Iranian Journal of Polymer Science and Technology
Year:2011 | Volume:24 | Issue:3 (ISSUE NO. 113)|Papers Count:8

Failure in timber structures occurs mainly in crucial points such as joints areas.Therefore, the idea of using composite sheets in timber joints has been introduced as a method in order to increase the strength and ductility behaviour of timber joints. This research aims to study the behaviour of bolted joints in poplar and pine woods, which are reinforced by two types of GFRP sheets. A single shear bolted joint consisted of 3 timber members whose length and width were 30 cm in length and 5 cm in width. The thickness of each member was 4 cm for internal part and 2 cm for external part. The employed steel bolt was 10 cm in length and 1 cm in diameter.In this respect, one layer of GFRP sheet was used to be bonded to timber members by using epoxy resin and left between the clamps for 24 hours. They were then kept at room temperature for three weeks. Also the effect of adding a wood veneer on the reinforced joints was investigated. The tensile strength of the reinforced and control samples (un-reinforced joints) was measured according to ASTM D5652-92 standard.The results show that the reinforced samples have higher tensile strength compared to that of reinforced joints, although it is not statistically significant. Also, two types of sheets influence the joint behaviour as the reinforced joints display more ductility behaviour.

In atom transfer radical polymerization (ATRP) of methyl acrylate (MA) with polyvinyl acetate macroinitiator in bulk at 90oC the plots of Ln [M]0/ [M] increased linearly with reaction time. The apparent propagation rate constant (kp app) of the reaction was obtained from the linear curve and used to calculate the free macroradical concentration ([Ro]) in polymerization medium. The [Ro] and also kp app values decreased with concentration of CuCl2 (deactivator). The slope and extrapolation values of the linear curve of (kp app) -1 versus CuCl2 concentrations and kinetic equations were used to calculate ka and kd/ki constants to be 2.576×10-4 M-1.s-1 and 222. The Mn values of block copolymers obtained by GPC were nearly in agreement with the theoretical values and increased linearly with conversion. Furthermore, PDI decreased with conversion due to the controlled/living behavior of the ATRP with PVAc macroinitiator. The kp app and [Ro] values increased with catalyst and macroinitiator concentrations and also decreased with monomer concentration. The polymerization medium undergone termination reactions were attributed to increases of the macroradical concentration. The ratio of kt/Keq=4.313×1020 was also calculated on the basis of Fischer equation. Furthermore, the Mn values of the block copolymers decreased with free macroradical concentration and the PDI values were also broadened due to termination reaction.

The organo-metal salt of aluminum triacrylate (ALTA) with a general formula of (CH2=CHCOO)3Al was synthesized as a reactive filler for elastomers through a two-step synthetic procedure. Fourier transform-infrared spectroscopy (FTIR), DSC and DTA were employed for ALTA analysis and to study its cure characteristics. In this research, two composites based on ethylene propylene diene monomer rubber (EPDM) with two types of reactive fillers of modified organoclay and ALTA were prepared by a laboratory two-roll mill. The types and different ratios of organoclay and ALTA on curing characteristics, mechanical properties such as tensile properties, hardness, and abrasion resistance were studied. The increase in filler content of both composites led to the incremental increase in tensile strength, modulus, hardness, elongation-at-break and also the incremental increase in abrasion resistance of both composites. The improvement in reinforcing properties of ALTA in comparison with nanoclay is attributed to homopolymerization and graft copolymerization of ALTA at the same time during curing of the EPDM composites by peroxide.Making such additives may be taken as an effective action to achieve more durable and cheaper way to reinforce elastomers.

Nowdays, production of high quality engine oils is one of the worries of our country’s engine oil industry. In this study, the behavior of four commercial polymers used in nation motor oil industry in obtaining the best viscosity index improver was investigated. In this regard, viscometric behavior, shear stability and polymers’ performance for engine cranking were compared at low temperature. In this respect, viscometry behavior of polymer solutions with different concentrations (0.3, 0.5, 0.7 and 1% by weight) in terms of physical chemistry parameters such as specific viscosity, intrinsic viscosity, viscosity ratio, thickening power and viscosity index were compared with each other. The activation energy of each polymer solution was calculated using the Arrhenius equation and polymer performance was evaluated with respect to activation energy changes and lower oil temperature sensitivity.In continuation, the shear stability of these commercial polymers in solution state was evaluated. Based on shear stability analysis an inverse relationship was found between polymers’ shear stability and their molecular weights. Finally, the behavior of the commercial polymers was investigated for determination of optimum performance in engine cranking at-15oC. Based on the obtained data, the most suitable polymer was identified and indicated as the best to fulfil oil industry’s purposes. In this respect the high-tech polymers, based on their molecular structures demonstrate the best performance compared to other polymers. Paratone and Viscotech polymers have relatively shown similar behaviors, although based on viscometric behavior the Viscotech is better than Paratone, and based on shear behavior the order of preference is reversed. Keltan polymer has just a better thickening power while, it is not considered suitable for high quality engine oil at low temperatures of engine cranking for its weak shear performance and low efficiency.

A mixture of sodium lauryl sulfate (SLS) as ionic emulsifier and stearyl alcohol as non-ionic emulsifier was employed in a vinyl chloride emulsion polymerization reaction to study the influence of various interactive parameters involved in the reaction system. It was found that the particle size was dependent on the amount and type of emulsifier. The average particle size of polyvinyl chloride was dropped by higher amount of emulsifying agents. At the gel point, more heat was generated by higher amount of vinyl chloride fed into the reaction system. The molecular weight of the polymer was decreased by increases in reaction temperature while, it increased by augmenting the amount of emulsifier. According to the 13C NMR and FTIR spectroscopic data no defect was detected in the chain structure of synthetic polyvinylchloride product. An optimization of polymerization reaction condition was reached based on ultimate particle size desired for its favorable distribution in plastisols.

Nanofiber mats of poly (e-caprolactone) /nanoclay nanocomposites were fabricated by electrospinning. The effects of the solution concentration and the nanoclay content of nanocomposite materials on the final nanofiber structure were investigated. Morphology and diameter of the nanofibers were studied using optical and scanning electron microscope. It was observed that the poly (e-caprolactone) at concentration of 5% to 8% could be electrospun into the fibrous structure. The results showed that the presence of the nanoclay promoted the creation of fibrous structures in comparison with the poly (e-caprolactone) without nanoclay. On the other hand, increasing the nanoclay content resulted in a lower average fiber diameter. Shear viscosity and conductivity of the solutions were also reported. The presence of nanoclay increased conductivity and shear viscosity of the solutions. Formation of the nanofibers and decrease in their diameters are discussed on the basis of shear viscosity and conductivity of electrospun solution. This electrospun nanofiber could be used for tissue engineering application.

In petrochemical industry, the production of polyvinyl chloride (PVC) is accompanied by formation of heavy end wastes which consist of a mixture of di and multichloro compounds as kind of materials which are generated in ethylene dichloride (EDC) purification. A high quantity of chloro compounds found in the heavy end waste allows it to be polymerized with alkaline polysulfides to form polysulfide polymers. Thus, according to this, the environmentally hazardous heavy ends waste can now be converted into useful polysulfide polymers without any environmental problem. There are some methods for synthesizing a polysulfide polymer (PSP) from this waste. PSP with a rubbery property can be used for modification of bitumen. In this research the effects of polysulfide polymer (PSP) and the polysulfide polymer prepared by heavy end waste (wPSP) on bitumen and asphalt have been studied. Samples of 1, 3, 5% of PSP and wPSP as modifiers in bitumen have been prepared and their physical and mechanical properties are compared. Using this new modifier causes a fall in softening point (PSP=39.5%, wPSP=27.6%) and increase in penetration point (PSP=17.8%, wPSP=15.5%) and in asphalt mixture it causes decreases in rutting but has a small effect on Marshall strength of asphalt samples (PSP=4%, wPSP=11.6%).