Mechanical Properties of Silicone Rubber Using Carbosilane Dendrimers as the Cross-linker

Peroxide-cured high-temperature vulcanized （HTV） silicone rubber was prepared by using allyl-capped carbosilane dendrimers, in which the core molecule is Si（CHaCH=CH2）4, as the cross-linker. It showed that this kind of allyl-capped carbosilane dendrimer improved the mechanical properties of silicone rubber.

Solid-state NMR of vulcanized natural rubber/butadiene rubber blends:Local organization and cross-linking heterogeneities This article is part of the virtual special issue“Solid-state NMR studies on polymers and biological solids”

Elastomer blends,among which natural rubber(NR)and butadiene rubber(BR),are involved in many components of the automotive/tire industry.A comprehensive understanding of their mechanical behavior requires,among other features,a detailed description of the crosslink density in these mixtures.In the case of vulcanized immiscible blends,the distribution of the cross-link density within each of the NR-and BR-rich domains is key information,but difficult to determine using the conventional approaches used for one-component crosslinked elastomers.In this study,the vulcanization within NR/BR blends is investigated using a robust^(1)H double-quantum(DQ)MAS recoupling experiment,BaBa-xy16.Two kinds of cross-linked NR/BR blends were considered with two different microstructures for the BR component.The bulk organization of the resulting blends was first probed by analyzing the^(1)H spin-lattice relaxation behavior.In a second step,BaBa-xy16 was used to investigate,in a selective way,the cross-link heterogeneities within NR/BR blends.In particular,for immiscible NR/BR mixtures,the distribution of the cross-link density between both phases was compared and the observed differences were discussed.

STUDY ON THE PROPERTIES OF BLEND OF NATURAL RUBBER LATEX/METHYL METHACRYLATE GRAFTED RUBBER LATEX BY GAMMA RADIATION

Natural rubber latex （NRL） and methyl methacrylate （MMA） grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The tensile properties, swelling ratio and permanent set were measured. The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy. Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose. Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends. The decreasing trend of permanent set is high up to 5 kGy absorbed dose, and beyond that dose, it becomes almost flat.

Design of next-generation cross-linking structure for elastomers toward green process and a real recycling loop

Currently adopted cross-linking methods in rubber industry are suffering from variable persistent issues, including the utilization of toxic curing packages, release of volatile organic compounds (VOCs) and difficulties in the recycling of end-of-life materials. It is of great importance to explore a green cross-linking strategy in the area. Herein, we report a new ‘‘green" strategy based on hydrolyzable ester cross-links for cross-linking diene-typed elastomers. As a proof of concept, a commercial carboxylated nitrile rubber (XNBR) is efficiently cross-linked by a bio-based agent, epoxidized soybean oil (ESO), without any toxic additives. ESO exhibits an excellent plasticization effect and excellent scorch safety for XNBR. The crosslinking density and mechanical properties of the ESO-cured XNBR can be manipulated in a wide range by changing simply varying the content of ESO. In addition, zinc oxide (Zn O) performs as a catalyst to accelerate the epoxide opening reaction and improve the cross-linking efficiency, serving as reinforcement points to enhance the overall mechanical properties of the ESO-cured XNBR. Furthermore, the end-oflife elastomer materials demonstrate a closed-loop recovery by selectively cleaving the ester bonds, resulting in very high recovery of the mechanical performance of the recycled composites. This strategy provides an unprecedented green avenue to cross-link diene elastomers and a cost-effective approach to further recycle the obtained cross-linked elastomers at high efficiency.

Novel Phosphorus Containing Flame Retarded RTV Silicone Rubbers

A reactive flame retardant cross-linker（SPTES） was successfully synthesized with dichloropentate and 3-triethoxysily-lpropylamine（APTES） in this research. Then it was further applied into the room temperature vulcanized（RTV） silicone rubber to prepare novel flame retarded RTV silicone rubbers containing phosphorus. The structure, thermal degradation stability, mechanical properties and flammability properties of the novel RTV silicone rubbers were tested and characterized. The results showed that the mechanical and flammability properties of the RTV silicone rubber simultaneously got better with the SPTES content increased. Compared with the sample prepared by APTES, the tensile strength of novel RTV silicone rubbers increased from 0.12 MPa to 0.38 MPa and the limit oxygen index increased from 19.8 to 23.5.

Current trends in bio-based elastomer materials

Elastomers play an irreplaceable role in our society due to their unique properties.Natural rubber is directly obtained from plants and is widely used in tires,shoes,etc.Recently,modified natural rubbers are proposed to expand the application of natural rubber.However,these natural rubbers have a limited variety of molecular structures and may not be able to meet ever-demanding applications.Traditional synthetic elastomers have a variety of molecular structures and their properties are used in various fields,but mainly originate from fossil resources.This review deals with bio-based elastomers,and more specifically natural rubber and bio-based synthetic elastomers.Based on reprocessability,bio-based elastomers can also be divided into bio-based chemically cross-linked ones and thermoplastic ones.Compared to traditional fossil-based elastomers,bio-based ones may alleviate environmental pollution and promote the sustainable development of the elastomer industry.