Journal of Elastomers & Plastics

Hybrid fillers of silicon carbide/glass fibres (SiC/GFs) are used to prepare SiC/GFs/bismaleimide (SiC/GFs/BMI) composites. Results show that the thermal conductivities of the SiC/GFs/BMI composites improved with the increasing content of SiC fillers, and the thermal conductivity coefficient is 1.64 W mK⁻¹ with 60 wt% modified SiC fillers. The heat resistance properties and dielectric constant values of the SiC/GFs/BMI composites also improved with the increasing content of SiC fillers. Furthermore, surface modification of SiC fillers is beneficial for further improving the thermal conductivities of the composites.

Hydroxyl-capped polylactic acid (PLA) oligomers are prepared by glycolysis reaction of PLA with ethylene glycol (EG) and used as a macromolecular cross-linker for epoxidized natural rubber (ENR). The glycolyzed PLA (GPLA) with three different molecular weights (2000, 10,000, and 44,000 g mol⁻¹) are prepared by varying the glycolysis conditions. Effects of GPLA chain lengths and GPLA/ENR feed ratios on cross-linking efficiency, chemical structures, and physical properties of the cured products are investigated. The cross-linking efficiency is examined using a moving die rheometer, solvent fractionation, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Optimum GPLA/ENR compositions for the curing reaction range from 20 wt% to 33 wt%, depending on the GPLA chain length. Because of their biodegradability, biocompatibility, and the ability to tune up their structures and properties, the cured rubber materials have high potential for use in various biomedical applications.

Extensive use of rubber in industrial articles and their eventual disposal at the end of their useful service life has created a major concern for the environment. In automotive applications, ethylene–propylene–diene rubber (EPDM) is used to manufacture various parts which will be difficult to dispose of or scrap. A microwave oven was used as a heating source, and with the aid of some chemical agents and aromatic and aliphatic oils, cured EPDM waste powder was devulcanized at temperatures ranging from 200°C to 260°C. The devulcanized waste powder was then revulcanized with a sulfur cure system and its cure and mechanical properties were measured.

It emerged that with the aid of the chemical agents, the waste powder devulcanized more efficiently in the aromatic oil than it did in the aliphatic one. The chemical agents had different effects on the devulcanization of the waste powder and mechanical properties of the revulcanized compound. In addition, devulcanization was more efficient at higher temperatures. The hardness, tensile strength, and elongation at break of the revulcanized compounds were in the range of 49–79 Shore A, 2.0–3.7 MPa, and 34–211%, respectively. These properties were influenced mainly by the composition and devulcanization conditions of the waste powder. There is scope to recycle and reuse some of these compounds in automotive applications.

Epoxidized low molecular weight natural rubber (ELMWNR) with 28 mol% epoxide groups and weight average molecular weight of 49,000 g mol⁻¹ was prepared by oxidative degradation of epoxidized natural rubber (NR) using periodic acid in the latex state. ELMWNR-28 was used at 10 parts per hundred parts of rubber (phr) loading in combination with bis-(triethoxysilylpropyl) tetrasulfide (TESPT) as the silane coupling agent in the range of 0–4.5 phr in silica-reinforced NR compounds. The use of TESPT in combination with ELMWNR-28 gives lower mixing torques and compound viscosities compared with the use of TESPT alone and the system without any compatibilizer. The bound rubber content, modulus, and tensile strength of the compounds with only TESPT strongly depend on the TESPT loading. The use of ELMWNR-28 as a compatibilizer clearly improves such properties compared with the non-compatibilized systems. By adding TESPT into the compound with ELMWNR-28, the properties further improve with increasing TESPT loading. The combined effect of ELMWNR-28 at 10 phr with a small amount of TESPT at 1.5 phr results in compounds with superior processability (i.e. low Mooney viscosity and Payne effect), and only slightly lower modulus and reinforcement index (M300/M100) compared with the use of the optimum content of TESPT. This compatibilizer/TESPT combination has the environmental benefits that the ELMWNR is a naturally based product, and that the reduced amount of TESPT silane coupling agent emits a greatly reduced amount of ethanol during processing.

In this study, polycarbonate/acrylonitrile–butadiene–styrene (PC/ABS) and polyamide 6/PC/ABS (PA6/PC/ABS) blends were reprocessed (recycled) five times and the influences of multiple molding processes on the thermal, chemical, morphological, rheological, and mechanical properties of the recycled and virgin specimens were investigated. The impact strength, tensile properties (elastic modulus, strength, and strain at break), and flexural properties (modulus and strength) were measured to determine the mechanical properties of the blends. The rheology of the samples was evaluated via measuring the melt flow index (MFI). It was concluded that the chemical structures, melting temperatures, and thermal properties of both blends did not significantly change with recycling. From the mechanical tests, in general, it was found that increasing the number of recycling processes did not considerably alter the flexural properties and tensile strength of PC/ABS blends, but decreased their MFI and impact strength. On the other hand, the elastic modulus and tensile strength of PA6/PC/ABS decreased with the number of recycling processes, whereas MFI, flexural properties, and impact strength of the ternary blends improved.

Epoxy-capped polyhedral oligomeric silsesquioxane (EP-POSS) is performed to modify bisphenol A cyanate ester (BADCy) to regulate its dielectric constant and thermal resistance. EP-POSS can be incorporated in the cross-linked network of BADCy via covalent bonds, which catalyzes BADCy self-polymerization to decease the initial temperature of forming triazine rings. EP-POSS is distributed in the BADCy matrix uniformly and there is no aggregation and phase separation between EP-POSS and BADCy matrix at a micrometer scale. The dielectric constant values of EP-POSS/BADCy are decreased with the addition of EP-POSS, but increased slightly when the mass fraction of the EP-POSS is more than 2 wt%. The thermal resistance of EP-POSS/BADCy is increased slightly with the addition of EP-POSS.