The influence of vulcanizer on the crystal transform of iPP during reactive extrusion process

The vulcanizers, sulfur (S) together with benzoyl peroxide (BPO), tetramethylthiuram monosulfide (TMTM) or tetramethylthiuram disulfide (TMTD) were added to isotactic polypropylene (iPP) during reactive extrusion process. The goal of this work is to investigate the influence of vulcanizers on the crystallization property of iPP. After addition of vulcanizers, iPP samples showed faster flow property, which indicated a low molecular weight formed during thermal degradable process. Moreover, a small characteristic peak at about 700 cm−1 was appeared, which indicated that some local cross-linking structure was formed by CS bond as investigated by FTIR. The results of non-isothermal crystallization dynamics showed that the addition could improve the crystallization temperature of 2-5 °C, and shortened the half time of crystallization from 0.97 to 0.92 min. Wide angle X-ray diffraction demonstrated that the addition contributed to form local cross-linking structure as a foreign phase to thick the (130) crystal plane of α-crystal lamellar from 19.1 nm to 21.4 nm and to evidently form γ-crystal of iPP greater than 30% within crystal phase. The data calculated from differential scanning calorimetry melting patterns also confirmed that modified iPP shows larger crystal size than pure samples.