Hydrogenated styrenic block copolymer modified

The use of olefin rubbers [18] as good impact modifiers for sPS when used in conjunction with S-B or S-B-S block copolymers, which may be hydrogenated in the butadiene phase, has also been described. Instead of butadiene, isoprene can be used. Examples of the olefinic polymers are polyethylene, ethylene-propylene rubbers (EPR) and polypropylene-(ethylene propylene rubber) block copolymers. Here the styrene block copolymers presumably function as... 

S/DPE copolymers can also be impact modified using triblock copolymers having as the centre block the rubber phase [6]. Typical examples are styrene-butadiene-styrene block copolymers where the butadiene phase is preferably hydrogenated S-B(H)-S, to remove the double bonds. This is advisable owing to the high processing temperatures involved in the S/DPE processing. 

The use of core-shell impact modifiers combined with styrene-hydrogenated poly butadiene block copolymers in sPS is described by Rohm and Haas [24]. The core of the former type is of polybutadiene or its copolymer, the shell consists predominately of polystyrene. Rohm and Haas found that a synergistic effect is present and that the Izod notched impact strength is higher when both rubber types are used instead of only one. 

As stated earlier, S/DPE copolymers are compatible with GPPS up to a DPE content of about 15wt%. This means that on modifying S/DPE(>15) with S-B(H)-S the impact modification decreases owing to decreased compatibility between the S/DPE matrix and the styrene blocks of the S-B(h>-S impact modifier. S-DPE, however, is prepared anionically and using this polymerization mechanism S/DPE-butadiene S/DPE block copolymers can be prepared. Thus the S/DPE blocks can be tailor-made to be compatible with the S/DPE polymer matrix. For compatibility, the DPE content of the blocks and the matrix should not differ by more than about 15 %. As with the S-B(H)-S block copolymers, the double bonds of the butadiene phase should be removed by hydrogenation. 

The universal compatibilizers are multi-component copolymers, with parts that either are soluble in some components of the blend, chemically bond to chain ends, or have a tendency for hydrogen bonding. Because of the universality, these materials are rather expensive to use. A better chance offers the proprietary compatibilizers-cwm-impact modifiers, formulated for specific types of polymer mixtures, viz. Blendex (polybutadiene-type compatibilizer for styrenics, PVC, TPU, PET), EXL (an acrylic-based additive for PEST), Fusabond (maleated-PO compatibilizer for PO/PET blends), Vector (is SBS-type block copolymer with stabilizers, designed for PO/PS commingled mixtures), and many others. 

Ethylene/vinyl acetate/vinyl alcohol copolymer Ethyl methacrylate Ferric oxide Fluorinated ethylene/propylene Food starch, modified Glyceryl triacetyl hydroxystearate Hexyl alcohol Hydrogenated styrene/2-methyl-1,3-butadiene block polymer Hydrogenated tallow lonomer resin... 

Polymer modified asphalt originated in Europe in the early 1960s. Atactic PP is still used today in asphalt compositions mainly in Europe, Mexico and Asia. A PP copolymer containing 2-10% ethylene is more popular in USA. Thermoplastic block copolymers with styrene end blocks or with a diene midblock like S-B-S and styrene-isoprene-styrene (SIS) and their hydrogenated versions are common modifiers for asphalt [40]. 

Besides copoljmiers synthesized specially for compatibilization of immiscible poljmiers, commercial products (typically used as impact modifiers) are utilized as compatibilizers in research as well as in practice. Typical examples are styrene-butadiene block copolymers and their styrene-hydrogenated butadiene analogues used for compatibilization of styrene pol5miers (PS, HIPS, SAN, ABS), with polyolefins (49), or ethylene-propylene copol5miers for compatibilization of various polyolefins (50). 

In a sense, the styrene-butadiene block copolymers, SB or SBS, (first reported in 1956) constituted the next stage of PS modification. The triblock styrene-diene thermoplastic elastomers were patented in 1962, and soon incorporated in blends with PS, PP, LDPE, HDPE, PPE, PET, PBT, or PC, either as impact modifiers or compatibilizers [Bull and Holden, 1977]. In the 1977-78 patents (applications in 1976) it was disclosed that selective hydrogenation of these copolymers leads to new materials, with properties particularly attractive for polymer blends. For example, blending hydrogenated-SBS, or SEES, generated phase co-continuity in blends with PP, PA, PC, PBT, PES, etc. [Gergen et al., 1987]. More recent modification of these copolymers involved incorporation of acidic or acid-anhydride moieties. 

There are numerous reports in the literature describing the synthesis of low polydispersity PNIPAm (co)poly-mers via CRP methods. For example. Binder et al. [54] described the synthesis of telechelic PNIPAm using functional NMP initiators modified via azide-alkyne cycloadditions. Efficient block copolymerization of NIPAm with styrene was achieved via sequential polymerization initiated by a-hydrogen alkoxyamine [55]. A PNIPAm block was first prepared and then chain extended with styrene yielding amphiphilic diblock copolymers. Initial attempts to use ATRP to prepare PNIPAm resulted in polymers with broad polydisperisities [56], but this problem was circumvented by utilizing a more efficient ligand for the initiator complex [57]. 

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