Effect of nature and extent of crosslinking on swelling and mechanical behavior of styrene–butadiene rubber membranes

The influence of crosslink type and crosslink density on the swelling and mechanical behavior of styrene–butadiene rubber (SBR) membranes were studied in four aliphatic hydrocarbons. To vary the crosslink type and crosslink density, SBR was vulcanized by four different vulcanizing systems viz conventional, efficient, peroxide and a mixture of sulfur and peroxide. SBR vulcanizates having mono or disulfidic crosslinks (efficient system) exhibited the highest solvent uptake whereas those with C–C bonds (peroxide system) showed the lowest. SBR crosslinked by the mixed system showed superior mechanical properties in the unswollen, swollen and deswollen conditions. Arrhenius and thermodynamic parameters were evaluated from the diffusion data. Finally, a comparison between theoretical and experimental diffusion results was carried out.     

Effects of ordered structure on non-isothermal crystallization kinetics and subsequent melting behavior of β-nucleated isotactic polypropylene/graphene oxide composites

Journal of Thermal Analysis and Calorimetry - In this paper, effects of ordered structure on non-isothermal crystallization kinetics and subsequent melting behavior of β-nucleated isotactic...     

Effect of a novel charring agent on thermal degradation and flame retardancy of acrylonitrile–butadiene–styrene

A novel charring agent poly(p-propane terephthalamide) (PPTA) was synthesized by using terephthaloyl chloride and 1,3-propanediamine through solution polycondensation and it was used together with ammonium polyphosphate (APP) to prepare a novel intumescent flame retardant (IFR) for ABS. The thermal degradation behaviour and flame retardancy were investigated, the results showed that PPTA could be effective as a charring agent, the flame retardancy of ABS and the mass of residues improved greatly with the addition of IFR. When the content of APP was 22.5 mass% and PPTA was 7.5 mass%, the limiting oxygen index (LOI) value of IFR-ABS system was found to be 32.4, and class V-0 of UL-94 test was passed. Moreover, the synergistic effects of two different adjuvants AlPi and MnO₂ in IFR-ABS system have been studied.     

Preparation and characterization of star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate

A universally significant method,which combines the anionic polymerization with photoinduced charge transfer polymerization,for preparation of soluble star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate,was described.The poly(ethylene oxide) (PEO) block was formed by initiation of phenoxy an-ions using p-aminophenol protected by Schiff's base as the parent compound Then the charge transfer system composed of PEO chains with deprotected-amino end groups and benzophenone initiated the polymerization of styrene and methyl metnacrylate sequentially under UV irradiation.The formed star triblock copolymer of styrene,ethylene oxide and methyl methacrylate could be purified by thin-layer chromatography (TLC) and characterized by IR,1H NMR,GPC (gel permeation chromatogrphy) and PGC (pyrolysis gas chromatography).     

Effect of graphite and common rubber plasticizers on properties and performance of ceramizable styrene–butadiene rubber-based composites

Journal of Thermal Analysis and Calorimetry - Ceramizable composites are highly filled polymer dispersion composites which create stiff porous and durable ceramic structure when exposed to fire or...     

Preparation,non-isothermal crystallization,and melting behavior of β-nucleated isotactic polypropylene/poly (ethylene terephthalate) blends

β-nucleated PP/PET blends were prepared using nano-CaCO₃ supported β-nucleating agent (β-NA), PP as matrix, and PET as dispersion phase. The effects of preparation methods, PET content, and melting temperature on the non-isothermal crystallization behavior and the melting characteristic and polymorphic composition of PP in the blends were investigated by differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD). The results indicated that the PP crystallized predominantly in β-modification in the presence of β-NA. However, efficiency of β-NA for PP crystallization decreased with addition of PET and increasing PET contents. The β-nucleation of β-NA for PP crystallization in the blends was dependant on the preparation methods. The high β-nucleation and high β-PP content were obtained for PP/PET blend prepared at the temperature of 265 °C and added the β-NA into the blend at the temperature of 180 °C. However, the addition of β-PP or β-NA into blends at 265 °C decreased the β-nucleation, and no β-PP was formed because the β-NA mainly dispersed on the PET dispersion phase or at the interface between PP and PET.     

Thermal decomposition and kinetics studies on the 2,2-dinitropropyl acrylate–styrene copolymer and 2,2-dinitropropyl acrylate–vinyl acetate copolymer

In the present work, kinetics of thermal decomposition of 2,2-dinitropropyl acrylate–styrene copolymer (DNPA/St) and 2,2-dinitropropyl acrylate–vinyl acetate copolymer (DNPA/VAc) was investigated by differential scanning calorimetry (DSC). The influence of the heating rate (5, 10, 15, and 20 °C min^?1) on the DSC behavior of the copolymer was verified. The results showed that, as the heating rate was increased, decomposition temperature of the copolymer was increased. Also, the kinetic parameters such as activation energy and frequency factor of the copolymer were obtained from the DSC data by the isoconversional methods proposed by Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO). Average activation energy obtained by KAS and FWO methods for the thermal decomposition reaction of DNPA/St and DNPA/VAc are 157.38 ± 0.27 and 147.67 ± 0.57 kJ mol^?1, respectively. The rate constants for thermal decomposition calculated from the activation parameters showed the structural dependency. The relative stability of two copolymers under 50 °C was in this order: DNPA/St > DNPA/VAc. The results of thermogravimetry (TG) analysis revealed that the main mass changes for DNPA/St and DNPA/VAc occurred in the temperature ranges of 200–270 °C. The DSC-FTIR analysis of DNPA/St indicates that the band intensity of nitro and other groups increased haphazardly from 230 °C due to thermal decomposition.     

Effect of Ag addition on crystallization kinetics and thermal stability of As–Se chalcogenide glasses

Chalcogenide glasses of (As₅₀Se₅₀)_100?xAg_x (0 ≤ x ≤ 25) were prepared using the melt quenching technique under non-isothermal conditions. Differential scanning calorimetry curves measured at different heating rates (5 ≤ β ≤ 40 K min^?1) are used to characterize the as-quenched samples. The thermal stability was monitored through the calculation of the temperature difference T _c ? T _g, stability parameter S and crystallization rate factor K _p. The glass-forming ability (GFA) was investigated on the basis of Hurby parameter H _r which is a strong indicator of GFA. In addition, the activation energy of glass transition E _t, activation energy of crystallization E _c and Avrami exponent n of the studied compositions were determined. The mechanism of crystallization was found to be a combination of two- and three-dimensional crystal growth.     

Effects of polyamide 6 on the crystallization and melting behavior of β-nucleated polypropylene

Non-nucleated polypropylene alloy with polyamide 6 (PP/PA6) and β-nucleated polypropylene (β-PP)/PA6 alloy, as well as its compatibilized version with maleic anhydride grafted PP (PP-g-MA) were prepared with an internal mixer. In the all alloys, PP formed a continuous phase with a dispersive PA6. Effects of PA6 on the non-isothermal crystallization behavior, melting characteristics and the β-PP content of alloys were investigated by differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD). The results indicated that the crystallization temperature () of PP shifts to high temperature in the non-nucleated PP/PA6 alloys due to the α-nucleating effect of PA6. However, in the β-nucleated PP/PA6 alloys, PA6 hardly has an effect on the of PP. The β-PP content in the alloys not only depends on the content of the PA6, but also on the melting temperatures. It is proved by etching the alloys with sulfuric acid that the nucleating agent mainly disperses in the PA6 phase and/or the interface between PP and PA6 when blended at high temperature. Addition of PP-g-MA promotes the formation of β-PP in the β-nucleated PP/PA6 alloys. The increase in the PA6 content has a little influence on the of PP and the β-PP content in the compatibilized β-nucleated PP/PA6 alloys. The non-isothermal crystallization kinetics of PP in the alloys was evaluated by Mo’s method.     

Thermal stability and flammability of butadiene–styrene rubber nanocomposites

Heterobimetallic oxalato complex precursors, manganese(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (MnOLa), cobalt(II)pentaaquatris(oxalato)lanthanate(III)trihydrate (CoOLa), nickel(II)pentaaquatris(oxalato)lanthanate(III)hexahydrate (NiOLa) and copper(II)diaaquatris(oxalato)lanthanate(III)monohydrate (CuOLa) of the type, M₃[La(C₂O₄)₃(H₂O) _m ]₂·nH₂O have been synthesized in aqueous medium. The precursors were characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. The good crystalline nature with monoclinic structures predominates in MnOLa and NiOLa whereas triclinic structures were found in CoOLa and CuOLa. The solid-state thermal behaviour of the precursors was explored using TG, DTG and DTA in air. The MnOLa generated a mixture species consisting mainly of MnO₂, Mn₃O₄, Mn₅O₈, La₂O₃ and LaMn₇O₁₂ at 1000 °C through the formation of several intermediate species at 380 and 570 °C. The studies revealed that CoOLa led mainly to LaCoO₃ and La₂CoO₄ along with some oxides of both the cobalt and lanthanum at 1000 °C. In case of nickel analogue the mixture species identified at 1000 °C are mainly of La₂NiO₄, La₂O₃, Ni₂O₃ and NiO_2. In case of CuOLa the product at 1000 °C consisted of La₂CuO₄, La₂Cu₂O₅ and oxides of copper and lanthanum. The nature of decomposition of the precursors in nitrogen were seen from DSC study and the kinetic parameters i.e., E ^* , lnk ₀, ΔH ^# , ΔS ^# and order of reaction of all the steps were evaluated and discussed.     

A critical analysis of the effect of crosslinking on the linear viscoelastic behavior of styrene–butadiene rubber and other elastomers

The linear viscoelastic behavior in dynamic shear and tensile creep at temperatures from −30 to 70 °C is measured for an styrene–butadiene rubber (SBR) elastomer cured with dicumyl peroxide to crosslinking densities between 0 and 23.5 × 10⁻⁵ mol/cm³. The G′, G″, and tan δ isotherms are analyzed by time–temperature superposition (TTS), where the tan δ master curves are consistent with those of Mancke and Ferry. However, to achieve the TTS in the lightly crosslinked SBR systems, an anomalous vertical shift is required in the narrow temperature region from 10 to 30 °C. The vertical shift factor in this temperature region is not the standard from rubber elasticity. No anomalous behavior is detected in the equilibrium modulus, which is a linear function of temperature in accordance with the classical theory of rubber elasticity. In contrast to SBR, standard vertical shifts are required to effect TTS for uncrosslinked polybutadiene and an ethylene propylene diene monomer elastomer. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

The effect of chlorosulphonated polyethylene on thermal properties and combustibility of butadiene–styrene rubber

This article describes the test results of thermal properties and flammability of the unconventionally cross-linked blends of chlorosulfonated polyethylene (CSM) and butadiene–styrene rubber (SBR) by means of zinc oxide or nano-zinc oxide. The thermal curves have been interpreted from the point of view of the chemical transitions of elastomers and their blends. It has been found that the content of combined chlorine in CSM exerts a significant influence on the cross-linking kinetics of CSM/SBR blends, their thermal properties and flammability.     

Synthesis and characterization of diblock copolymer of butadiene and 2-ethyl-2-oxazoline

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Influence of <Emphasis Type="Italic">m</Emphasis>-isopropenyl-α,α-dimethylbenzyl isocyanate and styrene on non-isothermal crystallization behavior of polypropylene

Non-isothermal crystallization kinetics of polypropylene (PP), m-isopropenyl-α,α-dimethyl-benzyl isocyanate grafted PP (PP-g-m-TMI), and styrene(St), as comonomer, together with m-TMI grafted PP (PP-g-(St-m-TMI)) was investigated by using differential scanning calorimetry (DSC) under different cooling rates. The crystallization rates of all samples increased with increasing cooling rate. The relation of the half time of crystallization (t _1/2) of the three samples, t _{1/2(PP-g-(St-m-TMI))} < t _{1/2(PP-g-m-TMI)} < t _1/2(PP), implying the introduction of St could effectively improve the degree of grafting of m-TMI, resulting in crystallization temperature increased, and the crystallization rate was the fastest. Three methods, namely, the Avrami, the Ozawa, and the Mo, were used to describe the crystallization process of the three samples under non-isothermal conditions. The Avrami and Ozawa neglected the secondary crystallization that follows primary crystallization. The Mo method can successfully describe the overall non-isothermal crystallization process of all the samples. It has been found that the F(T)_{(PP-g-(St-m-TMI))} < F(T)_(PP-g-m-TMI) < F(T)_(PP), also meaning that the crystallization rate of PP-g-(St-m-TMI) and PP-g-m-TMI were faster than that of PP. The activation energy (ΔE) for non-isothermal crystallization of all samples was determined by using the Kissinger method. The result showed that the lower value of ΔE for crystallization obtained for PP-g-m -TMI and PP-g-(St-m-TMI) confirmed the nucleating effect of St and m-TMI on crystallization of PP.     

Stabilization effect of potential antioxidants on the thermooxidative stability of styrene–butadiene rubber

Effects of several heterocyclic compounds containing nitrogen, trisubstituted amines and diamines and molecules based on N,N,N′,N′,N′′,N′′-substituted-[1,3,5]triazine-2,4,6-triamine in preventing thermooxidative degradation of styrene–butadiene rubber (SBR) have been studied using non-isothermal DSC measurements. The aim of this study was to determine and compare the stabilizing effect of individual compounds and to select the structures with the best antioxidative properties. In order to compare the stabilizing effect of the compounds, induction periods and protection factors have been calculated. The treatment of the experimental data was carried out using a method based on a non-Arrhenian temperature function. The results show that better antioxidative properties can be assigned to heterocyclic compounds. On the other hand, molecules containing triazine structures exhibited only negligible stabilizing effect on SBR at lower temperatures and even destabilizing effect at higher temperatures.     

Effect of sol–gel derived in situ silica on the morphology and mechanical behavior of natural rubber and acrylonitrile butadiene rubber blends

Silica particles were generated and grown in situ by sol–gel method into rubber blends comprised of natural rubber (NR) and acrylonitrile butadiene rubber (NBR) at various blend ratios. Silica formed into rubber matrix was amorphous in nature. Amount of in situ silica increased with increase in natural rubber proportion in the blends during the sol–gel process. Morphology studies showed that the generated in situ silica were nanoparticles of different shapes and sizes mostly grown into the NR phase of the blends. In situ silica filled NR/NBR blend composites showed improvement in the mechanical and dynamic mechanical behaviors in comparison to those of the unfilled and externally filled NR/NBR blend composites. For the NR/NBR blend at 40/60 composition, in particular, the improvement was appreciable where size and dispersion of the silica particles into the rubber matrix were found to be more uniform. Dynamic mechanical analysis revealed a strong rubber–in situ silica interaction as indicated by a positive shift of the glass transition temperature of both the rubber phases in the blends.     

Fabrication of organic–inorganic nano-complexes using ABC type triblock copolymer and polyoxotungstates

New organic–inorganic nano-complexes were produced from a micelle of tri-block polymers; poly(styrene)-b-poly(2-vinylpyridine)- b-poly (ethylene oxide) (PS-PVP-PEO) and tungsten compounds such as tungstate (W₁²⁻), undecatungstophospate (PW₁₁⁷⁻) and undecatungstosilicate (SiW₁₁⁸⁻) in acidic aqueous solutions. The size and morphology of the complexes were characterized by measurements of dynamic light scattering, atomic force microscopy, and scanning electron microscopy. This complex is assembled mainly by the charge interaction between the inorganic polyanions and the positively charged PVP block in the PS-PVP-PEO molecule, which was confirmed by zeta-potential and fluorescence spectroscopic studies. In the absence of the inorganic anions, the zeta-potential of the micelle was +11 mV at pH 3 due to the positive charge of the PVP block. When the inorganic anion was mixed with the PS-PVP-PEO micelle, decrease in the zeta-potential due to charge neutralization occurred with incorporation of inorganic anions into the PS-PVP-PEO micelle. The minimum zeta-potential was 0, −33, and −35 mV for W₁²⁻ /PS-PVP-PEO, PW₁₁⁷⁻ /PS-PVP-PEO, and SiW₁₁⁸⁻ /PS-PVP-PEO complexes, respectively. Excess negative charge which occurred in the latter two complexes indicates that PS-PVP-PEO molecules bound PW₁₁⁷⁻ and SiW₁₁⁸⁻ by forces other than charge interaction. In addition, the incorporation of an inorganic polyanion into the micelle gave a new morphology to the micelle. In the absence of the polyanion, the PS-PVP-PEO micelles showed an extended conformation due to repulsive forces working among the positively charged PVP blocks. Addition of the polyanion caused the formation of shrunken forms of the micelles, since the charge repulsion was cancelled by the polyanion. This feature may be useful in developing a new type of functioning micelle.     

Effects of stereo-defect distribution and molecular mass in the non-isothermal crystallization behavior of β-nucleated isotactic polypropylene

In this study, based on the synthesis of two Ziegler–Natta iPP with nearly same average isotacticity but different uniformities of stereo-defect distribution, we further prepared two series of β-iPP with different molecular masses by addition of different concentration of peroxide. We investigated the combination effects of stereo-defect distribution and molecular mass on the non-isothermal crystallization behavior and polymorphic composition behavior of β-iPP by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and scanning electron microscope (SEM). The results of non-isothermal crystallization kinetics revealed that the iPP molecular mass has only slight influence on the crystallization temperature of β-iPP, while the uniformity of stereo-defect distribution not only evidently influences the crystallization temperature, but also affects the dependency of crystallization temperature on cooling rate. β-iPP with less uniformity of stereo-defect distribution leads to higher dependency of crystallization temperature on the cooling rate. The calculation of crystallization activation energy ΔE showed that the lower the molecular mass, the lower the ΔE, indicating that it is easier for the occurrence of crystallization. Meanwhile, iPP with more uniform stereo-defect distribution has lower ΔE. Moreover, both stereo-defect distribution and molecular mass are important factors in determining the polymorphic composition. A more uniform stereo-defect distribution is more favorable for the β-phase crystallization; the lower the molecular mass, the harder for β-phase crystallization to take place. However, compared with iPP molecular mass, the uniformity of stereo-defect distribution is the first-order factor in determining the β-phase crystallization of iPP. Moreover, the thermal stability and the dependency of β-phase proportion on the cooling rate are also found to be highly dependent on the iPP molecular mass.