24 Hours Online
The wood fiber and plant fiber that can be used in the plastic wood composite material are rich in sources and low in price; the product has good dimensional stability, excellent electrical insulation, non-toxic during production and use, and can be repeatedly processed and utilized. Products are also widely used in construction, transportation, packaging and decoration industries. Although plastic wood composites have many advantages and my country has become a major producer of plastic wood composites, the performance of WPC products still needs to be improved, mainly in terms of mechanical properties and weathering resistance.
The addition of plant fiber reduces the toughness of the plastic itself, and because the wood fiber is polar and the plastic is non-polar, the interface bonding force between the two is very small, resulting in a decrease in the mechanical properties of WPC products, and the application is limited to non-structural Materials and occasions with lower requirements for mechanical properties such as impact performance and strength. Therefore, having good mechanical properties is the most basic requirement for plastic wood composite materials, and manufacturers and research institutions have always been committed to the research and development of this technology. So how to improve the method of improving the mechanical properties of plastic wood composites? According to the research, there are mainly the following three ways of enhancement:
1. Melt blending improves mechanical properties. Thermoplastics such as polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) are commonly used plastic substrates for plastic wood composites. The method of blending with flexible polymers is usually used to improve the toughness of plastic wood composites. Such as blending low-density polyethylene, polyolefin elastomer and rubber particles. In addition, the use of reinforcing fibers can also play a role in improving mechanical properties, such as glass fiber, carbon fiber, basalt fiber, mineral wool, polyester fiber and so on.
2. Improve interface compatibility. Chemical modification of the two main components of wood fiber or plastic can well improve the compatibility between the two, thereby improving the comprehensive mechanical properties of the composite material. Reagents such as polyethylene glycol (PEG), Na OH, and acetic anhydride can be used to modify wood fibers. Direct fluorination, discharge and flash degumming treatments also have obvious modification effects on the surface of plant fibers. Adding coupling agents in the process of melting and mixing of materials is a common method to effectively improve the compatibility of the interface, such as maleic anhydride grafted polyolefin and aluminum pickle coupling agent. A relatively new type of coupling agent is alkyl ketene dimer. Body (AKD) and ionic polymer. Natural oils as surfactants can also improve the interfacial adhesion between fiber and matrix and increase the thermal stability of composite materials. Compared with other natural oils, octanoic acid has the best effect on improving the thermal stability of composite materials.
3. New interface modification technology: super/subcritical fluid technology interface modification. Super/subcritical fluids have unique physical and chemical properties, excellent solubility, lower viscosity, higher diffusion coefficient and heat transfer coefficient. Small changes in pressure can cause large changes in thermophysical properties, especially near the critical point. The super/subcritical method has a certain improvement effect on the interface combination of wood fiber and plastic. The super/subcritical fluid mainly includes water, alcohol compounds (methanol, ethanol, propanol), CO2, etc.
Aging performance research
The easy aging of plastic matrix has been restricting the development of plastic wood composite materials. In the research, artificial aging methods such as natural aging, xenon lamp aging, freeze-thaw aging, and thermal oxidative aging are usually used to treat materials. Thermal stability, surface and interface microstructure and other test results evaluate its aging resistance performance. Studies have found that coating, adding plastic coatings, pigments, anti-ultraviolet agents, light stabilizers, antioxidants, minerals, vitamin E, etc. can improve the aging resistance of WPC to a certain extent. The most commonly used method is Add anti-aging agents and surface finishing pigments. Adding the ultraviolet absorber UV326 can delay the oxidation of the surface of the polyethylene composite material. It is proved that UV326 can improve the aging resistance of plastic wood composites from the aspects of material surface fading, bending performance, surface chemical composition and so on. In addition, the combined effect of ZB and UV326 is better than that of ZB and HALS.
The addition of metal oxides and inorganic particles can also improve the aging performance of plastic wood composites. Studies have shown that nano-zinc oxide and nano-clay can well enhance the anti-ultraviolet aging performance of plastic wood composites. At the same time, the color difference, cracks, bending strength reduction and aging degree of the plastic wood composites with nano-calcium oxide added are smaller than those of the blank group. Co-extrusion is used to prepare plastic wood composites, and the core layer is made of waste plastics, which is environmentally friendly and reduces costs; adding more anti-aging and antioxidant additives to the shell formulation will improve the performance of plastic wood composites. The anti-aging performance is very beneficial without increasing the cost too much.
How to improve the method of improving the mechanical properties of plastic wood composites?Using the above methods can be improved.