Sample Polymer Bulletin for one fortnightly update
Polyurethane Foams

We are informed in this article that a process which is just coming onto the market will make the moulding of composites and polyurethanes much more economical. Induction heating of mould surfaces is the key to the process, developed by RocTool, and likely to be used primarily for automotive parts. Full details of the new "Cage System" process are given here.

The first part of this short article introduces to us a new flame retardant system from ICL Industrial Products of Israel, especially for flexible PU foam. Brief details are given of new "SaFRon-7700". The second part of the article brings us up to date with the latest financial results for the ICL Group as a whole, and ICL Industrial Products in particular.

Details are given of the preparation of rigid PU-clay nanocomposite foams made with different clay types and different clay concentrations. The densities of the foams were determined for potential applications as structural materials and underwater buoyancy-related uses. The formation of the nanocomposites was followed using X-ray diffraction and TEM. The influence of the clay on compression properties and storage modulus of the foams was determined. 24 refs.

This article discusses edge treatments and potted inserts in honeycomb-cored panels for aircraft interiors. To prevent moisture ingress into the honeycomb and to provide a finished edge on cored panels, several options are available. One method surrounds the panel on all four sides with a "picture frame" of high-density foam, cut to the same thickness as the core itself. The panel's prepreg skins overlap the core slightly so that the foam edges are covered, and the entire assembly is co-cured. General Plastics Manufacturing has supplied Boeing-qualified high-density, high-temperature-resistant and flame-retardant PU foam for edge closeouts since the 1960s. Alternative sealing methods include using low-density syntactic epoxy compounds to "pot" the edge of a honeycomb panel, thus enhancing panel durability. To encapsulate fasteners within a foam-and-honeycomb-cored panel or part, manufacturers pot the fastener with a lightweight liquid adhesive. Huntsman supplies Epocast low-density liquid syntactic epoxy for fastener reinforcement.

Insulated steel doors still dominate the marketplace, but GRP entry doors are gaining steady market share. In mid-2005, GRP doors made up just 10% of the entry door market, but today account for nearly 25%. GRP is bringing to market a door that is pre-finished and looks like a wood door. Plastpro, the No.2 player in GRP entry doors, offers doors with exteriors made of SMC and filled with PU foam. The doors are covered with polyester film and have PVC composite edges. They are waterproof on all six sides. Typical GRP doors use 20% glass fibre reinforcing a polymer, but Therma-Tru, the No.1 producer, uses a higher percentage, about 25-35%.

A group of yachtsmen and composite experts have combined to revive the Westerly brand, once a byword among sailing enthusiasts for rugged and dependable cruising and racing yachts. The aim is to revive the Westerly name by re-launching selected models, but produced in carbon/epoxy composite rather than the previous glass/polyester. The manufacturing technology is a vacuum infusion system first developed as an adaptation of aerospace practice by New System Yachts. By building the yacht in Slovenia and sourcing from there a carbon fabric produced from low-cost precursor, the GK35 is priced at 109,000 pounds sterling, not excessive for a contemporary 35 ft carbon boat. At the other end of the scale, Wally Yachts of Italy and Monaco has developed the 143 ft long Esense which features a deck with a sharp, uncluttered minimalist look. Wally yachts are generally moulded using prepreg carbon/epoxy skins over Nomex core, with added composite stiffening. The low-weight properties and visual appeal of carbon are maintained throughout the vessel. Esense has a single ultra high-modulus carbon mast custom-built by Hall Spars, and even the main onboard shower stall/bath is carbon fibre. With the introduction of the Sunseeker 37M Tri-Deck Yacht in January, a new generation of super yachts' are now sporting composite hulls. The hull was constructed using an open-moulding, hand lay-up technique. Ashland AME 6000 resin, a 100% epoxy vinyl ester resin, was chosen for its low styrene content and good surface cosmetics.

Huntsman and NMG have created a Russia-based joint venture, ZAO Huntsman, to make and sell PU systems to the adhesives, coatings, elastomers and insulation markets. The two companies have had commercial links for nearly 10 years. The jv will be based at NMG's current headquarters in Obninsk, near Moscow. This abstract includes all the information contained in the original article.

IAL Consultants report that demand for PU additives is only growing at 2-3% per annum in western Europe, compared with 6-7% in eastern Europe. The other region covered in IAL's report, Middle East and Africa, is experiencing typical annual growth rates of 8-10%. Blowing agents and flame retardants account for 82% of the market in the three regions, which saw demand exceed 237,000 tonnes in 2005. Catalysts, mould release agents, surfactants and antioxidants make up the other 18%. Trends influencing consumption include entry of third generation HFC blowing agents for rigid and flexible foams in Europe. Mould release agents are being driven towards water-based and especially silicon-based types. Liquid antioxidants are gaining popularity in the EU as they are easier to handle.

A model is presented in which compression set of TDI foams is a result of thermal and stress-induced relative flow of the hard and soft phase following hydrogen bond disruption. The majority of the soft segment consists of a mobile phase that exhibits liquid-like dynamics. However, a significant fraction of the soft segment is immobilised due to hydrogen bond interactions with the phase-separated polyurea hard segment. As temperature is increased, the hydrogen bonding between the soft and hard segment progressively weakens until there is little or no interaction and the phases are free under stress to flow past each other. FTIR data do not indicate that changes in the hard-soft phase interactions are accompanied by changes in intra-hard segment hydrogen bonding. Upon cooling, the hard-soft segment hydrogen bond interactions can re-establish themselves in a new compressed geometry if the phase separated, co-continuous hard segment does not provide sufficient restorative force to regain the initial dimensions. This model is based on data obtained by DSC, SEM, temperature-dependent FTIR, solid state NMR, SAXS and compression set measurements. 45 refs. Copyright (c) 2007 Elsevier Ltd.

The distribution of the cell shape in the polyurethane foam was measured by using the image processing method. In addition, the cell shape was simply modelled. The analysis limited within the range of elasticity was done by using this model. As a result, the prediction of the mechanical properties was tried by applying the rule of mixture to the foam. The validity was examined. 3 refs.

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