Iranian polymer journal
Volume:18 Issue: 8, 2009

Particles sizes and melt processing of TiO2 play improtant role in thermoplastic systems. The mechanical and morphological properties of polypropylene (PP)/TiO2 composites were investigated by preparing the compostie by melt mixing technique in a twin screw extruder. The results show that after adding TiO2 particles of 42.3 nm (TD42.3) and TiO2 130 nm (TD130) sizes, the tensile strengths of PP composites decreased with increasing filler content and their stress-at-break values increased after filler addition. The effect of particle size showed that TD130 improved the mechanical properties of PP in relation to TD42.3 of smaller size. TiO2 of 130 nm size was added to PP using two different mixing conditions. PP composites prepared at screw speed of 50 rpm with 2 mixing cycles showed higher tensile strength, stress-at-break and Young''s modulus relative to samples prepared by the same screw speed and 1 mixing cycle. The impact strength of the samples prepared by 2 mixing cycles was higher than those prepared by 1 mixing cycle. Apparently, the 2 mixing cycles improved the impact strength of the composites due to the improved interfacial interaction between TD130 and the matrix and increased energy absorption during the impact process. The higher screw speed led to low mechanical properties. The dispersion of TD130 particles was relatively good when operated at 50 rpm and 2 mixing cycles with less aggregations in PP matrix.

Apreparation method for a permanently porous functionalized post-cross-linked polymer fibre is developed by chemical transformation of polypropylene fibre grafted styrene-divinylbenzene. The fibre post-cross-linking method involved the preparation of rigid three-dimensional networks in the entire polymer fibre and changing its specific surface area. As a cross-linker, cyanuric chloride was used in presence of a Friedel-Crafts catalyst. The effects of several important factors, e.g., reaction temperature, reaction time, catalyst type, and material ratio on Friedel-Crafts reaction were investigated in detail and the optimal synthetic conditions of postcross- linked polymer fibre were obtained. Under optimal synthetic condition, the specific surface area of the post-cross-linked polymer fibre could be 58.16 m2/g, over 900 times the initial polymer fibre. Compared with the initial fibre, the post-cross-linked polymer fibre shows high specific surface area, large pore volume, abundant pore structure, and excellent adsorption property for organic vapours, as well. The experimental results showed that the adsorption capacity for organic vapours(methanol, benzene, and toluene) on the post-cross-linked polymer fibre was increasedto about 3 times of that of the initial fibre. The adsorption capacity was related not onlyto the size of the pore network but also to the molecular size of organic vapours. Thepost-cross-linked polymer fibre has larger adsorption capacity for benzene than for theother organic vapours studied.

Among chelating resins, the amine containing resins which have excellent adsorption property for metal ions are especially applied widely in separation, enrichment, and removing of heavy metal ions. In this paper, new amine containing resins based on polyacrylonitrile (PAN-DTA and PAN-TETA) were prepared through the reactions of polyacrylonitrile with diethylenetriamine (DTA) or triethylenetetramine (TETA) by a rapid, simple, and economically feasible route. The prepared resins which are completely insoluble in water and common organic solvents were used to remove Ni(II) ion from aqueous solutions. The sorption behaviour of the resins for this ion showed that the greater sorption and distribution coefficients (Kd) were obtained at higher pH media. The highest sorptions of Ni(II) on PAN-DTA50, PAN-DTA100, PAN-TETA50 and PAN-TETA100 resins were determined as 1.9, 3.0, 1.8 and 2.9 mmol/g, respectively. It is shown that the amine capacity of the resins is dependent on the volume percentage of DTA or TETA and the maximum capacity of amines obtained are 6.25 and 9.0 mmol/g for PAN-DTA100 and PAN-TETA100, respectively. Also, the recovery of Ni(II) from PAN-TETA50 and PAN-TETA100 resins are estimated about 65% and 61%, respectively. The resins and their metal complexes are studied by FTIR spectroscopy, scanning electronic microscopy (SEM), and thermal gravimetric analysis (TGA). All the analytical methods have confirmed the presence of metal in the metal-resin complexes.

Poly (1,8-diaminonaphthalene) films as p-type semiconductors were easily synthesized potenitiostatically on the Au or indium-tin oxide vacuum deposited glass substrates. Optical transmissions of doped and dedoped films were measured within 250-1100 nm wavelength range and the corresponding optical band gaps were estimated to be 2.84 and 3.62 eV. The polymer was used for the construction of schottky barriers with In, Cu, and Ag metals. The current-voltage and capacitancevoltage characteristics of the diodes were studied to derive information on junction parameters. The electrical characteristics of the junctions at low range potential were analyzed based on the standard thermionic emission theory. The value of ideality factor (η) for In/polymer junction was found to be 9.93 which decreased to 5.23 and 6.30 for Cu and Ag electrodes, respectively. This can be attributed to the formation of complex between Cu and Ag during vacuum deposition of these two metals onto the polymer layer which reduces the thickness of oxide insulator interfacial layer. The capacitance-voltage characteristics of the diode were also studied and the built-in voltage (Vc), the charge carrier concentration (Ns), depletion width, and the work function of poly(1,8-DAN) were estimated. The value of 4.45 eV was obtained for polymer work function.

The differences and reliabilities of numerical results obtained by tyre models with simple tread and detailed patterns of rubber blocks are studied. The patterned tyre model was generated by combination of two separately developed finite element models. The first model consisted of all tyre components except tread pattern by revolving the tyre cross-section about its symmetry axis. On the other hand, the geometries of the rubber blocks in tread pattern are separately created and discretized to generate finite element mesh of the tread part. These two tyre models were combined and a single 3D finite element model with tread pattern was generated. The incompatibility between the tread pattern mesh and the other parts was considered by using a meshtying algorithm. The results showed that if the main purpose of the tyre analysis is to study the global behaviour of the tyre such as determining the load-deflection curve or dynamic radius of the rolling tyre then, a finite element model with simply ribbed tread is sufficient. However, accurate computations of the stress and strain fields as well as contact pressure need a finite element model of the tyre with detailed tread pattern.

Anew poly(urethane-imide) (PUI) was prepared by a condensation reaction of a -NCO terminated polyurethane prepolymer and 4,4''-(hexafluoroisopropylidene) diphthalic anhydride (6FDA). This prepolymer was prepared by a reaction of azo chromophore (dispersed red 19) containing two hydroxyl functional groups and isophorone diisocyanate (IPDI). The PUI was characterized by common spectroscopic methods such as UV-vis, FTIR and 1H NMR, and thermal studies using DSC and TGA. The results of DSC and TGA measurements indicated that the PUI exhibits high thermal stability up to its glass-transition temperature (Tg) of 201ºC and a weight loss of 5% at heat temperature of 238ºC, due to introduction of imide components and formation of strong hydrogen bonds. The weight-average molecular weight (Mw) was 52600 with a polydispersity of 2.14. The measurement of refractive indices (n) was performed using a multi-wavelength light Abbé refractometer with precise temperature control at single wavelength of an attenuated total reflection (ATR) setup. The values of n and thermo-optic coefficient (dn/dT) were used to calculate the dielectric constant (ε) and its variation with temperature (dε/dT), volume expansion coefficient (β) and its variation with temperature (dβ/dT) according to Lorentz-Lorenz equation. The dn/dT values were from -2.45×10-4 to -5.05×10-4 K-1 at multiwave-lengh light and from -4.1071×10-4 to -4.3875×10-4 K-1 at different single-wavelength lights. The dβ/dT values were from 0.3331×10-6 to 1.4668×10-6 K-1 at multiwave-lenght light and from 0.9449 ×10-6 to 1.1094×10-6 K-1 at different single-wavelength lights. The thermooptic coefficient was recorded as 10-4 K-1 which was nearly ten-fold that of inorganic materials such as SiO2 (1.1×10-5 K-1) and LiNbO3 (4×10-5 K-1). The results show that PUI may be useful as low loss optical communication devices and optical switches with low driving power.

Anew product of poly(vinyl alcohol)-g-fibroin peptides (PVA-g-FP) is produced by graft-copolymerization of PVA with allyl fibroin peptides (AFP). The AFP was obtained from a nucleophilic substitution reaction of fibroin peptides (FP) with allyl chloride. The optimal parameters of preparing the PVA-g-FP, corresponding to the acquired grafting efficiency, 10.1 wt%, were selected on the basis of the orthogonal experiments design of L1645, and the influence of reaction conditions on the grafting efficiency are discussed in detail, according to the data obtained from the orthogonal experiments. The FP was successfully modified and grafted onto the PVA macromolecules, which was confirmed by the analyses of the FTIR spectra of AFP and PVA-g-FP, and the reaction mechanisms for the formation of AFP and PVA-g-FP are proposed. The results of the orthogonal experiments have indicated that, relative to other parameters, the reaction temperature and the molar ratio of potassium peroxide sulphate (KPS) to AFP seemed to be more effective on the grafting efficiency. The highest grafting efficiency of FP was obtained under the reaction temperature of 60ºC for 3 h reaction time, with AFP/PVA weight ratio of 3/7, and molar ratio of KPS/AFP of 1/20, having a solution concentration of 10 wt%. The product may be potentially useful in the fields of biomaterials, textile industry, and chemical engineering.

Titanium oxide/poly(butylene terephthalate) (TiO2/PBT) composite nanofibres were prepared by electrospinning technique. The electrospun PBT and TiO2/PBT nanofibres were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Instron, and thermogravimetric analysis (TGA). The diameter of PBT and the composite nanofibres were in the range of 500-100±50 nm. The beads formation was observed when the amount of PBT was less than 10 wt % in the polymeric solution. The TiO2 (with size below 50 nm) nanoparticles were dispersed in the polymeric solution via sonication. The dispersion and embediment of TiO2 nanoparticles within the nanofibres were confirmed by TEM. The XRD result indicated that TiO2 nanoparticles were well loaded into PBT electrospun nanofibres mat and it was also observed that the composite nanofibres contain both forms (anatase and rutile) of TiO2. The mechanical properties such as specific tensile strengths and modulus of the PBT/TiO2 composite nanofibres were higher than those of pure PBT electrospun nanofibers. However, the elongationat- break value of composite nanofibres was lower than that of the pure PBT nanofibres, which implies that the incorporation of TiO2 nanoparticles made nanofibres stronger but less flexible.