Depends on which type of blowing agent you want to use.. is it chemical or physical? I guess IITD doesn't have super-critical fluid based blowing system ( I may be wrong) Also the composition of your TPE.
But the general strategy is plasticizing the soft segment of TPE with secondary blowing agents.. see this paper by CB Park's lab: http://onlinelibrary.wiley.com/doi/10.1002/pen.20422/abstract
Thanks sridhar for the reply .... By the way, we at mechanical department, iitd, have recently procured supercrtical based extrusion foaming setup, but we are not able to develop open-cell foams. Closed cell foams are easily manufactured, but porous foams are not being manufactured in this continuous process.
Good to know that IITD procured a sc-Extrusion foaming setup.
Highly porous foams (99%+) have been reported by CB Park by using secondary blowing agents.. the key here is controlling nucleation and cell growth. A new strategy is by adding nano fillers (like CNT, nano-clay) to control cell growth.
Read CB Park's papers.. he has done considerable work on foams.. All the best. mpml.mie.utoronto.ca/lab/Publications/publications.html
Sure the blowing agent is important, but another issueis the rheological behaviour of your melt. Closed cells structure may be favoured by low Trouton numbers, so higher Tr values might be in favour of open structure, provided that it does not decrease the expansion.