Iranian Journal of Polymer Science and Technology
Year:2005 | Volume:18 | Issue:3 (ISSUE NO. 77)|Papers Count:12

To optimize four properties of the top layer rubber compound of a general-purpose conveyer belt including its curing time, material cost, abrasion and tensile resistance a statistical experimental design method (Taguchi method) together with the overall evaluation criteria (OEC) method have been used. In the first step the OEC method has been used to combine these four properties in to one. Then 14 main factors and 12 interactions are considered and for them an L32 orthogonal array in two levels has been used. Statistical analysis of this step result showed that interactions are not important and so can be excluded from forwarding works. In the second step a L16 orthogonal array in 4 levels was considered, which resulted in one factor optimization and reaming of 4 others that are sent to the next step for additional works. In the third step, an L9 orthogonal array in three levels was considered in which all the remaining factors are optimized. The final optimized formulation in addition to having better mechanical properties than elementary formulation, showed a cost reduction more than 50% including the material and process cost reduction. All experiments were at least repeated twice to make completely sure of all the obtained data.

The objective of this study was to investigate the effect of combination of impact modifier on the mechanical properties and morphology of cellulose fiber polypropylene (PP) and high density poly ethylene (HDPE) composites. The impact modifier was ethylene-propylene-diene monomer (EPDM) for PP and ethylene vinyl acetate (EVA) for HDPE and fibers were of alpha cellulose and wastepaper. The elastomer (modifier) was mixed with composite at 5, 7.5 and 10% by weight and the fillers were mixed with PP at 35% and HDPE at 30% by weight. The results have indicated that the notched impact strength, elongation-at-break and bending strains have increased with the inclusion of elastomer, but the tensile strength, bending strength and modulus of elasticity have decreased. The impact modifier, however, did not affect the hardness. The fibers enhanced the tensile strength, bending strength, hardness and modulus of elasticity but decreases were noticed for the impact strength, tensile and bending strains. In fact the highest impact strength was obtained by adding 10% elastomer to the composites, and the highest value for tensile strength, bending strength, hardness and modulus of elasticity were attributed to the absence of elastomer (except the pure polymer).

A sandwich structure must have thin, dense, high strength facings, a low density core, which is usually thick, relatively weak, a rigid and strong attachment between them. Sandwich structures are being increasingly used in aerospace, buildings, and automotive industries, because they have high specific strength, stiffness, good thermal and acoustical insulation properties. Because of potentially low cost and high thermal resistance of phenolic resins they are attractive for using as the matrix in the facings and the core materials. Having a little knowledge of the manufacturing of phenolic sandwich, structures, in this research we have manufactured sandwich panels by compression molding employing two alternative methods: Co-cure and counter cure processes. In a co-cure process, the core and composite skins cured simultaneously but, in counter cure process the core with certain density and thickness are first prepared and cured with the skins as the second stage. The influence of the selected process on the flexural properties of the sandwich panels has been experimentally investigated, leading to the identification of the preferred processing conditions.

The rheological properties of the first stage (i.e., incorporation step) of mixing of rubber and carbon black in internal mixers are studied. The SBR and N330 were selected as the raw rubber and filler, respectively. Rheological measurements were carried out by the use of a modern rubber process analyzer instrument known as RPA 2000. A new method was developed based on experimental simulation of the mixing process in rheometer for the viscosity and modulus of rubber compound during incorporation step. A series of rubber/carbon black mixtures with different agglomerate sizes were first prepared in a laboratory internal mixer at various mixing times. Then an empirical relation was proposed to predict the effective filler volume fraction (EFVF) from mixing time, initial filler volume fraction, size of agglomerates and applied frequency in rheometer. A sharp increase in viscosity of a mixture during the incorporation stage is observed which is due to the immobilization of entrapped: rubber in filler agglomerates and increasing the filler content known as EFVF. A similar trend but in opposite direction was previously reported for the second stage of mixing and dispersion. The results of this research and those reported for the second stage of mixing are in close agreement.

Drying of PET chips is an important stage in the production of polyester fibers. This is because of high sensitivity of the ester groups in PET chips to hydrolysis due to the presence of water molecules. The PET continuous yarns have been spun at 3200 m/min so to become partially oriented yarn (POY) for further processing step such as texturizing. In this research the effects of drying condition of PET chips on the properties of resultant texturized yarn was studied. The drying temperatures of 170, 175 and 180°C were chosen for PET chips and the properties of resultant texturized yarn such as tenacity, elongation, dyeability, thermal shrinkage, loop formation and crystallinity were investigated. The results showed that drying temperature of PET chips has statistically meaningful influence on the properties of resultant texturized yarn.

Diisocyanate terminated polycaprolactone was prepared and characterized by FTIR spectroscopy. Then, two groups of blends were prepared by using: (1) LDPE/starch, (2) LDPE/starch/polycaprolactone prepolymer. By studying the mixing process, it was evident that torque of mixing decreased after increasing the starch content. The final melt temperature was slightly shifted above the set temperature. SEM was used to study dispersion of the starch granules and polycaprolactone prepolymer in polyethylene matrix as well as the morphology and interfacial adhesion between the two phases. It was found that by adding starch to polyethylene, tensile and elongational properties are decreased. Applying some biodegradable polycaprolactone prepolymer to the compound showed improvement to its final properties.