Tear resistance

Abstract: Natural rubber is reinforced with untreated sisal and oil palm fibers chopped to different fiber lengths. The effects of concentration and modification of fiber surface in sisal/oil palm hybrid fiber reinforced rubber composites have been studied. Increasing the concentration of fibers resulted in reduction of tensile strength and tear strength, but increased modulus of the composites. Composites were prepared using fibers treated with varying concentrations of sodium hydroxide solution and for different time intervals. The vulcanisation parameters, processability characteristics, and stress–strain properties of these composites were analysed. The rubber/fiber interface was improved by the addition of a resorcinol-hexamethylene tetramine bonding system. The reinforcing property of the alkali treated fiber was compared with that of untreated fiber. The extent of fiber alignment and strength of fiber-rubber interface adhesion were analysed from the anisotropic swelling measurements.

Abstract: The objective of this research was to show the reinforcing effects of nanofibers in an epoxy matrix and in a rubber matrix using electrospun nanofibers of PBI (polybenzimidazole). The average diameter of the electrospun fibers was around 300 nanometers, which is less than one tenth the diameter and 1/100 the cross sectional area of ordinary reinforcing fibers. The ultrafine fibers provide a very high ratio of surface area to volume. The nanofibers toughened the brittle epoxy resin. The fracture toughness and the modulus of the nanofiber (15 wt%)-reinforced epoxy composite were both higher than for an epoxy composite made with PBI fibrids (17 wt%), which are whisker-like particles. In an elastomeric matrix, The Young's modulus and tear strength of the chopped nanofiber-reinforced styrene-butadiene rubber (SBR) were higher than those of the pure SBR. Micrographs of the fracture surfaces were obtained by scanning electron microscopy (SEM).

Abstract: Carbon black (CB) and silica have been used as the main reinforcing fillers that increase the usefulness of rubbers. As each filler possesses its own advantages, the use of silica/CB blends should enhance the mechanical and dynamic properties of natural rubber (NR) vulcanizates. However, the optimum silica/CB ratio giving rise to the optimum properties needs to be clarified. In this research, reinforcement of NR with silica/CB hybrid filler at various ratios was studied in order to determine the optimum silica/CB ratio. The total hybrid filler content was 50 phr. The mechanical properties indicating the reinforcement of NR vulcanizates, such as tensile strength, tear strength, abrasion resistance, crack growth resistance, heat buildup resistance and rolling resistance, were determined. The results reveal that the vulcanizates containing 20 and 30 phr of silica in hybrid filler exhibit the better overall mechanical properties.

Abstract: Self-healing functionality is imparted to a poly(dimethyl siloxane) (PDMS) elastomer. This new material is produced by the incorporation of a microencapsulated PDMS resin and a microencapsulated crosslinker into the PDMS matrix. A protocol based on the recovery of tear strength is introduced to assess the healing efficiency for these compliant polymers. While most PDMS elastomers possess some ability to re-mend through surface cohesion, the mechanism is generally insufficient to produce significant recovery of initial material strength under ambient conditions. Self-healing PDMS specimens, however, routinely recover between 70–100 % of the original tear strength. Moreover, the addition of microcapsules increases the tear strength of the PDMS. The effect of microcapsule concentration on healing efficiency is also investigated.

Abstract: An improved amphiphilic diol is prepared with a controlled type and amount of alkylene glycol, hydrophobic and hydrophilic diol with diisocyanate and water. Critical selection of the type, molecular weight and ratios of hydrophilic to hydrophobic diol, isocyanate to hydroxyl groups, average molecular weight of the diol component, the amount of water in the reaction mixture produces a polyurethane having high slip, Shore A Hardness values, wet tensile strength and tear strength. This invention also includes uses of the polyurethane in catheters, shaving products, synthetic valves, veins and arteries, stents, ports, shunts and coatings. Preferably, the polyurethane is used in combination with a filler for application to rubber gloves. In addition, dispersions, lotions, gels and solutions can be formed of the polyurethane.