Iranian polymer journal
Volume:18 Issue: 5, 2009

Post-operative adhesions are an unavoidable and serious complication, which can cause severe pelvic pain, infertility and bowel obstruction. Many pharmacological and macromolecular polymers have been tested for adhesion prevention. Recently, physical barriers have greatly attracted people''s attention. In this paper, we study the efficacy of thermosensitive hydroxybutyl chitosan (HBC) in prevention of post-operative abdominal adhesions, using a rat side-wall defect-cecum abrasion model. HBC is a new derivative of chitosan whose main character is the intelligent response to changing temperature. HBC was prepared through chemical modification of 1,2-butylene oxide, whose molecular weight was higher than other reported products. The lower critical solution temperature was established as 20ºC at a concentration of 1% (w/w). When injected into the abdomen, HBC solution formed flexible hydrogels within 30-60 s. A durable physical barrier was formed between the defective cecum and the abdominal side-wall. Eight out of 10 animals in the control group developed adhesions with a score of 3, while only one of 10 animals treated with HBC showed such adhesions. Compared with non-cross-linked hyaluronic acid, HBC demonstrated more anti-adhesive activity. Furthermore, HBC was easy to handle during operation. Therefore, it may be effective in prevention of post-operative adhesions.

In situ polymerization of ethylene was used to prepare silica/PE parent material (46.8 wt% of SiO2), which was then blended with PE (and PP) to synthesize silica/polyolefin nanocomposites (a two-step method), such as PE05, PE10, and PE20 (or PP05, PP10, and PP20), whose silica contents were 0.5 wt%, 1.0 wt%, and 2.0 wt%. For comparison, silica/polyolefin nanocomposites with 2.0 wt% of SiO2 were also prepared via blending method (PE20M and PP20M). TEM, TGA and tensile test characterization results showed that the nanocomposite prepared via the two-step method behaved better than that prepared via blending method, as for nanosilica dispersion, thermal stability, crystallinity, and tensile mechanical properties. For example, the dispersion of nanosilica particles in PE20 was better than that in PE20M. The temperatures of maximum weight loss rate (Tp), crystallinity and strength of PE20 were 472ºC, 68.3% and 28.3 MPa that were improved compared with those of PE20M, which were 430ºC, 66.3% and 26.3 MPa, respectively. Furthermore, the two-step method could utilize minimum amount of in situ polymerization product to produce maximum amount of nanocomposite. All these findings have shown that the two-step method can easily and cheaply produce silica/polyolefin nanocomposites with high quality.

In the present work, ethylene-propylene block copolymer (EP90) and ethylene-propylenerandom copolymer (EPR) were separated from a PP/EPR in-reactor alloy. TheEP90 and EPR were then blended with neat isotactic polypropylene (PP) at variousproportions to obtain ternary blends. The isothermal crystallization kinetics and morphologyof the ternary blends were studied and were compared with those of PP/EP90 binary blend. It is observed that the Avrami exponent increases with crystallization temperature for all the blends, but the PP/EP90/EPR ternary blends compared to the PP/EP90 binary blend exhibit larger Avrami exponents. The crystallization rate decreases as the crystallization temperature increases, as it is indicated by the increase of crystallization half-time. At the same crystallization temperature, the PP/EP90 binary blend exhibits the slowest crystallization rate. The data of crystallization kinetics were also analyzed with Hoffman-Lauritzen crystallization regime theory. It is found that all the blends crystallize in regime III. The increase in the content of EPR in the ternary blends is followed by increases in secondary nucleation constant, the free energy of the chain folding surface, and the chain folding work. The blends were etched with xylene at room temperature and at 80ºC to remove EPR and EP90, respectively, and their morphology was studied with scanning electronic microscopy (SEM). The SEM results reveal that the block component EP90 is partially miscible with both PP and EPR, leading to increase in both domain number and domain size. Since both EPR and EP90 retard crystallization of PP in the PP/EPR and PP/EP90 binary blends, we speculate that the miscibility of EPR and EP90 can weaken the interference of EP90 on crystallization of neat PP.

Silver nano-sized particles were synthesized with strong antifungal activity againstthe wood staining fungi Ophiostoma flexuosum, O. tetropii, O. polonicum and O.ips. The average size and purity of the nano-sized particles were determined by scanning electron microscopy and XRD spectra, respectively. The structural characterizations of nano-sized particles were performed using IR spectrum and EDS. Radial diffusion method was carried out to reveal the antifungal activity of silver nano-sized particles on MEA agar plates. Strong fungicidal silver nano-sized particles were mixed with chitosan solution and then the chitosan membrane was prepared by solvent evaporation method. Glutaraldehyde was used as cross-linking agent for membrane preparation. Deacetylation degree, concentration and pH of chitosan were considered as a main factor for preparation of bioactive membrane. The quality and structure of membranes were analyzed by Fourier transform infrared spectroscopy. Thermostability of the membranes was confirmed by thermogravimetric analysis. Synthesized chitosan-glutaraldehyde-Ag membrane was tested against the wood staining fungi on MEA agar plates using inhibition zone method. The results showed that the antifungal activity of chitosan membrane increased with increasing in concentration of silver nano-sized particles. According to our results, synthesized chitosan membrane has been used as a good carrier for silver nano-sized particles in wood industries and these materials could be very efficient substitutions for chemical preservatives currently used to control fungal contamination in wood industries.

The gray single jersey knitted cotton fabric was bioscoured with pectinase enzyme and grafted with acrylonitrile monomer by potassium permanganate/citric acid redox system. The grafted cotton was hydrolyzed with alkali and acetone solvent in presence of a mild alkali solution separately. FTIR analysis was performed to study the changes that were imparted by the chemical modification. The absorption peak observed at 2259 cm-1 corresponds to the stretching vibration of C≡N, which confirms the grafting. Changes in the surface morphology were observed through the SEM studies. Because of more swelling nature of the fibres after hydrolysis process by 1.5N sodium hydroxide the sample image shows slightly bulkier than the other samples. TGA-DTA thermal analysis shows that the thermal stability was not much affected by the chemical modification. The solvent induced hydrolysis process shows good results than the alkali treatments. The grafted cotton shows higher thermal stability than the bioscoured fabric. The modified fabric shows higher degradation temperature than the grafted fabric. Dyeing was carried out with different salt concentrations. The acetone and alkali treated samples show 130% and 20-30% increase in dye uptake than the grafted and sodium hydroxide alone treated samples. Acetone treatment has brought some chemical changes to an alkali treated fabric in its structure and increases the affinity of the modified cotton towards reactive dye.

Several novel organic hybrid systems based on carboxylated nitrile rubber (XNBR) were prepared. The damping properties of organic hybrids consisting of XNBR, 2,2''-methylenebis(6-t-butyl-4-methylphenol) (AO-2246), and pentaerythrityl- tetrakis-[β(3,5-di-t-butyl-4-hydroxyphenyl)-propionate] (AO-1010) were investigated by dynamic mechanical analysis (DMA). Binary XNBR/AO-2246 system was compatible and showed only one damping peak associated with XNBR, whereas binary XNBR/AO-1010 system was partially compatible and a new damping peak appeared besides that of XNBR. FTIR measurements and SEM observation were carried out to clarify the molecular mechanism of the different additive effects of AO-2246 and AO-1010. DMA results of ternary XNBR/AO-2246/AO-1010 systems showed that the addition of a small amount of AO-1010 into XNBR/AO-2246 further enhanced the damping peak height and peak temperature remarkably, demonstrating that combined AO-2246 and AO-1010 had a synergistic effect on improving the damping property of XNBR. Furthermore, studies on the damping stability of such organic hybrids during ageing and annealing process revealed that the addition of small amount of AO-1010 into XNBR/AO-2246 obstructed the crystallization behaviour of AO-2246 and finally improved the damping stability. Thus, a series of XNBR-based high-performance damping materials with high damping peak and controllable peak position as well as better damping stability were obtained.

Different activator systems containing zinc oxide, zinc stearate, calcium oxide, thiodiglycol metal complexes and nano-zinc oxide were applied for sulphur vulcanization of NR/SBR blend. The systems were chosen in order to have better dispersion in rubber matrix, better metal ion release in vulcanization process and lower zinc content. The cure characteristics and physicomechanical properties were investigated. Results showed that zinc oxide could be reduced from 4 to 2 phr in the formulation, without any detrimental effects on properties. Zinc stearate was not a good activator but it could be employed in combination with zinc oxide to improve tensile properties. Calcium oxide did not show satisfactory results. Zinc complex of thiodiglycol was an acceptable substitute for zinc oxide due to better dispersion in rubber matrix and better ability for zinc ion release. Zinc content could be reduced to about 4.5 mmol per 100 g of rubber by using this complex. Calcium complex of thiodiglycol was not a good choice either and showed detrimental effects on properties. Application of nano-zinc oxide did improve abrasion and tensile properties due to better surface effects. An alternative mixing method which was used to improve the zinc oxide and nano-zinc oxide dispersion was good and showed better abrasion and tensile properties. The results are presented as patterns to achieve the desirable properties.