Mechanical properties of rotationally molded nyrim

Rotational molding is used primarily for the manufacture of products from powdered plastics. However, there are many advantages to be gained from the use of a liquid plastic feedstock. This paper describes the results of an investigation to study the effect of process variables, such as mold temperature, on the morphology and mechanical properties of parts manufactured by the rotational molding of a reactive liquid nylon, caprolactam plus a diol. Initial mold temperature has a significant effect on the degree of crystallinity, levels drop off sharply at mold temperatures in excess of 140°C, while spherulite size increases after this point. Flexural properties improve with increasing degree of crystallinity while impact strength decreases. A similar trend is observed in moldings containing fillers. A brief study of water uptake and dimensional stability of molded parts is also described.