Processing Aid ACR401 is a processing aid based on a high molecular weight acrylic copolymer,the industry standard for foamed PVC, efficiently improving the quality and processability of cellular PVC products by reducing foam density and increasing impact strength, surface quality, and uniformity.
link:http://www.repolyfine.com/pvc-processing-aid/acrylic-processing-aid/processing-aid-acr401.html