Nylon molded specimens

McGrath, Robeson, and Matzner investigated block copolymers and homopolymer-copolymer blends of bisphenol-A polysulfone and nylon-6 (7). They found improved ESCR as the content of the crystalline nylon-6 block increased. Similarly, Viswanathan, al. prepared random block copolymers of bisphenol-A pFTysulfone and the partially crystalline hydroquinone polysulfone (8). ESCR improved markedly as the hydroquinone content increased. However, while the copolymers "as made" are semicrystalline, the compression molded specimens used for ESCR studies are amorphous. Hence, recrystallization from the melt was quite slow. The improvement of ESCR is attributed to solvent-induced crystallization of the surface layers, which was presumed to restrict diffusion of the liquid into the bulk. 

Glass-reinforced nylon resins, equilibrium moisture-conditioned at 50% RH, have yielded up to a 40% increase in notched Izod impact strength when compared to the corresponding dry-as-molded specimens. ... 

All glass-reinforced nylon resin specimens are dry, as molded. 

These thermotropic liquid-crystalhne polymers have high melting points but can be melt-processed like other thermoplastics. The macroscopic orientation of the extended-chain crystals depends on the orientation imparted by flow during processing (molding, extrusion, etc.). Because of the fibrous nature of the extended-chain crystals, these plastics behave as self-reinforced composites, with excellent mechanical properties, at least in the chain direction. This is illustrated in Table 4.3 for molded specimens of a hquid-crystalline copolyester of ethylene glycol, terephthalic acid, and / -hydroxybenzoic acid [14]. In the direction parallel to the flow, the properties listed in Table 4.3 favorably compare with ordinary crystalline thermoplastics (nylons, polyesters) reinforced with up to 30% glass fibers. 

Initial adhesion tests were made with 3.5- X 1- X 0.064-inch specimens of aluminum (Aluminum Associates No. 2024) and cold-rolled steel (polished ASTM A-415). Later tests were made with strips of copper, chrome-coated steel (Weirton Steel Co.), and brass with molded nylon 66 bars and with Mylar 300A poly (ethylene terephthalate) film. Before use, the specimens were washed (scrubbed with a soft bristle brush) with a solution of Alconox detergent, rinsed with water, rinsed with acetone, and dried. 

Tensile specimens of polypropylene, polycarbonate. Mylar (polyester), Nomex (nylon paper), and Kapton (polyimide) had dimensions of 3 mm in width and 10 mm in guage length. The specimen thicknesses were 65 ym for polypropylene, 75 ]lm for polycarbonate, 85 ym for Mylar, 200 ym for Nomex, and 50 ym for Kapton. Their tensile axes were perpendicular to the rolling direction of the sheets. The molecular structures of these specimens are shown in Table I. Epoxy resins were tested by compression. The specimens of epoxy resin were made of Epikote 828 (bisphenol A type) hardened by K61B (tridimethylaminophenol) or polyamide in a teflon mold of 2 mm in diameter and about 6 mm in height. 

Fig. 34. Unnotched fatigue life in nylon-6,6 as a molded and equilibrated at 50% rh (155). The test specimen is 0.775 cm thick.

The electrical conductivities of injection-molded, CNT-filled polymer blends are summarized in Table 12.4. For comparison. Table 12.4 also includes the literature value of conductivities of neat polymers used in this study. For each polymer blend, electrical conductivities are measured in two directions (i.e.. Directions I and II in Fig. 12.2) to determine whether the specimen is isotropic or not. It is found that there is large difference in conductivity between Directions I and II. For the CNT-filled PET/PVDF, PET/PP, and PET/HDPE, the conductivity in Direction I is about 4-8 times higher than that in Direction II. For the CNT-filled PET/nylon 6,6, the conductivity difference in the two directions is even larger, with Direction I having more than 22 times higher conductivity than Direction II. The anisotropy found in all the specimens is related to the partial alignment of carbon nanotubes in the... 

Specimen Mold temperature 150°C, High Temperature Semicrystalline Glass Reinforced Nylon Copolymer... 

The tensile properties of polyamide 6 compoimded with the TC 2500 wood fibers are shown in Table 2. The neat resin properties based on directly injection molding test specimens are shown first. Next are compounds where the hot extrudate was immediately compression molded. The third set is for compounds that were extruded, conpression molded, coarsely ground, dried and then injection molded. The fiber contents shown are based on dissolving the nylon and weighing the recovered fibers. 

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