized landfills. If
nevertheless, in the production there was a leak of toxic substances, a puddle
sprinkle with wood sawdust. Well, after
the polyurethane foam will completely harden, it becomes safe for
human and for the environment.

The room, which is equipped for pouring polyurethane foam,
must have an excellent ventilation system. Indeed, in the production of polyurethane foam
some toxic elements are released, which upon contact with
split into safe air. The production itself is not
harm the environment if all safety rules are observed.

Advantages of polyurethane products over plastics

Polyurethane gives the product its own characteristics:

• elastic deformation;
• abrasion resistance;
• suppression of noise of mechanisms during operation;
• low cost of preparatory production work;
• preservation of elasticity at low temperature conditions;
• resistance to cold currents;
• shock resistance.

Benefits of Switching to Polyurethane for Automotive Suspension

For more than 20 years, polyurethane shock absorbers, bushings and cushions have been used in the construction of car suspensions, which allows achieving excellent quality compared to rubber. But the cost of such parts is more expensive.

Therefore, the main application of polyurethane is tuning the suspensions of armored cars, SUVs, sports models.

What are the inherent benefits of polyurethane?

The use of such material in suspensions and transmissions, in any operating conditions, creates a preservation of the shape of the suspension and controlled handling of the vehicle. Driving is enjoyable and smooth.

Replacement of rubber products with polyurethane analogues The issue of rapid wear and tear of original rubber parts is being radically resolved.

The indicators of stability of suspensions for fresh and sea water, oils, gasoline, alkalis, acids, chemicals for processing winter roads are increasing.

Long-term preservation of elasticity in a huge gap of operating temperatures, resistance to deformation under power loads, peeling and freezing, in comparison with rubber.

During shock loading, the return is only 30-35% of the received energy, the main 70% - turn into heat and dissipate (each silent block is a shock absorber).

Comparison of the physical and mechanical properties of polyurethane and rubber

* This parameter can be adjusted during production at your discretion.

Economic benefits

The service life, on average, for high-quality rubber hinges during hard work of the car is from 8 months to a year. If polyurethane is used in the suspension, then this period increases by 5 times, which means that at a price that is equal to the cost of the "original" made of rubber, significant savings are obtained on car repairs. If you have to change the entire structure of the silent block, complete with a shock absorber, a rod, a lever, it is even cheaper to make custom polymer products.

Manufacturing technology of parts

The production of polyurethane parts is carried out in several ways. There are different technologies: casting, extrusion, pressing and casting.

Casting is by far the most common. Manufacturers use this technology to create a variety of parts. The pouring method is popular due to the cheapness of the molds. As a result, the resulting product is notable for its low price.

With the help of rotary casting, large areas or cylindrical parts are covered with polyurethane raw materials. With the help of computerized equipment, such a polymer is applied to a shaft that rotates. The process takes place without heating, practically no waste remains.

With free casting, it is possible to create more complex shapes. It also uses computerized control. The raw materials are brought into the mold subject to careful control of dosage, temperature and pressure. The products are of high quality. It uses molds made of silicone, with the help of this technology, mainly limited series of parts are created. Among the advantages are the speed of production and the low cost of the product as a result.

The use of injection molding significantly speeds up the production itself - this technology is needed in the manufacture of large batches of products.

Equipment for the production of polyurethane foam

To choose a device for the manufacture of foam rubber, it is important to have an idea of ​​what type of material is needed for work. Polyurethane foam is:

• Hard. Material with a hidden porous structure. Does not absorb moisture, suitable for waterproofing. It is used as insulation in the construction industry
• Soft, elastic. It has an open porous structure, due to which it is most often used in the production of sponges, washcloths, furniture filler, etc.

Equipment for production must be of high quality and wear-resistant. Typical equipment of the PPU manufacturing device includes the following equipment assemblies:

• Foam generating machine;
• Grinder and device for mixing raw materials;
• Dispenser;
• Product forming unit;
• Automatic polyurethane foam manufacturing machine, which provides cutting into parts of the finished material;
• Packing machine;
• Waste recycling apparatus for their reuse in production.

The manufacture of formulations with advanced functions requires additional equipment capabilities - regulation of the portion ratio of raw materials. The operation of devices requires the presence of compressed air, as it is carried out under pressure

This point is important to consider when choosing. There are low and high pressure units, depending on the planned production volume

The higher the head, the greater the yield.

Low pressure filling complex