Styrene Block Copolymer Research Articles

Raman spectroscopy and molecular bases of elasticity: SEBS-graphite composites

For polymer-based (nano)composites, the strain/stress induced by reinforcing agents within the polymer may be identified and quantified at molecular level by Raman spectroscopy. The manuscript focuses on correlations between mechanical properties of composites and their Raman spectra, with emphasis on the displacements of the position(s) of Raman lines due to local strains/stress. Investigations on polystyrene-(ethylene-co-butylene)-styrene block copolymers filled with various amounts of graphite are reported. The modifications of Raman's parameters (line intensity, position, and width) upon the loading with graphite are analyzed. Raman revealed a strong dampening of molecular vibrations within the polymer, upon the loading with graphite, indicating a good mechanical coupling between the polymer and the reinforcing agent. Significant differences between Raman spectra obtained with green and red lasers, were reported; Raman spectra obtained with red laser are more sensitive to motions occurring within the polymer while the spectra obtained using green laser are more sensitive to graphite.

Improved DC Dielectric Performance of cPP-g-MAH/iPP/SEBS Composite with Chemical Graft Modification.

In order to achieve both high toughness and favorable dielectric properties of polypropylene materials, a styrene–butadiene–styrene block copolymer (SEBS) was employed as a toughening filler, in addition to a copolymerized polypropylene grafted by maleic anhydride (cPP-g-MAH) as a compatibilization modifier, to develop a novel isotactic polypropylene (iPP) composite (cPP-g-MAH/iPP/SEBS composite) with significantly improved direct-current (DC) dielectric performance and tenacity. The underlying physical and chemical mechanisms of modifying electric insulation were studied utilizing micro-structure characterization methods in combination with multiple thermal–mechanic–electric tests. The SEBS phase islands are uniformly distributed in the PP matrix with evidently improved dispersion due to cPP-g-MAH compatibilization. Compared with iPP, the elastic modulus of cPP-g-MAH/iPP/SEBS composites can be reduced by 58% with doubled thermal elongation, which is still superior to that of cross-linked polyethylene (XLPE), implying that the composites are qualified in terms of mechanical properties for use as power cables. The space charge accumulation and electric conduction are considerably suppressed in comparison with pure iPP and the iPP/SEBS composite. In the interest of charge-trapping characteristics modified by chemically grafting MAH, the deep traps introduced into polypropylene by grafting MAH were measured with a thermal stimulation current experiment to be 1.2 and 1.6 eV of energy level in trapping depth, verified through the first-principles electronic structure calculations with an all-electron numerical orbital scheme. It was concluded that the acquired high density of deep traps can effectively restrict the carrier transport and suppress the injection of space charge, resulting in a remarkable improvement of DC dielectric properties for the MAH grafted composites. The present work demonstrates that the cPP-g-MAH/iPP/SEBS composites are eligible to be applied to polypropylene-based high-voltage DC cables due to their excellent DC insulation performance, together with the appropriate mechanical properties.

Infiltration Synthesis of Diverse Metal Oxide Nanostructures from Epoxidized Diene–Styrene Block Copolymer Templates

Infiltration synthesis is a class of block copolymer lithography in which block copolymer templates are selectively infiltrated with metal or metal oxide precursors, which has been proposed as a me...

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

ABSTRACTThe 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.

Preparation and investigation of efficient flame retardant TPE composites with piperazine pyrophosphate/aluminum diethylphosphinate system

ABSTRACTThe piperazine pyrophosphate (PPAP) combined with aluminum diethylphosphinate (AlPi) with a certain mass fraction and then incorporated into thermoplastic elastomer (TPE) composites composed of oil extended styrene–ethylene–butadiene–styrene block copolymer and polypropylene. The fire retardancy, thermal behavior, mechanical performance, and flame retardant mechanism of TPE materials were investigated in detail. The results demonstrated that 1.6 mm TPE composites reached UL‐94 V‐0 grade during vertical burning tests and the limiting oxygen index value was 28.5% when 25 wt % PPAP/AlPi with the mass ratio of 4:1 was incorporated. The introduction of PPAP/AlPi improved the residual mass and thermal stability, and stimulated to produce the char layer with high quality. The formed char layer exerted shielding effect and AlPi could inhibit the flame in gas phase. Consequently, the PPAP/AlPi system evoked fire retardant effects in condensed and gas phase simultaneously, and the fire resistance of the TPE composites was enhanced. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 47711.

Reaction: Size Distribution in Olefin Block Copolymers: Not Bad at All

Hongyu Chen completed his PhD in macromolecular science at Case Western Reserve University in 2010. He is a fellow of the Dow Chemical Company, where he focuses on developing new products. He is also a fellow of the American Physical Society and American Chemical Society. Valeriy Ginzburg completed his PhD in polymer physics at the Moscow Institute of Physics and Technology in 1992. He is a senior scientist at the Dow Chemical Company and a fellow of the American Physical Society.

Synthesis and characterization of poly(styrene-b-methyl methacrylate) block copolymers via ATRP and RAFT

Well-defined block copolymers of styrene (S) and methyl methacrylate (MMA) poly(Styrene-b-methyl methacrylate) [poly(S-b-MMA)] with narrow molecular weight distribution were synthesized via atom transfer radical polymerization (ATRP) and recycle additive fragmentation chain transfer (RAFT) polymerization methods using macro RAFT macroinitiator in two step. Poly-S based RAFT macroinitiator was reported from the reaction of potassium salt of ethyl xanthegonate and homo Poly-S which is synthesized by atom transfer radical polymerization of styrene using 3-chloro-1-propanol initiator. Subsequently, the synthesis of poly(S-b-MMA) block copolymers were acquired via RAFT of poly-S based RAFT macroinitiator and MMA at 90 0C. Poly(S-b-MMA) block copolymers were comparatively acquired in high yield and high molecular weight. The characterization of homo poly-S, RAFT macroinitiator, and poly(S-b-MMA) block copolymers were carried out by nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis and elemental analysis.

Kraton looks to sell polyisoprene business

Seeking to recover from a sharp drop in its stock price last year, Kraton is exploring the sale of its Cariflex polyisoprene business. Polyisoprene is used as a nonallergenic substitute for natural latex in products such as condoms and surgical gloves. The business generated 2017 sales of $168 million, about 9% of Kraton’s total. Most of Kraton’s sales come from styrenic-block copolymers and pine chemicals.“Cariflex for the most part is a stand-alone business at Kraton, with minimal revenue or cost overlap with our polymer and chemical segments,” CEO Kevin M. Fogarty says. The business’s strong growth prospects are not reflected in Kraton’s stock price, he says, and it might fit better with another company.Last year was a tough one for Kraton. The company’s stock price tumbled from highs near $50 in September to less than $20 in December as trade woes and recession fears gripped financial markets. Additionally, the company

3D-Printable PP/SEBS Thermoplastic Elastomeric Blends: Preparation and Properties.

Currently, material extrusion 3D printing (ME3DP) based on fused deposition modeling (FDM) is considered a highly adaptable and efficient additive manufacturing technique to develop components with complex geometries using computer-aided design. While the 3D printing process for a number of thermoplastic materials using FDM technology has been well demonstrated, there still exists a significant challenge to develop new polymeric materials compatible with ME3DP. The present work reports the development of ME3DP compatible thermoplastic elastomeric (TPE) materials from polypropylene (PP) and styrene-(ethylene-butylene)-styrene (SEBS) block copolymers using a straightforward blending approach, which enables the creation of tailorable materials. Properties of the 3D printed TPEs were compared with traditional injection molded samples. The tensile strength and Young’s modulus of the 3D printed sample were lower than the injection molded samples. However, no significant differences could be found in the melt rheological properties at higher frequency ranges or in the dynamic mechanical behavior. The phase morphologies of the 3D printed and injection molded TPEs were correlated with their respective properties. Reinforcing carbon black was used to increase the mechanical performance of the 3D printed TPE, and the balancing of thermoplastic elastomeric and mechanical properties were achieved at a lower carbon black loading. The preferential location of carbon black in the blend phases was theoretically predicted from wetting parameters. This study was made in order to get an insight to the relationship between morphology and properties of the ME3DP compatible PP/SEBS blends.

Environmentally Friendly Packaging Materials Based on Thermoplastic Starch

Low-density polyethylene (LDPE) is extensively used as packaging material, and as such has a short service life, but long environmental persistence. The alternative to reducing the impact of LDPE as packaging material on the environment is to blend it with carbohydrate-based polymers, like starch. Therefore, the focus of this investigation was to prepare bio-based blends of LDPE and thermoplastic starch (TPS) containing different amounts of TPS using a Brabender kneading chamber. Due to incompatibility of LDPE/ TPS blends, a styrene–ethylene/butylene–styrene block copolymer, grafted with maleic anhydride (SEBS-g-MA) containing 2 mol % anhydride groups, was added as a compatibilizer. The effect of the biodegradable, hydrophilic TPS, its content, and the incorporation of the compatibilizer on the properties of LDPE/TPS blends were analysed. The characterization was performed by means of thermogravimetric analysis (TG), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and water absorption (WA). Based on the results of the morphological structure, a good dispersion of the TPS phase in LDPE matrix was obtained with the incorporation of compatibilizer, which resulted in better thermal and barrier properties of these materials.

Enhanced microphase separation of thin films of low molecular weight block copolymer by the addition of an ionic liquid.

We report on the use of a selective, non-volatile ionic liquid (IL) to enhance the self-assembly via solvent annealing of a low molecular weight block copolymer (BCP) of styrene and 2-vinylpyridine (2VP) suitable for generating sub-10 nm features. Diblock and triblock copolymers of different molecular weights of styrene and 2VP are individually blended with the IL and then solvent annealed in acetone, a non-preferential solvent for the BCPs. Differential scanning calorimetry indicates that the IL selectively resides in the 2VP block of the BCP, resulting in a decrease of the block's Tg and an increase of the effective Flory-Huggins parameter (χeff) of the BCP. The influence of the IL on the non-preferential window of a random copolymer brush used to treat the substrate for self-assembly of the BCPs is also analyzed. Well-defined lamellar patterns form when the optimal weight ratio of IL (∼1%) is added to the BCPs. A detailed analysis of the orientational correlation length and pitch size of the BCPs quantitatively shows that the addition of the IL enhanced the microphase separation of the low molecular weight version of the BCP. Subsequent treatment of the self-assembled BCP with sequential infiltration synthesis yields sub-10 nm AlOx lines.

Synergetic Toughening Effect of Carbon Nanotubes and β-Nucleating Agents on the Polypropylene Random Copolymer/Styrene-Ethylene-Butylene- Styrene Block Copolymer Blends.

Polypropylene random co-polymer (PPR)/styrene-ethylene-butylene-styrene (SBS) block copolymer blends with high toughness and favorable tensile properties were successfully obtained by blending with traces of multi-wall carbon nanotubes (MWCNTs) and β-nucleating agents (β-NAs). β-NAs can effectively induce the ductile β-form crystal in the PPR matrix. Although the addition of MWCNTs was reported to be only benefit for the tensile strength of PPR and relatively disadvantageous for the toughness, the obviously synergistic toughening effect in PPR/SBS blends was found when MWCNTs and β-NAs coexisted. The notched izod impact strength of PPR/30 wt % SBS blend with MWCNTs and β-NAs increased from 11.3 to 58.9 kJ/m2; more than 5-fold increment compared with pure PPR. Meanwhile, the tensile strength retention of this PPR blend is still above 72.2%. The micro-morphology indicated that the MWCNTs can act as bridges between SBS particle and PPR matrix, effectively transferring the stress and absorbing impact energy among SBS particles.

Chemical characteristics of bio-asphalt and its rheological properties after CR/SBS composite modification

The non-renewable characteristics and growing demand for crude oil is prompting the development of alternative materials such as bio-asphalt for pavement engineering. In this study, the chemical compositions of bio-asphalt extracted from castor marked as SHB were evaluated by elemental analysis, infrared spectroscopy and molecular weight distribution analysis. Results revealed that the chemical compositions of SHB bio-asphalt were similar to those of petroleum asphalt, yet the former cannot be directly utilized in pavement construction. Therefore, crumb rubber (CR) and styrene–butadiene–styrene block copolymer (SBS) additives were incorporated into petroleum asphalt blended with bio-asphalt to prepare composite modified asphalt. The ultimate high- and low-temperature performances of the proposed composite modified asphalt indicated that the percentages of raw additive materials were 15% for SHB, 18% for CR and 2% for SBS. Rheological properties were further evaluated using master curves and Han curves, which have been found that SHB addition benefited the high- and low-temperature performances of the CR/SBS composite modified asphalt.

Performance evaluation of bio-based asphalt and asphalt mixture and effects of physical and chemical modification

Adding bio-binder (BB) into petroleum-based asphalt (BA) to produce the sustainable pavement material of bio-based asphalt (BBA), and replace the BA partially or even fully could reduce the dependence of pavement engineering on fossil fuels. This study aims to investigate the effects of adding single-source BB from corn on asphalt binder and asphalt mixture performance. Rheological properties measured from Rotational Viscometer (RV), Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) showed that addition of BB increased the viscosity while decreased the temperature susceptibility of asphalt binder, the BBA became stiffer at high temperatures and more brittle at low temperatures. Pavement performance tests conducted at mixture level showed that adding BB is capable of improving rutting resistance while sacrificing low-temperature cracking resistance slightly, but moisture damage resistance decreased evidently. Therefore, chemical characterisation of BB and BA was conducted using Elemental Analysis, Gas Chromatography-Mass Spectroscopy (GC-MS), Fourier-Transform Infrared Spectroscopy (FTIR) and Saturates, Aromatics, Resins and Asphaltenes (SARA) Fractions Analysis was employed to investigate the performance variation mechanism due to the addition of BB. The results proved that a certain number of light and soluble components existed in BB. After that, physical and chemical modifications with the modifiers of Styrene–Butadiene–Styrene (SBS) block copolymer and o-Phthalic anhydride, respectively, were adopted to improve the performance of BBA. Mixture performance tests showed that physical method improved high- and low-temperature performance obviously while had no effect on moisture damage resistance. On the other hand, the chemical approach enhanced moisture damage resistance of mixture visibly while not affecting other performance criteria. The study findings emphasised that utilising BBA proposed to partially replace BA is potential and feasible with appropriate modification.

Fatigue Damage Characteristics Considering the Difference of Tensile-Compression Modulus for Asphalt Mixture

Abstract In order to reveal the difference and correlation of tensile modulus, compressive modulus, and flexural modulus, the four-point bending fatigue test is used on two kinds of asphalt mixtures—rock asphalt modified asphalt mixture and styrene butadiene styrene block copolymer modified asphalt mixture, were conducted using closed-loop test system. The fatigue damage variable was defined by the modulus attenuation based on the theory of damage mechanics, and the modulus attenuation equation was deduced. Under the same conditions, the initial value and the critical value of the tensile modulus were less than those of the compressive modulus, but the critical damage value and the attenuation slope of the tensile modulus were larger than those of the compressive modulus. The attenuation models of the tensile and compressive modulus of the asphalt mixture during the bending fatigue test were established. Based on the fatigue test results, a new concept of design and analysis was developed, in which the corresponding modulus and its evolution law is chosen according to its actual stress state at each point of asphalt pavement. The results indicate that under the bending fatigue stress state, there exists great differences between the attenuation law of the modulus of tension and compression for asphalt mixture and that the attenuation rate of tensile modulus is greater than that of compressive. Therefore, the tensile zone results in greater damage; the pavement structure of the tensile zone is damaged, which should be given more attention.

Thermal behaviors and flame retardancy of novel flame‐retardant, oil‐filled styrene–ethylene–butadiene–styrene block copolymer–polypropylene materials

AbstractA novel halogen‐free flame‐retardant material consisting of a novel cyclotriphosphazene‐based char‐forming agent, aluminum diethyl phosphinate, nickel trioxide (Ni2O3), an oil‐filled styrene–ethylene–butadiene–styrene block copolymer, and polypropylene was studied. On the basis of their UL‐94 ratings and limiting oxygen index (LOI) data, the flame retardants exhibited very effective flame‐retardant properties in the material. When the loading of flame retardant (FR) was only 35 wt %, the flame‐retardant material attained a UL‐94 V‐0 (1.6 mm) rating, and its LOI value reached 31%. The thermogravimetric analysis data indicated that the flame retardant effectively reduced the peak mass loss because of the formation of abundant char residue. Moreover, the flammability parameters of the material obtained from UL‐94, LOI, and cone calorimetry tests demonstrated that the fire safety performance of the material with Ni2O3 obviously improved. The morphological structure of the char residue of the material with the flame retardant and Ni2O3 showed a dense and continuous carbon layer. The high‐quality carbon layer formed on the surface of the polymer material matrix showed a heat‐insulating effect. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46888.

Heat‐activated pressure sensitive adhesives for linerless labels

ABSTRACTPressure‐sensitive adhesives (PSAs) suitable for use in label applications without a silicone‐coated release liner (so‐called “linerless” labels) were developed utilizing heat‐activated adhesive formulations comprised of dispersed styrenic block copolymers (SIS), dispersed plasticizers, and dispersed tackifiers. Various grades of SIS were investigated, as well as several different dispersants. The best results were obtained with an SIS polymer with 19% diblock dispersed with a long‐chain primary carboxylic acid. Of the four plasticizers studied, sucrose benzoate resulted in the best combination of high peel and low blocking in the end‐use application. Peel forces upwards of 10 N/25 cm were obtained for the heat‐activated adhesive, indicating their applicability for many label applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47048.

A novel approach for synthesis of poly(norbornene)‐co‐poly(styrene) block copolymers via metathesis polymerization and free‐radical polymerization

AbstractIt is successfully realized that block copolymers are synthesized via metathesis polymerization followed by free‐radical polymerization. This method is performed using styrene (St) and norbornene, one block is synthesized using the Grubbs second generation catalyst in the presence of chain transfer agents, and the subsequent polymerization of St is initiated by azo compounds to complete the additional blocks in the copolymers. The use of free‐radical polymerization instead of controlled radical polymerization or ionic polymerization can be potentially superior for industrialization. As a result, the molecular weights of the block copolymers ranging from 10.4 to 54.3 kDa and polydispersity indices ranging from 1.30 to 1.91 are obtained. In principle, this new method can be potentially useful to prepare a broad range of block copolymers with cyclic olefin groups in the main chains, which may be used in some particular applications.

Fluorine-Containing Styrenic Block Copolymers toward High χ and Perpendicular Lamellae in Thin Films

We propose a new approach to fluorine-containing, high-χ styrenic block copolymers (BCPs) via side-chain modification in one block. Polystyrene-b-poly(2,2,2-trifluoroethyl acrylate)s (PS-b-PTFEAs) ...

Recycling of poly(ethylene terephthalate) by chain extension during reactive extrusion using functionalized block copolymers synthesized by RAFT polymerization

ABSTRACTIn this study, a series of reactive block copolymers of glycidyl methacrylate (G), styrene (S), and maleic anhydride (MA) (GS–SMA–GS), with well‐defined properties and high number average functionalities, is presented. They were synthesized through reversible addition–fragmentation chain transfer polymerization (RAFT) and evaluated as chain extenders in reactive extrusion recycling of poly(ethylene terephthalate) (rPET). Modification of the process using GS–SMA–GS results in increased melt flow and intrinsic viscosities higher than those of conventional rPET. Results show that increasing epoxide content makes chain organization in rPET difficult and promotes lower crystallization rates and lower degrees of crystallinity, both of which are characteristics suited to produce preforms with the desired clarity. Chain‐extended rPET exhibits improved rheological characteristics with increasing glycidyl methacrylate content. Chain‐extended rPET using GS–SMA–GS shows enhanced complex viscosity; elastic and viscous modules, which are indicative of high melt elasticity, improved mechanical properties, and processability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46771.