Controlled-rheology resin, polypropylene

C. Tzoganakis, J. Vlachopoulos, and A. E. Hamielec, Production of Controlled-rheology Polypropylene Resins by Peroxide Promoted Degradation during Extrusion, Polym. Eng. Sci., 28, 170-180 (1988). 

The molecular structure and morphology of individual polypropylene resins can be readily modified at the reactor stage via new catalyst systems. Postblends of available resins with various additives promote impact resistance, controlled rheology, thermal stability, and other desirable characteristics of the polymer matrix. The incorporation of chemical coupling agents and mineral-filler or glass-... 

Syndiotactic polypropylene can be used as an impact modifier. Indeed, the addition of s-PP to i-PP can improve impact characteristics over pure i-PP [222-225]. When s-PP is blended with i-PP, the resulting resin has a processability better than that of i-PP and impact and transparency properties better than those of pure i-PP. As an impact modifier to a controlled rheology i-PP copolymer, s-PP does not crosslink or affect the peroxide efficiency of the copolymer while improving the Izod notched impact and maintaining the similar processability of the copolymer. 

These properties are all influenced by the vinyl resin, plasticizer type and concentration, as well as by rheology-control agents (viscosity depressants and thickness). The face fibre are often heat-sensitive (e.g., polypropylene fibers). Therefore the PVC polymers are typically low-molecular-weight vinyl chloride/vinyl acetate copolymers. Plasticizer levels range from 60 to 100 phr. The common practice is to use faster-fusing phthalate DIHP as the sole plasticizer or to use DIHP in dilutions of up to 50 percent with a GP-type plasticizer such as DINP. 

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