Iranian Journal of Polymer Science and Technology
Year:2003 | Volume:15 | Issue:5 (ISSUE NO. 61)|Papers Count:6

Flexible polyurethane foams are one of the most important groups among polymeric foams, and they have a great market. These foams generally consist of small and open cells. The aim of this work was the preparation of flexible polyurethane foam with large cell size as used for fabrication of ceramic filters. The foams with large cell size were prepared with controlling the gelation rate. This was accomplished with varying the amount of catalysts. Another polyol with low rate of reaction was used as well. Suitable foam was synthesized with the second polyol by optimizing the catalyst level. The effect of various materials as well as the density and cell size on the final products was studied.

The statistical empirical design is based on the statistical modeling of nonlinear polynomial equation and coding of these equations in the solution polymerization of vinylacetate in a factorial design. The surface calculation considers time, temperature and percent conversion as important factors in this polymerization reaction. In response, the influence of these factors is determined from the polynomial equations. Nonlinear regression is also used to model the hydrolysis of polyvinyl acetate. Variance analysis is used in the study of dispersion of experimental data. The confidence level in this design is reported from total sum of the square and statistical calculations.

Polyurethanes, both as thermoplastics and elastomers find variety of applications owing to their excellent physical and mechanical properties. Automotive tyre manufacturing is one among many uses of polyurethanes. Some manufacturers use polyurethane for tyres of off road tyres (OTR), industrial and agricultural machinery types, usually by reaction injection molding technique (RIM). In some cases tyres are also produced by millable polyurethane elastomer. Focusing on excellent abrasion resistance of polyurethanes, in this research blends of PU/SBR in different ratios are studied with different curing systems. The properties of the blends are studied before and after aging. Our analysis showed that PU/SBR blend with ratio of 25/75 has greater improved aging property, abrasion resistance and tear strength compared with non-blended SBR.

Two functional monomers of bisphenol A-glycidyl methacrylate using epoxy-based bisphenol-A (DGEBA) and methacrylic acid (MAA) were synthesized in presence of suitable catalyst. Reaction conversion was monitored with specific peak heights of reactants' FTIR spectra. The effect of temperature program on reaction time was also studied. The purified product was characterized using FTIR, H NMR, elemental analysis and titration. The results indicate that a product with high purity is synthesized. Finally a dental composite was made of the monomer, and the physical and mechanical properties of the composites were measured.

Leaf spring is the main member of heavy vehicle suspension system. The important role of leaf spring is the absorption of energy in the form of strain energy, due to various applied forces. Based on the strain energy relationship, the material with high tensile strength and low elasticity modulus is the best candidate for this purpose. Continuous fiber reinforced polymeric composites, in addition to the above mentioned properties, are of low density, so they can be used in manufacturing of leaf spring. In this work, the replacement of six layers of metallic leaf spring by a polymeric one, with the similar geometrical shapes, are investigated and analyzed. First, the geometric dimensions of polymeric composite leaf spring in comparison with the of metallic types were estimated, and then the behavior of composite leaf spring was studied using ANSYS software. The results showed that the designed polymeric composite leaf spring not only satisfied all the essential requirements of metallic one, but also it reduced the weight of leaf spring by 79%. The critical normal force for polymeric composite leaf spring is 26436 N and its stress distribution is more uniform than metallic type.

Monte Carlo method is one of the most powerful techniques to model different processes, such as polymerization reactions. By this method, without any need to solve moment equations, very detailed information on the structure and properties of polymers are obtained. The number of algorithm repetitions (selected volumes of reactor for modeling which represent the number of initial molecules) is very important in this method. In Monte Carlo method calculations are based on the random number of generation and reaction probability determinations. So the number of algorithm repetition is very important. In this paper, the initiation reaction was considered alone and the importance of number of initiator molecules on the results was studied. It can be concluded that Monte Carlo method will not give accurate results if the number of molecules is not satisfied to be big enough, because in that case, selected volume would not be representative of the whole system.