Iranian polymer journal
Volume:17 Issue: 7, 2008

The solubility of free monomers in polymer has an effective role in the product quality and on environment in various steps of polymer manufacturing. Therefore, it is important to find confident method to predict the solubility of monomers in polymers. For predicting the solubility of gaseous monomers in polymers, among the various methods used, equations of state are considered as the most effective tools due to the simplicity in their applications. However, the accurate solubility prediction with equations of state needs suitable binary interaction parameters. Unfortunately, these parameters often have unknown temperature and solute composition functionality and therefore, other empirical correlations methods are used. The correlation methods, however, generally consist of equations having several parameters which are to be evaluated from experimental data for each system at a given temperature and this imposes limitation on their applications. Artificial neural network (ANN) can be a powerful alternative tool for predicting gaseous monomers in polymers. In this work, the solubility of 1,1,1,2-tetrafluoroethane (HFC-134a), 1-chloro-1,1-difluoroethane (HCFC- 142b), butane and iso-butane in low-density polyethylene (LDPE) has been studied by ANN using back propagation method (BP). It was found that a 2-4-1 architecture can predict the gas solubility satisfactorily.

By using X-ray diffraction (XRD), infrared spectrometry (IR), scanning electron microscope (SEM) and transmission electron microscope (TEM), the worn specimens of poly(ether ether ketone), (PEEK), composites tested under unlubricated sliding friction and wear conditions at a constant sliding speed were investigated in order to reveal structural changes of polymer as well as wear mechanisms as a function of temperature. The results showed that the PEEK composites exhibited stable friction coefficient and lower wear ratio. The wear mechanism is that the particle abrasion occurs at low temperature, the adherence abrasion and particle abrasion take place at the temperature between 200~350ºC as revealed through wear morphology and wear debris analysis. The thermal degradation of PEEK does not occur until its temperature rises to higher than 350º. The stainless steel and carbon fibres bind strongly with the matrix PEEK and may be responsible for improving stability of the friction coefficients of the materials. Surface film, transition layer and matrix composed the superficial structure of friction material after wear test. Two kinds of surface film structures are formed: one is cystiform microstructure with PEEK matrix surrounded by single or multicrystal powder of fillers; the other is meshwork generated by resin base and friction fillings.

The applicability of medium density polyethylene (MDPE) gas pipes in hot climate areas of southern Iran (such as Khuzestan) has been one of the main concerns of local gas company officials and their engineers. This is due to the facts that buried pipes can experience sever stresses due to internal pressures, traffic load, soil height, daily and/or seasonal temperature variations if not properly designed and installed underground. This research investigates the sole effect of each parameter and their combination on maximum stress produced in MDPE gas pipes and their sockets which are made from PE100. The analysis was performed through a comprehensive finite element process and the results were compared to those of empirical equations, where possible. The maximum local stresses in pipes and sockets were determined and compared to their critical values for an operating pressure of 4 bars at various depths and temperatures. The design curves and the range of applicability of MDPE are then deduced based on a life time of 50 years. According to the results, assuming a target temperature of 30ºC for the pipe and its socket, then MDPE pipe and its HDPE socket (PE100) can well sustain the imposed load of a temperature rise of 15ºC at a depth of 120 cm, in presence of all other loads mentioned above. For higher temperature rises, some stress relief mechanisms must be employed. Hence, by applying the right procedure, these pipes can be used for gas transportation even in hot climate areas of Iran, where the ground surface temperature may reach a high value of 67ºC in summer time.

Natural rubber (NR)/sodium-montmorillonite (Na-MMT) nanocomposites were prepared by co-coagulating the mixture of NR latex and various amounts of Na- MMT aqueous suspension. Tapping mode AFM (for the first time in the present case), TEM and XRD were applied to characterize the structure of nanocomposites. Results showed that at the low loading of layered silicates, fully exfoliated structure could be achieved by this method. Both non-exfoliated (stacked layers) and exfoliated structures were observed in the nanocomposites when the amount of Na-MMT increased to 10 phr. The mechanical results on the vulcanized nanocomposites showed that nanocomposites present initial moduli and tensile strength greater than Na-MMTfreeNR compound. Furthermore, initial moduli increased with increasing the Na-MMT loading, indicating the reinforcement effect of Na-MMT on the mechanical properties of nanocomposites. The nanocomposites exhibit a higher glass transition temperature and lower tangent peak value in comparison with Na-MMT-free NR compound. TGA results indicated an improvement in the main and end decomposition temperature but there is no effect on the suppression of the initial decomposition temperature.

Ionic liquids (IL)s represent an attractive and potentially very valuable group of newsolvents, which have the benefit of low vapour pressure and therefore easier handlingthan many conventional solvents. These liquids, because of their unique properties,are attracting a lot of attention to replace volatile organic solvents, eco-friendlyand green media. This work describes microwave-assisted polyamidation reaction of 5- (2-phthalimidyl-3-methylbutanoylamino)isophthalic acid as a diacid monomer with various aromatic diamines such as 4,4''-diaminodiphenyl sulphone, 4,4''-diaminodiphenylether, 4,4''-diaminodiphenyl methane, benzidine, p-phenylenediamine, mphenylenediamine, 2,5-diaminotoluene and 1,5-naphthalene diamine in the presence of different imidazolium salts and triphenyl phosphite without adding extra compounds. This technique of polymerization is a very fast and green process for polymer synthesis. This polymerization method benefits the advantages of elimination of volatile and toxic solvents such as NMP, very short reaction time and direct polymerization, so there is no need of preparation of diacid chloride and therefore, saves time and energy in this procedure. This method gave polyamides (PAs) with inherent viscosities ranging from 0.32-0.66 dLg-1. The resulting wholly aromatic PAs with bulky pendent groups, each has polyisophthalimide backbone substituted with phthalimide and S-valine groups in ring position 5 of the diacid, and different aromatic diamines. These polymers have chiral centre in the pendant groups and show optical activity. They were characterized by FTIR, 1H NMR, elemental analysis and specific rotation techniques. Introduction of bulky and flexible clusters in these polymers pendant group; make them soluble in most polar aprotic solvents. Thermogravimetric analysis showed that these PAs exhibit high thermal stability.

Emerging community concerns and a growing environmental consciousness throughout the globe have forced the material scientists to synthesize new green polymer composite materials and processes for their better end uses. In the present research paper fabrication of Hibiscus Sabdariffa (HS) fibre reinforced phenolic resin matrix based polymer composites have been reported. Resorcinol-formaldehyde (RF) resin polymer matrix based composites have been fabricated through compression moulding technique developed in our laboratory. Mechanical properties such as tensile strength, flexural strength, compressive strength and wear resistance, etc. of fibre reinforced polymer composites have been investigated as a function of fibre loading (in terms of weight). The reinforcing of the polymeric resin with Hibiscus Sabdariffa fibre was accomplished in particle size of 200 (micron). The entire polymer composites fabricated showed a general trend of increase in properties with fibre loading up to 30% and beyond this loading the properties decrease. Fibre/matrix interaction has been analyzed from the mechanical data and morphological (SEM) studies. Thermal (TGA/DTA/DTG) studies have also been carried out on polymeric resorcinol-formaldehyde (RF) resin, Hibiscus Sabdariffa fibre and particle reinforced (P-Rnf) biocomposites.

An ambient self-crosslinking polymer acrylic (ASPA) microemulsion was prepared by a modified microemulsion polymerization, in which reactive emulsifiers allyloxy nonylphenoxy poly(ethyleneoxy) ether (ANPEO10) and ammonium sulphate allyloxy nonylphenoxy poly(ethyleneoxy) ether (DNS-86) and normal emulsifiers were employed. The ASPA microemulsions and their paint films were characterized with rotational viscometer, laser light scattering, Fourier transform infrared (FTIR), and differential scanning calorimetry (DSC). The results of the rheological properties showed that the apparent viscosity (ηa), consistency factor (K), and zero shear viscosity (η0) of the soap-free microemulsion containing reactive emulsifiers were increased, compared with those of conventional microemulsions prepared with normal emulsifiers. Compared with conventional microemulsions, the soap-free microemulsions showed fast drying speed and its films presented better water resistance. At last, the particle size and distribution were characterized. The results obtained showed that the soapfree emulsions were monodisperse nano-emulsions.