Styrenic Block Copolymers SEBS

Styrene-ethylene-butylene-styrene block copolymer (SEBS) Kraton G, Elexar... 

As more complex multicomponent blends are being developed for commercial applications, new approaches are needed for morphology characterization. Often, the use of Ru04 staining is effective, as it is sensitive to small variations in the chemical composition of the component polymers. For instance PS, PC, and styrene—ethylene/butylene—styrene block copolymers (SEBS) are readily stained, SAN is stained to a lesser degree, and PBT and nylons are not stained (158,225—228). 

Sulfonation is very useful chemical modification of polymer, as it induces high polarity in the polymer changing its chemical as well as physical properties. Sulfonated polymers are also important precursors for ionomer formation [75]. There are reports of sulfonation of ethylene-propylene diene terpolymer (EPDM) [76, 77], polyarylene-ether-sulfone [78], polyaromatic ether ketone [79], polyether ether ketone (PEEK) [80], styrene-ethylene-butylene-styrene block copolymer, (SEBS) [81]. Poly [bis(3-methyl phenoxy) phosphozene] [82], Sulfonated polymers show a distinct peak at 1176 cm"1 due to stretching vibration of 0=S=0 in the -S03H group. Another peak appears at 881 cm 1 due to stretching vibration of S-OH bond. However, the position of different vibrational bands due to sulfonation depends on the nature of the cations as well as types of solvents [75, 76]. 

CL has been employed to study the mechanism of degradation in polymers such as UV-cured aliphatic polyurethane-acrylate-based adhesives. In styrenic block copolymers, SEBS, the order of the reaction was determined, and the efficiency of antioxidants was evaluated. Also, the relationship between thermooxidation of SEBS and morphology was established, indicating that for these copolymers the oxidation started in the interfacial region. 

Even more complex recipes for coupling fibers in WPCs have been studied. For example, in one study, MAH grafted onto a styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MAH) was added at 1%, along with 2% PP-g-MAH, in a WPC system. This reportedly doubled the impact strength over PP-g-MAH alone, though it reduced the modulus. However, when researchers used a WPC that was also loaded with nanoclay (l%-5%), the SEBS-g-MAH likewise increased impact strength, but the nanoday hdped support the modulus value [14-6]. 

UncompatibUized blends of PP with 3-30 wt.% of either polystyrene (PS) or high-impact-PS (HIPS) were developed in 1971 for soda-straw tubes with pearly luster. Later, for improved mechanical performance, these blends were compatibilized by addition of either a tri-block styrene-butadiene-styrene copol)uner (SBS), a multiblock (SB) copol)uner. Addition of hydrogenated-SBS, i.e. styrene-ethylene/butylene-styrene block copolymer (SEBS) was found to improve impact and flexural strength, whereas incorporation of a linear three-block copolymer S1-D-S2 (where SI s S2 are PS-blocks and D = polydiene block) gave PP alloys with good crack and impact stress resistance [4]. 

SBS and SIS can be subsequently hydrogenated to form SEBS and SEPS, respectively. SEBS is obtained from SBS with a higher vinyl content (typically around 30%) in order to avoid crystallization of the mid-block. The properties of all four of these common styrenic block copolymers are displayed in Table 2. 

Anionic Styrenic block copolymers (SBS, SIS, SEBS, SEES) 1.0-1.1 Excellent... 

Diblock copolymers, especially those containing a block chemically identical to one of the blend components, are more effective than triblocks or graft copolymers. Thermodynamic calculations indicate that efficient compat-ibilisation can be achieved with multiblock copolymers [47], potentially for heterogeneous mixed blends. Miscibility of particular segments of the copolymer in one of the phases of the bend is required. Compatibilisers for blends consisting of mixtures of polyolefins are of major interest for recyclates. Random poly(ethylene-co-propylene) is an effective compatibiliser for LDPE-PP, HDPE-PP or LLDPE-PP blends. The impact performance of PE-PP was improved by the addition of very low density PE or elastomeric poly(styrene-block-(ethylene-co-butylene-l)-block styrene) triblock copolymers (SEBS) [52]. 

SEBS styrene, ethylene, butylene, styrene block copolymer... 

Linear low-density polyethylene (LLDPE) and PS resins were the same as described previously (Chapter 21). The various block copolymers that were used as compatibilizers have also been described (I). A series of crystalline copolymers (Q series) was prepared by hydrogenation of diblock and triblock copolymers of styrene and butadiene [styrene-hydrogenated butadiene (SEB) and styrene-hydrogenated butadiene—styrene (SEBS)J (1). Triblock copolymers of styrene and butadiene [styrene-butadiene-styrene (SBS)] and a noncrystalline hydrogenated block copolymer (SEBS) (Kraton) were supplied by Shell Chemical Co. Diblock copolymers of styrene and butadiene [styrene-butadiene (SB) (Vector)] were obtained from Dexco Polymers. The characteristics of the resins are given in Table I. 

PE with EVAc, CPE, BR, etc., have been chemically foamed at T = 150-210°C 5 to 95 wt% of LDPE or LLDPE with EAA PE with either poly(ethylene-co-vinylcarboxylate) or an acrylate PP with an ionomer and EBA-GMA PP with an ionomer, EBA-GMA and EPDM PO with a core-shell graft copolymer MBS-type PP with acidified-PP, or a carboxylic acid-modified EPR, SMM-MA, and either EMMA-GMA or EVAc-GMA LLDPE, PMMA and SEBS, EPR, or ethylene-styrene block copolymer (ES)... 

As noted, TPEs are either block copolymers or combinations of a rubber-dispersed phase and a plastic continuous matrix. The attribute contributed by the rubbery phase - such as butadiene or ethylenebutylene in an S-E-S or SEB-S styrenic block copolymer, or the completely vulcanized EPDM rubber particles in a polypropylene (PP)/EPDM EA - is classical elastomeric performance. The elastic properties of a rubber result from long, flexible molecules that are coiled in a random manner. When the molecules are stretched, they uncoil and have a more specific geometry than the coiled molecules. The uncoiled molecules have lower entropy because of the more restricted geometry and, since the natural tendency is an increase in entropy, the entropic driving force is for the molecules to retract. 

Maleated, styrene-ethylene/ butylene-styrene block copolymer rubber (m-SEBS) Anhydride 0.5-2 % MA High reactivity with the amine (NH2) end group of PA Amorphous rubber, low Tg leads to high-impact toughness down to -40 °C... 

Transparent-, impact-, and blush -resistant blends were obtained by compounding linear low-density polyethylene, LLDPE, with hydrogenated styrene-butadiene block copolymer, SEBS... 

Styrene block copolymers are the most widely used TPEs, accoimtingfor close to 45% of total TPE consumption worldwide at the close of the twentieth century. 1 They are characterized by their molecular architecture which has a hard thermoplastic segment (block) and a soft elastomeric segment (block) (see Fig. 3.2). Styrenic TPEs are usually styrene butadiene styrene (SBS), styrene ethylene/butylene styrene (SEBS), and styrene isoprene styrene (SIS). Styrenic TPEs usually have about 30 to 40% (wt) bound styrene certain grades have a higher boimd styrene content. The polystyrene endblocks create a network of reversible physical... 

Thermoplastic elastomers (TPEs), which combine the characteristics of both thermoplastics and elastomers, can be classified into two major groups. The first is made up of block copolymers formed by polymerizing a thermoplastic monomer with an elastomer comonomer, as in the case of styrene block copolymers such as styrene-ethylene-butadiene-styrene (SEBS). Engineering TPEs such as thermoplastic urethanes (TPUs), copolyesters (COPEs) and polyether block amides (PEBAs) can be included in this first group. Other types of copolymer are from the polyolefin family, consisting of the polyolefin... 

Abbreviations HIPS, high-impact polystyrene ABS, acrylonitrile-butadiene-styrene graft copolymer EPDM, ethylene propylene-diene copolymer CTBN, carboxyl terminated butadiene nitrile telomer M = 5000 g/mol) PC, polyearbonate SBS, styrene-butadiene-styrene triblock copolymer SIS, styrene isoprene styrene tribloek copolymer SEBS, SBS with hydrogenated center block PU, segmented (block copolymer) polyurethanes PDMS, poly(dimethyl siloxane) FIFE, polytetralluoroethylene. 

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