مجله ایرانی پلیمر
سال:1387 | دوره: | شماره: |تعداد مقالات:6

The kinetics and mechanism of cure reaction of DGEBA with 4,4’-oxydianiline(ODA) as curing agent in the presence of thermoplastic ABS was studied using isothermal FTIR and dynamic DSC techniques. The activation energy (Ea) by FTIR analysis was evaluated as 36 kJ/mol and decreased to 31 kJ/mol when the amount of ABS was increased from 10% to 30% by weight. Thermodynamic parameters (DH#, DS#, and DG#) for isothermal curing were calculated and the value of DG# did not change significantly by increasing the amount of ABS, while it increased with increasing isothermal curing temperature. The maximum temperature (Tp) of the exothermal peak in DSC thermo gram increased with increasing heating rate. The values of Ea by using DSC data and Kissinger, Ozawa-Flynn-Wall, and is conversional equations were in the range of 55-65 kJ/mol. There was a small decrease in the Ea value by increasing the amount of ABS which can be related to the ease of diffusion of functional groups through the network and/or the catalytic influence of the nitrile group (-CN) on the mechanism of cure reaction.

The aim of the study was to prepare bioactive and bioabsorbable composites of polylactide/wollastonite (PDLLA/W) and evaluate their mechanical properties and biocompatibility in vitro. PDLLA and wollastonite were physically mixed and the mechanical properties of the composition showed the influence of wollastonite, and that a partial composite, e.g., a PDLLA/wollastonite composition with 15 wt% wollastonite (PW-15) has similar mechanical properties compared to pure PDLLA. However, an in vitro biocompatibility testing showed that the composite has no deleterious effects on the osteoblast cells and facilitates both adhesion and proliferation of the osteoblast cells on the PDLLA/wollastonite film surface. The introduction of wollastonite could also induce the deposition of hydroxyapatite (HA) on the surface of the composite in simulated body fluids (SBF) which has important implications on bone regeneration. These mechanical and biocompatibility properties represent PDLLA/wollastonite composites as potential biomaterials.

The principal objective of this study was to explore the compatibility of a blend of two synthetic elastomers viz., ethylene-propylene-diene rubber (EPDM) and chlorobutyl rubber (CIIR). Various commercial grades of EPDM were blended with a specific grade of CIIR at different proportions. The mechanical properties such as tensile strength, tear strength, ageing resistance, etc. were studied. On the basis of the observed physical properties, two particular grades of EPDM were found to be compatible with CIIR. Differential scanning calorimetry and scanning electron microscopy confirmed the results. Chlorosulphonated polyethylene was added as a compatibilizing agent to overcome the phase separation of the other two incompatible grades of EPDM in blending with CIIR. The results revealed that the addition of compatibilizer greatly improves the compatibility and thereby the properties of the blends.

The effects of chain extender length on the gas permeability of polyether-based polyurethanes were investigated. Synthesized polyurethanes were based on 1000 and 2000 molecular weight polytetramethylene-glycol (PTMG) with toluene diisocyanate (TDI). Ethylene glycol, 1,4-butane diol (BDO), 1,6-hexane diol (HDO) and 1,10-decane diol (DDO) chain extenders were used to complete the conversion of prepolymers to the final polyurethanes. Membranes made from polyurethane were used to study the permeability and diffusivity of nitrogen, oxygen, methane, and carbon dioxide.Lag time method was used to determine the diffusivity of gases in polyurethanes. This study indicated that glass transition temperature of the polymers decrease by chain extender's length. The increase in chain extender's length makes the phase separation more probable. DSC and FTIR studies also indicate the extent of the phase separation in polyurethanes. Permeability and diffusivity of gases increase with the increasing length of the chain extenders. Selectivity of CO2/N2 changed by chain extender length, while selectivity of CO2/CH4 and O2/N2 did not show any remarkable changes. This study shows that solubilization is the dominant mechanism in gas permeation process in polyurethane membranes.

The liquefaction of palm oil empty fruit bunch (EFB) in phenol was carried out in the presence of sulphuric acid as a catalyst in the reflux-condenser system. The effects of the reaction temperature and sulphuric acid concentration on the liquefaction reaction, physical, and mechanical properties of phenolated EFB (PEFB) resin were studied. The reaction yield increased as the reaction temperature and catalyst concentration increased from 110°C to 150°C and 3% to 8%, respectively. However, no significant difference in results was observed between samples reacting at 130°C and 150°C using 5% and 8% catalyst. The thermal gravimetric analysis tests have indicated that the thermal stability of PEFB increases by increasing the catalyst concentration. However, the results do not show any important variation in the thermal stability by increasing the liquefaction temperature. From studies of differential scanning calorimetry it was found that the curing enthalpy of PEFB with hexamethylenetetramine increases by increasing the liquefaction temperature.

Superabsorbent polymer (SAP) materials are hydrophilic networks that can absorb and retain huge amounts of water or aqueous solutions. They can uptake water as high as 100,000%. Common SAPs are generally white sugar-like hygroscopic materials, which are mainly used in disposable diapers and other applications including agricultural use. This article reviews the SAP literature, background, types and chemical structures, physical and chemical properties, testing methods, uses, and applied research works. Due to variability of the possible monomers and macromolecular structure, many SAP types can be made. SAPs are originally divided into two main classes; i.e., synthetic (petrochemical-based) and natural (e.g., polysaccharide- and polypeptide-based). Most of the current superabsorbents, however, are frequently produced from acrylic acid (AA), its salts, and acrylamide (AM) via solution or inverse-suspension polymerization techniques. The main synthetic (internal) and environmental (external) factors affecting the acrylic anionic SAP characteristics are described briefly. The methods for quantifying the SAP practical features, i.e., absorption capacity (both load-free and under load), swelling rate, swollen gel strength, wicking capacity, sol fraction, residual monomer, and ionic sensitivity were discussed. The SAP applications and the related research works, particularly the hygienic and agricultural areas are reviewed. Meanwhile, the research findings on the effects of SAP in soil and agricultural achievements in Iran, as an arid country are treated as well. Finally, the safety and environmental issues concerning SAP practical applications are discussed as well.