Semicrystalline blends

As a route for improving the melt-elongational properties of semicrystalline polymers, Siripurapu et al. [7] proposed the blending of amorphous and semicrystalline blends of PS and PVDF nevertheless, their approach showed only limited success. In contrast, Reichelt et al. [29] successfully developed blends of HMS-PP and PP-fe-PE block copolymers. As could be shown, the melt strength increases with the HMS-PP content, while blends rich in HMS-PP also show the lowest densities. 

Chen et al. [67,68] further extended the study of binary blends of ESI over the full range of copolymer styrene contents for both amorphous and semicrystalline blend components. The transition from miscible to immiscible blend behavior and the determination of upper critical solution temperature (UCST) for blends could be uniquely evaluated by atomic force microscopy (AFM) techniques via the small but significant modulus differences between the respective ESI used as blend components. The effects of molecular weight and molecular weight distribution on blend miscibility were also described. 

The rate of crystal growth in a semicrystalline blend, will depend on the magnitude of k, k2 and AF. At low undercooling, AT = T ° - F, AF is high and hence G is small. However, if the blend Tg approaches or exceeds the melting point (F °) 2 prohibit crystallization regardless the value of AF ... 

Semicrystalline blends - for example COP + 50% PC, 210-220 "C/ 4 MPa/10 h - show the typical view of a smoothly cut brittle fracture in the crystalline phases and the deformational fracture of the amorphous parts (Figure 9.2). 

SANS experiments have indicated that blends of high density (linear) and long-chain branched low density polyethylenes (HDPE/LDPE) are homogeneous in the melt, though the components may separate on slow cooling due to the difference in crystallization mechanisms [43]. The semicrystalline blends form effectively two-phase systems in the solid state, and it was shown [43,44] that the Debye-Bueche (DB) [45,46] model was appropriate to describe the morphology, with a SANS cross section of the form... 

SAXS has been mainly used to study morphology of the semicrystalline blends, cf. how it is affected by composition, crystallization rate, compatibilization, additives, etc. However, it can also be used to study local structures in molten polymer blends, for example, within the interphasial region. The method has been used for liquid, glassy, and ciystaUine systems to determine the spinodal and binodal temperatures as well as to measure Xi2- A reasonable agreement between the values measured by different methods was obtained (Harris et al. 1983 RiedI and Prud homme 1984 Barlow and Paul 1987). 

Hydroxyetiier of bisphenol-A Single Tg, FTIR Semicrystalline blend had <20 wt% I Yuan and Ruckenstein (1998)... 

Similar to other semicrystalline blends [19, 20], the melting temperatures of PEO and PLEA decrease with increasing the amount of the second component in the blend... 

PBT is produced by the transesterification of dimethyl terephthalate with 1,4-butanediol by means of a catalyzed melt polycondensation (19). PBT is also semicrystalline and is an extremely tough resin. Several commercial resins use a blend of PBT with another resin, such as PET, polycarbonate, or nylon. Typically, composites of PBT contain 20—30 vol % fiber glass. 

Currently, important TPE s include blends of semicrystalline thermoplastic polyolefins such as propylene copolymers, with ethylene-propylene terepolymer elastomer. Block copolymers of styrene with other monomers such as butadiene, isoprene, and ethylene or ethylene/propy-lene are the most widely used TPE s. Styrene-butadiene-styrene (SBS) accounted for 70% of global styrene block copolymers (SBC). Currently, global capacity of SBC is approximately 1.1 million tons. Polyurethane thermoplastic elastomers are relatively more expensive then other TPE s. However, they are noted for their flexibility, strength, toughness, and abrasion and chemical resistance. Blends of polyvinyl chloride with elastomers such as butyl are widely used in Japan. ... 

The ability of the E-plastomers to participate in the peroxide-mediated chain-extension processes can be augmented in blends with EPDM, where the mixture is homogeneously cross-linked with free radicals [5]. The use of these blends of EPDM and E-plastomers leads to improved processing and physical properties of the combination, compared to the EPDM alone, though the resulting vulcanizates are somewhat harder than the EPDM vulcanizates alone due to the presence of the semicrystalline plastomers in the vulcanized mixture. 

Poly(butylene terephthalate) (PBT) (1) resins are semicrystalline thermoplastics used in a wide variety of applications, most commonly in durable goods that are formed by injection molding. Applications include electronic and communications equipment, computers, televisions, kitchen and household appliances, industrial equipment, lighting systems, gardening and agricultural equipment, pumps, medical devices, food handling systems, handles, power and hand tools, bobbins and spindles, and automotive parts in both under-the-hood and exterior applications. Additionally, PBT is very widely used to form electrical connectors. PBT, through its many blended products, can be tailored to suit numerous applications. 

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