Iranian Journal of Polymer Science and Technology
Year:2006 | Volume:19 | Issue:4 (ISSUE NO. 84)|Papers Count:10

Emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA) in water was carried out using a basic formula from the raw materials and a semi-batch method in a laboratory scale. Five series of lattices were synthesized by changing ratio of sodium dodecyl sulphate (SDS) to nonyl phenol polyethylene glycol ether (NP-20) in pre-feeding and emulsion solution and also the initiator concentration. All of the syntheses were carried out in the same condition using a constant molar ratio of monomers, water amount and sodium bicarbonate (as a buffer) with the aim of obtaining the highest conversion. The physical properties of the latex samples were also measured. The final conversion of the A 5-2 and A 5-3 samples was above 96% by using molar ratios of SDS to NP-20 in pre-feeding, 1.96 for both samples, and in emulsion solutions, 1.47 and 0.98, respectively and also 4 wt% solution of potassium persulphate for each synthesis. The typical sample, A 5-2 showed 14.5 min drying time, 3.88% absorbed water, the amount of adhesion IB and the cup flow time of 26.3s.

An experimental study has been carried out to evaluate the drag characteristics of different self- polishing acrylic copolymers (SPC) (tin base and tin-free) and a foul release coating. Drag measurements have been performed on a smooth cylinder and different painted surfaces using a rotor device, using differential length technique to avoid the end effects. Surface energy of the coated samples was determined using static contact angle measurement. Characteristic roughness measurements of different painted surfaces were evaluated with SEM technique. Drag measurements results showed that the frictional resistance of foul release coated test cylinders was lower than for all SPC coated cylinders. The surface become relatively hydrophilic when coated with self- polishing co-polymer paint. Foul release systems offer a low-energy surface that can prevent firm adhesion of fouling organism's underwater hulls. SEM Study revealed minor roughness of foul release system compared to SPC systems. The measurements indicate that the texture of the foul release surface is considerably different from SPC systems. It may be concluded that the drag characteristics are related to the surface free energy and the roughness parameters of the tested surfaces.

Using reclaimed rubber blended with virgin rubbers changes rheological and viscoelastic properties of rubber. In this research, the effect of adding reclaimed rubber to natural rubber is investigated using rubber processing analyzer (RPA). The results show that in low shear strain elastic modulus and elastic torque of reclaimed rubber are more than natural rubber due to the presence of filler in reclaimed rubber. But, in medium shear strains non-linear viscoelastic domain in reclaimed rubber is longer in comparison with natural rubber. In high shear strains zone, the non-linear viscoelastic behavior diminishes. The length of this zone in reclaimed rubber and reclaimed rubber/natural rubber blends is shorter than in natural rubber. Viscoelastic properties of each blend are similar to the major phase of the system. However, in all blends compositions the modulus and torque of the compound are lower than both reclaimed rubber and natural rubber. This can be attributed to non-homogeneity of phases.

Production and application of polymeric pipes are nowadays increased together with the progress in polymer science and technology. The conventional production of plastic pipes, i.e. using extrusion with plain die, is not technically evaluated due to the axial orientation of long polymeric chains and the existence of spiders which cause weld line (s), so the produced pipes have no significant hoop strength. To diminish the effect of weld line and to produce strong pipes in the hoop direction, the rotating die system can be used. In this work, the variation of mechanical properties of unreinforced and reinforced pipes was investigated as a function of die core rotation speed. The results show the hoop strength of HDPE, PP and glass reinforced samples (20% by weight) is increased 20%, 25% and 34%, respectively at 20 rpm rotation speed of inner member. Also, the results of hydrostatic tests indicate that the pipes produced with the rotating die system exhibit higher load-bearing capacity and good lifetime. In this case, 13% of extrudate increment at 30 rpm of inner member was observed. Also, isotropic properties for pipes produced with HDPE and pp were obtained at 10 rpm and 4 rpm of rotating inner member, respectively. X-Ray shows that the crystallinity increased by 20% at 20 rpm rotation speed of mandrel. In this system not only the die swell does not occur, but also deswelling phenomenon is observed.

Hydrolysis of ester bonds in alkyd and polyester resins is one of the major defects in water-reducible coatings. Shelf life of paints containing these kinds of resins is usually short because of this defect. In this research, hydrolytic stability of water-reducible alkyd resins has been improved by employing the polyacid acrylic copolymers in alkyd resin structure. The effect of reaction conditions and raw materials on the synthesis of the resins and their dried films were investigated. The results showed that acrylic copolymers with acid value of about 135 and oil length of about 25 are suitable for synthesizing these kinds of resins. It was also observed that the resins which were neutralized with DEA had a better hydrolytic stability comparing to those neutralized with TEA. The optimum extent of neutralization was obtained to be 50 percent. Finally, the results showed that the synthesized alkyd resins had very good hydrolytic stability. The acid value of the desired resin decreased only 23.5 percent after four months storage.

The effect of wheat and rice straw particles at three levels of 15, 30 and 40 % wt as well as straw particle size on mechanical properties of straw-high density polyethylene composites were investigated. Maleic anhydride as a coupling agent as well as dicumyl peroxide as initiator were used. In general, the results showed that adding wheat straw up to 30 wt% could result in improving tensile and bending strength. But at 40 wt% the aforementioned strength were decreased. Increasing straw resulted in decreasing impact strength. The composites containing fine particles showed higher impact and bending modulus, compared to those made of coarse particles. The composites made of wheat straw showed higher mechanical strength than the rice. Specimen containing 30 wt% straw-both fine and coarse particles with or without maleic anhydride, performed by statistical t-student test, were significantly different in terms of mechanical strength and the adhesive between the polymer and straw particles on the base of SEM result.

In this research, insoluble poly (3-mercaptopropylsiloxane) was prepared by hydrolyzing mixture of tetraethoxysilane (TEOS) with 3-mercaptopropyl trimethoxysilane (MPTS) in the presence of a tin catalyst. Many products were pre pared using different mole ratios of TEOS to MPTS (i.e., 5:1, 2:1, 1:1, 1:2, and 1:5).The best mole ratio, which gives the highest metal uptake for the ligand was chosen for further evaluation. Then, the capability of this ligand in extraction of heavy metal ions (i.e., Pb 2+,Cu 2+,Ni 2+,Zn 2+,Hg 2+,and Cd 2+) from their solutions was determined at different pHs (2 ≤ pH ≤ 8). Atomic absorption and complexometric titrations were used for determination of metal content in metal ion solution.

In this work, the effect of silane compounds on the adhesion strength of two acrylic lacquers with carboxyl and hydroxyl functionalities on the flame pretreated polypropylene (PP) was investigated. Contact angle measurements, SEM, AFM and FTIR-ATR techniques were employed to study the changes in the surface characteristics of PP after flame and silane treatments. The surface became relatively hydrophilic on exposure to the direct flame and a relative increase in the surface free energy of PP was observed. Investigations of the treated surfaces by SEM and AFM showed that the surface roughness increased after flame pretreatment. Two organ functional silanes with different concentrations were then applied on the flame pretreated surfaces using the wet method. FTIR-ATR Analysis showed formation of carbonyl group and carbon double bonds on the flame pretreated surfaces and also having applied the silanes, organofunctional group of the silane appeared on the surface. Using pull-off test method, adhesion strength of lacquers was measured. The experimental results showed that the silane compound with epoxy organofunctional group may considerably increase (300%) the adhesion strength of acrylic lacquer with carboxyl functionality to the flame pretreated polypropylene surface.