The processing of fiber reinforced thermoplastics using co‐rotating twin screw extruders

For short fiber reinforced thermoplastics the effect of fiber length and the fiber/matrix bond on the ultimate properties of the material are well understood. But, how the process conditions under which the composite is made affect the fiber length and the fiber matrix bond has not been so thoroughly reported in the literature. A study of this relationship has been made on a co‐rotating twin screw extruder incorporating 30 percent by weight of glass fiber into nylon 66 to make the composite. Experimental results are presented to show how machine variables such as mixing configuration and screw speed affect the material properties and process efficiency. The properties of the composite were assessed by measurement of the fiber length distribution and tensile strength. From the results in the text it is possible to select machine variables to give desired production conditions. Although most of the work concerns the twin screw extruder, some of the consequences of subsequent injection molding are also shown.