Iranian polymer journal
Volume:19 Issue: 10, 2010

The curing kinetics of bisphenol-A epoxy resin (BPAER) modified by liquid crystallinep-phenylene di-[4-(2,3-epoxypropyl) benzoate] (p-PEPB), with a diaminesuch as 4,4′-diaminodiphenyl ether (DDE) as a curing agent, was investigated bynon-isothermal DSC method. The correlation between apparent activation energy, Ea,and the conversion, α, was obtained by Ozawa method. The catalyzed effect ofhydroxyl groups was determined in DSC experiment and a molecular reactionmechanism was proposed. The results show that hydroxyl groups can accelerate thecuring reaction and lower the Ea value. The average values of Ea for p-PEPB/DDE andBPAER/p-PEPB/DDE systems are 122.4 and 72.28 kJ.mol-1, respectively. There is aphase separation in the curing process with LC phase formation. These curingreactions can be described by the model of Sestak and Berggren (S-B model). Theaverage reaction orders, i.e., m and n for p-PEPB/DDE system are 0.64 and 1.26 andfor BPAER/p-PEPB/DDE system are 0.48 and 1.35, respectively. The dynamicmechanical loss peak temperature is about 14°C higher than that of pure BPAERsystem when the content of p-PEPB is 5 wt%.

The effects of nanohydroxyapatite/gelatin (nHA/G) ratio, stirring rate and water/oilphase ratio (W/O ratio) on particle size and distribution of nanocompositemicrospheres based on nanohydroxyapatite-in-gelatin were investigated.Surface response model was used for tests design. The microspheres were fabricatedusing water-in-oil emulsion followed by their characterizations using optical microscopy,scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), X-raydiffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR).Statistical models with interaction terms were derived to model the particle size anddistribution of the microspheres. Addition of nHA to gelatin led to larger sizes ofmicrospheres, although the higher nHA/G ratio (0.5-1) led to their slightly smaller size.The data revealed that further increase in stirring rate resulted in microspheresize reduction. The results showed that at different stirring rates, W/O ratio has acteddifferently. By increasing in nHA/G ratio, the uniformity of the microspheres improved.The effect of stirring rate was dependent on nHA/G ratio. Various W/O ratios did notshow any significant effect on particle size distribution, and yet their higher ratiosenhanced the uniformity of particle size to some extent. Statistical analysis revealedthat the generated models are valid for modeling of the particle size and its distribution.SEM images showed that by addition of nHA to gelatin, the microspheres becomesmoother. At high ratios of nHA/G (>1) some cracks were observed on the surface ofthe microspheres. Calcium mapping of the surface and cross-section of themicrospheres confirmed the uniform distribution of nHA on the surface and within theirbulk. The XRD and FTIR studies showed that the fabrication process did not affect thechemical and physical characteristics of gelatin and nHA any longer.

Injecting a gelation system of a polymer and a cross-linker among available methodsto reduce water in petroleum industry is widely used. In this work, a hydrogel wasprepared by cross-linking of an aqueous solution of chromium acetate (III) and thecopolymer of 2-acrylamido-2-methyl-propanesulphonic-acid sodium salt (AMPS) andacrylamide (PAMPS). The phase diagram of bottle tests showed that the minimumconcentration of copolymer for gel formation is 5500 ppm (0.55 wt%). The study ofviscoelastic behaviour of hydrogels using dynamic rheometry showed that the storagemodulus of the hydrogels increased with increased copolymer concentration andcross-linker/copolymer ratio. At low concentrations of copolymer (5500 and 7500 ppm(0.75 wt%)) there would be no effects on the elastic modulus by increasing thecross-linker/copolymer ratio. Therefore, the effect of copolymer and cross-linker concentrations on the apparent plastic viscosity (ηpl) of the gel was investigated.Increasing the solvent ionic power led to decrease in latent gel strength, in which theeffect of divalent ions is higher than monovalent ions. A numerical codification for gelstrength magnitude is suggested in the range of 10-200 1/s shear rate by usingviscometric and bottle test results. The results show that a gel with copolymer concentration of 9500 ppm (0.95 wt%) and cross-linker/copolymer ratio of 1/5 is a suitable gel in terms of gel strength and gelation time.

Anovel method of introducing multifunctional groups onto butyl rubber (IIR) bycarbonyl addition reaction was investigated in this work. The resulting polymers(MFIIR) were characterized with FTIR, 1H NMR and GPC. The functional groupsC=O, CH=CH and -OH were introduced onto the butyl rubber backbone and themolecular weight of the resulting polymer was hardly any different from that of IIR. Thecuring properties of MFIIR and natural rubber (NR) and adhesive strength of bothsystems were studied and compared together by dynamic vulcanized analysis andtensile testing. Curing efficiency of MFIIR was improved significantly. TD5, TD10 andTD20 of MFIIR for 0.02/0.02 (mol/mol) of NaH/MAH increased by 157%, 51% and 34%,respectively compared to that of IIR. Moreover, TD5, TD10, and TD20 of MFIIRincreased further with increasing the molar contents of NaH and MAH. The values ofTD5, TD10 and TD20 for 0.06/0.06 (mol/mol) of MFIIR reached their highest levels. Thetensile strength values of MFIIR samples were all between those of IIR and BIIR andthe stress at 300% elongation of MFIIR samples (6.1 MPa) were higher than those ofIIR (5.2 MPa) and BIIR (4.3 MPa). Peeling strength between MFIIR and NR reached1.20 N/mm which was higher than the value of peeling strength between thebrominated butyl rubber (BIIR) and NR. Dynamic mechanical properties and thermalbehaviour were also investigated by dynamic mechanical analysis and thermogravimetricanalysis. The decomposition temperature of MFIIR (404.6°C) was slightly lowerthan those of IIR (412.8°C) and BIIR (406.0°C) and thus, the modification processseems to have made insignificant effect on the thermal stability of IIR. Butyl rubber wasmodified successfully and a kind of modified IIR with much improved curing efficiencywas achieved through this method.

Copolymers of butyl acrylate (BA) and glycidyl methacrylate (GMA) were prepared by batch emulsion copolymerization at 75°C, using potassium persulphate (KPS) as an initiator, sodium dodecylbenzene sulphonate (SDBS) as an emulsifier and sodium bicarbonate as a buffer. Composition of copolymers was determined by elemental analysis and the monomer reactivity ratios were estimated by five conventional linear methods at low monomer conversions, i.e., methods of Mayo- Lewis (ML), Fineman-Ross (FR), inverted Fineman-Ross (IFR), Ezrielev-Brokhina- Roskin (EBR) and Kelen-Tudos (KT). All methods resulted in higher reactivity ratios for GMA comparing to those of BA (ML: rB = 0.15 and rG = 1.51, FR: rB = 0.22 and rG = 1.85, IFR: rB = 0.16 and rG = 1.57, EBR: rB = 0.18 and rG = 1.77, and KT: rB = 0.30 and rG = 1.57). The results also showed that, compared to homogeneous polymerizations (bulk and solution), reactivity ratio of GMA is reduced in emulsion polymerization due to its relative water-solubility, whereas the reactivity ratio of BA is distinctly increased. The effect of the reactivity ratios on the monomer conversion was primarily studied, as well. The results showed that monomer conversion is increased when using higher GMA feed content due to higher reactivity of GMA.

Incorporating hyperbranched poly(phenylene sulphide) (HPPS) into polypropyleneprior to fibre spinning markedly enhances the dyeability of polypropylene with CIDisperse Red 202. Meanwhile, the mechanical properties are slightly affected by theincorporation HPPS. Dyeing tests show that the disperse dye display much greatersubstantivity towards the modified PP compared to its unmodified counterpart. The K/Svalues of hyperbranched poly(phenylene sulphide) modified PP fibre show no increasewith respect to increased dye concentration from 4% to 6% “on mass of fibres” afterreduction. This is clearly an indication of reaching "saturation" of polar groups availablein HPPS modified PP fibre. DSC tests show that the crystallinity (χc) of HPPS/PP fibresis slightly decreased, but this decrease is not sufficient to allow the dyeability ofHPPS/PP fibres. The knowledge that may validate higher dye uptake with increasedHPPS content can be attributed to its more polar groups and aromatic rings enteredinto the system. The test results of the drawn samples as well as their sonic velocitymodulus have almost the same trend. DMA tests show that HPPS/PP blendsconsist of single-phase amorphous regions. The SEM micrographs show that the sizeof the HPPS domains is in sub-micrometer order and they have good interfacialcompatibility with PP phases, though the former can be extracted by THF from thematrix.

Diacetone acrylamide (DAAM) was derived from alkaline hydrolysis of 2-methyl-4-oxo-N-[(1Z)-1(sulphooxy)prop-2-ene-1-ylidene]pentan-2-aminium as a precursorwhich the latter was prepared by condensation of acrylonitrile and acetonein sulphuric acid. Diacetone acrylamide was characterized by 1H NMR, FTIR and massspectrometry for structural conformation. The DAAM copolymer emulsions wereprepared by a two-stage seed batch emulsion polymerization of methyl methacrylate,butyl acrylate and DAAM using ammonium persulphate as an initiator, sodium laurylsulphate and nonyl phenol as emulsifiers. Diacetone acrylamide was used as afunctional monomer. Further, the DAAM copolymer emulsions were characterized andstudied as a function of DAAM concentration by laser light scattering, viscometry anddifferential scanning calorimetry. The results have shown that with increasedconcentration of DAAM in the emulsions there are increases in particle size, particlesize distribution and viscosity of the emulsions, whereas the glass transitiontemperature (Tg) of DAAM emulsions is reduced. These emulsions comprising differentconcentrations of DAAM were cross-linked with 1,3-diaminopropane and werecharacterized by FTIR. The cross-linking reaction was carried out at ambienttemperature resulting in formation of one-component thermoset acrylic emulsions.These emulsions which were used as coatings were evaluated for mechanical andchemical resistance properties. The results obtained showed that the coatingcomprised of 4 wt% of DAAM in copolymer emulsion exhibited improved chemicalresistance and mechanical properties.

Interfacial strength between polymeric matrix and lignocellulosic reinforcement hasdirect effects on the properties of wood plastic composites (WPCs). There are twoapproaches to improve the interfacial adhesion between two phases in WPC:modification of the polymeric matrix or modification of the lignocellulosic fibres. Thiswork focuses on the chemical modifications of natural fibres such as lignocellulosic,enhanced by silane, alkali, benzoyl chloride and acid acrylic. The chemically treatedfibres were then compounded with polypropylene at 190°C and 40 wt%, in an internalmixer equipped with cam rotor, for all samples. Changes in the chemical structure ofchemically treated fibres were tracked by Fourier transform infra red (FTIR)spectroscopy. The intensity of O-H bond at 3400 cm-1 and formation of ester bond at1740 cm-1 were indications of changes in the chemical structure of the fibres. Theinterfacial adhesion was evaluated using adhesion factor which was obtained fromdynamic mechanical thermal analysis data. The results showed that the minimumadhesion factor is related to silane treatment which provides the best interactionbetween polymer and fibres. The tan δ peak was shifted to higher temperature for filledsamples in comparison to neat polypropylene and the amount of shift was related to themethod of chemical treatment. Different morphologies were observed in samples dueto different chemical modifications of fibres and among them, silane treatment methodof the fibres provides the best wetting action by polymeric matrix. Tensile properties andimpact resistance of the samples were determined to evaluate the effect of interfacialadhesion on the performance of the composites.