Samples of nucleated polyamide 6 were quenched from the melt so as to monitor cooling histories. Their morphology and crystal structures were discussed in relation to sample thermal history; cooling history relevant to quenched sample morphology was recognized as being confined in the interval 110 to 160°C. In particular, samples were essentially amorphous for cooling rates larger than 200°C/s. The γ‐crystalline form was observed for cooling rates in the interval 70 to 200°C/s, whereas α crystalline structure was found dominant for yet lower cooling rates. Crystallinities evaluated from densities of quenched samples were compared with predictions of an isokinetic form of the Avrami model for polymer crystallization kinetics.
1 -(4-Tolylsulfonyl)-1,4,8,11 -tetraazacyclotetradecane (Tscyclam, 3) forms complexes with Ni" of stoichiometry: Ni(Tscyclam)X2.2H20 (X = CI, C104). The crystal structure has been determined for the chloride complex salt, which indicates that the complex is better described by the formula [Ni(Tscy~lam)(H~O)~]CI~. The salt crystallizes in the monoclinic space group P2,/n, with a = 13.030 ( 5 ) A, b = 7.859 (3) A, c = 22.640 (9) A, 0 = 93.17 (3)O, V = 2315 (2) A', and Z = 4. The structure was solved by using 3062 unique reflections with Io > 30(10). Anisotropic least squares refinement gave R = 0.1 I. The tetraaza macrocycle is folded and the two water molecules occupy two cis positions of a distorted octahedron. Average distance for the Ni"(high spin)-N(amine) bonds is 2.08 (2) A, whereas the Ni"(high spin)-N(amide) distance is 2.36 ( I ) A. The [Ni(Tsc y~l a m ) ( H~O )~]~+ chromophore keeps intact its stereochemical arrangement on dissolution both in water and in noncoordinating solvents (e.g. CHzC12). Tscyclam has been used as a carrier for the transport of Ni" across a bulk liquid membrane, displaying a much greater efficiency than the lipophilic version of cyclam (N-cetylcyclam, 2). The aqueous [Ni11(Tscyclam)(H20)2Jz+ complex, in the presence of CI-ions, is oxidized by persulfate to give the species [Ni"1(Tscyclam)C12]+, in which two equivalent chloride ions lie on the z axis and the tetraaza macrocycle is coplanarly chelated, as shown by the ESR of the frozen solution. Coplanar coordination of Tscyclam is now allowed due to the smaller dimensions of the Nil1' metal center compared to high-spin Nil1. The Ni"'/Ni" redox change could not be characterized through voltammetric investigations at the platinum electrode, but it was possible, through chemical evidence, to locate the potential for the [Ni~~1(Tscyclam)CIz]~/[Ni~~(Tscyclam)(H20)z]z~ couple at an especially low value (<0.42 V vs NHE), much lower than that determined for the [Ni"l(cyclam)C1z]+/[Nil~(cyclam)]z+ redox couple. (3) Fabbrizzi, L.; Forlini, F.; Perotti, A.; Seghi, B. Inorg. Chem. 1984, 23, 807. Buttafava, A.; Fabbriui, L.; Perotti, A.; Poggi, A,; Seghi, B. Inorg.
The fatigue-life diagrams of injection-molded nylon 6 gears with different reinforcements are shown for various lubrication modes (dry, grease, splash oil lubrication) and for different meshing combinations (plastic/plastic and steel/plastic gears). Tests using a suitably designed back-to-back rig have been carried out, and the results compared with previous experiments, performed using unreinforced nylon 6 gears. 232 gears (70 in unreinforced and 162 in differently filled nylon) were tested. More than 700 · 106 cycles have been totalled. From test data, and from the “matrix” of the gear/pinion material combination, the capabilities of differently reinforced nylon 6 gears in terms of fatigue and wear resistance have been outlined. These capabilities are the basis for a proper material selection in plastic gear design.
The fatigue-life diagrams of injection-molded nylon 6 gears with different reinforcements are presented for various lubrication modes (dry, grease, splash oil lubrication) and for different meshing combinations (plastic/plastic and steel/plastic gears). Tests have been carried out with a properly designed back-to-back rig; results are compared with previous experiments, performed with unreinforced nylon 6 gears. Tested gears have been 232 (70 in unreinforced nylon and 162 in differently filled polyamides). More than 700·106 cycles have been totalised. From test data, and from the “matrix” of gear/pinion material combination, the capabilities of differently reinforced nylon 6 gears for fatigue and wear resistance have been outlined. These capabilities are the basis for a proper material selection in plastic gear design.
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