Experimental Study on Fiber Attrition of Long Glass Fiber-Reinforced Thermoplastics under Controlled Conditions in a Couette Flow

Fiber attrition of long glass fiber-reinforced polypropylene in a Couette Flow was studied to obtain a fundamental understanding of the physics in fiber breakage. The developed experimental setup of the Couette rheometer in combination with the developed fiber length measurement technique is able to provide repeatable, accurate and robust data sets to quantify the fiber length reduction during the processing of fiber-filled materials. This article summarizes the first results of an ongoing experimental study on fiber breakage at the Polymer Engineering Center at the University of WisconsinMadison. The impact of fiber concentration, initial fiber length, residence time, melt temperature and processing speed was quantified and studied. The proposed procedure aims to isolate the effect of process variables on fiber breakage. Even for the gentlest processing conditions, the results indicate that the residual fiber length after processing is less than 50% of the initial fiber length. For the most severe processing conditions, the results suggest a reduction to less than 10% of the initial fiber length, which highlights the challenges that fiber breakage poses for processing of long glass fiber-reinforced thermoplastics.