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Many people do not know what additives are contained in wood plastic materials when they use wood plastic materials. Today we will learn more about the detailed explanation of WPC additives.
Additives: As wood flour has a strong water absorption, and very polar, and most of the non-polar thermoplastic, hydrophobic, so poor compatibility between the two, interfacial adhesion is small, often need to use suitable additives to modify the surface of polymers and wood flour, wood flour and resin in order to improve the interface between the affinity and capacity. Moreover, the high amount of wood flour filled thermoplastics melt dispersed in poor, often in the presence of some form of state of aggregation, so the melt flow is poor, extrusion processing difficulties must be added to the surface treatment agent to improve liquidity in order to facilitate extrusion. Meanwhile, the plastic substrate is also necessary to add various additives to improve the performance of its processing performance and finished products, improve the adhesion and the mechanical properties of the composite wood flour and polymer. Common additives include the following categories:
Coupling reagent: Between plastic and wood flour to make a strong interfacial bonding surface; water absorption while reducing flour, wood flour and plastic to improve the compatibility and dispersion, so that the mechanical properties of the composites increased significantly. Commonly used coupling agents are: isocyanates, cumene peroxide, aluminum esters, phthalic acid esters, silane coupling agent, maleic anhydride-modified polypropylene agent (MAN-g-PP), ethylene - acrylate (EAA). 1wt% ~ 8wt% of the amount of flour is generally added in an amount of coupling agent, such as silane coupling agents can improve adhesion plastic and wood powder, wood flour of improved dispersibility, reduced water absorption, but with an alkaline treated wood meal can only improve the dispersibility of wood flour, wood flour does not improve its water-absorbing plastic adhesion. It should be noted that the maleate salt of stearic acid coupling agent and lubricant will react repulsion, when used together resulting in product quality and yield.
Plasticiser: For some high glass transition temperature and the viscosity of the resin melt flow such as hardness PVC, with the wood flour composite processing difficulties, often we need to add a plasticizer to improve its workability. Plasticizer molecular structure containing non-polar and non-polar genes, shear at high temperatures, it can enter the polymer chains by genetic polarity attract each other forming a uniform and stable system, but it is longer polar molecules inserted weakened mutual attraction of the polymer molecule, making processing easy. In WPC often be added plasticizers dibutyl phthalate (DOS) and the like. As in PVC wood flour composites, adding plasticizers DOP can reduce the processing temperature, reducing the decomposition of wood flour and fuming, improving by agents DOP content increases, the tensile strength of the composite decline increased elongation at break.
Lubricant: WPC is often necessary to add a lubricant to improve the flow and quality of surface melt extrusion products, the lubricant used is divided into inner and outer lubricant lubricant. Internal lubricant selection and matrix resin used relevant, it must have good compatibility with the resin at high temperatures and have some plasticizing effect, reducing the cohesive energy within the resin molecules, weakening mutual intermolecular friction, in order to reduce resin melt viscosity, the purpose of improving the melt fluidity. External lubricant in the plastic molding process actually played a boundary lubrication between the resin and wood flour role, its main function is to facilitate the sliding of the resin particles. Typically a lubricant often both inside and outside the two kinds of lubricating properties. Lubricant for mold, barrel, screw life, extruder production capacity, production process energy consumption, low temperature impact properties of the product surface finish and profiles have a certain impact. Commonly used lubricants are: hard bile zinc ethylene bis-fatty acid amide, polyester waxes, stearate, lead stearate, polyethylene wax, paraffin wax, oxidized polyethylene wax.
Colorant: In the course of WPC, wood flour in a solvent material may migrate to the surface of the product is easy to make products bleaching, and eventually become gray, different products in a certain environment, will produce spots or rust. Therefore, the colorant in the production of wood-plastic composite material also has a relatively wide range of applications. It enables products are uniform and stable color and bleaching slow.
Vesicant: WPC has many advantages, but because of the composite resin and wood flour to reduce ductility and impact resistance, brittle material, density is large nearly 2 times faster than conventional wood products, limiting its widespread use. And after WPC foamed by the presence of a good cell structure, can effectively prevent passivation crack tip and crack expansion, which significantly increases the material's impact resistance and ductility, and greatly reduces the density of the article . Many different types of foaming agent, used mainly in two ways: endothermic foaming agent (such as sodium bicarbonate NaHCO3) and exothermic foaming agent (azodicarbonamide AC), different thermal decomposition behavior of polymeric viscoelastic foam morphology and composition of the melt have different effects, and thus to select the appropriate products according to the requirement of a blowing agent.
Application of UV stabilizers and other UV stabilizers along with the people to improve the quality of wood plastic composite materials and durability requirements of rapid development. It enables the composite polymer does not degrade or mechanical performance. Commonly used are hindered amine light stabilizers and UV absorbers. In addition, in order to make the composite can maintain a good appearance and perfect performance, often need to add a fungicide, fungicide is selected to consider the type of wood powder, containing added amount, the use of composite materials in the environment fungi, product water and other factors. Such as zinc borate preservative but can not prevent algae.
The detailed explanation of WPC additives is here, and interested friends can find out.