January 07, 2021
The technical characteristic of WPC is to mix two kinds of different materials with each other. Will be wood, plastic two into a composite material.
As an organic filler of plastic, wood powder (or fiber powder of crops) has the advantages of wide source, low price, low density, good insulation, and many other inorganic fillers, but it has not been widely used like inorganic fillers. The main reasons are as follows: one is the poor compatibility with the matrix resin; the other is the poor dispersion effect in the fused thermoplastic, resulting in poor fluidity and difficult extrusion processing. Because the main ingredient in wood flour is cellulose. Contains a large number of hydroxyl groups, which form intermolecular or intramolecular hydrogen bonds to make the wood powder absorbent. And it’s very polar. The majority of thermoplastic is non-polar, with water flow, so the compatibility between the two is poor, the interface adhesion is very small, the need to modify the surface of plastic and wood powder through additives. Improve the interface affinity between them. The modified wood powder has the reinforcing property and can transfer the stress between the filler and the plastic well, so as to enhance the strength of the composite material.
Extrusion molding, hot pressing molding, and injection molding are the main molding methods for processing WPC. Because of the short cycle and high efficiency of extrusion molding, extrusion molding is a common process.
From the technical characteristics of WPC composites, there are mainly the following categories: according to the raw materials, one type of plastic raw materials used is pure plastic or commercial-grade plastic; the other type USES single-component waste plastic with certain characteristics. According to the processing technology to divide. One is the two-step method. Namely plastic and wood powder after mixing directly for molding processing.
From the point of view of the forming mechanism, one is physical forming. Even thermal insulation adhesive is used. Plastic and wood powder are bonded together in the forming process; The other is physical and chemical molding. By adding additives.Under pressure and temperature control.A reticular fibrous material in which a mixture of raw materials is converted into a macromolecular state together with a relatively low molecular additive.The material made by this process. The internal structure is completely regenerated mesh molecular structure after fusion, which is better than the bending, compressive, and impact strength of other wood-plastic products.
At present, wood-plastic composite materials have the following advantages :(1) easy to process. The wood-plastic composite contains polyester and fiber. Therefore, it has similar processing properties to wood. It can be sawed, nailed, and planed. This can be done with woodworking tools. And the nail grip force is obviously better than other synthetic materials :(2) high strength, good durability. The wood-plastic composite material has a good elastic modulus. In addition.Because it contains wood fiber and is cured by resin. Therefore, it has the same physical and mechanical properties as hardwood, such as compression resistance and impact resistance, and its durability is obviously better than ordinary wood materials :(3) water resistance, corrosion resistance. Wood-plastic materials and their products can resist strong acid and alkali. Water and corrosion resistance. And it doesn’t breed bacteria. Not easily eaten by angiosperms.No growth of fungi :(4) strong adjustability. By adding different additives, polyester can undergo polymerization, foaming, curing, modification, and other changes. Thus change the density, strength, and other characteristics of wood-plastic materials. Meet the special requirements of anti-aging, anti-static, flame retardant, etc. :(5) wide sources of raw materials. Wood-plastic materials in addition to the use of a certain number of additives. More than 95% of the raw materials are polyester and wood fiber. They are widely available and inexpensive.