EFFECTS OF GRAFTED VINYL TRIETHOXY SILANE ON MOISTURE CROSSLINKED EPDM

ABSTRACT An EPDM terpolymer grafted with silane vinyl triethoxysilane (EPDM-g-VTES) was prepared by melt grafting, with dicumyl peroxide (DCP) as an initiator. Next, dibutyl tin dilaurate was added as a catalyst to promote moisture crosslinking of EPDM-g-VTES. By means of the rheological response of the rubber compound, Fourier transform infrared spectroscopy, and moving die rheometer, the VTES graft ratio and DCP partial crosslinking (pre-crosslinking) of EDPM-g-VTES were characterized to show the feasibility of moisture crosslinking. The mechanical properties of moisture crosslinked EPDM-g-VTES specimens were tested by universal material tester. The results showed that when the weight ratio of VTES to DCP was fixed at 15:1, the VTES graft ratio and DCP partial crosslinking of EDPM-g-VTES increased with the increase of VTES content. But the torque in the moisture crosslinking curve of EPDM-g-VTES increased significantly with the extension of crosslinking time, which proved that EPDM grafted with VTES was cured by moisture successfully. The tensile strength and elongation at break of EPDM-g-VTES were improved by moisture cure. Furthermore, the moisture cured specimen with 3 wt% VTES had the best mechanical performance.

The Microstructure of GNR and the Mechanical Properties of Biobased PLA/GNR Thermoplastic Vulcanizates with Excellent Toughness

A series of different contents of glycidyl methacrylate (GMA)-grafted natural rubber (GNR) copolymers were fabricated via green bulk melt-grafting reactions, and super-tough bio-based poly (lactic acid) (PLA)/GNR thermoplastic vulcanizates (TPVs) were achieved by in-situ dynamic vulcanization. Increasing the graft yield, gel fraction, and crosslinking density of GNR vulcanizates effectively improved the ductility of the PLA/GNR TPVs, while prolonging the dynamic vulcanization time and increasing the GMA graft yield led to a notable enhancement in the impact toughness of the PLA/GNR TPVs. PLA/30 wt % GNR TPVs exhibited a significantly increased elongation (410%) and notched impact strength (73.2 kJ/m2), which were 40 and 15 times higher than those of the PLA/30 wt % NR TPVs, respectively. The new bio-based PLA/GNR TPVs offer promise as replacements for petroleum-based polymers in the automotive, 3D printing, and packaging fields.

Acyloxyimide derivatives as efficient promoters of polyolefin C–H functionalization: application in the melt grafting of maleic anhydride onto polyethylene

Acyloxyimides as a new H-abstracting agent have been developed for the radical grafting of maleic anhydride (MA) onto polyethylene in the melt state.

Maleic Anhydride-Grafted Isotactic Polybutene-1 and Modified Polyamide 6

Maleic anhydride (MAH)–divinyl benzene (DVB) multi-monomer melt-grafting onto isotactic polybutene-1 (iPB-1) was carried out in a torque rheometer. The effects of dicumyl peroxide (DCP), MAH, and DVB concentrations, and temperature, on the reaction, were investigated. The optimized conditions were 170 °C, DVB/MAH = 4:6 (mass ratio). DVB as a comonomer enhanced the grafting degree (Gd) and grafting efficiency (Ge) of iPB-g-MAH better than styrene. The initiator DCP had little effect on Gd as its concentration over 0.2 phr, but the grafts’ melt flow rate (MFR) increased significantly, and relative molecular weight decreased remarkably with increased DCP concentration. With increasing Gd, the contact angle of grafts with water decreased, and there was a larger crystallization rate. The study of iPB-1 and iPB-g-MAH (Gd = 1.5%)-modified polyamide 6 (PA6) showed that iPB-g-MAH had an obviously toughening effect on PA6. With increasing iPB-g-MAH concentration, the blends of impact strength and elongation at break increased obviously, tensile strength decreased slightly, and MFR decreased prominently, which greatly slowed the processing degradation of PA6. The properties of iPB-1/PA6 blends deteriorated. Both DSC curves and SEM micrographs confirmed that PA6/iPB-g-MAH blends had much better compatibility than PA6/iPB. The reason was that the anhydride group in iPB-g-MAH reacted with amide group in PA6 to improve the compatibility between two phases, and iPB-g-MAH is an excellent modifier for PA6.

Mechanical and Morphological Properties of Poly(Butylene Succinate)/Poly(Hydroxybutyrate-co-Hydroxyhexanoate) Polymer Blends: Effect of Blend Ratio and Maleated Compatibiliser

Poly(butylene succinate)/Poly(hydroxybutyrate-co-hydroxyhexanoate) (PBS/PHBHH) blends were prepared using melt blending in an internal mixer at 160°C. Mechanical and morphological properties of the blends, with ratios of 10/90, 20/80, 30/70, 40/60 and 50/50, are studied by tensile test and microscopy analysis. The effects of maleated PHBHH (PHBHHgMA) compatibiliser on the blend’s mechanical and morphological properties are also investigated. The compatibiliser is prepared by melt grafting maleic anhydride (MA) onto PHBHH at 160°C, in the presence of dicumyl peroxide (DCP) initiator. In this study, the purified compatibiliser is added to the blends. The highest tensile strength was achieved by the 10/90 blend, with a value of 24.83MPa; which is slightly higher than the neat PBS. The tensile modulus of the blends decreased with increasing PBS ratio, and approximately followed the Rule of Mixtures. Meanwhile, the elongation at break achieved its optimum value at 10wt. % PBS loading. The addition of PHBHHgMA at 5wt. % improved the tensile properties of all blends; with the highest value being achieved by the 10/90 blend ratio. Morphological observation via SEM was conducted to observe phase morphology and compatibility between the blend’s components.

Effects of Maleated Natural Rubber on Mechanical Properties of Polylactic Acid/Natural Rubber Blends

Brittle Polylactic acid (PLA) was toughened by introducing 5-20 wt. % of Natural Rubber (NR) through melt blending in a twin screw extruder. The results of tensile strength and Young’s modulus of PLA/NR blends were dramatically decreased. Maleic anhydride grafted natural rubber (NR-g-MA) was prepared and used to enhance the blends performance. The preparation of NR-g-MA was carried out using internal mixer by free radical melt grafting reaction followed by Fourier transform infrared spectroscopy (FTIR) to analyze the incorporation of MA on the NR. The compatibilization effect on the mechanical properties of PLA/NR blends was investigated with addition of 3 phr NR-g-MA. Comparison between PLA/NR/Compatibilizer and virgin PLA/NR blends significantly improved on the mechanical properties. FTIR result confirmed grafting reaction occurred between MA and NR.