As a response to an earlier blog, I received this follow-up question…
Are there any additives on the market that help to lower melt flow
index MFI of polypropylene?
There are many additives that can be used with Polypropylene… but it requires research, and significant testing, into the application. I wish I could just recommend an additive, but I have encountered many additives which will either increase or decrease the number and size of semi-crystalline regions within the polymer.
Even colorants will have a significant affect on the degree of crystallinity within the final molded part. For example, the color green might cause the part to be larger than specification while another color, from the same supplier, causes the part to be significantly smaller than specification.
I have seen small amounts of additives significantly affect the optimal tact temperature of a polymer and even cause a process to become auto-thermic where the front zones of the machine actually become higher than the zone temperature setpoint.