Influence of electron beam radiation on mechanical and thermal properties of styrene‐butadiene‐styrene block copolymer

Electron beam crosslinking of elastomers is a special type of crosslinking technique that has gained importance over conventional chemical crosslinking method, because the former process is fast, pollution free, and simple. The technique involves the impingement of high‐energy electrons generated from electron accelerators and the subsequent production of free radicals on target elastomers. These radicals result in crosslinking of elastomers via radical–radical coupling. In the process, some chain scission may also take place. In this work, a high‐vinyl (～ 50%) styrene‐butadiene‐styrene (S‐B‐S) block copolymer was used as the base polymer. An attempt was made to see the effect of electron beam radiation on the mechanical and thermal properties of the block copolymer. Radiation doses were varied from 25 to 300 kGy. Mechanical properties like tensile strength, elongation at break, modulus at different elongations, hardness, tear strength, crosslink density, and crosslink to chain scission of the irradiated samples were studied and compared with those of unirradiated ones. In this S‐B‐S block copolymer, a relatively low‐radiation dose was found effective in improving the level of mechanical properties. Differential scanning calorimeter and dynamic mechanical analyzer were used to study the thermal characteristics of the irradiated polymer. Influence of a stabilizer at different concentrations on the properties of S‐B‐S at varied radiation doses were also focused on. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

RFL coated aramid short fiber reinforced thermoplastic elastomer: Mechanical, rheological and morphological characteristics

Composite based on a new generation metallocene catalyzed thermoplastic elastomer ethylene-octene copolymer (EOC) and resorcinol formaldehyde latex (RFL) coated aramid short fiber was prepared by varying the short fiber loading from 1 to 10 phr. The mechanical, morphological and rheological characterizations were carried out. The impact of a low molecular weight maleic anhydride grafted 1, 2 polybutadiene (MA-g-PB) on various properties was also investigated. It has been observed that with increasing the short fiber content both the low strain modulus and modulus at 100% increase but the tensile strength and elongation at break decrease. The improvements in tensile strength coupled with elongation at break and good fiber dispersion particularly at high fiber loaded composite were achieved with the incorporation of MA-g-PB, which indicates that it acts as an interface modifier through compatibilization between the fiber and the EOC matrix as well as a good dispersing agent. The understanding of adhesion between the fiber and the polymer and the sticking of polymer traces on the tensile fractured fiber surface of the composite by scanning electron microscopic analyses further support the compatibilizing action of MA-g-PB. The melt rheological behavior such as storage modulus, loss modulus, complex viscosity and storage viscosity of the composites were investigated using a Rubber Process Analyser (RPA) under strain and frequency sweep mode.     

Synthesis of hydrogels with a gradient crosslinking structure by electron beam radiation to an aqueous solution of poly(sodium acrylate)

Hydrogels were prepared by electron beam (EB) radiation to the aqueous solutions of poly(sodium acrylate) in the presence of potassium and ammonium peroxodisulfates. The effects of EB radiation dose, as well as polymer, and initiator concentrations on the formation of gels, were investigated. On the basis of the storage modulus, loss modulus, and complex viscosity of the isolated gels determined by rheological measurement, the relationship between the radiation conditions and the rheological properties of the gels was discussed. Furthermore, hydrogels with a gradient crosslinking structure in a depth direction were synthesized by controlling EB radiation dose.     

Influence of untreated and novel electron‐beam‐modified surface‐coated silica filler on the thermorheological properties of ethylene–octene copolymer

We developed surface‐modified silica fillers by coating these with an acrylate monomer, trimethylolpropane triacrylate, or a silane coupling agent, triethoxyvinyl silane, followed by electron‐beam irradiation at room temperature. These were incorporated in an ethylene–octene copolymer rubber. Thermorheological studies of the unvulcanized ethylene–octene copolymer and its untreated and modified silica‐filled composites were done with a shear dynamic oscillating rheometer. Modification of the silica filler, especially via the silanization process followed by electron beam treatment, significantly reduced filler–filler networking as revealed from the log–log plots of storage modulus and complex shear viscosity, and its real component. The rheological complexity of the compositions was analyzed from a double logarithmic plot of the storage modulus and loss modulus. The results obtained from the master curves constructed on the basis of the time–temperature superposition principle and the activation energy calculated from the Arrhenius equation for the flow of above these compounds further supported these findings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2453–2459, 2003     

Synthesis and characterization of exfoliated poly(styrene-co-methyl methacrylate)/clay nanocomposites via emulsion polymerization with AMPS

A method was described for synthesis of exfoliated poly(styrene-co-methyl methacrylate)/clay nanocomposites through an emulsion polymerization with reactive surfactant, 2-acrylamido-2-methyl-1-propane sulfonic (AMPS) which made the polymer end-tethered on pristine Na-MMT.AMPS widened the gap between clay layers and facilitates comonomers penetrate into clay. Silicate layers affect the composition of comonomers, for example A0.3M10S10T5 showed the elevated composition of MMA end tethered on silicate when compared to the feed ratio and polar methyl methacrylate (MMA) was considered to have the stronger interaction with clay layers than styrene.The exfoliated structure of extracted nanocomposite was confirmed by XRD and transmission electron microscopy. The onset of thermal decomposition for nanocomposites shifted to a higher temperature than that for neat copolymer. The dynamic moduli of nanocomposites increase with clay content. Dynamic storage modulus and complex viscosity increased as the clay content increased. In low frequency region all prepared nanocomposites exhibited apparent low-frequency plateaus in the linear storage modulus. Complex viscosity showed shear-thinning behavior as the clay content increases.     

High vinyl high styrene solution SBR

Objective: the objective of this study is to prepare high vinyl copolymers containing various levels of styrene and butadiene, and also to prepare random butadiene in high styrene content styrene-butadiene copolymers (SBR) while controlling the styrene block length. These materials could be used in race tread applications. Summary: This reports presents the synthesis and characterization of random, high vinyl copolymers containing styrene and butadiene (SBR's). The styrene content of these SBR's ranged from 10 to 80%. These SBR's were synthesized via anionic polymerization initiated by a catalyst system with a ratio of 1/0.4/5 of n-butyllithium (n-BuLi) to sodium dodecylbenzene sulfonate (SDBS) to N,N,N′,N′-tetramethylethylenediamine (TMEDA). Kinetic data as well as NMR and ozonolysis techniques confirm that random SBR copolymers are being produced for low styrene content polymers. The glass transition temperature (T_g), increased dramatically as the styrene content was increased. The amount of vinyl based upon the polymer's total composition within the copolymer was found to decrease linearly as you increase the amount of styrene in the polymer. TGA results show that high styrene content polymers degrade at lower temperatures. The RPA confirms that as the styrene content increases, the elastic modulus decreases. As the frequency increased, the tan delta decreased for each polymer. Tan delta does not appear to be a function of styrene content. TEM results helped to describe polymer microstructure.     

Solution microstructure of a micro-crosslinked acrylamide-based terpolymer

The hydrophobically associating copolymer poly (acrylamide/butyl styrene/sodium 2-acrylamido-2-methylpropane sulphonate) (PASA) is micro-crosslinked with a small amount of phenolic aldehyde (PL) to obtain the micro-crosslinked polymer PASA–PL with excellent liquidity and water solubility. After crosslinked, the critical association concentration of copolymer reduces in the brine solution with high NaCl concentration and PASA–PL displays much better thickening and anti-aging properties in brine solutions at low polymer concentrations. The contribution of micro-crosslink of PASA with PL to the associating structures is investigated by fluorescent probe and scanning electron microscope (SEM). The fluorescent probe results show that a large amount of hydrophobic microdomains with very strong non-polarity are formed because of greatly strengthened intermolecular hydrophobic association for the PASA–PL polymer in aqueous and brine solutions, and PASA and NaCl concentration greatly influence intermolecular hydrophobic association in PASA–PL brine solutions. SEM measurements show that continuous associative structures with huge sizes are formed in PASA–PL aqueous and brine solution.     

Properties of acrylonitrile–butadiene–styrene/polycarbonate blends with styrene–butadiene–styrene block copolymer

The importance of alloys and blends has increased gradually in the polymer industry so that the plastics industry has moved toward complex systems. The main reasons for making polymer blends are the strengthening and the economic aspects of the resultant product. In this study, I attempted to improve compatibility in a polymer blend composed of two normally incompatible constituents, namely, acrylonitrile–butadiene–styrene (ABS) and polycarbonate (PC), through the addition of a compatibilizer. The compatibilizing agent, styrene–butadiene–styrene block copolymer (SBS), was added to the polymer blend in ratios of 1, 5, and 10% with a twin‐screw extruder. The morphology and the compatibility of the mixtures were examined by scanning electron microscopy and differential scanning calorimetry. Further, all three blends of ABS/PC/SBS were subjected to examination to obtain their yield and tensile strengths, elasticity modulus, percentage elongation, Izod impact strength, hardness, heat deflection temperature, Vicat softening point, and melt flow index. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2521–2527, 2004     

UV photopolymerized hydrogels with β-cyclodextrin moieties

Hydrophilic hydrogels based on poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) block copolymers have potential applications in drug delivery, tissue engineering and other biomedical devices due to their excellent biocompatibility and environmental sensitivity. However, they also exhibit some shortcomings in terms of swelling and mechanical properties as well as affinity for water-insoluble or hydrophobic drug molecules. To address these limitations, new polymeric hydrogels with β-cyclodextrin moieties were prepared by UV photo-polymerization of maleic anhydride-substituted β-CD (MAH-CD) and the block copolymer macromer from Pluronic F68 and poly(ɛ-caprolactone). Their swelling and dynamic rheological properties were investigated with respect to the effects of feed compositions. It was found that the swelling ratio, storage modulus and loss modulus of the resulting hydrogel increased with the increase of MAH-CD amount. Incorporation of MAH-CD resulted in strong viscoelastic system with dominating elastic behavior.     

Rheological properties of styrene butadiene styrene polymer modified road bitumens

The use of polymers for the modification of bitumen in road paving applications has been growing rapidly over the last decade as government authorities and paving contractors seek to improve road life in the face of increased traffic. Currently, the most commonly used polymer for bitumen modification is the elastomer styrene butadiene styrene (SBS) followed by other polymers such as styrene butadiene rubber, ethylene vinyl acetate and polyethylene. This paper describes the polymer modification of two penetration grade bitumens with SBS. Six polymer modified bitumens (PMBs) were produced by mixing the bitumens from two crude oil sources with a linear SBS copolymer at three polymer contents. The rheological characteristics of the SBS PMBs were analysed by means of conventional as well as dynamic mechanical analysis using a dynamic shear rheometer (DSR). The results of the investigation indicate that the degree of SBS modification is a function of bitumen source, bitumen-polymer compatibility and polymer concentration, with the higher polymer concentrations in a high aromatic content bitumen producing a highly elastic network which increases the viscosity, complex modulus and elastic response of the PMB, particularly at high service temperatures. However, ageing of the SBS PMBs tends to result in a reduction of the molecular size of the SBS copolymer with a decrease in the elastic response of the modified road bitumen.     

Scrutinizing the influence of strain‐induced fiber orientation on the melt rheological behavior of short aramid fiber/thermoplastic elastomer composite using rubber process analyzer

The effect of fiber loading and its orientational changes on the melt rheological behavior of a short aramid fiber reinforced ethylene‐octene copolymer was explored as function of dynamic strain and frequency using a Rubber Process Analyser (RPA). The rheological responses such as the storage modulus and complex viscosity to a cyclic dynamic strain sweep and subsequent linear viscoelastic (LVE) frequency sweep were performed to probe the orientational changes of the short fiber within the sample. An enhanced elastic shear modulus was observed at the low strain regime with a few numbers of repeated strain sweeps and level off thereafter. This can be attributed to the orientational changes of the short fiber from an initial random orientation to a well‐ordered concentric fiber string and the string–string packing with repeated oscillatory shear strain. The complex viscosity measured as a function of LVE frequency sweep having the influence of a pre strain history was also found to increases in first few cycles, but very interestingly the complex viscosity measured at all the frequency sweep cycles shows similar values, which are not subjected to any strain history. The optical microscopic images of the samples before and after the RPA analyses clearly support the possibility of fiber orientations and their subsequent packing with repeated strain sweeps. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Unique shape memory behavior of polyolefinic blends with special reference to creep behavior,stress relaxation,and melt rheological study

Creep response, stress relaxation behavior, and melt rheological study of the shape memory polymer blend based on EOC‐EPDM has been studied in details. In this study, especially the effect of the crosslinks formation in presence of electron beam on the creep response, melt rheological study and stress relaxation behavior has been reported. With increase of electron beam dose, creep response becomes lower and the creep compliance value also comes down. Higher resistance creep response of the radiation crosslinked blends indicates the superior shape recovery behavior of the blends. Stress relaxation behavior of the crosslinked blend also shows the lower decay of stress value with time for higher radiation crosslinked blend. The lower relaxation ratio of the highly radiation crosslinked blend also supports the superior shape recovery behavior of the crosslinked blend. Apart from, melt rheological study shows the higher storage modulus value and higher complex viscosity of the radiation crosslinked blend which also supports the formation of higher crosslinked network structure. Tension set value also clearly indicates the better shape recovery behavior of the crosslinked blend. POLYM. ENG. SCI., 58:876–885, 2018. © 2017 Society of Plastics Engineers     

Interfacially compatibilized LDPE/POE blends reinforced with nanoclay: investigation of morphology,rheology and dynamic mechanical properties

Morphological, melt rheological and dynamic mechanical properties of low-density polyethylene (LDPE)/ethylene–octene copolymer (POE)/organo-montmorillonite (OMMT) nanocomposites, prepared via melt compounding were studied. The XRD traces indicated different levels of intercalated structures for the nanocomposites. Addition of a compatibilizer (PE-g-MA) improved the intercalation process. TEM results revealed existence of clay layers in both phases but they were mainly localized in the elastomeric POE phase. Addition of 5 wt% OMMT to the LDPE/POE blend led to reduction in the size of the elastomer particles confirmed by AFM. The complex viscosity and storage modulus showed little effect of the presence of the clay when no compatibilizer was added. As the extent of exfoliation increased with addition of compatibilizer, the linear viscoelastic behavior of the composites gradually changed specially at low-frequency regions. The interfacially compatibilized nanocomposites with 5 wt% OMMT had the highest melt viscosity and modulus among all the studied nanocomposites and blends. Also, this particular composition showed the best improvement in dynamic storage modulus. The results indicated that clay dispersion and interfacial adhesion, and consequently different properties of LDPE/POE/clay nanocomposites, are greatly affected by addition of compatibilizer.     

Preparation and rheological properties of SEM-25 containing associative thickener latexes and their mechanisms of thickening

Hydrophobically modified alkali-soluble acrylic latexes were prepared using varying level of SEM-25, triphenylethyl phenoxy polyoxyethylene ether methacrylate, a functional monomer bearing a long segment of ethylene oxide and a hydrophobic tetraphenyl group. Sharp increases in viscosity and light transmittance of the diluted associative thickener latexes were observed with ascendant pH starting from 7. And with further increase in the pH, viscosity of the thickener latexes rapidly fell down, while the light transmittance was kept relatively constant. It was revealed that a critical content of SEM-25 in the thickener copolymer, 5% in the present case, was required in order for the associative thickener to outperform the SEM-25 free counterpart. When used in thickening a latex of P(St–BA) (Poly(styrene–Butyl acrylate)) copolymer using a thickener copolymer with 12 wt% of SEM-25, addition of 0.34 wt% of the thickener polymer relative to P(St–BA) was necessary to have a higher viscosity than the same latex thickened using the thickener free of SEM-25. It seemed that incorporation of 0.275 mol% of SEM-25 was indispensable for the associative thickener to exceed the performance of conventional thickener.     

Influence of silica and electron beam radiation on the properties of a high vinyl styrene-butadiene-styrene block copolymer

Radiation crosslinking of polymers has gained importance over conventional crosslinking because the system is fast, pollution free and relatively simple. In high energy electron beam curing, which is one of the radiation curing methods, the material to be cured is bombarded with electrons of specified energy to produce free radials. These radicals unite to give rise to chemical crosslinks. In the process, some unwanted chain scission may also occur. The mechanical properties of such electron beam crosslinked systems can further be improved by the incorporation of nanosilica. In this work, a high vinyl (~50%) S-B-S block copolymer incorporated with varying doses of specific hydrophilic nanosilica was irradiated with electron beam at 25 and 50 kGy. Mechanical properties were studied and compared with that of the unirradiated system. The influence of a silane coupling agent was also investigated. Morphological studies were done to understand the dispersion of nanosilica in the polymer matrix. Relatively moderate amounts of nanosilica along with an optimum dose of the coupling agent were found to be effective in improving the properties. Rheological properties were also studied in details to understand the possibility of recycling the polymer.     

丙烯酰胺/丁基苯乙烯衍生物疏水缔合共聚物的溶液性能

采用自由基胶束聚合法合成了丙烯酰胺（AM）/丁基苯乙烯（BS）疏水缔合水溶性共聚物(PSAM).凝胶渗透色谱（GPC）测试结果显示,PSAM的重均分子量为1.6868×10⁵,环境扫描电镜（ESEM）照片显示,PSAM在水溶液中形成了疏水缔合网络结构,结果表明,PSAM的增黏能力主要依赖于疏水结构单元的分子间疏水缔合作用.PSAM溶液性能的研究结果表明,溶液质量浓度超过0.1 g·dl^-1时,共聚物具有优良的增黏、耐盐及耐温性能,在80℃时显示良好的抗老化性能;PSAM亚浓溶液为假塑性流体,具有良好的触变性,低剪切速率下在最初一段时间内呈现剪切增稠性质.     

Polyethersulfone/polyetherethersulfone copolymers with the same chemical composition and different melt‐viscosity

Random, block, and alternative polyethersulfone/polyetherethersulfone copolymers (phenyl: ether: sulfone =7 : 4 : 3) with similar molecular weights and polydispersity were synthesized using different synthetic strategies. DSC and DMA analyses indicated that all copolymers are amorphous and possess extremely close glass transition temperature. The random copolymer displayed higher modulus and complex viscosity. It is interesting to find that the alternative copolymer exhibited a melt viscosity of 281 Pa s, which is much lower than that of the block copolymer (646 Pa s) and the random copolymer (1641 Pa s) at 4 s^?1. Moreover, the alternative copolymer showed obviously higher elongation at break of 101.9%. These behaviors were highly related to their different sequence distribution. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40149.     

Rheological and mechanical properties of PEO/block copolymer blends

Small quantities of block copolymers from two families, styrene‐butadiene‐methylmethacrylate (SBM) and methylmethacrylate‐butylacrylate‐methylmethacrylate (MAM) have been added to a polyethylene oxide (PEO) in order to improve its processability, namely increasing its elastic modulus without increasing too much its shear viscosity. The copolymers contain one block of polymethylmethacrylate (PMMA) that is compatible with PEO; the other blocks create nano phases, dispersed in the PEO matrix. Considerable efforts were devoted to finding the best blending method, either melt processing or solution casting. PEO is very sensitive to shear, and was found to degrade both in the bulk and in solution. Degradation, which cannot be avoided, was quantified through intrinsic viscosity measurements. The rheological characterization of blends containing 1, 2, and 5 wt% block copolymer was carried out. The elastic modulus was found to increase more than the complex viscosity. Blends obtained by solution casting technique gave better results. The elongational viscosity obtained for one blend containing 5 wt% of SBM showed a slight increase with respect to the pure PEO. Mechanical properties were then investigated, through tensile tests and dynamic mechanical analysis in flexion and in torsion; the copolymer generally enhanced the mechanical properties. POLYM. ENG. SCI., 45:1385–1394, 2005. © 2005 Society of Plastics Engineers     

Enhancing and controlling the critical attributes of poly (N-vinylcaprolactam) through electron beam irradiation for biomedical applications

The primary aim of this body of work is to investigate the effect of an industrial scale electron beam sterilization process on novel PNVCL-based smart polymers. There is limited literature available that examines the effects of modifying PNVCL by electron beam irradiation, and as a means of potentially enhancing properties such as the lower critical solution temperature and mechanical behavior. Physically crosslinked poly(N-vinylcaprolactam)–vinyl acetate (PNVCL–VAc) copolymers were prepared by photopolymerization and were subsequently exposed to ionizing radiation via electron beam technology. The mechanical characteristics and phase transitions of the physically crosslinked PNVCL samples were tailored by controlling the electron beam irradiation dose. Importantly, PNVCL and PNVCL–VAc samples (5 wt % in solution) underwent a phase transition between 33.5 and 26.5 °C, following electron beam irradiation. Furthermore, all samples displayed a Young's modulus between 1024.3 and 1516.4 MPa depending on the addition of copolymer and electron beam irradiation dose. The industrial scale electron beam sterilization process proved successful in enhancing/modifying many key smart polymer properties, and this ability to formulate and sterilize in one step could prove a very attractive approach for many biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48639.     

Influence of untreated and novel electron beam modified surface coated silica filler on dynamic mechanical thermal properties of ethylene‐octene copolymer

An extensive study on dynamic mechanical thermal analysis has been carried out to investigate the effect of filler‐filler and polymer‐filler interaction in cured ethylene‐octene copolymer reinforced by unmodified and modified silica. The silica was treated with trimethylolpropane triacrylate (TMPTA) or triethoxyvinyl silane (TEVS), followed by electron beam irradiation at room temperature. Modification of the silica filler, especially via silanization, significantly reduces filler‐filler networking, as evidenced from the strain sweep tests, and thus helps reduce the Payne effect, particularly at high filler loadings. The effect of modification is quantified with the help of a new mathematical model correlating the storage modulus and the volume fraction of the filler. The enhancement in the storage modulus at high temperatures and changes in the loss tangent at the glass transition temperature suggest definite improvement in the polymer‐filler interaction in the case of these modified fillers. The results obtained from the master curves constructed based on the time‐temperature‐superposition principle further support the findings.