Thermoplastic elastomers characterization

Ban H.T., Kase T., Kawabe M., Miyazawa A., Ishihara T., Hagihara H., Tsunogae Y., Murata M. and Shiono T.A. New approach to styrenic thermoplastic elastomers S3Tithesis and characterization of crystalline styrene-butadiene-styrene triblock copolymers. Macromolecules, 39, 171, 2006. 

Chattopadhyay S., Chaki T.K., and Bhowmick A.K., New thermoplastic elastomers from poly(ethyle-neoctene) (engage), poly(ethylene-vinyl acetate) and low-density polyethylene by electron beam technology structural characterization and mechanical properties. Rubber Chem. TechnoL, 74, 815, 2001. Roy Choudhury N. and Dutta N.K., Thermoplastic elastomeric natural rubber-polypropylene blends with reference to interaction between the components. Advances in Polymer Blends and Alloys Technology, Vol. 5 (K. Finlayson, ed.), Technomic Publishers, Pensylvania, 1994, 161. 

Puskas, J.E. et al. Synthesis and characterization of novel dendritic (arborescent) polyisobutylene-polystyrene thermoplastic elastomers, J. Polym. Set A, 43, 1811, 2005. 

Between thermoplastics, characterized by easy processing but low elasticity, and elastomers, with their outstanding elastic properties but with more-complex processing (see Figure 4.131(a), relatively new materials appeared in the 1960s the thermoplastic elastomers or TPEs. 

Thermoplastic elastomers (TPE s) are characterized by the exceptional property that, without vulcanization, they behave as cross-linked rubbers. They are block-copolymers, in which blocks of the same nature assemble in hard domains, acting as cross-links between the rubbery parts of the chain. These hard domains lose their function when they reach their softening temperature, so that the material can then be processed as a thermoplast. One of the oldest member of the family of TPE s is SBS (styrene-butadiene-styrene block copolymer), but several other TPE s have been developed, i.a. on the basis of polyesters, polyurethanes and polyolefins. In their properties these polymers cover a broad range between conventional rubbers and soft thermoplastics. 

The synthesis, characterization, and mechanical properties of a novel star block copolymer thermoplastic elastomer with eight poly(isobutylene-b-sty-rene) arms radiating from a calix[8]arene was recently reported by Jacob et al. [41]. The process involved the synthesis of eight arm star PIB by a method essentially identical to that described above, followed by sequential addition of S after the IB conversion has reached 95%. To minimize alkylation and to obtain high MW PS blocks, moderate TiCl4 concentration (0.059 mol 1 x) and a 2- to... 

It is possible to classify polymers by their structure as linear, branched, cross-linked, and network polymers. In some polymers, called homopolymers, merely one monomer (a) is used for the formation of the chains, while in others two or more diverse monomers (a,p,y,...) can be combined to get different structures forming copolymers of linear, branched, cross-linked, and network polymeric molecular structures. Besides, on the basis of their properties, polymers are categorized as thermoplastics, elastomers, and thermosets. Thermoplastics are the majority of the polymers in use. They are linear or branched polymers characterized by the fact that they soften or melt, reversibly, when heated. Elastomers are cross-linked polymers that are highly elastic, that is, they can be lengthened or compressed to a considerable extent reversibly. Finally, thermosets are network polymers that are normally rigid and when heated do not soften or melt reversibly. 

As emphasized above, in contrast to common thermoplastics, thermoplastic elastomers contain a very soft phase (with Tg around —50°C), which is in a liquid state at room temperature and is characterized by a viscosity closer to that of low-molecular-weight liquids rather than a solid amorphous polymer. In this respect it seems useful to recall that the molecular weight of the PTMG and PEG used is 1000, i.e. one is dealing with typical oligomer systems. For this reason it looks reasonable to accept that such a liquid will be characterized by a negligibly small microhardness, in the equation ... 

Summarizing, it can be concluded that a relatively sharp (within 2-4% of deformation) drop in H is observed for copolymers of PBT but in comparison with homo-PBT this transition occurs at much higher deformations (between 25 and 30%). This difference as well as the following increase and decrease of H are related to the structural peculiarities of thermoplastic elastomers - the presence of a soft amorphous phase which first deforms and the existence of a physical network. The very low H values obtained for PEE are related to the fact that the PBT crystallites are floating in an amorphous matrix characterized by a low viscosity. 

After following the microhardness behaviour during the stress-induced polymorphic transition of homo-PBT and its multiblock copolymers attention is now focused on the deformation behaviour of a blend of PBT and a PEE thermoplastic elastomer, the latter being a copolymer of PBT and PEO. This system is attractive not only because the two polymers have the same crystallizable component but also because the copolymer, being an elastomer, strongly affects the mechanical properties of the blend. It should be mentioned that these blends have been well characterized by differential scanning calorimetry, SAXS, dynamic mechanical thermal analysis and static mechanical measurements (Apostolov et al, 1994). 

Details on the synthesis and characterization of three-arm star thermoplastic elastomer 0(PIB- -PaMeSt)3 are given in a presentation delivered in another Section of this A.C.S. Meeting (13) ... 

Thermoplastic elastomers (TPE) Styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene (SIS) block copolymers represent primary materials for other hotmelt adhesives. They are characterized by long open times, high elasticity levels, good spring qualities and a lasting stickiness, so that precoated surfaces always retain some of the qualities of PSAs. The melting temperatures of these adhesives are particularly low at about 65°C, so that they can be used for thermally sensitive materials (foams, fleeces, thin films). 

Intense commercial and academic interest in block copolymers developed during the 1960s and continues today. These materials attract the attention of industry because of their potential for application as thermoplastic elastomers, tough plastics, compatibilizing agents for polymer blends, agents for surface and interface mo dification, polymer micelles, etc. Academic interest arises, primarily, from the use of these materials as model copolymer systems where effects of thermodynamic incompatibility of the two (or more) components on properties in bulk and solution can be probed. The synthesis, characterization, and properties of classical linear block copolymers (AB diblocks, ABA triblocks, and segmented (AB)n systems) have been well documented in a number of books and reviews [1-7] and will not be discussed herein except for the sake of comparison. 

Nair, J.K., Reddy, T.S., Satpute, R.S., Mukundan, T., and Asthana, S.N., Synthesis and characterization of energetic thermoplastic elastomers (ETPEs) based on 3,3-bis(azidomethyl)oxetane(BAMO)-3-azi-domethyl-3-methyloxetane (AMMO) copolymers, J. Polym. Mater. 21 (2), 205, 2004. 

The elastomeric polypropylene materials studied in this chapter are from a class of thermoplastic elastomers since they possess the physical properties of elastomers along with the processing characteristics of thermoplastics. These materials are characterized by a low degree of crystallinity (23-26), where the crystalline regions dispersed in the amorphous matrix essentially provide physical cross-links to the amorphous elastomeric segments of the chain (19, 20). The size and distribution of these crystalline regions in the amorphous matrix thus have important influences on the mechanical properties. 

A series of PMMA-/7-PIB-Z7-PMMA block copolymers was successfully synthesized by telechelic PIB macroanions with high blocking efficiencies. Characterizations of these new thermoplastic elastomers were carried out by SEC, DSC, dynamic-mechanical, and stress-strain measurements. 

Blends of EPDM rubbers with polypropylene in suitable ratios have been marketed as thermoplastic elastomers (TPE), also commercially known as thermoplastic polyolefin elastomers (TPO). These heterophasic polymers, characterized by thermoreversible interaction among the polymeric chains, belong to a broad family of olefinic alloys that can now be produced directly during the polymerization phase, unlike blended TPE and TPO, and various compositions (with various compounding additives) can be formulated which are primarily tailored to meet different requirements of most of car applications. The TPE-based synthetic leather and foam sheets are typical examples. 

Determining the molecular weight and the chain microstructure is very difficult for some thermoplastic elastomers. Nearly all molecular weight characterization techniques rely on the ability to dissolve the polymer in a solvent in such a manner that the polymer chains behave individually. Since TPEs are usually... 

Well characterized copolymers have been commercially available since the mid 1960 s when Shell manufactured, by anionic polymerization, SBS and SIS copolymers. Both block and graft copolymers will chain segregate due both to low entropy contributions and to lack of interactions which would favour miscibility (1). The combination of melt processability, high strength and recoverable high deformability made these and related polymers attractive alternatives to elastomers which require chemical cross-linking. A key to the behaviour of the thermoplastic elastomers is the thennally reversible association of similar chain segments into domains, which for chains below the Tg can act as cross-links. 

The thermoplastic elastomers (TPE) are a new class of the polymeric materials, which combine the properties of the chemically cross-linked mbbers and easiness of processing and recycling of the thermoplastics [1-8]. The characteristics of the TPE are phase micrononuniformity and specific domain morphology. Their properties are intermediate and are in the range between those, which characterize the polymers, which produce the rigid and elastic phase. These properties of TPE, regardless of its t5 e... 

Aim TH, Park YH, Kim SH, Baik DH. Preparation and characterization of poly(ether ester) thermoplastic elastomers containing the 2,6-naphthalenedicarboxyl group. J Appl Polym Sci 2003 90(13) 3473-80. 

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