Increase In Styrene Content Research Articles

Effect of styrene content on mechanical and rheological behavior of styrene butadiene rubber

Styrene butadiene rubber(SBR) consists of two random polymerization units, styrene and butadiene. As a rigid segment, styrene chain provides strength and rigidity to the rubber. The content of styrene in SBR directly affects its strength and stiffness. In this paper, the effect of styrene content on the fatigue characteristics and rheological properties of SBR have been investigated. The stress relaxation of SBR was reduced and the cross-linking density of butadiene was increased with the increasing styrene content. Especially the dynamic fatigue life of precracked SBR samples was obviously prolonged via slow down crack growth rate when the styrene content increased, which was accompanied by an augment in the value of J-integral and tearing energy in the case of a same gap extension length. At the initial stage of crack growth, the growth of secondary crack played an important role in the growth of main crack, and when the main crack accelerates, the growth of main crack itself dominated. On the other hand, the glass transition temperature obviously increased with the increase of styrene content.

Thermo-rheological behavior and compatibility of modified asphalt with various styrene–butadiene structures in SBS copolymers

The knowledge of the morphological structure or effect of polymer structure on the performance of polymer-modified asphalt (PMA) is not systematic and completed yet. In this paper, SBS-modified asphalts were prepared by asphalts with different compositions and styrene–butadiene–styrene (SBS) copolymers with various styrene–butadiene structures, which in turn were subjected to frequency sweep tests, viscous measurements and fluorescence microscopy. The results revealed that the SBS-modified asphalt containing 30wt.% styrene had the optimal viscoelastic functions and the highest viscosity, indicating enhanced viscoelastic characteristics and less sensitivity to temperature changes. Furthermore, it is less susceptible to shear forces for asphalts as the increase of styrene content because larger and stronger aggregated polystyrene domains can render deformation and movement more difficult. For system studied, the compatibility becomes poorer as the increase of styrene contents and polymer phase sizes decrease with the enhancement of styrene contents as well as their volume proportions. The scope of distribution curves becomes narrower and the swelling degree is lower as the increase of styrene contents by image analysis. As a conclusion, there is a moderate styrene content for SBS to acquire equilibrium between the compatibility and viscoelastic characteristics.

Development and characterization of flax fiber reinforced biocomposite using flaxseed oil‐based bio‐resin

ABSTRACTIn this study, acrylated epoxidized flaxseed oil (AEFO) resin is synthesized from flaxseed oil, and flax fiber reinforced AEFO biocomposites is produced via a vacuum‐assisted resin transfer molding technique. Different amounts of flax fiber and styrene are added to the resin to improve its mechanical and physical properties. Both flax fiber and styrene improve the mechanical properties of these biocomposites, but the flexural strength decreases with an increase in styrene content. The mass increase during water absorption testing is less than 1.5% (w/w) for all of the AEFO‐based biocomposites. The density of the AEFO resin is 1.166 g/cm3, which increases to 1.191 g/cm3 when reinforced with 10% (w/w) flax fiber. The flax fiber reinforced AEFO‐based biocomposites have a maximum tensile strength of 31.4 ± 1.2 MPa and Young's modulus of 520 ± 31 MPa. These biocomposites also have a maximum flexural strength of 64.5 ± 2.3 MPa and a flexural modulus of 2.98 ± 0.12 GPa. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41807.

Surface Self-Assembled PEGylation of Fluoro-Based PVDF Membranes via Hydrophobic-Driven Copolymer Anchoring for Ultra-Stable Biofouling Resistance

Stable biofouling resistance is significant for general filtration requirements, especially for the improvement of membrane lifetime. A systematic group of hyper-brush PEGylated diblock copolymers containing poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) was synthesized using an atom transfer radical polymerization (ATRP) method and varying PEGMA lengths. This study demonstrates the antibiofouling membrane surfaces by self-assembled anchoring PEGylated diblock copolymers of PS-b-PEGMA on the microporous poly(vinylidene fluoride) (PVDF) membrane. Two types of copolymers are used to modify the PVDF surface, one with different PS/PEGMA molar ratios in a range from 0.3 to 2.7 but the same PS molecular weights (MWs, ∼5.7 kDa), the other with different copolymer MWs (∼11.4, 19.9, and 34.1 kDa) but the similar PS/PEGMA ratio (∼1.7 ± 0.2). It was found that the adsorption capacities of diblock copolymers on PVDF membranes decreased as molar mass ratios of PS/PEGMA ratio reduced or molecular weights of PS-b-PEGMA increased because of steric hindrance. The increase in styrene content in copolymer enhanced the stability of polymer anchoring on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be in the range between 1.5 and 2.0 with copolymer MWs above 20.0 kDa for the ultrastable resistance of protein adsorption on the PEGylated PVDF membranes. The PVDF membrane coated with such a diblock copolymer owned excellent biofouling resistance to proteins of BSA and lysozyme as well as bacterium of Escherichia coli and Staphylococcus epidermidis and high stable microfiltration operated with domestic wastewater solution in a membrane bioreactor.

N-Octyloxyallene homopolymerization and random copolymerization with styrene using catalyst system composed of lanthanide Schiff-base complexes and Al(i-Bu)3

The catalyst system composed of lanthanide Schiff-base complexes with [3,5-tBu2-2-(O)C6H2CH=NC6H5]3Ln(THF)(Ln(Salen)3, Ln = Sc, Y, La, Nd, Sm, Gd, Yb) and triisobutyl aluminum shows high activity for n-octyloxyallene (A) homopolymerization with narrow molecular weight distribution (MWD). The influences of reaction conditions on polymerization behavior are investigated, and poly(n-octyloxyallene) has a weight average molecular weight (M w) of 20.6 × 103 with MWD of 1.39 and 100% yield is obtained under the optimum conditions: [Al]/[Y] = 50 mol/mol, [A]/[Y] = 100 mol/mol, with polymerization at 80 °C for 16 h in bulk. The kinetic studies of n-octyloxyallene homopolymerization indicate that the polymerization rate is first-order with respect to the monomer concentration and shows some controlled polymerization characteristics. Random copolymer of n-octyloxyallene with styrene is obtained by using the same binary catalyst system; the reactivity ratios of the comonomer determined by Kelen-Tudos method are r A = 1.20 and r St = 0.35, respectively, the ratio of each segment and M w of the resulting copolymer could be controlled by varying the feed ratio of each monomer. Determined by differential scanning calorimetry, the copolymers obtained show only one glass transition temperature, which increases gradually with the increase of styrene content in the copolymer.

Effect of Formula on Microcellular Unsaturated Polyester

Formula for microcellular unsaturated polyester using chemical foaming method was studied. With the increase of NaHCO3 content, the cell size of microcellular unsaturated polyester slightly decreased with the increase of styrene content in the range of 1-2 %. The cell size increased in the range of 2-4 %. With the increase of curing agent content, the cell size increased in the range of 0.5-0.9 % and decreased in the range of 0.9-1.3 %. The cell size decreased with the increase of styrene content in the range of 30-40 %. The cell size had little variation when styrene content was in the range of 40-50 %. The average cell size and cell density of microcellular unsaturated polyester were strongly affected by accelerant content. The cell size decreased with the increase of accelerant content. The opposite was for the cell density. The microcellular unsaturated polyester prepared at 2% NaHCO3, 0.3% accelerantt, 0.9% curing agent, 40% styrene had the small cell size, high cell density, and strong compression strength.

Biofouling Resistance of Ultrafiltration Membranes Controlled by Surface Self-Assembled Coating with PEGylated Copolymers

Block and random PEGylated copolymers of poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) were synthesized with a controlled polydispersity using an atom transfer radical polymerization method and varying molar mass ratios of PS/PEGMA. Two types of PEGylated copolymers were self-assembly coated onto the surface of poly(vinylidene fluoride) (PVDF) ultrafiltration membranes for enhancing biofouling resistance. It was found that the adsorption capacities of random copolymers on PVDF membranes were all higher than those of block copolymers. However, the specific and overall protein resistance of bovine serum albumin (BSA) on PVDF membranes coated with block copolymers was much higher than that with random copolymers. The increase in styrene content in copolymer increased the amount of polymer coating on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be close to 2 for the best resistance of protein adsorption and bacterial adhesion on the PEGylated diblock copolymer-coated membranes. The PVDF membrane coated with such a copolymer owned excellent biofouling resistance to BSA, humic acid, negatively surface charged bacteria E. coli, and positively surface charged bacteria S. maltophilia.

Synthesis and evaluation of comb‐type copolymers prepared via atom transfer radical polymerization as possible cold flow improvers in GTL diesel fuels

AbstractStatistical comb‐type copolymers of styrene (Sty) and stearyl methacrylate (C18 MA) with varying [styrene]:[C18MA] ratios were synthesized by a controlled/living radical polymerization technique called atom transfer radical polymerization. The polymeric materials were evaluated in selected SASOL Fischer Tropsch gas‐to‐liquid diesels as possible cold flow improvers. Crystallization studies revealed that as the styrene content of the copolymer increased, a crystal growth inhibition mechanism was exhibited. With an increase in styrene content of the copolymer, differential scanning calorimetry and the cloud filter plugging point (CFPP) revealed a delay in onset of crystallization and lowered CFPP, respectively, whereas low‐temperature microscopy indicated modifications and size reduction of wax crystals. However, there appeared to be a styrene content, beyond which the additive's efficiency decreased. Homopolymer and copolymers with the highest styrene content led to long unfavorable needle‐shaped crystals. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis and characterization of styrene modified vinylester resin-clay nanocomposites

The influence of styrene as a reactive diluent on the morphology of vinylester resin-clay hybrids has been studied. Two mixtures of diglycidylether of bisphenol-A diacrylate as vinyl ester resin and styrene (20 and 40%) were prepared. Various weight ratios of styryl-functional organoclay were added to vinylester resin/styrene mixture, followed by polymerization of the mixture up to 160°C. The morphology of the hybrids studied by X-ray diffraction and Scanning Electron Microscope revealed that the dispersion of organoclay increased with the increase of styrene content. The inclusion of styrene to the system gave ordered intercalated nanocomposites. The surface hardness of the hybrid films decreased with adding a higher content of styrene. Thermogravimetric analysis indicates that clay is effective in promoting char-forming reaction of vinylester resin/styrene clay nanocomposites. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

ポリプロピレンと水添ポリスチレン‐ｂｌｏｃｋ‐ポリ（スチレン‐ｃｏ‐ブタジエン）‐ｂｌｏｃｋ‐ポリスチレンとの相容性と物性

Physical properties and morphology of a series of hydrogenated polystyrene-block-poly (styrene-co-butadiene) -block-polystyrene (SSEBS) were investigated using tensile test, transmission electron microscope and pulse NMR. Physical properties and miscibility of the blends of SSEBS with isotactic polypropylene (PP) also were investigated using the same methods. These SSEBS were prepared by hydrogenation of anionically polymerized polystyrene-block -poly (styrene-co-butadiene)-block-polystyrene (S-SB-S). The content of styrene in the SB block was varied from 0 to 25% in order to examine effects of styrene content. The total styrene contents of two end polystyrene blocks were about 15%. Tensile strengths and scratch hunting resistance of the blends of those S-SEB-Ss with PP increased with increase in styrene content of SEB block. However, the miscibility of the blends slightly decreased with increase in the styrene content.

Influence of molecular weight and tacticity on thermal stabilities of hydroquinone promoted CT polymerization of styrene and alkylmethacrylates

Thermal stabilities of copolymers of styrene and alkylmethacrylates synthesized by using hydroquinone (HQ) as promoter show an increase with increase in styrene content while the glass transition temperature decreases. The thermal stabilities are compared with analogue polymers synthesized with and without HQ. Though there is a drastic improvement in thermal stabilities of Sty–MMA copolymerization system, Sty–EMA and Sty–BMA systems did not exhibit enhanced thermal stabilities. It has been found that the decrease in molecular weight and polydispersity values as well as increased orderliness of structure in polymers are responsible for enhanced thermal stabilities.

Influence of hydrogenation and styrene content on the unaged and aged properties of styrene-butadiene copolymer

The influence of hydrogenation and styrene content on the properties of styrene butadiene copolymer (SBR) has been studied.There is an increase in glass transition temperature (Tg) associated with the reduction of double bonds by hydrogenation. The hydrogenated polymers demonstrate higher tensile strength, elongation at break and modulus values. The superior mechanical properties of HSBRs are due to the generation of polyethylene crystallites. The thermo-oxidative stability of saturated polymer is much higher than that of its unsaturated analogue. The samples with higher styrene content show higher modulus, but lower tensile strength and elongation at break, due to lower crystallinity. The thermo-oxidative stability of HSBR increases with increase in styrene content.

Synthesis, Characterization, and Glass-Reinforced Composites of an Acrylated Diglycidylether of Bisphenol-P

Abstract Glass-reinforced composites of acrylated diglycidylether of bisphenol-P were prepared using 2% benzoyl peroxide as hardener and different amounts (10% to 40%) of styrene as reactive diluent, and were evaluated for their physical, mechanical, electrical, and chemical resistance properties. The incorporation of styrene reduces %void content and shows improvements in mechanical properties such as tensile strength and Shore D hardness. The curing behavior of the resin-curing agent system was studied by differential scanning calorimetry. The kinetics of the thermal degradation was also studied. It is observed that the values of T max and IPDT decrease with increase in styrene content.

Space charges in ethylene-styrene copolymers irradiated by low-dose gamma rays

Space charges in ethylene-styrene copolymers irradiated by low dose gamma -rays were studied from the results of DC conduction, thermal pulse current, thermally stimulated current and residual voltage measurements. The number of carriers induced by gamma -rays and escaping from recombination becomes smaller with an increase in styrene content. The reason for this is thought to be that styrene absorbs the energy of electrons and increases the average energy necessary for ionization. The relationship between gamma -induced space charges and the morphological state of styrene is also studied in three kinds of polymers (random and graft copolymers and polymer blend). It can be said that styrene must be dispersed uniformly and bonded with ethylene in order to fully utilize the electron energy absorption effect of a benzene ring.

Molecular weight distribution of the graft copolymer comprising mixtures of styrene and acrylamiae on cellulose acetate film by means of gel permeation chromatography

AbstractStyrene portion of the radiation‐induced graft copolymer comprising styrene and acrylamide was separated by acid hydrolysis and the effects of various grafting parameters (e.g., reaction time, reaction temperature, solvents, monomer composition, etc.) on molecular weight distribution were evaluated by means of gel permeation chromatography. When a single monomer or mixture of two monomers are grafted, the molecular weights is found to increase, but polymer dispersity decreases with the increase of reaction time or reaction temperature except at a higher reaction time due to the continuous enlargment of the growing chain through increased swelling and molecular motion of the trapped radicals. At higher reaction time the degradation of the graft chains lead to lower molecular weight and higher polymer dispersity. Effects of solvents (e.g., methanol, ethanol, and t‐butanol) on the molecular weight and molecular weight distribution were discussed on the basis of swelling property and chain transfer constants of the solvents. Styrene‐type graft radical being long lived compared to acrylamide type, gave long‐chain styrene graft with the increase of styrene content in the reaction mixture. A comparison of the effect of one‐and two‐component systems on a molecular weight distribution is also discussed.

Intermolecular effects in macromolecular reactions—2. Decomposition of tert.butyl acrylate-styrene copolymers

Decomposition of tert.butyl acrylate (TBA) units in copolymers of TBA and styrene (STY) at 453 K has been studied. The rate diminishes with increase of STY content in the copolymer; pronounced autoacceleration is observed for all samples. Calculations revealed inadequacy of the intrachain mechanism of acceleration. Experimental data have been interpreted quantitatively in terms of both intra and intermolecular interactions of ester and carboxylic groups. Rate constants of the thermal and autocatalytic stages of the reaction appear to be independent of copolymer composition. The results confirm previous conclusion about determining contribution of intermolecular effects in the kinetics of the decomposition of poly TBA.

Anionic Polymerization and Copolymerization of Hydrocarbon Monomers Catalyzed by Organobarium Initiators

Abstract The barium salt of the dimeric dianion of 1,1-diphenylethylene (Ba-DPhE) initiates polymerization and copolymerization of monomers capable of anionic polymerization (butadiene, isoprene, styrene) in ethereal and hydrocarbon solvents. Ba-DPhE is more stereospecific in butadiene polymerization (up to 70% of cis-1, 4-units in hydrocarbon medium) than initiators based on other metals of Groups I and II. The relative reactivity of monomers in copolymerization processes in THF decreases in an order typical for anionic polymerization: styrene > butadiene > isoprene. The most interesting feature of organobarium initiators is their ability to form random butadiene-styrene copolymers with high cis-1,4-butadiene unit content when copolymerization proceeds in a hydrocarbon medium. A new phenomenon in anionic polymerization, the dependence of diene units structure on copolymer composition, was observed. Thus an increase of styrene content in butadienestyrene copolymer leads to conversion of cis-1,4-butadiene units into trans-1,4-units (in benzene) or to conversion of 1,4-units to 1,2-units (in THF). Similarly, an increase of butadiene content in its copolymer with isoprene (in benzene) leads to conversion of cis-1,4-isoprene units into trans-1,4-units. Spectrophotometric, conductometric, and viscometric methods were used to study organobarium active centers. Certain anomalies connected with the formation of specific aggregates due to coupling of bifunctional hydrocarbon chains with bivalent counterions were observed.

MECHANICAL RROPERTIES OF POLYPROPYLENE-STYRENE GRAFT COPOLYMER

Static and dynamic mechanical properties of polypropylene-styrene graft copolymer were studied in comparing with those of polypropylene-polystyrene blend and each homopolymer. These properties were interpreted in relation with their fine structure.Yield stress and strength at break of graft copolymer were increased with the increase of styrene content, but Young's modulus did not change remarkably and elongation at break decreased with grafting more than the value of polypropylene homopolymer but was still greater than the value for polystyrene homopolymer and blend.In stress-strain curve, a yield point was observed in graft copolymers and for polypropylene, but not observed in blend and polystyrene.The shape of loss modulus-temperature curve and the peak position of the absorption curve for the graft copolymer are different from that in the blend. Moreover, the curve for the graft copolymer whose powder or small pieces of the film was mixed and melt pressed was different from the curve for the original graft copolymer film, annealed after grafting. The absorption curve for the graft copolymer and blend showed two peaks; one at about 10°C. and another at 110-120°C. The former absorption indicates the αa-absorption of polypropylene which is due to the segmental motion of amorphous chains of the polymer and the latter absorption indicates the main dispersion of polystyrene.The peak temperature of the absorption curve at the higher temperature region for the original graft copolymer and blends agrees with the temperature for polystyrene, but the peak temperature for which was melt pressed and annealed graft copolymer shifted about 10°C. to higher temperature side from the peak temperature for polystyrene. This shift suggests that the molecular mobility of polystyrene branches in the graft copolymer may be restricted by the crystallites of polypropylene. In other words, polystyrene branches exist in the circumstance where crystallites of polypropylene may affect the molecular motions of the polystyrene branches.In the case of blends polystyrene molecules must be excluded from crystallites, and in the original graft copolymer the grafting must take place only on the amorphous chains of polypropylene.

Tensile Fracture Properties of Filled SBR Vulcanizates with Various Styrene Contents

To investigate the tensile fracture mechanism of rubber vulcanizates, in particular to determine the relationship between the tensile properties and polymer structure, styrene-butadiene copolymers (SBR) with various styrene contents were studied in this paper. The following conclusions were obtained from the results of tensile measurements and physical properties.(1) Failure for the SBR vulcanizates (carbon black filled), at the temperature region over the necking phenomena, occurred mainly at the site of the main chain, not between rubber molecule and carbon black.(2) If the number average molecular weight, network chain density and the type of combined sulfur are considered nearly the same, the same molecular motional region (which was discussed from the view of viscoelastic study and nuclear magnetic resonance study in this paper, but it can be mentioned as the glass transition temperature in general) was shifted for the higher temperature side with the increase of styrene content in SBR, and the characteristic temperature for the failure properties (the inflection point for the tensile strength-temperature curve and the maximum point for the ultimate elongation-temperature dependence) was also shifted in the same quantity.(3) Shifting the tensile data in the same quantity as the transition temperature, only one master curve was obtained for the tensile strength, even if the styrene contents were changed. For the ultimate elongation, however, the master curves were not the same for the various contents of styrene, but the value of the ultimate elongation after shifting decreased with the incresae of styrene parts in polymer. This result was successfully interpreted by the hypothesis that the elongation of polymer molecule depends on the carbon atom in butadiene monomer unit, not on the carbon atom in styrene unit.

Dipole moments and molecular structure of copolymers. II. Dipole moment of methyl acrylate‐styrene copolymers

AbstractThe dielectric properties of methyl acrylatestyrene copolymers in benzene solution were measured, and it was found that the value of dipole moment, μ, of methyl acrylate monomer unit in the copolymers increased with an increase of styrene content, e.g. from 1.46 D (for polymethyl acrylate) to 1.61 D (for the copolymer of which mole fraction of methyl acrylate is 0.23) at 20°C. The theoretical treatment described in the preceding paper has been applied to the experimental results and the variation in values of μ is discussed from a consideration of the detailed arrangement of polar monomer units in the copolymer molecule.