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A design of a four square gear test rig that allows the wear of polymer and composite gears to be monitored continuously during operation is described. The wear behavior of three typical gear materials is examined and it is shown that the wear characteristics differ greatly. For Acetal there is a sharp rise in wear as the transmitted torque is increased, effectively limiting the torque that can be transmitted by an Acetal gear pair. This wear transition is shown to be associated with the maximum surface temperature of the gear reaching the melting point of Acetal. This provides an indirect method of checking the accuracy of existing models for the maximum surface temperatures in polymer gears. Very large discrepancies are found. A simple, alternative model for the average and maximum gear temperatrues is developed and is shown to predict the wear transition with far greater accuracy.

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Copolyesters were synthesized by using ring-opening polymerization of cyclic poly(butylene terephthalate) oligomers (c-PBT) and -caprolactone monomer (CL) in the presence of stannoxane catalyst at an elevated temperature. The in-situ copolymerization was conducted with various c-PBT/CL feed ratios. The copolyesters were characterized by GPC, NMR, and FT-IR techniques. Phase separation and the relaxation behavior of the resultant copolyesters were investigated by DSC, DMTA, and dielectric spectroscopy measurements. Mechanical properties (stress-strain behavior) are also reported and can be adjusted by varying the -caprolactone content of the copolymer.

Recent developments in production methods for polymeric materials have meant that thermoplastics for high temperature mechanical performance can now be selectively laser sintered. This paper describes the performance and the potential applications of EOS PEEK HP3: a high temperature, laser sintered thermoplastic material. Thermal, tensile, flexural, compressive and fractural tests were conducted to assess the mechanical response of the material. Physical properties, such as porosity and roughness are also presented along with a discussion on the failure mechanisms of the material during testing. Finally, the significance of this material in the production of prototype parts, the mechanical requirements of the polymer and limitations of its applications are outlined.