Iranian Journal of Polymer Science and Technology
Year:2006 | Volume:19 | Issue:3 (ISSUE NO. 83)|Papers Count:10

In this research two major methods for production of synthetic papers based on polyvinyl chloride (PVC) was studied.The effect of stretching and extraction on films based on neat PVC and PVC/NBR (butadiene acrylonitrile rubber) blends to obtain paper-like cellulosic property was analyzed. In the extraction method, PVC and PVC/NBR blends in the stretching method only the PVC/NBR blend were used. Sugar was used as extractable filler with solvent (water) to produce 35-40 percent volume porosity measured by Archimedes methods. Also, it was shown that by decreasing sugar particle size, average pore size is reduced as well. It was also shown that temperature effect on permeation is greater than acid concentration. This paper like substrates for writing with pencil and pen were assessed fair to poor. In the second part the effects of temperature, rate and extent of stretching on the ink dispersion as a criterion of surface roughness or irregularity compared to cellulose paper were investigated. The results indicate a direct correlation of ink dispersion increase with increase in temperature and the degree of stretching. But the increase in stretching rate would result in lesser dispersion at constant temperature and stretching rate.

The properties of acrylonitrile-butadiene rubber and poly (vinyl chloride) (NBR/PVC) blends are governed by mixing procedure, which can be quantitatively expressed in terms of the mixing conditions and feed forward of any polymer to the mixing chamber. In this research, the effect of mixing procedure on mechanical and rheological properties of NBR/PVC blends is investigated. NBR/PVC blends with different mixing temperatures and rotors speeds were melt mixed in internal mixer. The effect of these parameters was studied using torque-time profiles of internal mixer, curing characteristics, swelling index measurement and mechanical properties. Results show that NBR/PVC blends properties change with mixing at various temperatures and rotor speeds. The optimized conditions were achieved from the results. Also, it is evident from the data when PVC content in the NBR/PVC blends increases, the tensile strength, modulus and hardness increase but resilience of the blends decreases.

Due to good properties of polypropylene, such as stiffness, inertness to foods, stress crack resistance, clarity and high service temperature, it is a natural fit for many applications that are fabricated by thermoforming process. In spite of these benefits, excessive sagging and narrow forming window are disadvantages of PP in thermoforming. One of the methods to improve the thermoform ability of this material is incorporation of mineral filler into PP. The filler used at the present research was calcium carbonate (CaCO3) at three levels (10, 20, 30 wt. %). Compounding was carried out in a ZSK25 co-rotating twin screw extruder. Sagging behavior and mechanical properties at elevated temperatures were evaluated to estimate the thermoforming behavior of mineral-filled PP. The load at yield and elastic modulus increased by CaCO3 while elongation-at-yield decreased. Incorporation of CaCO3 into PP up to 20% wt improved the sagging resistance of polypropylene.

In accordance with specific properties of fungal chitosan, the chitosan production in solid substrate fermentation (SSF) by fungi has been introduced as a new method to produce this valuable biopolymer. In this work A. niger strains were grown on different solid substrates of soybean, corn seed, cotton seed and colza seed residue as nitrogen containing substrates to study the production potential of chitosan. The effects of nitrogen content, fungal strain and moisture content of solid substrate in chitosan production were studied. The results of this study illustrate that, in all of A. niger strains, PTCC 5012, PTCC 5103, PTCC 5010, the amount of chitosan at 4th day of fermentation with ca. 37% moisture and pH =6.4 (in case of cotton seed and soybean) was about 12.691 (g/kg dry substrate). The highest amount of production by PTCC 5012 strain in soybean residue substrate at ca.37% moisture in 12th day of fermentation reached 17.053 (g/kg dry substrate), and by PTCC 5010 strain in cotton seed residue medium in the 8th day, 17.97 (g/kg dry substrate) chitosan was obtained.

In this research the effect of four different coupling agents, widely used in rubber industry, on mechanical properties of natural rubber/reclaim rubber blend is investigated. Used coupling agents are triallyl ciyanurate (TAC), bis (3-triethyloxysiloylpropyl) tetrasulfide (Silane Si69), m-phenylenedimaleimide (HVA-2), and Rhenofit 1986, a combination of activating substances based on urea and surface-active agent. The results show that HVA-2 and Rhenofit do not improve mechanical properties of natural rubber/reclaim rubber blend. Silane (Si69) increases tensile strength and hardness while it does not enhance elastic based properties such as resilience, fatigue life and compression set resistance. While TAC coupling agent increases the tensile strength but has no significant effects on modulus and elongation- at-break.

The joint adhesion strength of low density poly ethylene to thermoplastic plasticized starch (TPS) and their compatibilized versions with poly (ethylene-co-vinyl acetate) (EVA), maleated polyethylene (PE-g-MAH) and maleated styrene-ethylene-butadiene-styrene block copolymer (SEBS-g-MAH) were investigated with peel-test. For localization of the compatibilizers at PE/TPS interface, they were blended with TPS. In addition, thermodynamic work of adhesion between joint components was evaluated by contact angle measurements by applying the existing theories.The results obtained showed the thermodynamic work of adhesion increment from 64 mJ/m2 for PE/TPS to 70, 79, 86 mJ/m2 for compatibilized interface by EVA, PE-g-MAH, and SEBS-g-MAH, respectively. The adhesion improvement was attributed to comatibilizer migration to the interface during high temperature joint formation and resultant enhanced stress transfer capability at the interface. Furthermore, joint loss function was to depend not only on joints main components tan d ratio at room temperature but also on tan d of the thin layer of compatibilizers. Therefore, a new parameter was introduced namely tan d of the peel arms to the adhesive tan 8 multiplied by the compatibilizers tan d to rationalize the observed data.

Low and high molecular weight chitosan microspheres have been prepared by spray drying. The morphology, particles size distribution, the rate of prednisolone release as a model drug has been studied. The polymer-drug interaction has been examined by SEM, laser light scattering, cell diffusion differential scanning calorimetry. The results have shown that the particles obtained are totally spherical with some surface contraction. The size of chitosan microspheres with high molecular weight is higher than particles with low molecular weight. The average size of microspheres has increased from initial 1.3μ to 9μ as molecular weights have increased. This can be attributed to viscosity increase of high molecular weight chitosan solution. The rate of prednisolone sodium phosphate release from chitosan microspheres of high molecular weight, due to the compact structure and high solution viscosity is less than the micro spheres obtained from low molecular weight. The DSC thermograms demonstrate the interaction between phosphate groups of the drug and amine groups of chitosan.

The shrinkage of unsaturated polyester (UP)/styrene system cured at low temperature can be reduced by the presence of low-profile additives (LPAs), especially thermoplastics. In this study the effect of molecular weight of polyvinyl acetate (PVAc) (Mw =100 × 103 and Mw =290 × 103 g/mol) as low-profile additive on the volume shrinkage and the rate of volume change was investigated by dynamic shrinkage curing apparatus at room temperature. The phase separation and reaction kinetics during curing were also investigated. Shrinkage kinetic study shows that with decreasing molecular weight, the shrinkage starts at earlier stage. Finally it is revealed that the effect of polyvinyl acetates on shrinkage control is independent of its volume fraction of thermoplastic-rich phase and the phase separation period.