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The material composition and performance of PVC wood plastic composite
PVC wood plastic composite materials are made of PVC resin, wood powder, inorganic fillers, lubricants, stabilizers, white/yellow foaming agents, foaming regulators, toners and other related additives (plasticizers, tougheners, coupling Agent) and other components.
1. Good resin fluidity is good for foaming.
2. The filling is mainly wood powder and calcium powder. The calcium powder is generally light calcium carbonate. The higher the filling mesh, the smaller the particle size is preferred.
3. Lubricants use stearic acid, paraffin wax, PE wax, etc. to form a wood-plastic lubricant system according to the required ratio. Stearic acid and paraffin wax are cheap and have good lubricating properties. The disadvantage is that the melting point is too low (more than 50 degrees) and easy to precipitate. The low-melting lubricant imparts lubricity while also plasticizing, which will affect the rigidity and vicat of the product. , thermal deformation leads to large product deformation and easy precipitation, which affects the continuity of production. Improper use of paraffin wax can also affect the foaming effect. PE wax will not affect the product's vicat. If the PE wax manufacturer uses recycled PE and adds a certain proportion of stearic acid and paraffin to reduce costs, it is not a real PE wax and will also affect the performance of the product. It is recommended PE uses a melting point of 105 degrees.
4. Stabilizer: The stabilizers used in PVC production include composite lead salt stabilizers, organotin, calcium-zinc stabilizers, rare earth environmental protection stabilizers, etc. The stabilizer generally used for wood plastic composite is a composite lead salt stabilizer. The advantages are low price and good thermal stability, but the disadvantage is that it is toxic and not environmentally friendly. However, the proportion of composite lead salt stabilizer lubricants is about 50%. If the lubricants added are all low-melting lubricants, the performance of the product will also be affected. With the strengthening of environmental protection requirements, the attention and use of environmental plasticizers are put on the agenda earlier.
5. The foaming agent is generally used in combination with AC and endothermic white foaming agent NC. The advantage of AC is that the amount of air is large and the amount is small. The disadvantage is that the decomposition is not complete and the residue will be left. This will affect the appearance of the product during use, and the foaming agent will migrate to the product surface to cause spots and affect the weather resistance of the product to accelerate the aging of the product. At the same time, AC decomposition will release a lot of heat, causing the product to decompose and turn yellow and discolor. With a certain amount of endothermic white foaming agent NC, it can balance the excess heat released during the AC decomposition process and improve various performance indicators of foamed products.
6. Foaming regulator is a material that will be added to foamed products. Foaming leads to a sharp decline in the melt strength of the overall PVC formula. At this time, in order to prevent small bubbles from merging into large cells, forming string bubbles, foaming or even splitting when the layer phenomenon occurs, a foaming regulator must be added for reinforcement, so that the product foams uniformly and the cells are dense, thereby reducing the density and reducing the weight. In the past, the regulators used in wood-plastic products were plasticized quickly and the melt strength was low. With the continuation of the price war, most manufacturers began to use more and more small-tube materials, etc., resulting in faster plasticization of the overall formula. Therefore, plasticized slow-melt foaming regulators with high strength are more and more adapted to market demand.
7. Toners generally use yellow, red, black, titanium dioxide, etc. There are two kinds of yellow and red toners: inorganic and organic. The advantages of inorganic toners are that they are better than organic toners in terms of weather resistance, migration resistance, and high temperature resistance. The disadvantage is that the addition amount is large, the color is matte, but the price is cheap. The opposite is true for organic toners. PVC ecological wood is generally used with organic and inorganic toners. There are two types of titanium dioxide, rutile and anatase. Rutile type has better hiding power and weather resistance than anatase type, so PVC ecological wood generally uses rutile type titanium dioxide.
8. Commonly used plasticizers are DOP and epoxy soybean oil. DOP can reduce the force between resin molecules and improve fluidity, and has a certain degree of lubricity, which is beneficial to production and processing. But reducing the product's vicat, one kilogram of DOP can reduce the vicat by 3 degrees. Soybean oil's plasticizing effect is not as good as DOP and has certain thermal stability, which will also reduce the product's vicat. At present, in order to enhance the overall performance of the material, it is recommended to add less or no plasticizer.
9. Toughening agent CPE or the same type of toughening agent can improve the toughness of the product. CPE has
always occupied a large market share due to its low price, good toughening effect, and the highest comprehensive cost performance.