Block copolymer hysteresis behavior

Short fiber reinforcement of TPEs has recently opened up a new era in the field of polymer technology. Vajrasthira et al. [22] studied the fiber-matrix interactions in short aramid fiber-reinforced thermoplastic polyurethane (TPU) composites. Campbell and Goettler [23] reported the reinforcement of TPE matrix by Santoweb fibers, whereas Akhtar et al. [24] reported the reinforcement of a TPE matrix by short silk fiber. The reinforcement of thermoplastic co-polyester and TPU by short aramid fiber was reported by Watson and Prances [25]. Roy and coworkers [26-28] studied the rheological, hysteresis, mechanical, and dynamic mechanical behavior of short carbon fiber-filled styrene-isoprene-styrene (SIS) block copolymers and TPEs derived from NR and high-density polyethylene (HOPE) blends. 

It was the objective of this work to investigate the effect of variation in block architecture (number and the order of the blocks) on the crystallinity level, morphology, the stress-strain and hysteresis behavior of this series of polymers. In addition, the composition ratio of the two block types is expected to play a crucial role in determining the bulk material properties of the block copolymers. This is related to the fact that the mechanical properties of block copolymer are typically influenced more substantially by the behavior of the continuous phase, as will be demonstrated.(1,22)... 

Hysteresis Behavior. The hysteresis behavior of the HBIB triblock copolymers are given in Figure 13A and of that of the inverted HIBI block copolymer is given in Figure 13B. The difference in the behavior of these two series of block copolymers is tremendous. The origin of these differences are again directly related to the morphology and the architecture of the polymers. 

The hysteresis behavior of the diblock copolymer HBI-50 is not shown but is very similar to that of HIBI-49. In summary then, the difference in hysteresis behavior of the HBIB series to that of HIBI and HBI is related to the ability of the members of the first series to form permanent entanglements, by entrapment of the end blocks in the semicrystalline domains, whereas no such arrangment is possible for neither HIBI nor HBI series. The permanent entanglement serves as a physical crosslink which promotes recovery of the polymer after the deforming stress has been removed. At the same time, much less energy is lost as heat. 

As with other block copolymers, the nature of the soft segments determines the elastic behavior and low-temperature performance. TPUs based on polyester soft blocks have excellent resistance to nonpolar fluids and high tear strength and abrasion resistance. Those based on polyether soft blocks have excellent resistance (low heat buildup, or hysteresis), thermal stability, and hydrolytic stability. 

Bosker et al. studied the interfacial behavior of polystyrene-block-maltodextrins at the air-water interface via Langmuir-Blodgett technique [124]. Owing to the slow adsorption/desorption of the polysaccharide chains and block copolymer aggregation, the systems show interfacial pressure hysteresis between consecutive compression and expansion cycles of a monolayer. 

Vega DA, Sebastian ]M, Loo YL et al (2001) Phase behavior and viseoelastic properties of entangled block copolymer gels. J Polym Sci B Polym Phys 39 2183-2197 Wang J, Wu C, Liu R et al (2014) Enhanced dielectric behavior in nanocomposites of polyurethane bonded with copper phthalocyanine oligomers. Polym J 46 285-292 Watanabe M, Suzuki M, Hirako Yet al (2001) Hysteresis in bending electrostriction of polyurethane films. J Appl Polym Sci 79 1121-1126... 

The glass transition is described in Sect 3.43 with respect to its basic thermodynamics, and in Sect 4.7.3 with respect to its microscopic theory, kinetics, and hysteresis behavior. The behavior of copolymers and solutions with respect to the broadening of the glass transition is illustrated in Fig. 436. A final remark is made here about block copolymers and the discovery of rigid amorphous polymers, the amorphous portions of molecules that are restrained by crystals. 

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