Effects of Alkyl-Substituted Polybenzoxazines on Tribological Properties of Non-Asbestos Composite Friction Materials

A series of substituted polybenzoxazines was synthesized and studied as binders in non-asbestos friction composite materials. The structures of the polybenzoxazines were varied in a systemic fashion by increasing the number and position of pendant alkyl (methyl) groups and was accomplished using the respective aromatic amines during the polymer synthesis step. By investigating the key thermomechanical and tribological characteristics displayed by the composite materials, the underlying structure-properties relationships were deconvoluted. Composite friction materials with higher thermomechanical and wear resistance properties were obtained from polybenzoxazines with relatively high crosslink densities. In contrast, polybenzoxazines with relatively low crosslink densities afforded composite friction materials with an improved coefficient of friction values and specific wear rates.

DERIVATIZATION OF SOYBEAN OIL TO ENHANCE PERFORMANCE AS A PROCESSING OIL IN SBR-BASED RUBBER COMPOUNDS

ABSTRACT Although soybean oil (SBO) has been used as a bio-based processing oil (PO) for rubber compounds, direct replacement of a conventional petroleum-based PO with SBO often results in a reduction of some important properties. As a result, it was of interest to investigate two higher molecular weight SBO-derived materials as POs, namely, sucrose octasoyate (SS) and poly(2-vinyloxyethyl)soyate (P2VOES). When these compounds were used in carbon black (CB)-filled SBR, mechanical properties were significantly improved. This result was mainly attributed to higher crosslink densities resulting from their higher degree of unsaturation per molecule as compared with SBO. Higher unsaturation per molecule increases the probability that the PO will be incorporated into the crosslinked network as elastically effective crosslinks as opposed to dangling chain ends. With regard to tire tread performance, both SS and P2VOES-based vulcanizates showed a lower predicted rolling resistance than the SBO-based control, and the P2VOES vulcanizate showed a better balance between rolling resistance and wet traction. Vulcanizates derived from SS and P2VOES showed a small tangent delta peak between −13 and 35 °C that might be associated with relatively highly crosslinked domains rich in SS or P2VOES.

Grafting-through ROMP for gels with tailorable moduli and crosslink densities

A new class of chemically-crosslinked network was synthesized by grafting-through macrocrosslinkers with ROMP, exhibiting highly-tailorable storage moduli through independent control of the network junction functionality and molecular weight between crosslinks.

Food Simulating Organic Solvents for Evaluating Crosslink Density of Bulk Fill Composite Resin

Objectives.To evaluate crosslink densities of two bulk fill composite resins and determine if the used Food Simulating Organic Solvent (FSOS) affected them.Methods.Forty specimens were prepared from SureFill and SonicFill bulk fill composite resins, 20 each. All specimens were stored dry for 24 h. Each group was divided into 2 subgroups: stored in ethanol (E) 75% or in methyl ethyl ketone (MEK) 100% for 24 h. Crosslink density was evaluated by calculating the difference between the Vickers hardness numbers of the specimens stored dry and after their storage in FSOS. The data were statistically analyzed usingt-test.Results.The means of crosslink density in E and MEK were 6.99% and 9.44% for SureFill and 10.54% and 11.92% for SonicFill, respectively.t-test displayed significant differences between crosslink densities of SureFill and SonicFill: (P<0.0001) in E and (P=0.02) in MEK and between crosslink densities of SureFill in E and MEK (P=0.02).Conclusions.Crosslink density of bulk fill composite resin can be evaluated using E or MEK. SureFill has higher crosslink density than SonicFill in both E and MEK.

Mechanical and hydrodynamic swelling characteristics of bovine tanned leather post-treated by acrylic and glutaraldehyde tanning agents

Chromium tanned cow hides collected at two different stages (i.e. pre-neutralization and pre-finishing) have been treated separately with acrylic and glutaraldehyde based tanning agents. Both mechanical and hydrodynamic swelling properties of these treated samples were investigated. Observed results revealed that overall tensile properties and resistance against hydrodynamic swelling have been improved in all the treated samples as compared to those of untreated samples. Such improvement has been realized through measurement of crosslink densities via fitment of Mooney-Rivlin equation on the tensile plot. Leather post-treated with acrylic copolymer has envisaged superior results as compared to leather post-treated with gluteraldehyde based tanning agent. After one swelling / deswelling cycle, slight material loss has been incurred in all the samples, which is the highest for leather post-treated with glutaraldehyde. Such post-treatment of leather can be a useful measure to enhance the performance properties of leather samples already manufactured in the tannery.Bangladesh J. Sci. Ind. Res. 51(1), 1-12, 2016

Role of ZDC/S ratio for pervaporative separation of organic liquids through modified EPDM membranes: rational mechanistic study of vulcanization

Variations in crosslink densities and crystallinity due to mono-, di- and poly-sulphide linkages in EPDM vulcanization are achieved using different sulfur/accelerator weight ratios and therefore the separation factor and membrane selectivity of toluene.