فهرست مطالب

Iranian polymer journal
Volume:15 Issue: 1, 2006

  • تاریخ انتشار: 1385/01/11
  • تعداد عناوین: 8
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  • Mostafa Rezaei, Nadereh Golshan Ebrahimi, Azadeh Shirzad Page 3
    The effect of different processing variables on the mechanical properties of UHMWPE/PET composites has been investigated using robust design (Taguchi method). Among the different processing variables, the fibre weight fraction had the greatest effect on the results. PET fibres have been used to improve abrasive wear behaviour of UHMWPE matrix. Reduction of PET fibres to an optimum level (5 % wt) and surface modification of UHMWPE powders were two methodologies to reach optimum mechanical properties. The surface modification of UHMWPE powder was performed using chromic acid etching. For surface characterization of UHMWPE powders the X-ray photoelectron microscopy (XPS) was used. The chromic acid etching causes surface chemical oxidation in the samples so the oxygen to carbon (O/C) atomic ratio increased from 0.2% in unmodified UHMWPE powder to 4.94% in modified one. The results indicate that the reduction of fibre weight fraction to 5% and surface modification of powder improve themechanical properties of UHMWPE/PET composites.
  • Bakhshali Massoumi, Ali Akbar Entezami Page 13
    Polypyrrole (PPy) and polyaniline (PANI) are of the most promising materials for multifunctionalized applications. The application of conducting polymers for the direct conversion of electrical energy to mechanical energy in electro-mechanical ctuators is analyzed using theoretical and experimental results. Electrically conducting rganic polymers and a novel class of "synthetic metals" that combine the chemical and echanical properties of polymers with the electronic properties of metals and semiconductors. hese polymers become conductive upon partial oxidation or reduction, a rocess commonly referred to as doping. One of the unique aspects for conducting polymers s controlled-release devices, as well as biologically active ions and drugs such as denosine 5-triphosphate, heparin, dexamethasone phosphate, glutamate and sulphosalicylic cid as a model of sulphonic drugs. During the last decade, polymers have gained tremendous recognition in the field of artificial sensor in the goal of mimicking natural sense organs. Better selectivity and rapid measurements have been achieved by replacing classical sensor materials with polymers involving nano-technology and exploiting either the intrinsic functions of polymers. In this review, application of conducting polymers such as PPy and PANI in drug delivery systems, biosensors and preparation of artificialmuscle such as robots, artificial limbs are discussed.
  • Mehdi Nekoomanesh, Hamid Mobedi, Hossai Orafaei, Houri Mivehchi Page 31
    Controlling the rate and behaviour of the biodegradable polymer matrix is importantin the development of drug delivery systems. In this project, we succeeded to controlthe speed of degradation and changing the degradation site from the bulk to the surface by addition of excipients. Antiacid excipients, such as Mg(OH)2 have significant effects on rate and behaviour of biodegradation, by neutralization of the acidic microclimate pH in polymer. We synthesized high molecular weight poly(L-lactide) by using tin- 2-ethyl hexanoate as catalyst. The polymer has been characterized by GPC, DSC and SEM. Mixtures of the polymer with Mg(OH)2 at 1, 3 and 5% w/w were prepared and the degradation of the samples, kept at in vitro condition after 3 and 6 months, were studied. The results of average molecular weight changes, thermal characteristics and morphology of samples after 3 and 6 months revealed that it is possible to redirect the bulk degradation towards su rface degradation. It is found that the ratio of bulk degradation to surface degradation and speed of degradation has reverse relationship with the additives concentration and when Mg(OH)2 increases, the speed of degradation decreases as well. In samples with Mg(OH)2, the polymer degradation rates were reduced by 2-3 folds and the percentage of crystallinity increased by maximum 90% (3% Mg(OH)2) after 6months.
  • Mohammad Karrabi, Alireza Shakeri Page 47
    Treatment of carbon black (CB) through polymerization compounding not only increases the adhesion between polymer and CB but also helps to disperse CB into a viscous matrix with existing equipment. Polymerization compounding was used to graft poly(ethylene oxide) (PEO) chains on the CB. Scanning electron micrographs suggest a strong interaction between the polymer and the treated CB. The rheological properties of poly(ethylene oxide)(PEO) composites containing treated CB and untreated CB at four levels CB (5, 10, 20 and 30% by wt) were studied. The complex viscosity of the composites containing up to 10% of treated CB was found to be smaller than that of the polymer matrix and considerably smaller than that of composites containing untreated CB. The elastic characteristic time based on the ratio of storage and loss modulus was found to be approximately independent of the CB content and of the surface treatment.
  • Dariush Salari, Azadeh Jodaei Page 55
    This study investigates the process for manufacturing of petroleum resin from pyrolysis gasoline feedstock taken from Tabriz Petrochemical Company. These resins have been used extensively in a wide variety of areas such as adhesives, paint, and printing inks industries. This product is prepared through polymerizing a petroleum fraction containing unsaturated hydrocarbons with the presence of Friedel-Crafts catalyst. The resins were characterized by 1H NMR and IR spectroscopy and the effective factors in the production of petroleum resins, reaction temperature, amount of catalyst and solvent types were analyzed. Analysis of the polymerization temperature demonstrates that resins with high molecular weights and softening points are produced at low temperatures. The optimal amount of catalyst to prepare resins with high molecular weight and softening point is achieved at 0.45-1.25 wt% of the feedstock. When polymerization takes place in the presence of aromatic solvents, the molecular weight and softening point of resins are reduced. The addition of compounds such as indene and styrene led to an increase in molecular weight and softening point while it reduced the resin yield dramatically.These compounds can be utilized to regulate molecular weight.
  • Marc J.M. Abadie, Vanda Yu. Voytekunas, Alexander L. Rusanov Page 65
    High performance polymers are commonly and widely used in advanced technologies and cover large varieties of applications such as micro and nanoelectronics, civil and military transportation, defense, etc. It is important for these technologies to design tailor-made high tech materials by focusing on molecular structure/processability/ properties relationships of high performance polymers such as heterocyclic polymers known for their outstanding thermal properties and their good mechanical behaviour or even functionalized polymers or inorganic polymers. Nowadays, there is a strong demand of such resins since the development of composites and recently nanocomposite materials. Of the high temperature polymers commercially available, one can cite poly(arylene ethers), polybenzimidazoles, resins from cyanates, resin from bismaleimides, organofluoro polymers, certain silicones and liquid crystalline polyesters. Polyimides and poly(arylene ether)s have attracted the attention of scientists and engineers more than other polymers. This attention is not only due to the attractive combination of properties but also because polyimides and poly(arylene ether)s can be readily tailor- made for specific applications. This article gives an account of developments in high temperature organic polymers during the last 5 years with major emphasis on linear, hyperbranched or dendritic structures concerning polyimides family, polyphenylquinoxalines and end-capped polymers such as bis-maleimides, PMR-15 and acetylene-terminated resins, highlighting the chemical structure with their ultimate physico-mechanical properties and focusing on the parameters which govern their processability.Processability and different applications will be presented as films (membranes for fuelcell), photosensitive products (microelectronics) or prepregs.
  • Fatemeh Rafiemanzelat, Shadpour Mallakpour Page 79
    In connection with our interest in preparing thermally stable optically active polymers,this work deals with a detailed study on the synthesis and characterization of threeseries of novel optically active poly(ether-urethane)s (PEU)s based on polytetrahydrofuran(PTHF), polyoxyethylene (POE) and polypropyleneglycole (PPG). Also the possibilityof their thermal modification by introducing the imide and amide functions in the PEUbackbone through the reaction of a new imide containing diacid, bis(p-amido benzoicacid)-N-trimellitylimido-L-leucine (BPABTIL) (1) with 4,4í-methylene-bis-(4 phenylisocyanate) (MDI) (2) was explored. The effect of different reaction conditions such as reaction temperature, reaction time, catalysts, reaction solvent, soft segment length and type, method of preparation and addition of chain extender on the properties of copolymers including solubility, viscosity and thermal behaviours were investigated.
  • Jianzhi Diao, Jianmin Zhang, Qi Zhao, Huifang Yang Page 91
    Hyperbranched poly(amide-ester) (HBP) has a compact, highly branched, threedimensionalstructure, which has a high density of functional end groups and inherently low viscosity. The HBP additives are able to behave as lubricants during processing and as compatibilizing agents in the blend. In this work, polypropylene/poly(vinyl chloride)/hyperbranched poly(amide-ester) (PP/PVC/HBP) blends were prepared by melt mixing; the PP/PVC (80/20 mass ratio) blends were investigated in detail. Mechanical and rheological properties were measured. The tensile strength of the blends reached the maximum value when the content of hyperbranched poly (amide-ester) was 3 phr; the impact strength of the blends was small changed as that of pure PP/PVC. The viscosity of the PP/PVC/HBP blends was higher than that of pure PP/PVC blends, whereas the viscosity of the PP/PVC/HBP blends dropped with added more HBP. The scanning electron microscopy (SEM) showed that a two-phase morphology was characteristic of blends and dual-continuous morphology of PP/PVC/HBP (80/20/3) blend. With more or less HBP, the PVC spherical droplets of the minor phase dispersed in a PP continu ous matrix phase, whereas there was a large difference between/among the minor-phase particle size. The SEM photos also confirmed that HBP could enhance the adhesion at the interface and reduce the phase separation of PP/PVC blend. The tensile strength of blends was in accord with morphology and DSC of blends.