Iranian polymer journal
Volume:19 Issue: 12, 2010

Structure and Properties of Alkaline Lignin-filled Poly(butylene succinate) PlasticsJin Huang; Dongkuan Fan,; Peter R Chang,; Ning Lin,; Jiahui Yu, The Effects of Carbon Black-based Interactions on the Linear and Non-linear Viscoelasticity of Uncured and Cured SBR CompoundsSomayyeh Mohammadian-Gezaz,; Mohammad KarrabiEffect of Conformational Parameters on Thermal Properties of Some Poly(oxadiazole-naphthylimide)sRadu-Dan Rusu,; Mariana-Dana Damaceanu,; Maria Bruma,; Inga A RonovaEffect of Processing Parameters on PP/EPDM/Organoclay Nanocomposites Using Taguchi Analysis MethodMir Hamid Reza Ghoreishy,; Gholam Reza Bakhshandeh,; Ramin Khosrokhavar,; Ghasem NaderiSynthesis and Characterization of Epoxidized Acrylated Natural Rubber Cross-linked by Star-shaped PolystyreneJianxin Li,; Xiaoyan Zhang,; Lei Chen,; Qi Zhang; Yan HuangSynthesis and Characterization of High Molecular Weight Polyacrylamide Nanoparticles by Inverse-emulsion PolymerizationMohammad Barari,; Mahdi Abdollahi; Mahmood HemmatiSynthesis and Polymerization of Vinyl Saccharides "as Glycomonomers" Bearing 2,3:5,6-Di-O-isopropylidene-α-D-mannofuranoseHassan Namazi; Farzaneh Salimi

Two different monoethers, CH3CH2CH2CH2OCH3 (NBME) and (CH3)2CHCH2-OCH3 (IBME), and Ph2Si(OCH3)2 were used as external donors in propylenepolymerization using MgCl2/TiCl4/DIBP catalyst (DIBP: diisobutyl phthalate)activated by triethylaluminium (TEA). The monoethers alone showed no improvementin the isotacticity index of polypropylene (PP). When one of the ethers andPh2Si(OCH3)2 were added together in the polymerization system as compositeexternal donors, the propylene polymerization activity and isotacticity index wereincreased as compared to those of the systems with only silane as external donor,though the melting temperature and melting enthalpy of PP decreased. The effects ofthe external donors on the active center distribution of the catalyst system aredemonstrated by deconvolution analysis of the PP molecular weight distribution intomultiple Flory components, and the mechanism of external donor regulation effects isdiscussed. All the results show that adding monoether in MgCl2/TiCl4/DIBP-TEA/silanecatalyst system can reduce the stereoregularity of the isotactic chains of the polymerwhile, it maintains the atactic PP fractions at a very low level

Many additives, e.g., flame retardants and/or appropriate nanoparticles directlyincorporated into the base polymer can be employed to protect polymericmaterials against attack by fire. Nowadays, novel nanomaterials including polyhedraloligomeric silsesquioxane (POSS) are employed to impart potential flameretardation characteristics to polymers, which open up new ways to prepare flameretarded materials. In this work, octaphenyl polyhedral oligomeric silsesquioxane(ph-POSS) and its bromide derivative (Br.ph-POSS) were used as novel fillers for polystyreneand the differences in their enhanced combustion properties were investigatedand discussed. The microstructures of composites were characterized by TEM, whichindicated that POSS nanoparticles were dispersed in the base polymer homogeneouslyand the amount of fillers were gradually increased with higher amount of POSS. Thecombustion behaviour of the composites was tested by cone calorimetry, whichshowed that their flame retardant properties were also greatly improved by increasedamounts of POSS fillers. Nevertheless, there are some differences in the combustionproperties of the composites which are due to different kinds of POSS nanoparticles,i.e., Br.ph-POSS system was more effective in reducing the peak heat release rate(pHRR) (the largest relative decline in pHRR was 84.2%), while ph-POSS resulted inslower smoke production rate (SPR) and rather bigger drops in peak values of COrelease rate (CORR) and CO concentration (COC) during the combustion test (thelargest relative decline in peak values of CORR and COC were 81.8% and 84.3%,respectively). These improvements are attributed to the homogenously dispersedPOSS nanoparticles and related Br-Sb synergistic effects, while the differences are dueto the presence of different substituents and/or elements in dissimilar POSS cages.

Aqueous mixture of NaOH/poly(ethylene glycol) (PEG) at a ratio of 9/1 was foundto be an excellent solvent for untreated cellulose. Na-Cellulose complex andhydration of the subsequent alkali ions are the key factors to the dissolutionmechanism. The role of PEG molecules is believed to be the acceptor of hydrogenbonding which connects the hydroxyl groups in cellulose and prevents the regenerationof cellulose through the inter- and intra-chains association. The formation of a highconcentration of spinning dope in NaOH/PEG aqueous solution provided an excellentpotential for formation cellulosic fibres with high mechanical properties. Novelcellulose multi-filament fibres were spun successfully, for the first time, from thecellulose-NaOH/PEG dope on a laboratory scale spinning machine. Coagulation wasaccomplished in a bath with H2SO4/Na2SO4 (10 / 5 wt%) aqueous solution. The tensilestrength, elongation-at-break, and crystallinity of the resulting fibres, in the given ordercorrespond to 1.94 cN/dtex, 5.72% and 54%. The morphology and structure of theregenerated fibres were characterized by different techniques, e.g., scanningelectron microscopy (SEM), nuclear magnetic resonance (13C NMR), wide-angle X-raydiffraction (WAXD), and Fourier transform infrared (FTIR) spectroscopy. The novelfibres possess circular cross-sections as well as relatively high molecular weights, andcrystallinity indexes comparable with cellulose II family crystal structure, leading togood mechanical properties. This new approach offers great potential for cellulosefibres on an industrial scale with a cheap, non-polluting and shorter production cyclecompared to that of viscose technology.

In order to investigate the applicability of ammonium pentaborate (APB) as additivein wood-based composites, the effects of APB and wood together on cure kinetics ofphenol formaldehyde (PF) resin were analyzed by using both dynamic andisothermal differential scanning calorimetry (DSC). ASTM E698-79 and model freetechnique were used to analyze dynamic DSC data, while the isothermal DSC curingkinetic parameters were obtained via the nth-order model technique. The resultsshowed that both poplar and Masson pine had little influence on the apparentactivation energy of PF resin, while APB slightly reduced it by increasing the pH valueof APB/wood mixtures. Both poplar and poplar/APB reduced the reaction enthalpy,dramatically. The activation energy dependence on the degree of conversion indicatedthat poplar and APB together accelerate the addition reactions at the early stage of PFresin curing process, but delay the condensation reactions at the later stage. Theearlier acceleration is contributed to the phase change from continuous to dispersed,and the latter is the result of a predominantly diffusion control. The isothermal DSCanalysis confirmed the dynamic DSC result that mixing of wood and/or APBaccelerates the curing reaction rate at lower temperature range. In other words, itimproves the addition reaction of curing process and at the same time, the reactionorders of all specimens are not changed either

Variation of the linking positions of the arylene groups in polyarylene vinyleneblock copolymers can be used as an effective method to fine tune the polymersemissive characteristics. Through Wittig reaction mechanism 2,5-dioctyloxy-1,4-dicarboxaldehyde and varying positional isomers of naphthalene bis(methyl triphenylphosphonium)dibromide gave alternate-block copolymers of poly(2,5-dioctyloxyphenylene vinylene-co-1,4-naphthalene vinylene) (P1), poly(2,5-dioctyloxy phenylenevinylene-co-1,5-naphthalene vinylene) (P2), and poly(2,5-dioctyloxy phenylenevinylene-co-2,6-naphthalene vinylene) (P3). These polymers were highly soluble incommon organic solvents. The chemical and physical characteristics of these polymerswere carried out using TGA, FTIR, 1H NMR, optical absorption and emission spectralmethods. The thermal stabilities of the first two polymers (P1 and P2) were significantlyhigher than the third polymer (P3). The glass transition temperatures of thesepolymers were found to be around 70°C. The first two polymers (P1 and P2) showedabsorption maxima around 360 nm, whereas the last case showed it at 406 nm. As thinfilms, all three polymers exhibited red-shifted absorptions. The photoluminescence (PL)emission maxima of P1, P2 and P3 polymers were 467 nm, 484 nm and 495 nm, in thegiven order. Polymers P1-P3 also showed red-shifted PL emission for their thin films.The differences in the absorption maxima and PL emission maxima of P1 to P3 are dueto the strain force between the vinylene and naphthalene protons. While, P3 polymerexhibited electroluminescence maxima at 540 nm

The introduction of cleaner technologies has become a major concern worldwideand therefore, the search for alternatives to the unsafe volatile solvents hasbecome the greatest priority throughout the academy and industry. Due toenforcement of policies in protecting the environment, "green chemistry" has receivedmuch attention since 1990's which it is still progressing. Green chemistry is understoodto be a superior, innovative chemistry which is cost-effective and has minimumdeleterious impact on environment. Highly polar conventional solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, pyridine, N-methylpyrrolidone andchlorinated solvents which are used in polycondensation polymerizations are volatileand most of them are flammable, toxic, quite hazardous and harmful compared to ionicliquids (ILs). Hence, there is a basic obligation for the advancement of new methodologiesof polymerizations by using environmentally benign media which could replacethe conventional solvents and enhance adequate solubility for polymerizationprocesses. Ionic liquids have great potential as a non-volatile organic medium forpolymerization and polymer processing due to their near-zero vapour pressure,nonflammability, low cost and ease of production. However, implementation of ILs assolvents for polymerization processes has afforded some marked advantages such asincreased molecular weight and narrower polydispersity in comparison to organicsolvents. Owing to their higher performance and characteristics, the demand forhigh-performance polymers is growing steadily. Hence, the synthesis and properties ofhigh-performance polyamides in the green media using ILs are reviewed to develop amethodology for "green polymer chemistry".