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Micro-foamed wood-plastic composite materials

Company News > Micro-foamed wood-plastic composite materials

Wood-plastic composite materials have a series of special properties superior to wood and plastics; they have a wooden appearance and secondary processability similar to wood. But the dimensional stability is better than wood, and the water absorption is small. It is not afraid of insects, and will not crack and warp like wood. It has the processability of thermoplastic plastics, but it has higher hardness than plastics, wear resistance and aging resistance, preservative. The addition of various additives can give it more special properties. Such as antibacterial, flame-retardant, strong acid and alkali resistance, etc. Such as adding colorant, film or composite surface layer can be made into beautiful products with various colors and patterns. It is particularly worth mentioning that wood-plastic composite materials can not only use recycled waste plastics and waste wood as raw materials, but they can also be recycled and reused, which is of great significance to reducing environmental pollution and protecting forest resources.

In addition to the advantages of the above-mentioned wood-plastic composite material, the micro-foamed wood-plastic composite material formed by introducing very small cells into the wood-plastic composite material through the gas core can passivate the crack tip due to the good cell structure inside the material, to prevent the expansion of cracks; thus, it can effectively overcome the shortcomings of general wood-plastic composites such as high brittleness, ductility and low impact stress, and reduce the density of the material, which not only saves raw materials, but also has better sound insulation and heat insulation performance. It is widely used in building structural materials, automotive interiors, aerospace, logistics, gardens, interior decoration, etc. At present, the main molding methods of micro-foamed wood-plastic composites are continuous extrusion molding and injection molding. Continuous extrusion molding has the advantages of short processing cycle, large output, high efficiency, simple molding process, etc., compared with other processing methods (compression molding, injection molding) in industrial production, it has a wider range of applications. At present, the equipment that can be used for the extrusion molding of micro-foamed wood-plastic composites is mainly single-screw and twin-screw extruders. Among the four most common types of micro-foamed wood-plastic composite materials are: polyethylene (PE)/wood fiber, polyvinyl chloride (PVC)/wood fiber, polypropylene (PP)/wood fiber, polystyrene (PS)/ Wood fiber.

1. Research status at home and abroad

wood fiber contains a large number of functional groups such as polar hydroxyl and phenolic hydroxyl, and the surface exhibits strong polarity. It has poor compatibility with non-polar plastics, and is easy to absorb water and has poor dispersibility. The addition of wood fiber will have varying degrees of impact on the foaming of composite materials and the physical and mechanical properties of the final product. Therefore, research at home and abroad mainly focuses on improving the interface compatibility and the factors that affect the foaming degree and cell structure of composite materials.

2. Analysis and summary

The research content of micro-foamed wood-plastic composites at home and abroad includes the surface modification of wood flour and plastics, the amount of wood flour, the type and amount of foaming agent, processing aids, process parameters, etc. The structure and its distribution, as well as the final impact on the mechanical and other properties of the product, such as tensile strength, bending strength, impact strength, weather resistance and flame retardant properties.

2.1 Achieved research results

(1) In terms of improving the interface compatibility, the polar functional groups on the surface of wood fibers are esterified, etherified, graft copolymerized, and surface coated, and other non-polarization treatments are carried out to polarize the polymer surface and use phases. The solvent improves the interface bonding degree between the wood filler and the polymer matrix;

(2) The factors that affect the cell structure are comprehensively investigated, including process parameters such as the temperature of each section of the extruder, extrusion pressure and screw speed, the type and amount of foaming agent, and the amount of wood powder;

(3) The effect of wood powder water absorption and its dosage on the properties of composite materials and treatment measures. Wood flour easily absorbs water and affects its dispersibility, and ultimately affects the performance of composite materials. Generally, wood flour needs to be dried and pretreated before processing. Moreover, as the amount of wood powder increases, the fluidity and permeability of the melt become worse, and the thermoplastic melt cannot fully bond the wood powder, which makes the mechanical properties of the composite material worse, the ductility and impact resistance decrease, and the material becomes brittle. The water absorption rate increases;

(4) The influence of various types of additives on the properties of wood-plastic composite materials;

(5) The cells weaken the connection between the wood fiber and the polymer matrix, which reduces the strength of the micro-foamed wood-plastic composite material. The performance of the composite material can be improved by adding a certain amount of second reinforcing fiber;

(6) Using the water in wood powder containing a certain amount of water as a foaming agent, the micro-foaming plastic composite material was successfully produced.

2.2 Future research directions

(1) Research on improving the interface compatibility between wood fiber and plastic matrix needs to be further developed

(2) Increase the amount of wood powder in the micro-foamed wood-plastic composite material and study the effect of the orientation, length and distribution of wood fibers on the microcellular structure, and the flow of the melt during processing

(3) Improve the foaming ratio, improve the cell structure, and develop micro-foamed wood-plastic composite materials with light weight and excellent performance;

(4) Research on the mechanism of the performance of the second reinforcing fiber reinforced composite material and the effect on the microstructure of the composite material needs to be carried out;

(5) In-depth research is needed on the combination of water in wood flour and wood flour as well as the nature and size of the binding force. The development of industrialized technology that uses the water in the technical flour for foaming will reduce production costs and save energy.

(6) The systematic research on the comprehensive influence of foaming agent coupling agent impact modifier, wood flour surface modifier, etc. on the fluidity and other mechanical properties of composite materials needs to be carried out in depth. Research and develop compound additives that avoid side effects among additives and can achieve multiple functions;

(7) Carry out research on processing equipment, including specialization of forming molds, to improve the processing technology of industrialized production.

3. Outlook

Micro-foamed wood-plastic composite material has excellent cost performance and better specific strength, and the addition of additives can give it more performance, so it has been applied in many industrial fields. High-performance micro-foamed wood-plastic composite materials are used in the automotive and aerospace industries to process high-strength and light-weight components. It is predicted that the world wood-plastic composite material market will maintain a good growth trend before 2010. The largest application is the extrusion of high-performance and light-weight wood-plastic composite materials in the automotive interior and door and window markets. Big application. The future development direction of wood-plastic composites is to realize the diversification of raw materials, specialization of equipment and technology, high-grade products, development of micro-foaming plastic products with high fiber content, wide application fields, high comprehensive performance and long service life. The micro-foamed wood-plastic composite material produced by using waste plastics and waste wood is not only conducive to pollution control, but also saves wood resources, has good social and economic benefits, and will be a material with extremely promising applications.

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Micro-foamed wood-plastic composite materials

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