The control of mold surface temperature is an important factor that affects sample surface morphology, frozen orientation and cooling stresses close to the skin. The possibility to have a hot mold during filling and a quick cooling soon afterward is precious for micro injection molding.
In this work, a thin electrical resistance was designed and used to generate a fast temperature increase on mold surface (by joule effect), followed by a fast temperature decrease soon after the contact with the molten polymer. If the whole temperature evolution takes place in few seconds, one can couple the advantages of a high (also very high) surface temperature with the advantages of a low mold temperature (fast cooling and low heating dissipation). The technique offers high potential also toward the increasing of weld lines strength and finishing.
Some experiments were performed with an iPP, exploring the effect of the heating time (under constant power) on morphology: the thickness of the fibrillar layer decreased by effect of longer heating times. Obviously, also the thickness of the skin layer decreased by effect of surface heating and its morphology was significantly affected.
