Controlling the rheological behavior of nucleated polypropylene via incorporating dimethylbenzylidene sorbitol (DMDBS) masterbatch

Dimethylbenzylidene sorbitol (DMDBS) is a common nucleating/clarifier agent used in polypropylene (PP). So many researchers have looked at different aspects of incorporating this additive on the crystallization behavior of PP. The current study is focused on a rather new topic and that is the role of the carrier resin of DMDBS masterbatch on the rheological behaviour of polypropylene. This objective has been achieved through studying the role of the carrier resin on the phase separation behavior of DMDBS upon cooling. It has been shown that a permanent bond is formed between the molecules of carrier resin and DMDBS in the masterbatch and this bond slows down the crystallization kinetics of DMDBS in the final blend which in turn, influences its rheological behavior. Frequency sweep experiments conducted on a block copolypropylene showed that lower values of storage shear modulus (G¢), loss shear modulus (G²), and complex shear viscosity (ɳ*) are observed if DMDBS is incorporated as a masterbatch. Interestingly, a different effect was observed when the masterbatch constituents were employed directly into polypropylene, illustrating the importance of the mentioned bond between DMDBS and the carrier resin in the masterbatch.