Thermoplastic elastomers rheology

Veenstra H., Hoogvfiet R.M., Norder B., De B., and Abe P. Microphase separation and rheology of a semicrystalUne poly(ether-ester) multiblock copolymer, J. Polym. Sci. B. Polym Phys., 36, 1795, 1998. Garbrieelse W., SoUman M., and Dijkstra K., Microstmcture and phase behaviour of block copolyfether ester) thermoplastic elastomers. Macromolecules, 34, 1685, 2001. 

Such soft-touch materials are usually TP Vs or thermoplastic elastomers (TPEs) which combine the moldability of thermoplastics in the melt state with elasticity, lower hardness, fracture resistance, and surface characteristics of elastomers. However, plastics and elastomers respond differently to mechanical stress. Hence, both rheological behavior and mechanical strength will to a large extent depend on the morphology of the blend which may change with change in the composition. 

Medintseva, T.I., Dreval, V.E., Erina, N.A., and Prut, E.V., Rheological properties thermoplastic elastomers based on isotactic polypropylene with an ethylene-propylene-diene terpolymer, Polym. Sci. A, 45, 2032, 2003. 

Freitas LDL, Stadler R. Thermoplastic elastomers by hydrogen bonding. 3. Interrelations between molecular parameters and rheological properties. Macromolecules 1987 20 2478-2485. 

There is a growing interest in the synthesis of star-block thermoplastic elastomers (TPEs) on account of their unique mechanical and rheological properties [71-73]. PIB-based TPEs exhibit excellent mechanical properties and have superior thermal and oxidative stabiHties relative to polydiene-based TPEs [73,74]. 

Processing oil is a well-known additive for rubbers and is commonly employed in PP/EPDM TPVs [10-12]. It lowers the hardness and improves the processability. The oil, in most cases paraffinic oil, can be considered as a low molecular weight olefin. The difference in polarity between the three components is small, and the oil is present in both the PP and in the elastomer phases [67]. In order to understand the mechanical and the rheological properties of olefinic thermoplastic elastomers (OTPEs), the concentration of oil in each phase must be known. 

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Ektar Performance Plastic s trade name for its family of copolyester thermoplastic elastomer, elastic constant See modulus of elasticity, elastic deformation See deformation, elastic en-ergy, plastic work rheology, elastic fracture See melt fracture, elastic hysteresis See hysteresis, elastic, elasticity A property that causes plastic to return to its original size and shape after removal of a force causing deformation. See coefficient of elasticity deformation and toughness extruder-web stretching and... 

S. Saikrasun, S. Bualek-Limcharoen, S. Kohjiya, and K. Urayama. Thermotropic liquid-crystalline copolyester/thermoplastic elastomer in situ composites. I. Rheology, morphology, and mechanical properties of extruded strands. J. Appl. Polym. ScL, 89 2676-2685, 2003. 

Mousa, A., Halim, N. A., and Al-Robaidi, A., Rheological and mechanical properties of clay-thermoplastic elastomers derived from PVC and NBR, Polym. Plast. Technol. Eng., 45,... 

VI. Thermoplastic Elastomers at Surfaces Vn. Rheology and Processing Vin. Applications References... 

S. Shahbikian, Phase Morphology Development and Rheological Behavior of Non-plasticized and Plasticized Thermoplastic Elastomer Blends (Ecole Polytechnique, Mraitreal, 2010),... 

Block polymers and polymer blends deserve now a great intere because of their multiphase character and their related properties. The thermodynamic immiscibility of the polymeric partners gives rise indeed to a phase separation, the extent of which controls the detailed morphology of the solid and ultimately its mechanical behavior. The advent of thermoplastic elastomers and high impact resins (HIPS or ABS type) illustrates the importance of the industrial developments that this type of materials can provide. In selective solvents, and depending on molecular structure, concentration and temperature, block polymers form micelles which influence the rheological behavior and control the morphology of the material. 

Injection pressure is a fimction of flow length, wall thickness, and melt rheology, and it is calculated to achieve uniform mold filling. The Arnitel injection pressure range is <5000 to >20,000 Ib/in (<34 to >137 MPa). Thermoplastic elastomers may not require back pressure, and when back pressure is applied, it is much lower than for thermoplastics that are not elastomeric. Back pressure for Amitel is about 44 to 87 Ib/in (0.3 to 0.6 MPa). Back pressure is used to ensure a homogeneous melt with no bubbles. 

S. Hui, T.K. Chaki, S. Chattopadhyay, Dynamic and capillary rheology of LDPE-EVA-based thermoplastic elastomer effect of silica nanoflller, Polymer Composites 31 (3) (2010) 377-391. 

CARBON BLACK-FILLED BLOCK COPOLYMER THERMOPLASTIC ELASTOMER SYSTEMS, 714 Fundamentals for Black-Filled Systems, 714 Experimental, 715 Rheology, 716... 

Even though thermoplastic elastomer has been widely studied [1-23], there has been relatively little serious research of the rheological behavior of the block copolymer systems [20-31]. Data on the effects of carbon black on the extrusion behavior are even more limited. In this work, we investigated the effects of carbon black on the triblock copolymer thermoplastic elastomers SBS (styrene-butadiene-styrene), SIS (styrene-isoprene-styrene), and SEES (styrene-ethylene/butylene-styrene). 

As previously mentioned, the growth of the block copolymer thermoplastic elastomer industry has now reached a high level of commercial importance. However, it is still difficult to study the rheological behaviors of thermoplastic elastomers because they exhibit complex behavior that combines the elastomeric final product properties with the processing characteristics of thermoplastics. Recently, the rheological behavior of the styrene block copolymers (SBS, SIS, and SEES) was studied by Kim and Han [31]. A series of systematic investigations for the viscoelastic behavior of triblock copolymer thermoplastic elastomers also were conducted by Mathew et al. [22,23]. Kim and Hyun [20] reported the viscoelastic properties of SEES. 

Unfortunately, for block copolymer thermoplastic elastomers, any trials to accommodate the viscosity changes by carbon blacks into theoretical considerations, or to fit the equations cited onto the rheological behavior of black-filled systems have not been conducted up to now. Of course, such trials will be relatively complex and time-consuming work because thermoplastic elastomer shows intricate properties due to its unique microstructure. 

A segmented thermoplastic elastomer, Hytrel 5526 (HT), as a flexible filler is added to PET phase to modify the rheological behavior of PET/PE MRCs [34]. The flexibility of the microbrils with low HT loading has no obvious influence on the viscosity of MRCs. With the increase of HT content, especially for the 30 wt% HT, the microfibrils flexibility increases, causing the viscosity of MRCs to have a slight decreasing trend shown in Figure 12.19. Moreover, the more flexible microfibrils lead to lower melt elasticity of MRCs. 

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