Thermal stability and decomposition kinetics of styrene-butadiene rubber nanocomposites filled with different particle sized kaolinites

A series of styrene-butadiene rubber (SBR) nanocomposites filledwith different particle sized kaolinites are prepared via a latex blending method. The thermal stabilities of these clay polymer nanocomposites (CPN) are characterized by a range of techniques including thermogravimetry (TG), digital photos, scanning electron microscopy (SEM) and Raman spectroscopy. These CPN show some remarkable improvement in thermal stability compared to that of the pure SBR. With the increase of kaolinite particle size, the residual char content and the average activation energy of kaolinite SBR nanocomposites all decrease; the pyrolysis residues become porous; the crystal carbon in the pyrolysis residues decrease significantly from 58.23% to 44.41%. The above results prove that the increase of kaolinite particle size is not beneficial in improving the thermal stability of kaolinite SBR nanocomposites.

Influence of the structural characteristic of pyrolysis products on thermal stability of styrene-butadiene rubber composites reinforced by different particle sized kaolinites

A series of rubber composites were prepared by blending styrene-butadiene rubber (SBR) latex and the different particle sized kaolinites. The thermal stabilities of the rubber composites were characterized using thermogravimetry, digital photography, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Kaolinite SBR composites showed much greater thermal stability when compared with that of the pure SBR. With the increase of kaolinite particle size, the pyrolysis products became much looser; the char layer and crystalline carbon content gradually decreased in the pyrolysis residues. The pyrolysis residues of the SBR composites filled with the different particle sized kaolinites showed some remarkable changes in structural characteristics. The increase of kaolinite particle size was not beneficial to form the compact and stable crystalline carbon in the pyrolysis process, and resulted in a negative influence in improving the thermal stability of kaolinite/SBR composites.

Influence of kaolinite particle size on cross-link density, microstructure and mechanical properties of latex blending styrene butadiene rubber composites

Cross-link density, microstructure and mechanical properties of styrene butadiene rubber (SBR) composites filled with different particle sized kaolinites are investigated. With the increase of kaolinite particle size, the cross-link density of the filled SBR composites, the dispersibility and orientation degree of kaolinite particles gradually decrease. Some big cracks in filled rubber composites are distributed along the fringe of kaolinite aggregates, and the absorbance of all the absorption bands of kaolinites gradually increase with the increase of kaolinite particle size. All mechanical property indexes of kaolinite filled SBR composites decrease due to the decrease of cross-linking and reduction of interface interaction between filler and rubber matrix.

Ultrasonic degradation of butadiene, styrene and their copolymers

Ultrasonic degradation of commercially important polymers, styrene-butadiene (SBR) rubber, acrylonitrile-butadiene (NBR) rubber, styrene-acrylonitrile (SAN), polybutadiene rubber and polystyrene were investigated. The molecular weight distributions were measured using gel permeation chromatography (GPC). A model based on continuous distribution kinetics approach was used to study the time evolution of molecular weight distribution for these polymers during degradation. The effect of solvent properties and ultrasound intensity on the degradation of SBR rubber was investigated using different pure solvents and mixed solvents of varying volatility and different ultrasonic intensities. (C) 2011 Elsevier B.V. All rights reserved.

Observation of inverted phases in poly(styrene-b-butadiene-b-styrene) triblock copolymer by solvent-induced order-disorder phase transition

We report observation of inverted phases consisting of spheres and/or cylinders of the majority fraction block in a poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer by solvent-induced order-disorder phase transition (ODT). The SBS sample has a molecular weight of 140K Da and a polystyrene (PS) weight fraction of 30%. Tapping mode atomic force microscopy (AFM) and transmission electron microscopy (TEM) were utilized to study the copolymer microstructure of a set of solution-cast SBS films dried with different solvent evaporation rates, R. The control with different R leads to kinetic frozen-in of microstructures corresponding to a different combination parameter chi (eff)Z of the drying films (where chi (eff) is the effective interaction parameter of the polymer solution in the cast film and Z the number of "blobs" of size equal to the correlation length one block copolymer chain contains), for which faster evaporation rates result in microstructures of smaller chi (eff)Z. As R was decreased from rapid evaporations (similar to0.1 mL/h), the microstructure evolved from a totally disordered one sequentially to inverted phases consisting of spheres and then cylinders of polybutadiene (PB) in a PS matrix and finally reached the equilibrium phase, namely cylinders of PS in a PB matrix. We interpret the formation of inverted phases as due to the increased relative importance of entropy as chi (eff)Z is decreased, which may dominate the energy penalty for having a bigger interfacial area between the immiscible blocks in the inverted phases.

Cationic cyclization of styrene-butadiene rubber

Controlled cyclization of styrene-butadiene rubber (SBR) was achieved with the aid of cationic catalyst system based on diethylaluminium chloride (AIEt(2)Cl) and benzyl chloride (C6H5CH2Cl) and by working in xylene solution at high temperature (T > 100 degreesC). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility, free gel were obtained. The products were characterized with IR H-1-NMR, DSC, GPC. The polycyclic structure was determined. (C) 2001 Published by Elsevier Science Ltd.

Compositional dependence of the microphase separation transition in styrene-butadiene-styrene triblock copolymer/polystyrene blends

The change in the microphase separation transition (MST) temperature of a styrene-butadiene-styrene (SBS) triblock copolymer induced by the addition of polystyrene (PS) was investigated by small-angle X-ray scattering. It was found that the transition temperature was determined from the molecular weight (M(H)) Of the added PS in relation to that of the corresponding blocks (M(A)) in the copolymer. The MST temperature decreased with added PS if M(H)/M(A) < 1/4, while it increased with added PS when M(H)/M(A) > 1/4 Analysis of the theoretical expression based on the random phase approximation showed exactly the same tendency of change in the transition temperatures as that observed experimentally. The interaction parameter, chi(SB), obtained by nonlinear fitting of the scattering profiles of SBS/PS blends in the disordered state, was found to be a function of temperature and composition. Composition fluctuations were found to exist in SBS/PS blends, increasing with increasing addition of PS but diminishing with increasing molecular weight of the added PS.

Copolymerization of styrene with butadiene and isoprene using a rare earth catalyst

In the copolymerization of styrene-butadiene and styrene-isoprene, a novel rare earth catalyst system (CF3CO2)(3)Ln/R(3-n)AlH(n)/(CH3)(3)CCH2Br (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; R = Me-, Et-, i-Bu-, and Oct-; n = 0 and 1) has been studied. The 1, 4 unit contents in the copolymers obtained are found to range from 64.4 to 99.6% with St contents of 5.2 to 59.9%, and intrinsic viscosities of 0.1 to 0.5 dl g(-1) measured by i.r., H-1 n.m.r. and C-13 n.m.r. spectra. From the calculated data of linked ratios, a change in the microstructure is induced by the styrene unit, probably adjacent to the butadiene or isoprene unit. An interesting result is that the ratios of styrene unit linked with 1, 2 or 3,4 units in the copolymers are far higher than in copolymers obtained with the nickel catalyst. The experimental results are discussed in terms of rare earth pi-allyl coordination and back-biting mechanism.

MISCIBILITY, MICROSTRUCTURE, AND DYNAMICS OF BLENDS CONTAINING BLOCK-COPOLYMER .1. MISCIBILITY OF BLENDS OF HOMOPOLYSTYRENE WITH STYRENE-BUTADIENE BLOCK-COPOLYMERS

The miscibilities of blends of homopolystyrene/styrene-butadiene/styrene (PS/SBS) and PS/SB-4A (4-arm star block copolymer) have been studied by dynamic mechanical analysis (DMA) and C-13 CPMAS NMR techniques. The results indicate that the miscibilities o

MISCIBILITY, MICROSTRUCTURE, AND DYNAMICS OF BLENDS CONTAINING BLOCK-COPOLYMER .2. MICROSTRUCTURE OF BLENDS OF HOMOPOLYSTYRENE WITH STYRENE-BUTADIENE BLOCK-COPOLYMERS

The microstructures of styrene-butadiene triblock (SBS) and styrene-butadiene four-arm star block (SB-4A) copolymers and their blends with homopolystyrene (PS) of different molecular weights, MPS, have been investigated by means of small-angle X-ray scatt

MISCIBILITY, MICROSTRUCTURE, AND DYNAMICS OF BLENDS CONTAINING BLOCK-COPOLYMER .3. MOLECULAR-MOTION IN HOMOPOLYSTYRENE AND POLYSTYRENE 4-ARM STYRENE-BUTADIENE STAR BLOCK-COPOLYMER BLENDS

The proton spin-spin relaxation times (T-2(H)) at different temperatures (from 160 to 390 K) have been determined for polystyrene (PS) and four-arm star styrene-butadiene block copolymer (SB-4A) and its blends with PS of different molecular weights (M(PS)

EFFECT OF ANTIOXIDANTS ON PROPERTIES AND MORPHOLOGY OF POLY(ACRYLONITRILE BUTADIENE STYRENE) POLYCARBONATE BLENDS

Poly(acrylonitrile-butadiene-styrene), polycarbonate (PC), and two types of antioxidants have been blended by an extruder twin screw. Notched Izod impact strength, tensile property, and melting flow index (MFI) were measured for the blends including diffe

ON THE PHASE-STRUCTURE OF BLENDS OF POLYCARBONATE WITH POLY(ACRYLONITRILE-BUTADIENE-STYRENE)

Polycarbonate (PC) and poly(acrylonitrile-butadiene-styrene) (ABS) was co-extruded at different weight ratios by a single screw extruder. In order to obtain a finer blend, two times extrusion was carried out. In this case, a ''network'' structure with two-continuous phases was observed for the blends with two compositions of PC/ABS, being 80/20 and 70/30. It is found that the blends with these two compositions just have maximum values on the curves of notched Izod impact strength, flexural modulus and flexural strength vs. composition, respectively. This was never observed in previous publications.

EXCIMER FLUORESCENCE STUDY ON THE MISCIBILITY OF POLY(VINYL METHYL-ETHER) AND STYRENE-BUTADIENE STYRENE TRIBLOCK COPOLYMER

The excimer fluorescence of a triblock copolymer, styrene-butadiene-styrene (SBS) containing 48 wt% polystyrene was used to investigate its miscibility with poly(vinyl methyl ether) (PVME). The excimer-to-monomer emission intensity ratio I(M)/I(E) can be used as a sensitive probe to determine the miscibility level in SBS/PVME blends: I(M)/I(E) is a function of PVME concentration, and reaches a maximum when the blend contains 60% PVME. The cloud point curve determined by light scattering shows a pseudo upper critical solution temperature diagram, which can be attributed to the effect of PB segments in SBS. The thermally induced phase separation of SBS/PVME blends can be observed by measuring I(M)/I(E), and the phase dissolution process was followed by measuring I(M)/I(E) at different times.