Effects of Reinforcing Fiber Length on the Properties of Injection Molded Polypropylene

An engineer, designing any given part, will always reach a stage where the specification of a material is required. For example, if parts consolidation or lighter weight is the criterion, injection moldable thermoplastic is often the material of choice. It remains necessary, however, to always satisfy the structural and thermal load requirements of a part. The selection of the right material can save considerable time and money. The choice is often difficult when the part needs to function in an environment that sees a combination of fatigue, creep or strength requirements due to various applied temperatures. A dilemma occurs when the engineer selects a material and fiber length based on limited published room temperature and short term properties. Material selection based on room temperature properties alone may be unsuitable at elevated temperature or under long term loading. The objective of this paper is to aid the engineer in a better understanding of the effects that the length of the glass reinforcement has on various properties. The properties to be examined are strength, creep, and impact at different temperatures. Dimensional stability will also be addressed.