Abstract
The author has inquired experimentally into the effect of the temperature ranging between 20°C and 200°C upon the Rockwell hardness and the thermal expansion behavior of several virgin plasticses after casting, such as phenolic, urea, melamine, polyester, epoxy, nylon 6, polypropylene, polytrifluoroethylene and polytetrafluoroethylene.
Generally, the hardness of plastics goes down gradually as temperature rises and drops suddenly at a special temperature region, which nearly corresponds with the deflexion point in thermal linear expansion-temperature curve. The hardness is somewhat recovered again when the temperature surpasses this discontinuous point.
The thermoplastic plasticses have generally lower values and more sensitive temperature dependence in Rockwell hardness number as compared with the thermosetting plasticses.
The thermosetting plasticses, which contain the filler having more durability against high temperature than the resin itself, show lower temperature dependence for hardness, and a little amount of drop in hardness number at the discontinuous point as compared with the plastics having no filler.
