Iranian polymer journal
Volume:11 Issue: 5, 2002

Addition of vinyltriethoxysilane (VTEOS) in carbon black provides beneficial effects by improving various mechanical properties of styrene-butadiene rubber (SBR) vulcanizates. In addition to this, the incorporation of (VTEOS) strikingly improves their aging behaviour. This experiment was carried out to understand the behaviour of SBR vulcanizates due to the addition of VTEOS in the range of 0 to 2.73 phr. Evaluation of properties was made through compression moulded sheets as per standard industrial practices. The VTEOS increases the fatigue-to-failure (FTF) cycles of the vulcanizate containing 2.73 phr of VTEOS by three times at an extension ratio of 1.80, which is the maximum value of FTF reported here, in comparison to the vulcanizate containing no VTEOS. However, the other mechanical properties namely tensile, tear, compression, resilience and hardness show an improvement at around 0.5 to 1 phr of VTEOS. The aging behaviour of vulcanizates at this 0.5 phr of VTEOS is comparatively better. It was seen that the VTEOS plays the roles of coupling agent and softener. It acts as a coupling agent up to 0.5 phr and beyond it acts as softener. A small amount above this coupling action is beneficial for many uses. It appears that the optimal dosage of addition of VTEOS to this system to be around 0.5 to 1 phr.

Dyeing behaviour of chitosan pretreated cotton fabric with reactive dyes is the subject of this study. Cotton fabric is treated with chitosan using five different techniques, consisting of exhaustion, pad-dry, pad-batch, pad-steam and pad-drysteam methods. To find the influence of concentration of chitosan on the dyeability behaviour, different amounts of chitosan were used and the suitable concentration was determined. It is observed that chitosan pretreatment increases the exhaustion of reactive dyes and the highest dye up-take is achieved for pad-dry method. The effect of the period of storage of chitosan treated sample before dyeing process on dyeability of fabrics is examined by comparison of samples which was dyed immediately after treatment with the one which was kept for 48 h after treatment. The results show that dyeing immediately after treatment leads to higher dyeability and the effect of treatment decreases for the samples which were pkept for 48 h before dyeing process. The light and wash fastnesses of treated samples are measured and some reduction in light and wash fastnesses were observed.

Bitumen in pure form is not suitable for modern roads and present traffic. This has forced engineers to modify bitumen to improve its performance during service life. Two routes are known for bitumen modification, namely: chemical and physical modifications. Therefore, there are chemical and physical modifiers. Among physical modifiers polymers (thermoplastics, rubbers and thermosets) are the most interesting ones. Rubbers are very good bitumen modifiers. In this work, non-vulcanized rubbers were incorporated into bitumen. The resulting range of blends showed higher and intermediate performance compared to the base bitumen. The improved properties are lower penetration degree and higher softening point. The low temperature property such as Frass breaking point was not improved. New formulae for estimating bitumen’s performance using the results of conventional Frass and ring & ball tests were introduced. The morphology of the blends depending on the rheological properties and compatibility of the rubber with bitumen was different. Polybutadiene formed a continuous phase mixture in bitumen. This was observed due to the compatibility of this rubber with bitumen. Due to lesser compatibility between polymer and bitumen, SBRs and natural rubber formed polymeric inclusion dispersed in bitumen.

Suggestion has been made about the nucleophilic reaction mechanism of a binary accelerator system when derivatives of thiourea are used as secondary accelerators in rubber vulcanization. The idea of our investigation is to give some conclusive evidence to the nucleophilic reaction mechanism proposed. In our studies we found that N- amidino-N''-phenyl thiourea (APT) functions effectively as a secondary accelerator in mercaptobenzothiazyl disulphide-APT, tetramethyl thiuram disulphide-APT, and cyclohexyl benzthiazyl sulphenamide-APT binary systems in filled natural rubber (NR) vulcanization. The above binary systems were prepared using carbon black/precipitated silica as filler.Evaluation of cure-characteristics of these mixes showed appreciable reduction in the optimum cure time for the mixes containing APT compared to reference mixes. This indicates a nucleophilic reaction mechanism, as APT is a more active nucleophilecompared to the references. Considering the non-reverting characteristics of some of the mixes containing APT, this amidinothiourea derivative seems to function as an antioxidant as well. Important physical properties of these vulcanizates were also evaluated. Most of the physical properties of the vulcanizates studied were also found to be better, comparable to those of the reference mixes. Heat aging of these vulcanizates showed good retention of these properties after aging. The optimum dosage of the secondary accelerator required has also been derived.

This research work is devoted to the numerical study of the non-linear finite element analysis of pneumatic tyres. The purpose of the present work is to find appropriate numerical schemes for the non-linear stress-strain analysis of such complex structures. Different numerical options including full and modified Newton-Raphson methods, order of interpolation functions, incompatible modes and type of non-linear formulations (total Lagrangian and up-dated Lagrangian) have been considered during this parametric study. These methods have been applied to the finite element analysis of a homogeneous tyre under axisymmetrical pressure loading. The final decision on the selection of the best approach has been made by the comparison of the numerical results with available experimentally measured data. It is shown that the combination of incompatible modes in case of lower order elements or total Lagrangian formulation with higher order elements as well as the use of full Newton-Raphson method provide the best accurate results.

The effect(s) of four different types of surfactants on the enzymatic hydrolysis of cellulosicfabric was studied. Amount of reducing sugar produced during the reactionwas used as a measure of extent of the hydrolysis. The non-ionic surfactant increased the rate of the reaction by approximately 12% while in the presence of amphoteric, anionic and cationic surfactants the rate of the hydrolysis decreased by 36, 38, and 50%, respectively. The physical properties, such as tensile strength and crease recovery (angle) of the cellulosic fabrics were measured. In the presence of non-ionic surfactant, the tensile strength loss for cellulase treated fabric was increased by 17%. The loss of tensile strength did not change using cationic surfactant while in the presence of amphoteric and anionic surfactants, the strength loss decreased rather insignificantly. All the results obtained from measuring the physical properties of the enzymatic treatment of the cellulosic fabric were in agreement with those from reducing sugar measurments. Moreover, the Michaelis-Menten equation, which has been used in the previous work of this group, was also used in the present study and the maximal velocity, V''max, and the half-saturation constant, K''m, both were calculated. In order to measure the catalytic specificity of the cellulase on this hydrolytic reaction on the tested fabrics, the ratio of V''max/K''m, was determined. The catalytic specificity for the fabrics treated with non-ionic surfactant was increased, although this ratio for the fabrics treated with amphoteric, cationic, and anionic surfactants decreased. The performance of these surfactants in relation to this enzymatic reaction was discussed.

Hydantoin and thiohydantoin derivatives 4(a-e) were synthesized from reactions of benzil and benzil derivatives 3(a-e) with urea and thiourea. 5,5-dimethylhydantoin 4f was synthesized from the reactions of acetone cyanohydrin 3f and ammonium carbonate. Benzil and benzil derivatives 3(a-e) were obtained from oxidation of benzoin and benzoin derivatives 2(a-e) with concentrated nitric acid. Benzoin and benzoin derivatives were obtained from benzoin condensation of benzaldehyde and benzaldehyde derivatives. Hydantoin and thiohydantoin derivatives 4(a-e) were characterized by melting points, elemental analysis, FTIR, 1H NMR and 13C NMR spectroscopy. The polycondensation reactions of 4,4-carbonyl-bis(phthaloyl-L-alanine) diacid chloride 5 with six different derivatives of hydantoin and thiohydantoin compounds 4(a-f) were carried out in DMAc solution in the presence of pyridine. The resulting poly(amide-imide)s, PAIs, 6(a-f) with inherent viscosities about 0.15-0.38 dL/g were obtained in high yield and were optically active and thermally stable. All of the above compounds were fully characterized by means of FTIR spectroscopy, elemental analysis, inherent viscosity (ηinh), solubility test and specific rotation. Thermal properties of the PAIs 6(a-f) were investigated using thermal gravimetric analysis (TGA).