Study on the effect of dibenzylidene sorbitol as a nucleating agent on the crystallization and morphology of poly(ethylene terephthalate)

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Abstract
The effect of dibenzylidene sorbitol (DBS) as a nucleating agent on the crystallization of poly(ethylene terephthalate) (PET) has been studied. It has been found that DBS, when incorporated into the polyester, at a 0.5–1.0 wt % level, significantly lowers the induction period and reduces the half‐time of crystallization. Thermal studies clearly show that the addition of DBS results in decreasing the temperature of crystallization, Tch, when heated from the glassy state as well as increasing the temperature of crystallization, Tcc, when cooled from the melt. Maximum spherulitic radius at 110°C has been determined for pure and nucleated PET. The spherulitic size has been found to decrease slightly with the increase in the level of DBS. Optical transmittance measurements reveal that PET containing 0.5–0.7 wt % of DBS gives the best clarity, and, beyond this level of DBS, the clarity decreases. This is probably due to the formation of agglomerates of DBS which in turn scatter visible light, thus making the film appear more hazy.