Acrylic processing aid for sheet
In PVC foaming sheets, the purpose of adding high molecular weight Acrylic processing aid is to promote plasticization of PVC. The second is to improve the melt strength of PVC foaming materials and prevent the bubbles from merging to obtain the products with uniform foaming. The third is to ensure that the melt has good fluidity to obtain the products with good appearance.
Based on different extruders, technology, raw materials and lubrication system, so we developed foaming regulator series with different performance to meet the different needs of end users.
1. Definition of foaming material.
Foamed PVC is also called foaming sheet, which is made of PVC contains a large number of bubbles, which can be said to be a composite material filled with gas.
2. Classification of foamed sheet materials.
According to the different foaming ratio, it can be divided into high foaming and low foaming, which can be divided into hard, semi-rigid and soft foam plastics according to the degree of hardness.According to the bubble hole structure, it can be divided into closed-cell foam and open-hole foamed plastics.The common PVC foamed sheet material belongs to the low foaming sheet of hard closed hole.
3. Application of PVC foamed sheet material.
PVC foam sheet has the advantages of chemical corrosion resistance, weather resistance, flame retardancy, widely used in various aspects, including the display panel, tag, billboards, partition, building board, furniture plate etc.
4. The key factors to evaluate the quality of foamed sheet.
For foaming materials, the size and uniformity of bubble hole are the key factors affecting the quality of sheet.For the low-power foamed sheet, the bubble hole is small and uniform, the foamed sheet material toughness is good, the strength is high, the surface quality is good.In order to reduce the density of foamed sheet, it is possible to reduce the density further only if the hole is small and uniform, and it is difficult to further reduce the density.
5. Control key points of PVC foaming process.
The plastic foaming process is divided into three processes: the formation of bubble nuclei, the expansion of bubble nuclei and the solidification of the bubble body.For the PVC foaming sheet with chemical foaming agent, the expansion of bubble nucleus has a decisive influence on the quality of foamed sheet.PVC belongs to linear molecules, molecular chain is shorter, low melt strength, in the process of bubble nuclear expansion into bubbles, enough to melt cladding bubbles, gas overflow easily merged into big bubble, reduce foam sheet product quality.
The key factor to improve the quality of PVC foamed sheet is to improve the melt strength of PVC.From the analysis of the processing characteristics of polymer materials, there are many ways to improve the strength of PVC melt, but the most effective way is to add additives to improve melt strength and reduce the processing temperature.The PVC belongs to amorphous material, and the melt strength decreases with the melt temperature, whereas the melt strength increases with the melt temperature, but the cooling effect is only auxiliary.ACR processing agent has the effect of improving melt strength, and the foaming regulator is the most effective.The melt strength increased with the content of foaming regulator.In general, as long as the screw has enough dispersion and mixing capacity, the high viscosity of the foaming regulator is more obvious to improve the melt strength.