مجله ایرانی پلیمر
سال:1380 | دوره: | شماره: |تعداد مقالات:9

Reactive urethane prepolymer, as a base material for the process of gluing in medicine. has been studied. For this purpose castor oil and toluene diisocyanate (TDI) were used as polyol and diisocyanate components to synthesize the isocyanate terminated urethane prepolymer. The molecular structure of this prepolymer was investigated by infrared spectroscopy ((FTIR) and vapour pressure osmometry (VPO). The obtained infrared spectrum confirmed the presence of free NCO groups bonded to the prepolymer backbone. The wetting behaviour of the synthesized prepolymer was evaluated by surface tension measurement. The surface behaviour of the cured thin films of the prepolymer was characterized using contact angle measurements. The cytotoxicity of the cured prepolymer film was evaluated by in vitro cell culture experiment. Results showed a compatible cell response with no signs of toxicity.

The rheology, vulcanizational, and the physico-mechanical properties of a composition of siloxane rubber and ultra-high molecular weight polyethylene are discussed. It is shown that such materials combine elasticity and strength. Inclusions of ultra-high molecular weight polyethylene in siloxane matrix, with large-sized globular structure, imparts material a good impact resistance property. Compositions developed may be used as polymer inserts for new generation of endoprosthetic appliances for hip joints.

This paper reports the synthesis of oligomeric dispersed dyes based on α-naphthol-formaldehyde (NF) oligomer by coupling of various diazonium salt to α-NF oligomer. α-NF oligomer was prepared by the condensation of a-naphthol with formaldehyde in presence of oxalic acid. To achieve suitable oligomer in the present study, several variables namely molar ratios of reactants, temperature, time and catalyst have been optimized in the synthesis. A series of oligomeric azo dyes have been prepared by coupling various diazonium salts of aromatic amines to α-NF oligomer. Their dyeing on polyester, nylon and wool resulted in attractive hues an fibres. In this study of oligomeric azo-NF dyes the dyeing of the fibres completed in short time and most important is that no patches were observed on the fibres, while earlier reported oligomeric dyes form patches on the fibre. They were characterized in terms of their softening points, yield, colour, solubility and UV-visible spectra. Structure-property relationships are discussed and dyeing on polyester (PET), nylon-6, 6 and wool are assessed to have excellent fastness properties.

Poly(urethane-imide)s were prepared by polycondensation reaction of four imides containing diisocyanates with poly (tetramethylene oxide) glycol. Synthetic procedures for the preparation of the diisocyanates were described. The chemical structures of the monomers and polymers obtained were characterized by IR, 1H NMR, and mass spectroscopies. The physical properties of polymers including solution viscosity, solubility properties, thermal stability and thermal behaviour were studied as well. The polymers showed excellent solubility in polar aprotic solvents such as DMF, DMAc and NMP. Their inherent viscosities were in the range of 0.50-0.55 dL/g. T10 % obtained as a criterion of thermal stability was in the range of 316-335 degreesC for the polymers.

Bisphenol A (BPA) is the most important bisphenols, which is used industrially for the manufacture of polycarbonate resins and epoxy resins. These Two applications have achieved greatest significance in recent years and consume over 90% of the BPA output. BPA was prepared in our laboratory by condensation reaction of acetone with excess phenol in presence of an acid catalyst and promoter in high yield and high state of purity at optimum conditions of variables, in this paper we discuss the mechanism and kinetics aspects of BPA condensation reaction to acquire a better understanding of the course of the reaction.

Polyurea microcapsules containing 2-chloro-N-(2,6-diethylphenyl)-N-(methoxy methyl)acetamide as the active agent were prepared by the method of interfacial polycondensation with methylene bis(phenyl isocyanate) as the multifunctional isocyanate, hexamethylene diamine as the diamine, and anionic sodium lignin sulphonate as the emulsifying agent. Thermal stability of the microcapsules was investigated with a thermogravimetric analyzer coupled to a mass spectrometer and surface topography of the micro-capsules was investigated with atomic force microscopy. The release behaviour of the microcapsules was studied by extraction in deionized water or calcium chloride aqueous solution, drying under ambient conditions, and examining with scanning electron microscopy. Results indicate that as calcium chloride is added to the aqueous suspension of microcapsules containing anionic sodium lignin sulphonate as the surfactant, a gel phase is formed. This gel phase encompasses the microcapsules and increases the stability and modifies the release behaviour of the microcapsules.

This research work is devoted to development of a non-linear finite element model for a bias tire under inflation pressure and contact loads. The model was developed by a pre-processor program for NSTAR which is the nonlinear module of COSMOS/M software. Three-dimensional isoparametric brick elements with total Lagrangian formulation have been used to construct the finite element mesh of the tire model. Applying appropriate rim displacement toward a rigid surface simulated the contact load. The stress-strain relationships of composite sections (plies, breaker and bead) are described by linear orthotropic constitutive equation while Mooney-Rivlin incompressible model was used for the description of the behaviour of rubbery parts. The analysis was performed in a Lagrangian framework to take the geometrical non-linearity of large deformation of tire into account in conjunction with Newton-Raphson iterative procedure to solve the final set of working equations. Comparisons of the numerical results with laboratory measured tire deformations and also available tire Standards, confirm the general suitability of the developed mathematical model.

In this study homo- and copolymers of glycolide and l-lactide were synthesized and subjected to in vitro hydrolytic degradation. Glycolide and l-lactide were prepared from glycolic and l-lactic acid, respectively. Stannous octoate was used as polymerization catalyst. Poly(l-lactide) with M-w=9.4x105 and a polydispersity of 1.89 was synthesized and characterized. Also copolymers of l-lactide and glycolide were prepared. Polyglycolide and its lactide copolymers with high proportion of glycolide do not dissolve in organic solvents. Degradation studies were conducted at 37 degreesC and pH=7.35. The concentration of released glycolic acid was determined by chromotropic acid reagent. Purified polyglycolide powder shows a fast degradation profile in the first 10 days, after which it levels off. A copolymer obtained from 10 mol% l-lactide and 90 mol% glycolide shows different degradation pattern as polyglycolide, because of its amorphous nature it exhibits a higher degradation rate.

The present paper describes the release of benzocaine from polymer carrier. The chemically controlled release method has been applied in which the benzocaine (drug) with active group (NH2) links up with the spacer group p-hydroxybenzaldehyde) by imine bond formation. The resulting schiff base reacts with the monomer p-styrenesulphonyl chloride. The obtained monomer is polymerized by AIBN as an initiator at the temperature range 60-70 °C. The obtained polymer was identified by IR and NMR spectroscopies. Gel permeation chromatography (GPC) was used for determination of average molecular weight of drug pendant polymer. The hydrolysis of drug polymer conjugates was carried out in cellophane membrane dialysis bag containing aqueous buffer solution (pH 1.2) at 37 °C. Detection of hydrolysis solution by UV spectroscopy showed that the drug can be released by hydrolysis of imine bond between the drug and spacer group.