Injection molding of long fiber-reinforced thermoplastics: A comparison of extruded and pultruded materials with direct addition of roving strands

• Published in: Polymer engineering and science 1991-09, Vol.31 (18), p.1316-1329
• Main Authors: Truckenmüller, F., Fritz, H.-G.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Forms of application and semi-finished materials; Polymer industry, paints, wood; Reinforced plastics; Technology of polymers
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.760311806

An injection molding process is proposed whereby roving strands are directly incorporated into the polymer melt by using a reciprocating‐screw‐plasticating unit. The direct incorporation of continuous fibers (DIF) offers the possibility to substitute the relatively expensive and limited pultrusion process currently used to produce long fiber pellets. In this preliminary study experimental investigations on glass fiber‐reinforced polyamide‐6,6 are carried out, starting with short and long fiber pellets in comparison to the direct incorporation of roving strands into the polymer melt. Some special aspects of the processing of long fiber‐reinforced thermoplastics are discussed. The results of fundamental mechanical and physical property investigations are presented, including fiber length distribution, fiber concentration, fiber bundling/clustering and fiber orientation. The influence of fiber diameter and fineness of strands (tex) on the feed‐in behavior and the resulting property profile is also discussed.