The orientation of the glass fiber reinforcement affects strength, thermal expansion, and mold shrinkage. There tends to be more alignment of glass fibers parallel to the direction of flow during mold filling, and the mechanical strength of Ryton® PPS compounds can be up to 60% greater in the flow direction as compared to the transverse direction. Part and mold design should exploit the enhanced strength from glass fiber orientation along axes that will experience more stress in service, while minimizing potential stress transverse to glass fiber alignment. In some cases, it may be necessary to increase wall thickness to compensate for lower strength transverse to glass fiber alignment. Bear in mind that the mechanical strength values reported on technical data sheets are measured in the flow direction. It is also important to note that thermal expansion will typically be at least twice as much along axes transverse to glass fiber alignment as compared to along axes parallel to glass fiber alignment. See Mold Shrinkage and Typical Molding Tolerances for information on how glass fiber alignment affects mold shrinkage.
