Engineering plastics curing

The rise of T xp as a result of chemical side reactions is not desirable with respect to the material s properties. Usually, after such post-cure, polymers have higher Young moduli but become more brittle. The brittleness seriously lowers the applicability of these polymers as engineering plastics and matrices of advanced composites. 

Adhesives for this new engineering plastic are polyurethane (cure at room temperature to 150°C), RTV silicones, hot-melts (polyamide types) curing at 205°C, and epoxies (non-amine type, two-part). ... 

This is an engineering plastic designed for thermal/electrical applications requiring high dimensional stability. This material exhibits superior electrical and mechanical performance at continuous use temperatures ranging from -60 to 260 °C. Pyropel HDT polyamide-imide (PAI) produced by Albany International [35] has enhanced properties without the need for post-curing. 

Bolong Yao, Tonghua Yang, Kan Luo et al. Study and application of UV-curing composite modified by CaCOj whisker. Engineering Plastics Application, 35(12) 29-32, 2007. 

High Performance Polymers and Engineering Plastics Table 8.10 Mechanical properties of cured polytriazole resins. 

Hofmann K, Glasser WG (1993) Engineering plastics from lignin. 22. Cure of Ugnin-based epoxy resins. J Adhes 40 229-241... 

Epoxies, however, are not always the best adhesive for bonding small engineering plastic components as the dispensing of the two-part versions can be problematic (see Section 8.1) and they are relatively slow to cure compared to most adhesive technologies (although the cure speed can be accelerated by heat). Some hardeners can be toxic and have a high odour and so this can cause health and safety issues in the workplace or at the dispensing station. 

Unsubstituted and nonheat-reactive phenolic resins are used to a very limited extent due to their nonfilm-forming character. These resins are generally used as hardeners with epoxy resins to produce thermoset systems with high-quality engineering plastic properties. The base-catalyzed curing produces a crosslinked polyether structure, as shown in reaction (30), which is resistant to chemicals and heat and shows good barrier properties against moisture vapour. 

PA6 is one of the most important engineering plastics and is widely used as fibers, molded articles, and binders for composites. However, the applications of PA6 are still restricted in many fields owing to its poor flame retardant property and low limiting oxygen index (LOl) 21, and because it bums easily. Fang et al. [257] synthesized hb polyphosphate bisphenol-S ester to improve the flame retardancy of PA6. Chen et al. [258] synthesized hb polyphosphate ester (Scheme 27) and used it as curing agent and flame retardant in epoxy resins. 

J.C. Cruz, T.A. Osswald and M. Kemper, Rrecise curing analysis of accelerated unsaturated polyester reactions under Raman spectroscopy. Proceedings, 64th Annual Technical Conference - Society of Plastics Engineers (ANTEC), Charlotte, NC, USA, May 7-11, 2006, Society of Plastics Engineers, Brookfield, CT, 2828-2832. 

Luniewski, R.S. and Bly, J.H. in Proceedings of Regional Technical Conference Irradiation and other Curing Techniques in the Wire Industry, Newton, MA, March 20-21, 1975, sponsored by Electrical and Electronic Division and Eastern Section of Society of Plastics Engineers. 

Kwan, K. M., and Benatar, A., Investigation of Non-Thermal Effects Produced by Ultrasonic Heating on Curing of Two-Part Epoxy Adhesive, Society of Plastic Engineers Annual Technical... 

Fig. 19. Plot of viscosity and dissipation factor during cure of an epoxy resin illustrating camelback in dissipation factor and the correspondance of the minimum viscosity with the minimum between the two dissipation factor peaks. (Reprinted from Ref.42) with permission of the Society of Plastics Engineers)...

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