Zhihai Song

Effect of elastomeric nanoparticles on toughness and heat resistance of epoxy resins

A new composite consisting of epoxy resin and elastomeric nanoparticles with high toughness and high heat-distortion temperature is prepared. The size of the nanoparticles used was less than 90 nm. The excellent properties of the composite seem to be due to stronger interactions between the carboxyl groups of the nanoparticles and the epoxy groups of the resin, and to enhanced hydrogen bonding between the nitrile groups of the rubber and the hydroxyl groups of the resin.

The study of rubber-modified plastics with higher heat resistance and higher toughness and its application

For rubber-modified plastics, toughness enhancement is generally at the cost of heat resistance. Of significance, this paper reported a finding that rubber-modified plastics with a special morphology could enhance toughness and heat resistance cooperatively. The special morphology was such that an interface in situ formed between plastic matrix and rubber particle had higher hardness than plastic matrix. As a result, the hard interface not only helped rubber soft component integrate with plastic matrix by covalent bonds to impart plastic matrix high toughness, but also covered rubber nanoparticles as hard shells to protect them from deforming at high temperature. The special morphology had been achieved in rubber-modified epoxies and phenolic molding material. The forming mechanism of the hard interface was studied in detail with AFM, DSC and in situFTIR, by using rubber-modified epoxy resin as an example. The finding could be applied to any rubber-modified plastics as long as the special morphology could be realized.

One-step process to make electrically conductive thermoplastic vulcanizates filled with MWCNTs

Electrically conductive thermoplastic vulcanizates (TPVs) filled by multi-walled carbon nanotubes (MWCNTs) are prepared by a simple one-step melt mixing process, based on linear low density polyethylene (LLDPE) and ultrafine full-vulcanized rubber particles (UFRP). An ideal morphology with controlled localization of MWCNTs in continuous LLDPE matrix and appropriate size of finely-dispersed UFRP can be achieved at the same time. The controlled localization of MWCNTs in the continuous phase facilitates the formation of conductive pathway, and thus the volume resistivity of the as-prepared LLDPE/UFRP/MWCNTs thermoplastic vulcanizates is significantly decreased. The results show that both the blend ratio of LLDPE/UFRP and the loading of MWCNTs have remarkable effect on the volume resistivity. Significantly, the electrically conductive TPVs exhibit good mechanical properties duo to the fine dispersion of UFRP in LLDPE. The added MWCNTs are capable of imparting reinforcement effects to thermoplastic vulcanizates with just a slight loss of stretchability and elasticity.

AN EVA/UNMODIFIED NANO-MAGNESIUM HYDROXIDE/SILICONE RUBBER NANOCOMPOSITE WITH SYNERGISTIC FLAME RETARDANCY

A novel EVA/unmodified nano-magnesium hydroxide (NMH)/silicone rubber ternary nanocomposite was prepared by using a special compound flame retardant of NMH and silicone rubber (CFR). The flammability of the ternary composite was studied by cone calorimeter test (CCT). Synergistic effect on flame retardancy was found between silicone rubber and NMH. EVA/CFR ternary nanocomposite showed the lowest peak heat release rate (PHRR) and mass loss rate (MLR) among the samples of virgin EVA, EVA composites. The synergistic flame retardancy of silicone rubber and NMH in EVA system is attributed to the enhanced char layers in the condensed phase that prevents the heat and mass transfer in the fire.

Novel conductive core–shell particles of elastomeric nanoparticles coated with polypyrrole

For the first time, an ultrafine conductive particle with core–shell structure, acrylonitrile-butadiene elastomeric nanoparticle (NBR-ENP) coated with polypyrrole (PPy), was prepared by in situ oxidative polymerization. The resistivity of NBR-ENP/PPy particle could reach to 25 Ω m. By using NBR-ENP/PPy latex, PVA/NBR-ENP/PPy composite with resistivity of 170 Ω m was prepared. For comparison, carboxylic acrylonitrile butadiene-ENP/polypyrrole (CNBR-ENP/PPy) with core–shell structure and styrene butadiene-ENP/polypyrrole (SBR-ENP/PPy) with raspberry-like structure were also prepared. It was found that both CNBR-ENP/PPy and SBR-ENP/PPy have much higher resistivity compared with NBR-ENP/PPy. Their resistivity differences were analyzed and the possible reason was proposed.

The abnormal behavior of polymers glass transition temperature increase and its mechanism

AbstactIn terms of the classical theory in textbooks, the two components with phase separation in a binary polymer blend will, depending on their compatibility, have their respective Tg get closer or remain in their original values. According to the classical theory, the Tg of plastic component shall remain unchanged or move toward the lower Tg of rubber component in a rubber/plastic blend. However, ultra-fine full-vulcanized powdered rubber (UFPR) with a diameter of ca. 100 nm can simultaneously increase the toughness and the Tg of plastics, which is abnormal and is difficult to explain by classical theory. In this feature article, the abnormal behavior and its mechanism are discussed in detail.