Haosheng Ye,Chaojie Li,Yao Zhang,Yan Xia,Hengti Wang,Yongjin Li
Rubbery core–shell particles (usually rigid core and soft shell) demonstrate superior toughening efficiency to classical homogeneous rubber counterparts for glassy polymers, but such a toughener has been rarely exploited by the simple reactive processing strategy. Here, a feasible construction strategy of the core–shell particle with high shape stability in a glassy polymer is proposed by feat of melting temperature (Tm) difference between the core and the matrix. Taking the ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EGMA)/polylactide (PLLA) toughening system as an example, poly(butylene terephthalate) (PBT) (higher Tm than Tm of PLLA matrix) was incorporated and utilized as a rigid core via reactive processing. First, PBT and EGMA were premixed at 240 °C and then blended with PLLA at 190 °C. It can be envisaged that the shape and size of spherical PBT particles could be immobilized and maintained during the subsequent melt processing owing to the higher melting temperature (205–230 °C) than that of PLLA (160–180 °C). The dual grafting of rigid PBT (premade) and molten PLLA (in situ) chains onto EGMA leads to the in situ formation of controllable core (PBT)–shell (EGMA) particles in the PLLA matrix. The obtained core (PBT)–shell (EGMA)-toughened PLLA blends exhibited high toughening efficiency (the notched impact strength of the core–shell particle-toughened PLLA is as high as 87.7 kJ/m2, about 15 times higher than that of homogeneous EGMA-toughened PLLA blend) as well as synergistically enhanced heat resistance and crystallization rate. The underlying origin of the impact toughening mechanism was clearly elucidated. This simple core–shell particle construction strategy can be generally applied to other engineering plastic toughening systems. More importantly, this work established a platform for further investigation on organic rigid core–soft shell particles for polymer toughening and reactive blending.
Chemically crosslinking can enhance mechanical strength , dimensional stability and heat-resistance of thermoplastic polyolefin elastomers . However, chemically crosslinked elastomers suffer from reduction of flowability and strong shrinkage after reprocessing. In this work, inspired by vitrimer concept, olefin block copolymer (OBC) elastomer was chemically modified with dynamic boronic ester bond through one-step reactive processing. Based on the swelling test, FT-IR sperctra and DMA investigation, OBC vitrimer with tunable composition of dynamic Boron–Oxygen(B–O) bonds has been successfully prepared. Based on classical Arrhenius theory, the calculated activation energy (E a ) of OBC vitrimers ranges from 7.838 kJ/mol to 46.851 kJ/mol due to combined effect of chemical and dyanmic crosslinks. The prepared OBC vitrimers shows good creep-resistance, great reprocessability and good mechanical properties including tensile strength up to 15 MPa, elongation at break of 2300%, and elastic recovery of 90% at 300% strain. Interestingly, OBC vitrimers show significantly improved high-temperature mechancial property, i.e., tensile strength of ∼0.12 MPa and elongation excess 1200% at 120 °C where both OBC and OBC-DCP samples break instantly. Therefore, our work shows a promising industrial-scale strategy to prepare vitrimer elastomers via reactive processing, and provides guidance for molecular design of high-performance vitrimeric polyolefin elastomers.
Jiang Wang,Qi Tang,Xiaoming Ren,Yingkui Yang,Qunchao Zhang,Weiwei Lei,Zhi Li,Tao Jiang,Dean Shi
Selectively dispersed functional nanoparticles within one phase or at the phase interface in polymer composites with co-continuous morphology is the most effective way to reduce the percolation threshold of the nanoparticles . In this study, amino-modified nanosilica particles (mSiO 2 ) have been selectively localized at the interface of the PS/PA6/mSiO 2 composites with co-continuous morphology via reactive extrusion . Styrene maleic anhydride (SMA) with different maleic anhydride (MAH) contents is used as compatibilizers . Nanosilica particles can be induced to the interface of PS and PA6 phases by SMA macromolecules through the chemical reaction between the amino groups on nanosilica particle surfaces and MAH groups in SMA macromolecules. The MAH content of SMA macromolecules has large effect on the distribution of nanosilica particles. When nanosilica particles are premixed with SMA2, whose MAH content is 23 wt% and more compatible to PA6 phase, only ∼26% of the nanosilica particles can be induced to the interface; However, when nanosilica particles are premixed with SMA3, which contains only 8 wt% of MAH and is more compatible to PS phase, nearly 95% of the nanosilica particles can be located at the interface. This work creates a new facile approach to prepare polymer composites where nanoparticles are selectively distributed at the phase interface.
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