High‐melt‐strength polypropylene with electron beam irradiation in the presence of polyfunctional monomers

Abstract

SYNOPSISHigh-melt-strength polypropylene (PP) was achieved with irradiation by an electron beam generated from an accelerator in the presence of polyfunctional monomers (PFM). Among 16 PFMs, the relatively shorter molecular chain bifunctional monomers such as 1,4-butanediol diacrylate (BDDA) and 1,6-hexanediol diacrylate (HDDA) were the most effective for enhancing the melt strength of PP. The concentration and dose of the HDDA 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 measurement and dynamic mechanical analysis showed that the thermal behavior of the high-melt-strength PP was different from that of the original PP. Crystallinity and crystallization temperature during cooling after heating were lower and higher in high melt strength PP than original PP, respectively. Elongational viscosity at 180°C of the high-melt-strength PP showed a remarkable increase at a certain elongational time with constant strain rate, demonstrating the typical property of highmelt-strength samples. This implies that a few higher molecular chains of PP, formed by intermolecular combination of its chain by HDDA in irradiation, give higher melt strength to induce entanglement of molecular chains. 0

Impact of processing history on rheological properties for branched polypropylene

“…Further, the modification technique by peroxide and/or radiation has been studied extensively [7][8][9][10][11][12][13][14]. Such kind of PP is called high-melt-strength (HMS) PP, which is commercially available in a decade.…”

Rheological study of polypropylene irradiated with polyfunctional monomers

“…For instance, the so-called HMSPP (high melt strength polypropylene) produced by radiationinduced grafting presents a structure composed of long chain branches of propylene polymer. These radiationinduced grafts can be obtained by at least three known processes: (i) PP irradiated with high energy electrons in N 2 atmosphere followed by a step of free-radical recombination and annihilation as it is stated in Basell patent [4]; (ii) PP irradiated with gamma rays in acetylene followed by free-radical annihilation as it was proposed by our group [5,6]; and (iii) PP mixed with polyfunctional monomers irradiated with high energy electron in N 2 atmosphere followed by a step of free-radical recombination and annihilation as proposed by Makuuchi's group from JAERITakasaki [3].…”

“…The reduction of molecular weight together with the reduction of molecular weight distribution yields a number of specific advantages regarding the processability and final properties of the PP product. Nevertheless, this process increases the costs due to the extra infra-structure, energy and peroxides used [1][2][3][4][5][6].…”

“…The balance between these reactions depends on the control of oxygen content. In addition, the control of crystalline morphology is proved to be essential in controlling the kinetics of these reactions [1][2][3][4][5][6][7][8][9][10][11]. When PP is modified by gamma radiation and/or peroxide in the presence of polyfunctional monomers, the reaction is very complex.…”

Review on the production process and uses of controlled rheology polypropylene—Gamma radiation versus electron beam processing

“…A few radiation processes, using electron beam irradiation, were proposed to produce HMSPP: Yoshii et al (1986) proposed the use of liquid acrylic multifunctional monomers ; Ra¨tzsch et al (1999) proposed the use of low-energy electron beams. This group also proposed other solid state methods to graft PP; Lucas et al (1995) proposed the use of high content of antioxidants irradiating with gamma or electrons; Debras et al (2004) proposed the irradiation of PP with electrons of at least 5 MeV, using 10 kGy.…”