Mechanism and function of PVC foaming regulator

Foaming mechanism

In PVC foaming products, the purpose of adding ultra-high molecular weight polymers is: firstly, to promote the plasticisation of PVC; secondly, to improve the melt strength of PVC foaming materials and prevent the merging of bubbles in order to get uniformly foamed products; thirdly, to ensure that the melt has a good fluidity in order to get products with good appearance. Since different foam products manufacturers have different products, the equipment, process, raw materials and lubrication system used are different, so we have developed foam conditioners with different properties to meet the different needs of users.

Definition of foamed material

Foamed plastic, also called foam, is a composite material with plastic as the basic component, containing a large number of gas bubbles, which can be said to be filled with gas.

Classification of foamed sheet material

According to the different foaming multiplicity, it can be divided into high foaming and low foaming, and according to the softness and hardness of the bubble texture, it can be divided into rigid, semi-rigid and soft foam. According to the bubble structure can be divided into closed-cell foam and open-cell foam. Generally common PVC foam sheet belongs to rigid closed-cell low foaming sheet.

PVC foamed sheet has the advantages of chemical resistance, weather resistance, flame retardancy, etc. It is widely used in many aspects, including display panels, markers, billboards, partitions, panels for construction, and panels for furniture.

Key factors for evaluating the quality of foamed sheet materials

For foamed materials, the size and uniformity of the bubble holes are key factors affecting the quality of the sheet. For low-foaming sheet, small and uniform bubble holes, good toughness of foamed sheet, high strength, good surface quality. From reducing the density of foamed sheet considerations, only small and uniform bubble holes to further reduce the density of the possibility of bubble large scattered difficult to further reduce the density.

PVC foaming process control key points

Plastic foam moulding is divided into three processes: the formation of bubble nuclei, the expansion of bubble nuclei and the curing of the bubble body. For the addition of chemical blowing agent PVC foam sheet, the expansion of the bubble core of the quality of the foam sheet plays a decisive role in the impact of PVC belongs to the straight-chain molecules, molecular chain is shorter, the melt strength is low, in the expansion of the bubble core into a bubble process, the melt is not enough to cover the bubble, the gas is easy to overflow and merge into a large bubble, reducing the quality of the product of the foamed sheet.

The key factor to improve the quality of PVC foam sheet is to improve the melt strength of PVC. From the analysis of polymer material processing characteristics, to improve the melt strength of PVC has a variety of methods, but the most effective way is to add to improve the melt strength of the additives and reduce the processing temperature.PVC belongs to the amorphous material, with the increase in melt temperature melt strength decreased, and vice versa with the decrease in melt temperature melt strength increased, but the role of the temperature reduction is limited only to play a supporting role.ACR class processing agents have to improve the melt strength of the role, of which the foam regulator is the most effective. ACR processing agents all have the effect of increasing the melt strength, of which the foam regulator is the most effective. Melt strength increases with increasing foam conditioner content. Generally speaking, as long as the screw has enough dispersion mixing ability, add high viscosity foam regulator to improve the melt strength effect is more obvious.