Photocrosslinking of styrene–isoprene–styrene; effect of benzoin and ethylene glycol dimethacrylate on physical properties

Crosslinking reaction of polymer by ultraviolet (UV) irradiation has been important in industries. In this work, photocrosslinking of styrene–isoprene–styrene (SIS) triblock copolymer in the presence of benzoin photoinitiator and a dimethacrylate monomer as crosslinking agent was investigated. Curing of samples was initiated under UV irradiation. Benzoin was used as photoinitiator because it contains chromophore group that could absorb UV irradiation. Ethylene glycol dimethacrylate (EGDMA) was used as crosslinking agent, since it has alkene functional groups that could react with the alkene group of SIS. ATR-FTIR spectra of samples show that absorption band of double bond at 1500–1600?cm^?1 decreases after UV exposure. Increasing the concentration of benzoin (0.1–1?phr) and EGDMA (1–10?phr) leads to an increase in gel content and hardness, while swelling ratio decreases. After 5?min heating at 150?°C, about 20%wt of the unirradiated compound became insoluble, because heating of compound at 150?°C causes crosslinking reaction without any irradiation.     

Enhanced properties of poly(styrene–b–ethylene–co–butylene–b–styrene) nanocomposites with in situ construction of interconnected graphene network

In this work, such elastomeric nanocomposites were fabricated with graphene (GE) sheets selectively distributing between polymer matrices and forming three-dimensional networks. The solvent evaporation process was first introduced to produce poly(styrene–ethylene–co–butadiene–b–styrene) (SEBS) microspheres and then reduced GE oxide attached to the surface of SEBS microspheres via electrostatic interaction and sonication-assisted reduction. The microstructure of nanocomposites, prepared by compression molding using SEBS/GE microspheres, was investigated using scanning electron microscopy and transmission electron microscopy. The results showed that interconnected GE networks formed in heat-pressing composite and was destroyed after twin-roll mixing. The SEBS/GE nanocomposites showed enhanced electrical, thermal, and mechanical properties. The electrical resistivity of nanocomposites obtained via heat-pressing reached to 1.1 × 10³ Ω m at a 2.5 wt % (1.07 vol %) content of GE. The thermal and mechanical properties were also characterized. It was found that the initial degradation temperature increased by nearly 40 °C and the mechanical properties continued to rise with GE content below 0.5 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47118.     

Chemical modification of styrene–butadiene–styrene (SBS) rubber by reactive grafting with maleic anhydride

A procedure to increase the adhesion of block styrene-butadiene-styrene (SBS) rubber consisting of the reactive grafting with maleic anhydride (MA) in the presence of an organic peroxide radical initiator is proposed. The influence of the reactive grafting on the surface properties of SBS has been studied with special emphasis on the improvement of the adhesion to polyurethane adhesive. The grafting of MA onto SBS was carried out in the presence of different concentrations of 2,5-dimethyl-2,5-di(tertbutyl peroxy) hexane (DBPH) as initiator to generate oxygen radicals by thermal decomposition, which induce the grafting reaction. The modification process was performed in the molten state using a Brabender mixer to premix the reactants and a hot press to initiate the functionalizing reaction. ATR-IR and XPS spectroscopies were employed to verify the grafting of MA on SBS. The changes in wettability on the modified SBS rubber were determined by contact angle measurements. Adhesion properties were evaluated from T-peel tests of SBS rubber/polyurethane adhesive joints. Reasonable extents of MA grafting on SBS were obtained (evidenced by the presence of a weak carbonyl vibration at 1700 cm^-1 in the ATR-IR spectra and by the carbon- oxygen band at a binding energy of 287.0 eV in the XPS spectra). The higher the DBPH amount, the higher the MA amount grafted onto the SBS surface. The maximum grafting level was obtained using 2 wt% MA. Grafted species seemed to be mainly concentrated on the surface of the SBS-molded sheets. The wettability of the modified rubber increased with respect to the original polymer, new carbon-oxygen moieties were created and the C/O ratio increased. A noticeable enhancement in peel strength values was observed, which was ascribed to the creation of interfacial interactions between the polyurethane and the SBS rubber surfaces.     

Synthesis of silane monomer-modified styrene–acrylate microemulsion coatings by photopolymerization

A relatively concentrated silane monomer-modified styrene–acrylate microemulsion coating with high monomer to surfactant ratio of 7.5:1 has been prepared by microemulsion photopolymerization. The properties and the structure of the microemulsion coatings were investigated using TEM, FTIR and UV–vis measurements. The microemulsions are transparent with high transmittance in the visible range. The particle sizes of the produced latexes are in the range of 34–52 nm with the number average diameter of 40.9 nm and D_w/D_n of 1.16. FTIR spectrum indicates the possible structure of the silane monomer-modified styrene–acrylate copolymer, and confirms the hydrolysis and condensation resulting in siloxane bonds between polymer particles. The microemulsion coatings show enhanced acid, base and water resistance with decrease of surfactant content and increase of silane coupling agent.     

Water uptake and pore volume determination of porous styrene–divinylbenzene copolymers

The relationship of water uptake and pore volume has been investigated for porous styrene–divinylbenzene (St–DVB) copolymers prepared in the presence of different inert diluents. It was found that the copolymers prepared in some conditions significantly increased their volume on taking up the water (swelling), and thus the use of water to measure the pore volume of porous St–DVB copolymers could hardly be recommended because the water uptake measurement does not always give a true value of the pore volume in dry state.     

Effect of drying catalysts on the properties of thermal copolymers from conjugated linseed oil–styrene–divinylbenzene

The effect of addition of a varying concentration of a drying catalyst (cobalt salt as primary drier) and a combination of catalysts such as cobalt, zirconium (secondary drier) and calcium (auxiliary drier) in a fixed concentration (1%) to a 50:20:30 compositions of 87% conjugated linseed oil, styrene (ST), and divinylbenzene (DVB) has been studied by characterizing the resulting polymers from thermal polymerization with various techniques such as soxhlet extraction, ¹H NMR (¹H nuclear magnetic resonance) spectroscopy, dynamic mechanical analysis (DMA), mechanical and thermogravimetric analysis. The thermal polymerization is performed in the temperature range of 85–160 °C. By soxhlet extraction, it is observed that the polymers contain approximately 64–77% crosslinked materials and the crosslinked insoluble fraction increases with an increase in cobalt catalyst concentration. For fixed concentration (1%) of catalysts, the insoluble fraction from the soxhlet extraction is maximum for the cobalt–zirconium mixture and minimum for the cobalt–calcium mixture. The micro-composition of these polymers obtained from the ¹H NMR spectroscopy indicates that the crosslinked materials are composed of both soft oily and hard aromatic phases. The polymers with varying cobalt concentrations up to 0.6 wt% exhibit two separate glass transition temperatures, indicating the presence of two separate phases, one soft rubbery phase with sharp glass transition temperature of −50 °C and a hard brittle plastic phase of broadened glass transition temperature of 70–120 °C. On the other hand, instead of sharp peaks, the polymers with 0.8 and 1.0% cobalt salts exhibit two humps and a distinct peak in between the humps in the tan δ plots, indicating the presence of an additional phase comprised of a copolymer of linseed oil–styrene and DVB. For fixed concentration (1%) of catalysts, the cobalt–calcium combination follows the similar trend in the tan δ as that for the polymers with 0.8–1.0% cobalt whereas other combinations exhibit two phases. These polymers possess crosslink densities of 0.63–0.91 × 10⁴ mol/m³ and compressive strengths of 2.0–26.6 MPa. The catalyzed polymers are thermally stable below 300 °C and exhibit a major thermal degradation with a maximum degradation of 82–88% at a temperature of 500 °C.     

Ultra-stretchable thermoplastic elastomeric materials based on styrene–isoprene–styrene triblock copolymer: Influence of calcium copper titanate on mechanical and dielectric properties

Conventional charge storage devices made of ceramic materials have limited deformability and configurability due to their extreme stiffness. The high demand for compliant dielectrics has led researchers to look beyond conventional ceramics, despite their very high dielectric properties. In this work, a mechanically robust, highly-flexible and ultra-stretchable thermoplastic elastomeric material with dielectric characteristics has been fabricated by introducing calcium copper titanate [CaCu₃Ti₄O₁₂] (CCTO) dielectric material onto macromolecular chains of styrene–isoprene–styrene (SIS) triblock copolymer via a solution-based polymer processing technique. CCTO powders have been synthesized using sol–gel technique. The resulting composite is ultra-stretchable with strain at break of ~3200% and has high dielectric permittivity of ~10. High dielectric property is attributed to the well-dispersed dielectric CCTO fillers within the SIS matrix, which provide sites for interfacial polarization and space charge accumulation. The influence of CCTO on dielectric properties has also been validated using the modified Cole–Cole model.     

Effect of nanoclay on mechanical and thermal properties of triblock SBS (styrene–butadiene–styrene) and its binary blend nanocomposites: comparison between polyethylene and polystyrene

ABSTRACT

In this study, the effect of organo-modified nanoclay (OMMT) on the mechanical and thermal properties of SBS and its blend with low-density polyethylene (LDPE) and polystyrene was investigated. The effect of nanoclay content in the presence of LDPE or PS on the final properties of SBS was studied by tensile tester, dynamic mechanical thermal analysis (DMTA), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Addition of nanoclay affected the mechanical and rheological properties. From X-ray and DMTA results, it was found that due to more affinity between the nanoparticles and the SBS/PE blend, the 2 theta characteristic peak of nanoclay shifted to lower angles. SEM studies showed better dispersion and lower inter-particle distance of nanoparticles in SBS/PE composites in comparison with SBS/PS and SBS composites, confirming the XRD and DMTA results. It can be concluded that nanoclay acts as a compatibilizer in the SBS/LLDPE blend. TGA studies showed higher stability of SBS/PS composites compared to SBS and SBS/PE ones.     

Effects of overhalogenation of a synthetic vulcanized styrene–butadiene rubber sole on its adhesion behavior

The effects of halogenating the same synthetic vulcanized styrene–butadiene rubber (R2) (used as a sole material in the shoe industry) twice (double halogenation) using solutions of trichloroisocyanuric acid (TCI) in MEK were studied. The R2 rubber was treated with 0.5 and 2 wt% TCI/MEK solutions and after 1 h re-treated with additional 0.5 (0.5 + 0.5 wt% TCI/MEK) and 2 wt% TCI/MEK (2 + 2 wt% TCI/MEK) solutions. The results obtained were compared with those obtained by treating the R2 rubber once with 1 and 4 wt% TCI/MEK solutions. The surface modifications produced by the double halogenation of the R2 rubber were analyzed using advancing and receding contact angles (variations in wettability), XPS and ATR-IR spectroscopy (characterization of chemical modifications) and SEM (morphological modifications). T-peel tests on doubly halogenated R2 rubber/polyurethane adhesive joints were carried out to quantify the adhesion properties of the treated R2 rubber. The degree of chlorination was higher with increasing amount of chlorinating agent. Furthermore, the most efficient removal of hydrocarbon substances from the R2 rubber surface was obtained by double halogenation and by increasing the TCI concentration. Similar trends in surface chemistry of the R2 rubber were obtained using 0.5–2 wt% TCI/MEK, with or without double halogenation. On the other hand, by comparing the effects of treatments with 0.5 + 0.5 wt% TCI/MEK and 1 wt% TCI/MEK or with 2 + 2 wt% TCI/MEK and 4 wt% TCI/MEK, less effective removal of zinc stearate and less degree of chlorination were obtained by double halogenation although similar outermost surface modifications were produced. The second application of the TCI/MEK solution on the already halogenated R2 rubber dissolved the unreacted TCI and/or the isocyanuric acid crystals on its surface. The mechanical properties of the treated R2 rubber decreased because it became stiffer. Higher and relatively similar peel strength values were obtained in all adhesive joints prepared using treated R2 rubber. A cohesive failure in the rubber close to the chlorinated layer was always obtained.     

Melting and crystallization behaviors of compatibilized poly(trimethylene terephthalate)/acrylonitrile–butadiene–styrene blends

The melting and crystallization behaviors of poly(trimethylene terephthalate) (PTT)/acrylonitrile–butadiene–styrene (ABS) blends were investigated with and without epoxy or styrene–butadiene–maleic anhydride copolymer (SBM) as a reactive compatibilizer. The existence of two separate composition-dependent glass-transition temperatures (T_g's) indicated that PTT was partially miscible with ABS over the entire composition range. The melting temperature of the PTT phase in the blends was also composition dependent and shifted to lower temperatures with increasing ABS content. Both the cold crystallization temperature and T_g of the PTT phase moved to higher temperatures in the presence of compatibilizers, which indicated their compatibilization effects on the blends. A crystallization exotherm of the PTT phase was noticed for all of the PTT/ABS blends. The crystallization behaviors were completely different at low and high ABS contents. When ABS was 0–50 wt %, the crystallization process of PTT shifted slightly to higher temperatures as the ABS content was increased. When ABS was 60 wt % or greater, PTT showed fractionated crystallization. The effects of both the epoxy and SBM compatibilizers on the crystallization of PTT were content dependent. At a lower contents of 1–3 wt % epoxy or 1 wt % SBM, the crystallization was retarded, whereas at a higher content of 5 wt %, the crystallization was accelerated. The crystallization kinetics were analyzed with a modified Avrami equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study of the phase morphology and toughness in poly (vinyl chloride)/acrylonitrile–styrene-acrylic/styrene–butadiene–styrene ternary blends influenced by interfacial/surface tension

The effect of interfacial interaction on the phase morphology and toughness of poly (vinyl chloride) (PVC)/acrylonitrile–styrene-acrylic (ASA) terpolymer/styrene–butadiene–styrene (SBS) block copolymer ternary blends has been investigated. Water and diiodomethane liquids were used for static contact angle measurements to get surface tension and calculate interfacial tension. A dispersed phase morphology of ASA and SBS in the PVC matrix was predicted by the spreading coefficient theory, which was calculated through interfacial tensions between different polymer pairs. Extraction experiment and scanning electron microscopy were combined to verify this morphology. When the volume fraction of SBS was small, SBS was dispersed in the matrix as droplets and the strong PVC/styrene–acrylonitrile interfacial interaction made up for the poor interfacial adhesion between SBS and PVC. Herein, SBS showed an effective toughening effect on PVC/ASA blends. With the addition of 2.5- and 5-phr SBS, the blends had the highest impact strength of 88.75 kJ/m² at 23 °C and 9.98 kJ/m² at 0 °C, respectively. With the further increase of the SBS content, the diameter of the SBS drops increased largely and the poor interfacial adhesion between SBS and PVC played a leading role, resulting in a sharp decrease in toughness and a sharp ductile–brittle transition. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47721.     

Effects of styrene–acrylic emulsion on bond performance and interface microstructure of repair mortar of ternary cementitious system

This study investigates the effects of styrene–acrylic emulsion (SAE) as a modifier and interfacial agent on the interfacial bond performance of ordinary Portland cement–aluminate cement–gypsum (PAG) repair mortar. The hydration products and interfacial microstructure are analyzed via x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that the addition of SAE can effectively enhance the tensile bond strength and flexural bond strength of the PAG repair mortar, and the optimal addition amount of SAE is 10 wt%. The tensile and flexural bond strengths of the PAG repair mortar with SAE interfacial agent at 40% concentration are 1.38 and 1.34 times than those of the mortar without the interfacial agent, respectively. XPS and FTIR analyses reveal that the carboxyl groups in SAE and Ca²⁺ generated from cement hydration form Ca²⁺–carboxyl complexes. The SEM and XRD analyses indicate that SAE can alter the distribution and size of crystals at the bond interface and considerably reduce the thickness of the bond interface; however, SAE cannot change the type of hydration products at the bond interface.     

Study of the styrene–acrylic emulsion modified by hydroxyl-phosphate ester and its stoving varnish

A styrene–acrylic copolymer emulsion containing hydroxyl-phosphate as flash-rust functional monomer and hydroxypropyl acrylate as cross-linking monomer was synthesized. The effects of the hydroxyl phosphate dosage, the hydroxypropyl acrylate dosage as well as the ratio of soft to hard monomer on the emulsion and coating film were investigated. The results showed that the emulsion of 4% hydroxyl phosphate function monomer and 3% hydroxypropyl acrylate with soft and hard monomer ratio of 1:1.6 and modified emulsion and amino resin ratio of 6:1 resulted in a coating film with the best performance.     

Thermal and mechanical enhancement of styrene–butadiene rubber by filling with modified anthracite coal

Anthracite is the highest rank of coal with a layered structure similar to that of graphite. Here, styrene–butadiene rubber/modified anthracite (MA) composites were prepared and analyzed. The microstructure and dispersion of the anthracite were improved by ball milling with the modifier bis-(γ-triethoxysilylpropyl)-tetrasulfide (KH-Si69). The particle size of the modified coal was decreased significantly to ~3 μm, while surface interactions with the modifier yielded enhanced lamellar morphology and hydrophobic surfaces. The anthracite lamellae were well dispersed in the rubber matrix, providing good reinforcement; the tensile strength of the composite exceeded that of a composite with carbon black (CB) N660 filler (16.65 vs. 14.68 MPa). Moreover, low-level CB or silica compositing further promoted the dispersion of coal particles in the rubber, effectively enhancing the mechanical reinforcement behavior of the coal particles as well as the thermal stability of the rubber composite. Notably, it led to a 10.63% improvement in tensile strength and a 9.96 °C increase in the 5% mass loss temperature compared to the composite with a single MA filler. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48203.     

Preparation and characterization of natural rubber/ultrafine full-vulcanized powdered styrene–butadiene rubber blends

In this paper, natural rubber (NR)/ultrafine full-vulcanized styrene–butadiene powdered rubber (UFPSBR) blends were prepared and studied for the first time. Scanning electron microscopy and thermogravimetric analysis were employed to characterize UFPSBR. Equilibrium swelling method was used to determine the crosslink density of NR/UFPSBR vulcanizates. The results on mechanical properties showed that when NR/UFPSBR ratio was 100/5, the formulation exhibited favorable performances compared to pure NR vulcanizates. The heat build-up temperature also decreased after adding UFPSBR into the NR formulation. In dynamic mechanical analysis, in the temperature range of ?10 to ?5 °C, loss factor (tanδ) values of NR/UFPSBR vulcanizates showed an increasing trend over the given temperature range and exhibited a peak value at approximate ?5 °C. This indicates that wet traction and rolling resistance of samples were improved after UFPSBR was added in NR. This research demonstrates that UFPSBR can be incorporated into a conventional NR formula to successfully improve the comprehensive performances and dynamic mechanical properties of NR formula.     

Preparation and properties of soapless poly(styrene–butyl acrylate–acrylic acid)/SiO2 composite emulsion

Soapless emulsion polymerization of styrene-butyl acrylate-acrylic acid was carried out using single or combined polymerizable emulsifiers, such as hydroxypropyl methacrylate sodium sulfate (HPMAS), sodium vinyl sulfate, and vinyl alkylphenol polyether sulfates (NRS-10), in the presence of colloidal nano-SiO₂ solution in order to obtain films with high degree of hardness and water-resistance. Monomer conversion, formation of coagulum, viscosity, particle size, size distribution, and surface tension of the emulsions, as well as the film properties, were determined and compared with those of an emulsion prepared with the conventional emulsifier sodium dodecyl sulfate and polyoxyethylene octylphenol ether. Emulsions prepared from a mixture of two polymerizable emulsifiers NRS-10 and HPMAS (1:1, weight ratio) have presented high monomer conversion, low coagulum, and small particle sizes. When the emulsifier level increased within a certain level, the monomer conversion increased but particles size decreased. Increased amounts of reactive emulsifiers led to low monomer conversion, large amount of coagulum and small particle sizes. With the increase of nano-SiO₂ the particle sizes and the viscosity of the emulsion also increased. The introduction of reactive emulsifiers improved the water-resistance of the resulting films, and the addition of nano-SiO₂ increased the hardness of the coatings. Under optimal conditions, the coatings made from emulsions produced from a combination of reactive emulsifiers such as NRS-10 and HPMAS (1:1, weight ratio) at 2?% level (based on monomer weight) exhibited remarkable hardness, adhesion force and water-resistance.     

Synthesis of emulsion styrene butadiene rubber by reversible addition–fragmentation chain transfer polymerization and its properties

Emulsion polymerization is generally used to synthesize styrene butadiene rubber (SBR), and the molecular weight of this rubber can be easily increased. However, the broad molecular weight distribution (MWD) of SBR increases energy loss and adversely affects the dynamic viscoelastic properties. To overcome this disadvantage, reversible addition–fragmentation chain transfer (RAFT) polymerization, which is a type of living polymerization, is applied to emulsion polymerization for preparing RAFT emulsion SBR (ESBR). The molecular weight and microstructure of RAFT ESBR are compared to those of commercially available ESBR 1502 by gel permeation chromatography and proton nuclear magnetic resonance spectroscopy. The aforementioned two polymers are used to prepare unfilled ESBR compounds, which are compared in terms of key physical properties (abrasion resistance, mechanical properties, and dynamic viscoelastic properties). It is confirmed that various physical properties of RAFT ESBR are improved due to its narrow MWD. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47069.     

Synthesis, characterization, microstructure determination and thermal studies of poly(N-vinyl-2-pyrrolidone–maleic anhydride–styrene) terpolymer

A series of poly(N-vinyl-2-pyrrolidone–maleic anhydride–styrene) terpolymers have been synthesized using titanium(III)-dimethylglyoxime redox initiator system. The usage of redox initiators in the terpolymerization was limited; hence it should be considered as a new approach. The reactivity of the monomers has been studied by well-accepted Kelen-Tudos and Fineman-Ross linear methods and compared with the nonlinear RREVM method. The results also suggested that the RREVM method is the most reliable and superior method for the estimation of reactivity ratios. The reactivity ratios for the terpolymer (r ₁ 0.99 and r ₂ 0.05) obtained from the RREVM method showed that the N-vinyl pyrrolidone-maleic anhydride complex was more predominant than styrene in the terpolymer and the complex had more attraction toward itself than styrene. The microstructure determination study depicts that alternating polymer can be prepared by increasing the styrene feed content. The resonance factor and polarity of the complex were calculated as 5.01 and 0.93, respectively, which were different from those of the individual monomers. These calculations would help in predicting the association of monomers during copolymerization. It was observed that the glass transition temperature of the terpolymer increased as the complex ratio in the terpolymer increased. The terpolymer was thermally stable up to 323 °C.