Iranian Journal of Polymer Science and Technology
Year:2004 | Volume:17 | Issue:2 (ISSUE NO. 70)|Papers Count:8

PVC is one of the most important and widely used plastics in polymer industries. Blending is an effective method to improve the undesirable properties of PVC such as stiffness and brittleness. One of the most important blends of PVC is its mechanical mixing with nitrile rubber, but it should be reminded that despite of expensiveness, it has not desirable tear strength. In this work, SBR was added to the blend of PVC/NBR with the purpose to achieve better tear strength with lower cost. The effect of adding SBR and also mixing factors on mechanical properties of ternary blend were investigated using experimental design, i.e. Taguchi method. With the aid of replacing 7% by weight of NBR by SBR in PVC/NBR-SBR ternary blend the tear strength increased twice to the initial value.

It is about three decades that glass optical fibers have found applications in electronic and telecommunication industries. The laws of governing transmission of optical signals are compiled, and due to the revelation of weak points in glass fibers including their utilization for limited range of electromagnetic waves, and with the rapid developments in polymer science, scientists began to utilize polymer fibers and it is about a decade that polymer optical fibers are used in industry. Glass fibers, for their specific structure, are only used for electromagnetic waves in the range of 1400-1600 nm( near infrared range) but polymer optical fibers, due to their varieties, can be used in different ranges of optical waves. Polymer optical fibers have brought about radical changes in spectroscopy. Polymer optical fibers have made distant infrared spectroscopy workable. By utilization of polymer optical fibers, chemical reactions and their electronic signals are recorded as spectrum while the spectrometer could be quite far from the location of chemical reactions. With this method, the distant control of dangerous chemical reactions such as a poisonous reaction has been possible. In this paper, the potentialities of polymer optical fibers in comparison with glass fibers and also characteristics of some polymer optical fibers have been investigated. Meanwhile, the physical fundamentals of transmission of light in polymer optical fibers such as attenuation, refraction and total reflection of light are described. At the end by utilization of a special type of polymer optical fibers, synthesis of N' (3,4-dichlorophenyl)-N,N'-dimethylure a with dimethyl amine and 3,4-ichlorophenylisocyanate in the range of near infrared electromagnetic wave (NIR)from the beginning till the end is controlled. In this method the amount of changes in 1473 cm-1 band for first overtone 2 NH with respect to time as an indication for the start and the end of a reaction is evaluated.

In this research work, the pigment dispersion quality methods for color masterbatches were investigated and several commercial masterbatches were studied. Light microscopy and image processing were used as quantitative methods for studying pigment dispersion and distribution in the masterbatches. The results obtained showed that the quality of dispersion varies from one color to another for the same producer and line over all trends showed that masterbatches produced locally are of lower quality in comparison to the imported masterbatches. The new method for studying pigment dispersion presented in this paper is simple and less expensive than the other methods available. This method can be used for quantitative analysis of pigment dispersion.

The elastomeric O-rings play important roles in industry. In this research, the behavior of O-ring, which is used in dialyzers' filter, is analyzed under service condition. To describe the stress-strain behavior of elastomeric O-ring, two mathematical models called, Mooney-Rivlin and Arruda-Boyce, are used. The theoretical results from Mooney-Rivlin model in tensile mode and Arruda-Boyce model in compression mode display good correlation with experimental results. The stress distribution in the O-ring is also investigated and the contact stresses, which have an important role in prediction of behaviors, are calculated.

In this paper, the production of polyethylene foam crosslinked by gamm irradiation is reported. At first the behavior of polyethylene against gamma irradiation was studied. Gel-content experiments were performed to investigate the efficiency of two crosslinked promoters, DCP and TMPTA. The results showed that these additives had significant effect in increasing the gel percent at low doses. But their effect was diminished at higher doses. The next phase was to determine the optimum dose and level of crosslinking promoters. To do this, rheometry experiments were performed on both crosslinked and virgin polyethylene and also the states of foaming of polyethylene in different gel percents were compared together. In the next stage, compression moulding technique was selected after examining different alternatives such as direct heating in oven or extrusion. Mould temperature and residence time of sample,were determined based on the results of DSC and TGA thermographs. The results showed that increase in blowing agent from 10 to 15 phr leads to cell rupture and an increase in density and thermal conductivity. Therefore, the concentration of 10 phr of blowing agent was reported as the optimum content in which the product had minimum density and thermal conductivity. The SEM micrographs confirmed previous results. Other experiments such as tensile strength and water absorption were also performed on samples and acceptable results proved the quality of the produced foams.

In this study, some internal microstructural models with different mobility tensors are investigated for polymer melts and concentrated solutions in shear flow. The time evolution equations for conformation and stress tensors in the reviewed models have root in the generalized Poisson Bracket formalism. Two different families of conformational models have been selected for this study. The first family is with the finitely modified extensible non-linear elastic (FENE-P) energy and the other family is with the Hookean Helmholtz free energy function. Several expressions for the mobility tensor with the mentioned energy functions are used to obtain those models. The sensitivity of both models towards the choice of the mobility tensor on the prediction of material functions in transient and steady flows is discussed. Also, the effect of shear rate on the material functions in start-up and relaxation shear flows for both models are studied. The predictions of models are compared to experimental data taken from the literature for some polymer melts. These results show that the families of volume preserving rheological models are able to predict the shear flow material functions in steady and transient regimes in an extended range of deformation rate, where the family of FENE-P models can only predict the behavior of some specified polymer melts.