Wood-plastic Composite Material Modification Technology Upgrade

Individual plastics and woods have their shortcomings, and combining them is what we call wood-plastic composites. It not only has good elastic modulus, but also can achieve anti-aging, anti-static, fire-retardant, etc. special requirements. After many years of efforts by scientific and technical personnel, under the support of the National Science and Technology Support Program, the modification technology of wood-plastic composite materials has been greatly innovative and has made encouraging progress.

With the increasing scarcity of wood resources and increasing prices, most of wood-plastic composite materials have recently used biological resources—plant fibers (crop waste) as raw materials. China is a big country in agriculture and its crop waste is very abundant. According to statistics of the Ministry of Agriculture, the total amount of straw in China in 2010 reached 726 million tons. In the past, a large amount of remaining straw was abandoned in the field or burned directly. Now it can be used as waste material through modified technology to make high-performance wood-plastic composite materials. It is widely used in construction, transportation, household appliances, automobiles, and landscapes.

Dehumidification is an important step, and dehumidification will not seriously affect the performance of wood-plastic products. A traditional dehumidification method cannot meet the process requirements of wood-plastic products. The new process adopts the three-stage dehumidification method of wood fiber high-speed mixing and dehumidification, constant temperature dehumidification, and exhaust dehumidification to overcome the bottleneck that the wood fiber is difficult to dehumidify, and the moisture content thereof reaches the extrusion requirement.

Wood flour without treatment, directly with the recycled plastic blends, due to the interface adhesion is small so that the mechanical properties of the product is poor, so you must add additives to activate the wood flour to bond well with the plastic. However, the use of a single auxiliary is also not up to the requirements. The new technology adopts the addition of coupling agents, grafting agents, lubricants, plasticizers, heat stabilizers and other five types of composite additives to improve product performance.

Using low-temperature solid-phase heating technology, according to the influence of the amount of compatibilizer, chain extender, PE type and compatibilizer type on the structure and performance of the blend, the low temperature solid phase extrusion in the front zone and the high temperature rapid reaction extrusion process in the back zone . The hydrolysis and thermal degradation of the blend during the extrusion process are reduced, so that the polyolefin crosslinked structure forms a multiple network structure, limiting the recrystallization of the polymer during the extrusion process. At the melting point of the polymer, extrusion above the glass transition temperature, extrusion at a temperature close to the melting point of the polymer, saves significant energy.