Iranian Journal of Polymer Science and Technology
Year:2015 | Volume:27 | Issue:6 (ISSUE NO. 134)|Papers Count:7

Nano-fillers have displayed excellent mechanical properties and are widely used in different polymeric matrices for high performance applications. Recently, epoxy resins modified by nano-reinforcing fillers such as multi-walled carbon nanotubes (MWCNTs) and nanoalumina (Al2O3) have been developed for adhesive applications. In this work, the influence of 1.5 weight percent of various nanofillers namely nanoalumina, MWCNT, nanosilica (SiO2) and talc on the thermal stability, strength adhesion and morphology of diglycidyl ether of bisphenol A (DGEBA)/epoxy novolac adhesives was studied. Thermal stability and degradation, adhesion strength and morphology were measured by the thermogravimetry analysis (TGA), lap shear strength test and scanning electron and transmission electron microscopic techniques, respectively. The results showed that incorporation of the nanoalumina and MWCNT into the DGEBA/epoxy novolac adhesives increased the lap shear strength. Moreover, the thermal stability of the epoxy adhesive in terms of onset of degradation temperature and char yield (after 800oC) was improved to some extent. By addition of one and half weight percent nanoalumina and/or MWCNTs in the epoxy adhesives, the lap shear strength increased by about 70 and 25 percent, respectively. Among the investigated fillers, nanoalumina demonstrated the best performance in terms of improvements in the lap shear strength, thermal stability and degradation of the epoxy adhesives. When a combination of nanoalumina and MWCNTs reinforcing fillers (0.75 weight percent nanoalumina and 0.75 weight percent MWCNTs) was used as a hybrid filler in the epoxy adhesive, a synergism effect on the char yield was observed.

Chitosan is a deacetylated derivative of chitin, which is a naturally abundant mucopolysaccharide, supporting the matter of crustaceans, insects, and fungi. Because of its unique properties, such as non-toxicity, biodegradability, and biocompatibility, chitosan has a wide range of applications in various fields. The objective of the present work is to extract the polymer chitosan from Persian Gulf shrimp shells. In order to determine the physicochemical characteristics of the extracted chitosan, degree of deacetylation, molecular weight, water and fat binding capacities extraction rate, and apparent viscosity were measured using a variety of techniques including viscometry, weight measurement method and Fourier transform infrared spectroscopy (FTIR). The results of the study of the physicochemical properties, molecular weight (6.7´105 Da), degree of deacetylation (57%), ash content as well as yield (0.5%) of the prepared chitosan indicated that shrimp processing wastes (shrimp shells) are a good source of chitosan. The water binding capacity (521%) and fat binding capacity (327%) of the prepared chitosan are in good agreement with the other studies. The elemental analysis showed the C, H and N contents of 35.92%, 7.02%, and 8.66%, respectively. In this study, the antimicrobial activity of chitosan was evaluated against Staphylococcus aureus and Escherichia coli. The results indicated the high potential of chitosan as an antibacterial agent. Moreover, the results of the study indicated that shrimp shells are a rich source of chitin as 25.21% of the shell’s dry weight.

Polyethylene terephthalate (PET), one of the thermoplastic polymers, is encountered with arduous problems in its recycling. After recycling, its mechanical properties drop dramatically and therefore it cannot be used to produce the products as virgin PET does. Polyethylene is a thermoplastic polymer which can be easily recycled using the conventional recycling processes. The decreased mechanical properties of virgin polyethylene due to the environmental factors can be improved by reinforcing fillers. In this paper, we studied the effects of adding recycled polyethylene terephthalate (rPET) as a filler, in various amounts with different sizes, on the physical and mechanical properties of recycled polyethylene. Composite samples were prepared using an internal mixer at temperature 185oC, well below rPET melting point (250oC), and characterized by their mechanical properties. To improve the compatibility between different components, PE grafted with maleic anhydride was added as a coupling agent in all the compositions under study. The mechanical properties of the prepared samples were performed using the tensile strength, impact strength, surface hardness and melt flow index (MFI) tests. To check the dispersity of the polyethylene terephthalate powder in the polyethylene matrix, light microscopy was used. The results showed that the addition of rPET improved the tensile energy, tensile modulus and surface hardness of the composites while reduced the melt flow index, elongation-at-yield, tensile strength and fracture energy of impact test. We could conclude that with increasing rPET percentage in the recycled polyethylene matrix, the composite became brittle, in other words it decreased the plastic behavior of recycled polyethylene. Decreasing particle size led to higher surface contacts, increased the mechanical properties and made the composite more brittle. The light microscopy micrographs of the samples showed a good distribution of small rPET particles in the polyethylene matrix.

The properties of prepregs are characterized in terms of their volatile content, resin content, the degree of pre-cure, void content, tack and flow ability. Resin content is one of the most important properties of prepregs so that its changing will result in altered properties such as, tack and resin flow. In order to monitor the resin content, a quantitative relation to the processing parameters such as line speed, viscosity and distance between the resin up taking rollers have to be determined. In this study, a tri-axial E-glass fabric with the areal weight of 1025 g/m2 and an epoxy resin (Epon 828) were used to produce the prepreg by the dipping method. In the theoretical part of this work, the free coating is studied and as a result the thickness layer of the coating resin through the resin bath is calculated by Landau-Levich model. In continuation, the achieved thickness was considered as a feed for the calendering process. Using the momentum equation for the passing impregnated fibres through the extra resin uptake rollers, the relation between the internal resin layer thickness and final coating resin layer thickness was achieved in an integral equation form. In order to solve this integral equation, MAPLE software was applied. The theoretical results were in good agreement with the experimental data and showed that the resin content increased linearly with increasing the distance between rollers, the radius and roller angular velocity. In contrast, the resin content decreased with increasing the line speed. According to our calculations, the effect of the resin viscosity variation on the resin content was negligibly small.

In recent years, for economical, ecological and technical reasons, the tendency to use self-lubricant materials in tribological applications has been increased. Among self-lubricant materials, the engineering plastics and their composites, especially polyamides due to their suitable physical and mechanical properties, have gained a special attention in tribological applications. Since engineering polymers in their pure form are not capable to satisfy the tribological requirements, the application of different fillers seems to be necessary. In this research, in order to improve the tribological behavior of polyamide 6, an irradiated polytetrafluoroethylene (IR-PTFE) powder as a solid lubricant with the percentages of 5, 10 and 15% was used. The composites were prepared by the melt mixing method and then formed by the injection process. In order to investigate the dispersion of IR-PTFE as the second phase in the polymer matrix, electron microscopy was used. The results showed a proper distribution of IR-PTFE powder particles and a low adhesion of the powder to the polymeric matrix. The mechanical properties in uniaxial tension for determination of a suitable percentage of the filler were used. Also, the samples were subjected to water absorption and tribological long-term experiments. The formation of the transfer films in the pure polymer and the composite containing 5wt% of IR-PTFE powder as the second-phase polymer was observed with an optical microscope. The results showed that the composite containing 5wt% the irradiated polytetrafluoroethylene powder had the least effect on decreasing the mechanical properties. Also, the addition of IRPTFE powder increased the transfer films and decreased the coefficient of friction, contact surface temperature and wear rate of polyamide 6. In addition, the application of proper quantity of the irradiated polytetrafluoroethylene powder decreased the water absorption of the composites.

Relating polymer structure to its performance properties is a primary motivation for determining the structure of a polymer chain. If a polymer chain is completely characterized and the structural basis of its properties is known, one can optimize and control polymerization to produce the best possible properties from the chemical system. Infrared (IR) spectroscopy represents a powerful technique for characterization of the polymers. Several relative and absolute methods have been developed to determine the copolymer composition. Among these methods, IR technique as a relative method is a considerably faster and lower cost procedure than other methods like absolute nuclear magnetic resonance (NMR) analysis. In the present work, vinyl acetate/vinyl benzoate copolymers were synthesized by reverse iodine transfer polymerization (RITP) with different molar ratios of comonomers in the initial feed in the presence of iodine as in situ generator of the transfer agent and 2, 2′-azobis(isobutyronitrile) as the initiator at 70oC. Fourier transform infrared (FTIR) spectroscopy was used to determine the composition of the vinyl acetate/vinyl benzoate copolymers. Based on the five copolymers with known compositions determined by 1H NMR spectroscopy, a FTIR calibration curve was obtained. The composition of the synthesized vinyl acetate/vinyl benzoate copolymers with unknown compositions was then determined from the calibration curve and FTIR data. Feed composition and individual and overall molar conversions of the comonomers were calculated after determining the copolymer composition. The results obtained from the FTIR method were in good agreement with those obtained theoretically, indicating the accuracy of the method presented in the present research.

In tubular reactors, there are different parameters which can affect the degree of conversion. The type of fluid motion and velocity profile of substances in the reactor are of most central measures. Different rheological models can be employed to study the behavior of fluids; power law model is one of the most commonly used models. In this study, the rheological behaviour of polymerization reaction of methyl methacrylate was examined. Due to the similarity function of tubular and batch reactors, the number of test tubes are used to prepare the solution. After preparation of the reactor solution, the n value of power law model was estimated within the span of 0.3492 to 0.9889 by curve fitting. Employing these rheological data, a reactor has been designed. Moreover, the effects of parameters such as reaction temperature, initiator wt%, the concentration of monomer and reactor’s radius on the degree of conversion have been studied. The obtained results in the research indicate a direct proportionality of conversion with the reaction temperature, initiator wt% and the concentration of monomer and also an inverse proportionality of conversion with reactor’s radius. Finally, the amount of conversion was obtained equal to 56.47% and according to its laboratory proportion which was 55.88% we have reached the conclusion that the modeling duly undertaken is applicable and valid.