Iranian Journal of Polymer Science and Technology
Year:2013 | Volume:26 | Issue:1 (ISSUE NO. 123)|Papers Count:8

This study is devoted to the study of carbon black blends in passenger tire tread compounds with respect to their mechanical, dynamical and thermal properties. A reference compound based on SBR/BR and 60 phr carbon black as reinforcing filler was initially designed. Ten samples based on this compound were prepared using four different types of carbon black. The mechanical, dynamical and thermal tests were carried out on appropriate samples made from these compounds to determine tensile strength, elongation-at-break, abrasion resistance, hardness, resilience, tan δ and heat build-up. The results indicated that the compound containing N550 carbon black has the lowest abrasion resistance and temperature rise. On the other hand, the compound containing N220 carbon black showed the highest temperature rise, energy dissipation and abrasion resistance due to high structure and iodine adsorption number. To achieve improvement in mechanical and dynamical properties, mixtures of carbon blacks were used and the best results (low rolling resistance, high abrasion resistance and high traction) were obtained. We have shown in our previous research works that the viscoelastic behavior of cured compounds can be accurately described by the experimental data of tensile deformation vs. force of rubber strips and its corresponding finite element models. Therefore, a new method for calculating the energy dissipation was proposed which was based on the finite element modeling of the tension in an in-house designed rubber sample. The results obtained by employing this technique were in very good agreement with the experimentally measured dynamical data.

Fluid properties with constant improvement in efficiency have been noticeable as important criteria in drilling operation. The main drilling fluid properties highly depend on utilization of new polymers with high efficiency in drilling fluid composition. In this paper, the performance of a new polymer, called partially hydrolyzed polyacrylamide polymer (PHPA), is studied which has recently entered the drilling fluids industry in Iran. Hence viscosity property, fluid loss control and shale inhibition of this polymer have been evaluated based on an international standard method of API-13-I by considering the drilling and operational priorities of the country. Then the thermal effect, salt contaminants such as sodium chloride, calcium chloride, magnesium chloride and pH tolerance effect as major pollution indicators are also investigated in relation to polymeric fluid properties. The results obtained by the tests show that furthermore polymer PHPA increases rheological properties (apparent viscosity, plastic fluidity and yield point) and it plays important role in increases in fluid loss. This polymer has also demonstrated acceptable resistance toward sodium chloride contaminants, but its efficiency decreases toward calcium and magnesium ion contaminants. The thermal tests show that polymer PHPA has high thermal stability up to 150°C. This polymer improves shale inhibition property and by encapsulation mechanism prevents dispersion of shale cuttings into the drilling fluid system as it stops any changes in fluid properties which will finally results in wellbore stability.

The substituted (bis-2-PhIndZrCl2) and non-substituted (bis-IndZrCl2) indenylbased metallocene catalysts were synthesized and used in homogenous and heterogeneous forms for copolymerization of ethylene and 1-hexene. The MCM- 41 nano silica was used as support in heterogenization of the catalysts. The substituted (bis-2-PhIndZrCl2) metallocene catalyst in homogenous and heterogeneous forms showed lower activities in comparison to non-substituted (bis-IndZrCl2) metallocene catalyst. The microstructures of the obtained copolymers were investigated by techniques such as DSC, CNMR and TRRF. The kinetic study showed that the decay index (DI) was decreased for both homogeneous catalysts due to unstable kinetic behaviors. However, the decay index contents approached one, using heterogeneous forms of catalyst which was an indication of stable kinetic behaviors. The kinetic results also displayed negative effect on the catalysts activities both in the homogeneous and heterogeneous forms by addition of comonomer on the polymerization. The triad distributions of obtained polymer by NMR technique exhibited the higher ratio of EEH, EHE, EEE triads than the other triads. The comonomer incorporation acceptability of substituted metallocene catalyst (bis-2-PhIndZrCl2) was higher than non-substituted catalyst (bis-IndZrCl2) as its comonomer acceptability increased from 1.3% to 5.4% by substitution mechanism. Microstructures of copolymers obtained by supported metallocene catalyst showed more non-uniform comonomer distribution in comparison with unsupported catalyst. The lamella thickness distributions for polymer obtained by supported substituted metallocene catalyst (bis-2-PhIndZrCl2) were in the ranges (3-8 Ao). However, for supported metallocene non-substituted catalysts (bis- IndZrCl2) the lamella thickness were in the ranges (3-16 Ao).

Alginate belongs to a group of natural polymers called polysaccharides. They have carboxylic functional groups beside hydroxyls which are common in all polysaccharides. These materials show interesting properties due to their functional groups. One of these properties is the ability of this polymer as a suitable carrier of protecting and transferring drugs and biomolecules. The particle sizes of these polymers are very important for their applications, so different techniques were used for preparation of these materials. In this way polymeric nanoparticles of calcium alginate which are excellent carriers in drug delivery systems were prepared by addition of calcium chloride solution to dilute solution of sodium alginate. Investigation of the size and distribution of nanoparticles were analyzed by SEM method. The concentration effects of both alginate and calcium ions on the size and distribution of nanoparticles were studied in this research. Results showed that the size of nanoparticles obviously decreased with decreasing polymeric alginate concentration because of lower active sites in polymer chain. On the other hand, the size and distribution of nanoparticles are significantly improved with increase of calcium cation concentrations. The mean particle size 40-70 nm and spherical shape are the main characteristics of the prepared nanoparticles.

Microcapsules containing n-hexadecane (HD) as the core and melamineformaldehyde (MF) prepolymer as the shell were prepared by in-situ dispersion polymerization. The effects of surfactants type and amount were studied in relation to the morphology and thermal properties of microcapsules. The morphology of the microcapsules was studied using scanning electron microscopy (SEM) and thermal properties were detected by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SEM images showed that the increase in the amount of Triton X-100 (non-ionic) to SDS (ionic) ratio resulted in the agglomeration of the prepared microcapsules. This increase led also to lower encapsulated hexadecane and thermal stability of microcapsules. As a result, the optimum composition of the above surfactants for obtaining higher thermal stability and proper morphology was found to be 20 wt% of Triton X-100 and 80 wt% of SDS in the recipe. The optimum total amounts of surfactants was 4 wt%, which resulted in spherical and separate microcapsules. DSC and TGA analyses revealed that a sample prepared with 4 wt% of surfactants was not only successful in encapsulation of hexadecane but also showed higher thermal stability compared with other formulations.

Dynamic and transient shear flow experiments along with TEM, SAXS and SEM analyses were performed for 75/25 and 25/75 (wt%/wt%) PP/PET blends containing two types of montmorillonite organoclays namely, Cloisite 20A and Cloisite 30B. The weight ratio of Cloisite 20A to Cloisite 30B was equal to PP/PET weight ratio in the blend nanocomposites. The TEM and SAXS analyses revealed that all clays were almost localized at the interface of PP-rich blends whereas in PET-rich blends they were localized at both PET matrix as well as the interface of the blend. The SEM analysis showed that in a PET-rich system the size reduction of minor phase by addition of the organoclay was more than that of the PP-rich system. In contrast to the neat blend, the PP-rich blend nanocomposite showed thermo-kinetically stable phase morphology under annealing at a high temperature. In agreement with the morphological findings, the rheological investigations under oscillation shear flow field at low and high frequencies as well as those under transient shear flow field at low and high shear rates revealed that addition of organoclays to the blends had stronger effect on the rheological behavior of the PET-rich system as compared to that of the PP-rich blend. This was explained by the different localization of the organoclays and the different weight ratio of the two types of clays in the PP-rich and PET-rich blend systems leading to a stronger network-like structure formation of clay layers in PET- rich blend nanocomposites.

Novel collagen-based hydrogel nanocomposites were synthesized by graft copolymerization of acrylamide and maleic anhydrid in the presence of different amounts of montmorillonite, using methylenebisacrylamide (MBA) and ammonium persulfate (APS) as crosslinker and initiator, respectively. The optimum amount of clay on the swelling properties of the samples was studied. It was found that the hydrogel nanocomposites exhibited improved swelling capacity compared with the clay-free hydrogel. Gel content was also studied and the results indicated that the inclusion of montmorillonite causes an increase in gel content. The sorption behavior of heavy metal ion from aqueous solutions was investigated by its relationship with pH, contact time, initial concentration of metal ion and also, montmorillonite content of the nanocomposites. The experimental data showed that Cd2+ion adsorption increases with increasing initial concentration of Cd2+ion in solution and the clay content. Also, the results indicated that more than 88% of the maximum adsorption capacities toward Cd2+ion were achieved within the initial 10 minute. Functional groups of the prepared hydrogels have shown complexation ability with metal ions and improving hydrogels’ adsorption properties. It was concluded that the nanocomposites could be used as fast-responsive, and high capacity sorbent materials in Cd2+ion removing processes. The prepared hydrogel nanocomposites were characerized by means of XRD patterns, TGA thermal methods and FTIR spectroscopy. The XRD patterns of nanocomposites showed that the interlayer distance of montmorillonite was changed and the clay sheets were exfoliated. Furthermore, the results showed that by increasing the montmorillonite content, thermal stability of the nanocomposites was clearly improved.