Construction plastics refer to the general term for plastic products used in construction projects. Commonly used molding methods for manufacturing construction plastic products include: calendering, extrusion, injection, molding, coating, lamination, etc. Plastic is a material that uses synthetic polymer compounds or natural polymer compounds as the main base material. It is mixed with other raw materials under certain conditions and plasticized to form materials that can maintain the shape of the product under normal temperatures and pressures. Plastic has a greater shape under certain temperature and pressure, and can be easily made into products of various shapes and sizes required. After molding, it can maintain the established shape and necessary strength at room temperature.
Name introduction
A general term for plastic products used in construction projects.
The main component of plastic is synthetic resin. According to the different properties of the resin and products, different additives are required, such as stabilizers, plasticizers, reinforcing agents, fillers, colorants, etc. Plastics are divided into thermoplastics and thermosetting plastics. Plastics that can be softened by heating, hardened by cold, and can be processed repeatedly within a specific temperature range are collectively called thermoplastics, such as polyvinyl chloride, polyethylene, polypropylene, polystyrene, etc. Those that cannot soften after being heated or cured due to certain conditions are collectively called thermosetting plastics, such as phenolic plastics, amino plastics, etc. Plastic can be processed into products of various shapes and colors. The processing method is simple, the degree of automation is high, and the production energy consumption is low. Therefore, plastic products have been widely used in industry, agriculture, construction and daily necessities. Commonly used molding methods for manufacturing construction plastic products include: calendering, extrusion, injection, molding, coating, lamination, etc.
Plastic is lightweight, a good insulator of heat and electricity, and highly resistant to chemical corrosion. When processing certain plastics, by appropriately changing the dosage of plasticizers and reinforcing agents, soft or hard products suitable for various uses can be obtained. Plastics have low elastic modulus, are prone to deformation, have large thermal expansion coefficients, and have poor flame resistance, but they can be improved through reinforcement, compounding, and appropriate application. Some of the strength-to-weight ratios of fiberglass- reinforced plastics are even higher than those of steel.
Plastics are mostly used in construction as non-structural materials. Only a small part is used to manufacture structural components that bear light loads, such as plastic corrugated tiles, waiting sheds, commercial kiosks, water storage towers, inflatable structures, etc. However, it is more commonly used in combination with other materials, which can give full play to the characteristics of plastics, such as covering insulation materials for wires, veneer materials for artificial panels, various composite exterior wall panels and roof panels with foam plastic sandwich layers, etc.. Therefore, construction plastics are a building material with broad development prospects.
Product type
There are many types of construction plastic products, mainly including the following:
Plastic pipes and fittings
Pipes and joints made of plastic have been widely used in pipeline projects such as indoor drainage, tap water, chemical industry, and wire threading pipes. Commonly used plastics include rigid polyvinyl chloride, polyethylene, polypropylene and ABS plastic (acrylonitrile -butadiene- styrene copolymer). The main advantages of plastic drainage pipes are corrosion resistance and low fluid friction; because it is difficult for the debris flowing through to adhere to the pipe wall, the sewage discharge efficiency is high. Plastic pipes are light in weight, only 1/6 to 1/12 of the weight of cast iron pipes, which can save labor, and their prices and construction costs are lower than cast iron pipes. The disadvantage is that the linear expansion coefficient of plastic is about 5 times greater than that of cast iron, so flexible joints need to be installed on long plastic pipelines. Plastic pipes are mostly made by extrusion molding, and pipe fittings are mostly made by injection molding. In addition to the gluing method, plastic pipe connection methods include hot welding, threaded connection, flange connection and socket connection with rubber sealing rings. When pressurized liquid passes through the PVC pipe, the liquid temperature shall not exceed 38°C. If it is a non-pressure pipeline (such as an indoor drainage pipe), the temperature of the liquid passing continuously shall not exceed 66°C; the temperature of the liquid passing intermittently shall not exceed 82°C. When PVC plastic is used for water supply pipes, the use of toxic stabilizers and other raw materials is not allowed.
Construction plastic classification
Construction plastic pipes include:
1. Rigid polyvinyl chloride (PVC-U) pipe. Mainly used for non-potable water supply pipes, drainage pipes, and rainwater pipes. The diameter is usually 40-100mm, and the operating temperature is not greater than 40 degrees.
2. Chlorinated polyvinyl chloride (PVC-C) pipes. Mainly used for hot and cold water pipes, fire water pipe systems, and industrial pipes. Their lifespan can reach 50 years and the service temperature can be as high as 90 degrees Celsius.
3. Random copolymer polypropylene pipe (PP-R pipe) is used for hot and cold water pipes and drinking water pipes. It must not be used in fire water supply systems.
4. Butene pipe (PB pipe). Used in hot and cold water pipes and drinking water pipes such as floor radiant heating systems.
5. Cross-linked polyethylene pipe (PEX pipe) is mainly used for coil pipes in floor radiant heating systems.
6. Aluminum-plastic composite pipes are used for hot and cold water pipes and drinking water pipes.
Resilient floor
There are two categories of plastic elastic flooring : semi-rigid PVC floor tiles and elastic PVC coiled flooring. The basic size of floor tiles is a square with a side length of 300 mm and a thickness of 1.5 mm. Its main raw material is polyvinyl chloride or a copolymer of vinyl chloride and vinyl acetate, and the filler is heavy calcium carbonate powder and short fiber asbestos powder. The surface of the product can have wear-resistant coatings, color patterns or embossed patterns. According to regulations, the residual dent of the product shall not be greater than 0.15 mm, and the wear amount shall not be greater than 0.02 mg/cm.
The advantages of elastic polyvinyl chloride rolled flooring are: there are few seams on the ground and it is easy to keep clean; it has good elasticity and comfortable walking feeling; it has good thermal insulation and sound absorption properties. When a polyvinyl chloride foam floor with a thickness of 3.5 mm and an apparent specific gravity of 0.6 is used in combination with a hollow reinforced concrete floor slab with a thickness of 120 mm, its heat transfer coefficient can be reduced by 15% and the impact noise absorbed can reach 36 decibels. The width of coiled flooring is 900~2400 mm, the thickness is 1.8~3.5 mm, and each roll is 20 meters long. Commonly used in public buildings are non-foamed laminated plastic floors, with a transparent wear-resistant layer on the surface and a pattern printed on the lower layer. Asbestos paper or glass cloth can be used as the bottom layer. Laminated plastic flooring with a foam layer in the middle is used in residential construction. Adhesives used to bond plastic floors and floor slabs include neoprene emulsion, polyvinyl acetate emulsion or epoxy resin.
Chemical fiber carpet
It is a new product that appeared after 1945. Its usage quickly exceeded that of carpets made of traditional raw materials such as wool. The main materials are nylon filament, nylon short fiber, acrylonitrile, cellulose and polypropylene. The main properties of carpets are wear resistance, elasticity, resistance to dirt and staining, ease of cleaning, and difficulty in generating static electricity. The performance of acrylic, nylon and polypropylene fibers is comparable to that of wool. There are a variety of weaving methods for chemical fiber carpets, and the thickness is generally in the range of 4 to 22 mm. Its main advantage is that it feels comfortable when you step on it, but its disadvantages are that it has static electricity, is prone to dust accumulation, and is difficult to clean. Similar to carpets, there are non-woven carpets, which are also made of chemical fibers.
Doors, Windows and Accessories
In the past 20 years, due to the continuous development of thin-walled hollow profile extrusion technology and foam extrusion technology, door and window frames, cabinet components and various interior decoration accessories welded with plastic profiles have achieved significant development and have been favored by many Attention to wood and energy-scarce countries. Interior decoration accessories made of rigid foamed polyvinyl chloride or polystyrene, commonly used in wallboard corner guards, door and window caulking strips, gypsum board caulking strips, skirting boards, mirror hanging lines, ceiling return edges, Stair handrails, etc. It also has the dual functions of building structural components and artistic decorations, which can not only improve the decoration level of the building, but also take advantage of the beautiful appearance and easy processing of plastic products.
Wallpapers and veneers
PVC plastic wallpaper is a high-quality decorative material for decorating indoor walls. It can be made into a variety of printed, embossed or foamed beautiful three-dimensional patterns. This kind of wallpaper has certain breathability, flame retardancy and pollution resistance. The surface can be scrubbed with clean water, and there is a layer of base paper on the back to facilitate the use of various water-soluble glues to paste the wallpaper on a flat wall. Transparent paper impregnated with melamine formaldehyde resin is laminated with book cover paper with wood grain or other patterns printed on the surface, and is hot-pressed to become a hard plastic veneer; or it is made of polyethylene diallyl phthalate impregnated with transparent paper. (DAP) printed paper is laminated with medium-density fiberboard or other artificial panels and hot-pressed into decorative panels, which can be used as indoor partition panels, door core panels, furniture panels or floors.
Styrofoam
It is a lightweight porous product that is not easy to collapse and does not lose its thermal insulation effect due to moisture absorption. It is an excellent thermal insulation and sound-absorbing material. Products are available in plate, block or special shapes, and can also be sprayed on site. Among them, those with interconnected cells are called open-cell foams, which have better sound absorption and buffering properties; those with disconnected cells are called closed-cell foams, which have smaller thermal conductivity and water absorption. Commonly used in construction are polyurethane foam, polystyrene foam and urea-formaldehyde foam. The advantage of polyurethane is that it can be foamed by spraying at the construction site. It has good adhesion to other wall materials and is resistant to mold erosion.
Fiberglass (Reinforced plastic)
Plastic products made of glass fiber reinforced thermosetting resin are usually called fiberglass. Commonly used in construction include transparent or translucent corrugated tiles, lighting skylights, bathtubs, integral bathrooms, foam sandwich panels, ventilation ducts, concrete formwork, etc. Its advantages are high strength-to-weight ratio, corrosion resistance, heat resistance and good electrical insulation. The thermosetting resins used include unsaturated polyester, epoxy resin and phenolic resin. FRP molding methods generally use hand lay-up molding, spray molding, winding molding and compression molding. Hand lay-up molding is to spray a layer of colored gel-like surface layer on the surface of the mold shell first, so that the product will have a beautiful and shiny surface after demoulding. Then, the glass cloth or glass felt layer soaked in the resin mixture is manually applied on the gel layer, and can be demoulded after curing. The spraying method uses a special spray gun to mix the resin mixture and short glass fibers cut to a length of about 2 to 3 centimeters, and spray them directly and evenly on the surface of the mold shell. Although the use of short fibers reduces the strength of FRP, its production efficiency is high and it can save labor. FRP pipeOr the tank mostly adopts the winding molding method, that is, the glass fiber braided tape or long glass fiber bundle soaked in the resin mixture is wound on the rotating tire mold according to the force direction of the product, and is demoulded after solidification. Some tanks are lined with aluminum inner tubes to enhance the tank’s seal. The molding method is to place thin sheets of resin-impregnated fiberglass cotton felt or cloth evenly in a model, and then hot-press them to form various finished products, such as bathtubs, washbasins, etc. The molded products have beautiful and wear-resistant surfaces on both the inner and outer sides, and have high production efficiency and good product quality. Fiberglass products for construction that are developing rapidly include cooling water towers, water storage towers, integrated assembled toilets, semi-assembled toilets, etc.
Properties of plastic
Main advantages
- Light weight and high specific strength;
- Good processing performance;
- Small thermal conductivity;
- Excellent decorative properties;
- Versatility;
- Economy.
Main disadvantages
- Poor heat resistance and flammable;
- Easy to age;
- Large thermal expansion;
- Small stiffness.
In short, the advantages of plastics and their products outweigh the disadvantages, and the disadvantages of plastics can be improved by taking measures. With the continuous development of plastic resources, the development prospects of construction plastics are very broad.
