(Powder Engineering Laboratory of Tsinghua University Department of Materials, Beijing 100083)
This research was supported by the National Natural Science Foundation's project "Nano-regulation of mineral particle surface and its filling characteristics in polymer", Shandong Binzhou Brilliance New Building Materials Company's project "Development of annual plant straw filling to prepare plastic-wood composites" and Zhangjiagang Lianguan Science and Technology Development Company's project "Study on powder modification and production system optimization of plastic-wood composites".
First, the content introduction
(A) the main features
Wood powder was coated with talcum powder, and then it was processed with waste plastics into wood-plastic composites with special wood-plastic processing equipment. Its characteristics are as follows: ① coating superfine talcum powder on the fiber surface can reduce the internal resistance of composite materials during extrusion molding, and achieve the effects of improving processing technology and improving material properties. (2) Due to the addition of talcum powder, the viscosity and energy consumption are reduced, and the mechanical properties, weather resistance and heat resistance of the material are improved. ③ The special die for composite profile extrusion designed by computer-aided plastic die analysis software can effectively improve the mechanical properties, dimensional accuracy and production efficiency of the product during the molding process. ④ This series of equipment has the advantages of reasonable design, compact structure, simple operation, fully computer-controlled production process, high degree of automation, no pollution, low noise, high single machine output and fast extrusion speed.
On the basis of a large number of experiments, engineering development is carried out from the aspects of equipment structure design and system configuration optimization.
(B) comprehensive characteristics and innovation
In the process of developing the processing technology of plastic-wood composite materials, based on theoretical research and application practice, drawing lessons from advanced technologies at home and abroad, starting from the national conditions and market demand, we strive to achieve reasonable technology, energy saving and consumption reduction through optimized combination. Its technological innovation is as follows.
1) talcum powder coated with wood powder can reduce the melt viscosity, act as a lubricant, improve the processing technology, reduce energy consumption and improve the comprehensive physical and chemical properties of wood-plastic composites during extrusion.
2) The coating modification technology and formula of talcum powder were studied. More than 95% of the raw materials are waste plastics, mineral powder and agricultural waste fibers, which reduces the amount of resin.
3) Plastic-wood composites and their products have the dual characteristics of wood and plastic, and the performance indexes of products can be comparable to hardwood products. At the same time, the rigidity (elastic modulus) and toughness (impact strength) of products are improved, and products can bear both static load and dynamic load and impact, and the cost performance is obviously better than other plastics or wood products.
4) The plastic-wood composite material can be recycled at 100%, which is a real "green" product, especially suitable for the sustainable development of China's economy, and is also an ideal wood substitute material.
Second, popularization and application
Aiming at the problems existing in the existing plastic-wood composite technology, such as high viscosity of extrusion system, poor extrusion technology, poor performance to be improved, and difficulty in meeting the requirements of ordinary plastic mixing equipment. Tsinghua University cooperated with enterprises to carry out a series of research, successfully developed a series of production equipment of plastic-wood composite materials and the extrusion technology of talcum powder coated wood powder, which solved the above problems and applied for patents with independent intellectual property rights, and the actual situation was good.
At present, four enterprises have adopted this technology, and through the continuous improvement of technology, it will have a wide range of application objects and broad market prospects.