HIGH-MELT-STRENGTH POLYPROPYLENE WITH ELECTRON-BEAM IRRADIATION IN THE PRESENCE OF POLYFUNCTIONAL MONOMERS

High-melt-strength polypropylene (PP) was achieved with irradiation by an electron beam generated from an accelerator in the presence of pol yfunctional monomers (PFM). Among 16 PFMs, the relatively shorter mole cular chain bifunctional monomers such as 1,4-butanediol diacrylate (B DDA) and 1,6-hexanediol diacrylate (HDDA) were the most effective for enhancing the melt strength of PP. The concentration and dose of the H DDA to obtain the high melt strength PP in irradiation under nitrogen gas atmosphere were 1.5 mmol/100 g PP and 1 kGy, respectively. DSC mea surement and dynamic mechanical analysis showed that the thermal behav ior of the high-melt-strength PP was different from that of the origin al PP. Crystallinity and crystallization temperature during cooling af ter heating were lower and higher in high melt strength PP than origin al PP, respectively. Elongational viscosity at 180 degrees C of the hi gh-melt-strength PP showed a remarkable increase at a certain elongati onal time with constant strain rate, demonstrating the typical propert y of high-melt-strength samples. This implies that a few higher molecu lar chains of PP, formed by intermolecular combination of its chain by HDDA in irradiation, give higher melt strength to induce entanglement of molecular chains. (C) 1996 John Wiley & Sons, Inc.