Processing aids for vinyl foam

Foamed PVC has been commercially available for at least 20 years, but is now becoming increasingly important because of recent improvements in technology and a broadening of applications. It has becomes one of the fastest growing markets in the vinyl industry, sparking enthusiasm among processors over new opportunities for vinyl foam, particularly in many wood-replacement applications. 

Free foam formulation Inward foaming formulation  

FUNCTION/BENEFITS OF PROCESSING AIDS IN RIGID VINYL FOAM 

Processing aids are used in rigid vinyl foam formulations for much the same reasons that they are used in other PVC formulations. The processing aid provides faster fusion and ensures a more homogeneous melt, but most importantly it helps increase the melt elasticity, which contributes to density reduction [1,2]. The processing aid also imparts melt strength to the PVC foam extrudate to form a smooth skin surface during formation of the cellular structure. 

Faster fusion at lower temperatures in the vinyl foam extrusion process gives better (more efficient) dispersion of blowing agent, a faster melt seal which prevents gases from escaping and results in lower densities, and a more homogeneous melt in the die. 

---

London, Kluwer, 1998, p.526-34. 5 PROCESSING AIDS FOR VINYL FOAM... 

Guidelines for the use of processing aids in rigid vinyl foam 533... 

In foam layers for vinyl siding and in foamed sheet generally, synchronization of cell development and fusion limits lubricant content, and higher levels of processing aids are used. ... 

---