Polyurethane Processing Recent Developments

Recent trends in protective coatings used on buried pipelines have been away from reinforced hot applied coal tar and asphalt enamels and butyl rubber laminate tapes, particularly where applied over-the-ditch . The more recently developed coatings based on fusion bonded epoxies, extruded poly-ethylenes, liquid-applied epoxies and polyurethanes, require factory application where superior levels of pipe preparation and quality control of the application process can be achieved. 

This book series presents in-depth reports on the most important new developments in urethane technology. Volumes 2-5 contain papers written only by Japanese specialists. A number of these papers concern rigid and flexible foams. Polyurethanes and polyisocyanurates are widely used in Japan. The papers cover recent developments in chemistry, processing, properties and applications. 

Classical rubber processing is time and effort consuming because of the high polymer viscosities working in of vulcanization accelerators, fillers, plasticizers, activators, etc., must be carried out on roll mills, the vulcanization must take place in heated presses. In contrast, liquid rubbers have low viscosities, and so, can be more easily processed. These have already been known for a long time in the case of silicones, polyurethanes, polyesters, and polyethers, but have only been very recently developed in the case of diene rubbers. 

Recent developments include systems with better colour fidelity and handling properties. Dover s Doverphos HiPure 4 and 4-HR are high-purity tris-nonylphenyl phosphite (TNPP) processing and heat stabilizers, claimed to reduce overall costs. With 0.1% residual nonyl phenol, they are FDA-approved for food-contact applications and also used in medicals, colour-critical polyolefins, and styrenic block copolymers. They are effective also in acrylics, elastomers, nylon, polycarbonate, polyurethanes, polystyrene. PVC. ABS, and PET. 

In this chapter, we reviewed some of the recent developments in modeling and predicting the mechanical properties of polyurethane elastomers as a function of their formulation. Based on the knowledge of the formulation and processing history, one can roughly predict the degree of the microphase separation between the hard and soft phases. That, in turn, enables the construction of constitutive micromechanical models for the calculation of elastic, viscoelastic, and nonlinear tensile and compressive properties. 

The commercial prodnction of PPC is still quite modest at several kilotous annually and its use is limited primarily to binder applications in ceramic sintering processes where it benefits from a lower decomposition temperature compared to other binders [25]. More recently developed cobalt salem catalysts [26] and proprietary catalysts with improved activity and selectivity are able to prodnce tailored PPC polyols with specific molecular weights and hydroxyl group functionalities [27,28]. The polyurethanes synthesized from these polyols are reported to exhibit increased strength and durability caused by the polycarbonate backbone [29]. Besides C02-based PPC, other poly(alkylene carbonate)s are produced in pilot-scale processes [27]. 

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