Ask the Extrusion Expert: Allan Griff tackles your questions on plastics and extrusion


How does a black speck from molecular breakdown due to heat look different than a black speck caused by contamination? Is there an epoxy that bonds to PpBT? Can the degree of crystallinity be manipulated during processing? Why are some knit lines stronger than others? Answers to these and more in this article.

Allan Griff, independent consulting engineer and plastics extrusion expert, has agreed to extend his relationship with PlasticsToday. Already the host of our well-received Extrusion Expert webinar series, Allan now also authors this weekly column. The formula is simple: you send questions, and Allan chooses the best or most intriguing and answers them.

Our aim is that this column becomes the leading source of extrusion information on the web, but don't shy away if your question is focused more on materials than extrusion. Have a question for Allan? Send it to him at We will not publish your name or company name unless you expressly ask us to do so, but also will not accept anonymous questions as this opens the opportunity for a supplier to send a "baiting" question for which the answer might highlight his products.
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