The Prospect of Straw Biomass Plastic Wood Composite Material
With the increasing shortage of wood resources, the choice of raw materials for traditional plastic wood composite materials began to turn to crop straw. Straw, reed straw, rice straw, cotton straw, etc., as important crop straw resources, are large in quantity and cheap, renewable, degradable, and have great utilization value. Traditional utilization methods are difficult to produce industrial products with high added value, and the comprehensive utilization rate is low. A large amount of straw has not been used effectively and reasonably for a long time, leading to it becoming a waste resource. Combined with improper disposal methods such as incineration, it wastes precious biomass resources and brings serious environmental pollution.
In recent years, the industry has gradually formed a new demand of “replacing wood with straw”. In the field of plastic wood composite material manufacturing, the straw of straw plastic composite material was first put forward in China in recent years. Straw-plastic composite (SPC) is a kind of Straw-plastic composite (SPC) composed of Straw, cotton stalk, bagasse, and other fibers that grow less than one year old. After crushing and interfacial compatibilization treatment, it is blended with thermoplastics and auxiliaries. It is a new environment-friendly recyclable material that is made by extrusion, hot pressing or injection molding process and has the characteristics of bio-based material and plastic. In the current under the background of sustainable development, renewable resources more and more attention, and the straw is used in the production of the plastic wood composite materials, to produce green environmental protection, plastic wood products with high added value, not only expanded the straw utilization way, relieve the contradictions of supply and demand of timber resources of China, also note the fresh blood for the plastic wood industry, It is of profound significance to strengthen the recovery and utilization of agricultural and forestry residual resources and to reduce the pressure of environment and ecology.
The results show that the surface of straw fiber contains strong polarity hydrophilic groups and the surface of plastic with strong hydrophobicity. It is difficult to form good interface compatibility. Therefore, how to solve the poor interfacial compatibility between straw and plastic and how to optimize the interfacial adhesion property of straw and plastic composites are the top priority in the research of straw and plastic composites. Remarkably, compared with wood powder/bamboo powder, a layer of biomass straw surface lipid components, suppresses the glue the private agent of straw internal penetration, in addition, the single direction of straw powder fiber catheter group, fiber low load rate, and weakened the plastic after the melting of straw fiber with sex, and caused the straw plastic straw composition content in the composite material is difficult to ascend. Therefore, when the straw is used to produce plastic wood composite material, its interface modification process will be different from the traditional plastic wood composite material, and it has certain particularities. The related technology and research achievements of interface modification in the preparation process of straw plastic composites include physical modification, chemical modification and biological modification.
Straw and wood chemical compositions are similar, but the scale is different, different regions of the straw in the component ratio would be a slight difference, between the chemical composition of straw and spruce, for example, wheat straw fiber content is relatively low, but the ash content and hot water extract mineral content is much higher than that of wood, and concentrated on the straw outer layer. The main component of the hot water extract of straw was the wax layer on the surface of the wheat straw. As an agricultural country in the world in our country, as well as plastic products consumption big country, each year a large number of straw and recycled plastic for the straw plastic composite production has laid a good raw material base, and overcome the straw and plastic interface incompatible characteristics is boosting straw plastic composite plastic wood composite materials in our country manufacturing industry promotion is a key problem that must solve.
The interface modification technology of straw plastic composites is different from that of the traditional strawboard, mainly due to plastic’s incompatibility to polar straw surfaces. Therefore, the interface modification technology of straw plastic composites mainly promotes mechanical bonding by increasing the specific surface area and gap of the adhesive from the physical point of view. The specific implementation means mechanical grinding, high frequency, and high temperature and ion treatment, etc. From the chemical point of view, reduce the polarity of straw surface or increase the polarity of plastic and enhance the binding ability of plastic to straw by increasing the coupling agent’s capacity. The specific implementation methods include maleic acid grafting plastic polymer, coupling agent grafting straw, alkali and biological treatment of straw.
However, to realize the industrialization of the interface modification technology of straw plastic composites, there are still many practical problems to be faced. Straw-plastic composite material is a beneficial supplement to the wood-plastic industry. No matter from the raw material cost, or the strength, durability, environmental protection and other aspects of the product, it can be completely comparable with wood plastic composite decking material, and even has better mechanical properties. The unique advantages of straw plastic make its products in the high-end market prospects are very broad. Although the new straw plastic material has a good development prospect, the modification and plasticizing process in the production process is more complex, the production cost is higher, and it is not conducive to the competition in the low-end market. Its product research and development is still in the initial stage, the production and application of this new material still need continuous research and innovation.