The study reveals previously unknown details of the production process that will help manufacturers avoid excessive power consumption and defects in the end product. “You see, while we understand well how so-called thermosetting polymers behave during pultrusion, this is not the case for thermoplastic polymers, such as the polypropylene in this study. But pultrusion could make much sense with those polymers, too,” said Associate Professor Alexander Safonov of Skoltech Materials, the project’s principal investigator.
Unlike thermosetting polymers, their thermoplastic counterparts can be repeatedly melted and consolidated. For a PVC window frame scaffold made of fiber-reinforced polymer parts this has a number of advantages, Safonov explains: “They can be welded. They are recyclable. Their manufacture releases no harmful volatile organic compounds into the environment. Also, the source materials — that is, tapes — are convenient because of their very long shelf life.”
These considerations led the Skoltech researchers to experiment with the pultrusion of composite profiles made of glass fiber-reinforced polypropylene.
“In the die, the tapes are heated from below and from above, and if you imagine a cross section of a rectangular profile manufactured by this process, we did not know how the temperature is distributed throughout it. And this is important, because if some part of the profile does not get enough heat, the product will be defective. Also, we wanted to see just how much heat is really needed for the profile to consolidate, because if you crank up the heat every time just to make sure, you will face unnecessary utility costs,” said the study’s lead author Kirill Minchenkov, a PhD student at Skoltech Materials.