Injection-molded blends

The morphology of the injection molded blends is shown in the optical micrographs of Fig, 5. 

The mechanical properties of the injection molded blends and composites are shown in Table 3. 

Figure 1. Relationship between (normalized) tensile strength and HPL content of injection molded blends with ethylene vinyl acetate copolymer. (Vinyl acetate content of the thermoplastic copolymer is given in parentheses.) (Strength values expressed in percent of unblended copolymer.) (From Ref. 11, with permission by Marcel Dekker, Inc.)...

The interphase between the continuous and the discontinuous polymer phases differs with respect to blend preparations. Solution-cast blends produce inclusions that are pulled away from the matrix, whereas injection-molded blends show HPL striations that are closely associated with the matrix. 

Figure 5 presents the results of tensile tests for the HPC/OSL blends prepared by solvent-casting and extrusion. All of the fabrication methods result in a tremendous increase in modulus up to a lignin content of ca. 15 wt.%. This can be attributed to the Tg elevation of the amorphous HPC/OSL phase leading to increasingly glassy response. Of particular interest is the tensile strength of these materials. As is shown, there is essentially no improvement in this parameter for the solvent cast blends, but a tremendous increase is observed for the injection molded blend. Qualitatively, this behavior is best modeled by the presence of oriented chains, or mesophase superstructure, dispersed in an amorphous matrix comprised of the compatible HPC/OSL component. The presence of this fibrous structure in the injection molded samples is confirmed by SEM analysis of the freeze-fracture surface (Figure 6). This structure is not present in the solvent cast blends, although evidence of globular domains remain in both of these blends appearing somewhat more coalesced in the pyridine cast material.

The impact properties of an injection-molded blend of PP and EPDM are sensitive to blend composition, processing variables, and test conditions. At all temperatures tested, the impact strength of blends of PP with up to 30% EPDM increase with EPDM content and decrease with test temperature. The temperature dependence of the impact strength increased with the fraction of EPDM. The impact strength appears to... 

Figure 4. PSF/PSX dispersion in polysulfone (5% injection-molded blend observed at 172X)...

Important processing methods coating, injection molding, blending, compression molding, lamination, thermoforming... 

Engberg et al. [67,68] prepared blends based on Vectra A950 and several flexible chain polymers. The order parameter of the PLC component in injection molded blends of polyethersulfone (PES) and Vectra, referring to the whole cross-section (thickness of specimen 1.5 mm), was according to X-ray scattering data close to 0.4 and also independent of the composition of the blend [67]. The lower chain orientation found in these samples reflects the fact that shear flow is less effective in orienting PLCs than extensional flow. 

Table 14.7 Stiffness constants (in GPa) of injection molded blends of polycarbonate and Vectra A...

PC/ABS Effects of polycarbcmate oUgcaner on morphological and mechanical properties of the weldline in injection molded blend Uemura et al. 2008... 

Skin/core morphologies are common in blends of LCP s and thermoplastic polymers and they play a significant role in defining the properties of both extruded and injection molded samples. Usually, LCP s in the skin have a higher degree of orientation than in the core when the blends are extruded or injection molded (Husman et al. 1980 Hedmark et al. 1989 Lee 1988). Baird et al. (Baird and Mehta 1989 Baird and Sukhadia 1993) observed a skin/core morphology in blends of PA 66 with HBA/HNA and 40 PET/60 PHB and 20 PET/80 HBA copolyesters. More LCP fibers were present in the skin than in the core for both systems. Isayev and Swaninathan (1994) also reported shell-core structure in the fracture surfaces of injection molded blends of HNA/HBA liquid crystalline copolyesters and poly (etherimide). 

Figure 1.25 Dispersed number average phase size as a function of injection rate and mold temperature for an 80/20 polyamide 6/HDPE injection molded blend.

BLEND MANUFACTURE Injection molding BLEND MORPHOLOGY Dispersed GRADES... 

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