Synthesis, Structure And Properties Of Isotactic Polypropylene/Isotactic Polybutene-1 In-Reactor Alloys

Isotactic polybutene-1 (iPB) exhibits excellent advantages, such as excellent re-sistance to creep and environmental stress cracking and good abrasion resistance. iPB is widely used as hot-water pipes. However, the slow room temperature polymorphic transformation of iPB from metastable phase ? to stable phase I, which adds complex-ity to the production of goods with stable mechanical properties, low modulus and strength limit the application of iPB. In this paper, iPP component was incorporated in the alloys through the reactor granule technology. It is expected that iPP component can not only accelerate the crystal transformation rate and increase the modulus of iPB, but improve the low temperature brittleness of iPP due to the high toughness of iPB.In this paper, sequential two-stage polymerization was used to synthesize the iPP/iPB alloys in the reactor. The first stage of polymerization, propylene monomer was used to synthesize the highly isotactic polypropylene particle. In the second stage of polymerization, the butene-1 monomer was breathed into the polymerization system to synthesize the iPP/iPB in-reactor alloys by using the polypropylene particles.The iPP/iPB in-reactor alloys were separated into three fractions by using Soxhlet extraction fractionation method, and the fractions were characterized by DSC, FTIR, 13C-NMR, et. al. The results showed that the alloys were mainly composed of isotactic polybutuene-1, isotactic polypropylene and a small amount of polypropyl-ene-block-poly(butene-1) block copolymers and amorphous polymer (atactic polypro-pylene and atactic polybutenen-1). The formation mechanism of different components of iPP/iPB in-reactor alloys was illustrated.The particle morphologies of catalyst, iPP, iPB and iPP/iPB in-reactor alloys were observed by SEM. It could be observed that the catalyst showed porous and spherical particle morphology, the alloy particles replicated the morphology of the catalyst and also presented regular spherical morphologies. Moreover, the morphologies of exter-mal surface and cross sections of particles were characterized by SEM and a particle growth model of iPP/iPB in-reactor alloy was proposed.Compared with mechanical blends, iPP/iPB in-reactor alloys with 25 phr iPP components showed better mechanical property, such as improved flexural and impact properties, increased vicat softening point and hardness. The crystal transformation rate of iPP/iPB in-reactor alloys was much faster than that of pure iPB.