2013-11-02 by seoer8First you have no problem with white blowing agent , PVC foam blowing agent is the use of heat generated by the decomposition gases cause porosity, when the processing temperature step decomposition temperature of the blowing agent can achieve when nature is not foamed . Different types of blowing agent decomposition temperature difference, even if the same kind of blowing agent decomposition temperature of different manufacturers are not identical , to choose your foam. PVC material with no problems , not all are suitable for PVC foam, may choose a relatively low degree of polymerization , such material processing temperature is low , such as S700, you want to use 1000 may not be the same with the 700 , possibly blowing agent decomposition of PVC have not already light of it . In addition, other additives . Normal decomposition temperature of the blowing agent is higher than the PVC processing temperature , if not suitable additives , the result is PVC decomposition ( yellow or black ) AC No decomposition ( foaming ) , it must be added stabilizer to make PVC remained stable ( at AC trial temperature does not decompose ) , plus other additives to promote AC foaming reduce the AC decomposition temperature , so that it matches . There additives is to make a small hole and dense foam , foam is to avoid large contiguous reduce product strength . Since the temperature is low, the longer yellow, I can confirm that your original high temperature , causing yellowing of PVC decomposition and decomposition of PVC is a self- promoting effect of the reaction , the decomposition of the material that is more to promote further decomposition , so often you can see the situation is : the temperature is not high right, higher temperature on the large number of decomposition . You can now do is to check your use of PVC and foaming agent , there is no problem for further study your stabilizer and foaming accelerator bar, foam regulator problem now temporarily not consider the issue because it is not contiguous cannon but not fat issue.