Gel-based RIM elastomers have novel touch qualities

Gel-based RIM elastomers have novel touch qualities

Technogel technology is one of the latest products of polyurethanes'' extraordinarily versatile chemistry.

A polyurethane gel based on a Bayer patent flows under pressure load like a liquid, but without losing its structural properties, so that after the removal of the pressure it returns to its original shape. This makes it suitable for such comfort applications as hospital mattresses and wheelchair cushions.

But with increasing interest being shown in its technical and aesthetic properties by the design community— and with the development of new systems that can be processed by reaction injection molding—more uses are also being found for it. Gels are classified as being halfway between solid and liquid.

The gel, called Technogel, is made by companies of the same name in Germany (Duderstadt) and Italy (Pozzoleone). They are joint ventures between Otto Bock GmbH, a leading supplier of polyurethane foams (through Otto Bock Schaumsysteme) and orthopaedic equipment, and Royal Medica, which first started using gels around 1990—first for cushioning for hospital use, and later for office equipment, shoe soles, bicycle saddles (through Selle Royal), and other products.

The first concepts for cast and spray elastomers with Technogel characteristics were developed at Otto Bock Schaumsysteme in 2002, and the first systems were commercialized in Germany last year.

Technogel, which is completely free of plasticizers, is a polyaddition product of a high-molecular, branched polyether polyol with an aliphatic or aromatic polyisocyanate. Compared with conventional polyurethanes, the amount of polyisocyanate is low, creating an elastomer with a low degree of crosslinking. The mechanical-physical properties such as touch can be controlled via the ratio of the two components, as well as the functionality of the polyether polyols and polyisocyanates.

Technogel shows remarkable elongation properties, stretching to much more than 860% without tearing. Normal PUR foams for upholstery generally obtain values of less than 200%. Another surprising aspect of this behavior, given the material''s low level of crosslinking, is that permanent deformation is very low (around 1% in long-term dynamic compression stress tests).

Technogel meets RIM

Speaking at a conference last year organized by the German foamed plastics trade association FSK (Fachverband Schaumkunststoffe, Frankfurt), executives from Otto Bock said that in developing TechnoRIM elastomers for reaction injection moldable skins for automotive and furniture applications, they were aiming for a soft elastomer with the touch and physical properties of Technogel.

Technogel is a two-component system that cannot be easily mixed. Its very high mixing ratios necessitate low pressure casting technology. But to make RIM skins, it is absolutely necessary to manufacture the material on high-pressure units. Furthermore, development of the system revealed that the change of the processing technology also required a change of the chemical matrix.

Numerous modifications of the basic components helped to develop a soft cast elastomer with very good physical properties. TechnoRIM can be processed on an unmodified, conventional, high-pressure unit. Thixotropically adjusted systems with a comparable chemical setup can also be used on spray systems by means of static mixers.

The good physical properties of the RIM system come from the Technogel technology. Further property improvements such as heat-aging resistance; color fastness after heat and hot-light aging; improved abrasion behavior; adhesion to carrier material; and a highly accurate reproduction of detail on grained surfaces, are the result of additives and mold release agents. Hardness can be widely varied.

In components combining skin, backfilling foams and carrier material, volatile emissions are said to be clearly reduced compared to parts made with other film materials.

Another important factor is the lightfastness of the TechnoRIM, which is based on aliphatic isocyanates. This means that no protective paint coating is needed.

Bock is continuing to develop systems with improved physical properties, capable of meeting, among others, specifications from Daimler-Chrysler for spray and powder skins, and from General Motors for spray skins. Technogel Italia SRL, Pozzoleone, Italy; +39 0444 462840; www.technogel.it

RESINS/COMPOUNDS ETP suppliers cook up applications in ovenware

The plastics frying pan may never hit the hob, but several announcements in recent months show that suppliers of engineering thermoplastics are taking a renewed interest in multitrip ovenware —and not just for microwaves.

Dow Chemical has developed the WA210 series of injection moldable Questra syndiotactic polystyrene (sPS) resins for food- and water-contact applications. The first application is the Q-Pan industrial baking tin, which recently won an innovation award at the 2003 International Bakery Show.

Working with Clean Baking Products (CBP) of Belgium, Dow helped create the tin for German bakeware producer Anneliese Mertes GmbH. Dow says baking pans made from Questra are a sustainable alternative to pans made out of coated metal. "They save energy and costs, and provide environmental and significant ergonomic advantages over traditional baking pans," it says.

Metal tins with nonstick surfaces require recoating to maintain a nonstick finish and need to be greased to enable an easy release of the baked product. The greased tins then have to be cleaned with solvents. The Questra baking tin has none of these disadvantages, and weighs 75% less, making it easier to handle in commercial baking quantities. Plastics also provide excellent thermal transfer, reducing baking time and energy consumption—even giving bread a better crust, Dow says.

General Electric Advanced Materials, the new division that groups together the old GE Plastics and GE Silicones (as well as GE Quartz), is attacking the market on several fronts. With its Ultem XHT grades of polyetherimide copolymers, which have deflection temperatures under load of around 30C higher than regular Ultem PEI, it is targeting industrial baking products currently made in PTFE-coated metal. A key advantage is that the Ultem parts will have much longer lifetimes. Final food contact approvals are currently pending. GEAM also sees big opportunities for liquid silicone rubbers in bakery molds.

Last year, housewares company Tupperware launched a range of tableware capable of going straight from the freezer to the microwave to the table. BASF developed special grades of its Ultrason polysulfone and polyethersulfones for the application. These can handle temperatures from -50 to 220C, and "not even boiling oil can ruffle their composure," BASF says. The transparent containers are available in a wide variety of colors. BASF notes that even curry sauce and tomato paste, which easily leave stains on many plastics, have no effect on the containers and lids. It added UV stabilizers to the plastics to enable them to be used for picnics, too. Tupperware gives a guarantee of 30 years on its new tableware in Germany. Dow Engineering Plastics, Horgen, Switzerland; + 32 3 450 2240; www.dowep.com. GE Advanced Materials, Bergen op Zoom, The Netherlands; +31 164 292097; www.geadvancedmaterials.com. BASF AG, Ludwigshafen, Germany; +49 621 604 3348; www.basf.com

Cross-laminated film offers high strength, more stiffness An idea which is expected to compete against heavy-duty paper, as well as woven sacks and bioriented polypropylene bags, is counting on its light weight and high strength to corner market share.

Developed by Ole-Bendt Rasmussen, director of O-B R. Enterprise (Walchwil, Switzerland), the cross-laminated film, with miniflutes on one side of the structure, takes advantage of high tear-propagation resistance provided in the cross-laminated films much like the crisscross grain of plywood.

One side of the material is a film oriented in the transverse direction, which can be printed, while the other machine-direction-oriented web consists of a fluted film structure. Each flute is about 1 mm, running parallel to the main direction of the orientation.

The flutes provide stiffness and resilience while reducing weight. Channels formed by the flutes can be used to bury protective substances such as oxygen scavengers or fire retardants. Such a solution can solve problems of highly sensitive additives, which could potentially decompose at high extrusion temperatures.

The fluted configuration is produced by intermeshing rollers, one with sharp crests and heated to 70C, the other with rounded slots operating at room temperature. The film, which meets the crests, is preheated. The flutes are shaped and heated on a transfer roll at 110C and then heat laminated, or spot welded, to the cross-stretched substrate film. The rolls can be designed to spot-burn microholes for substance release in the miniflutes.

Rasmussen previously developed Valeron, a cross-plastics, high-strength film, for packaging processor Van Leer (Essen, Belgium), which is still being produced. But the lack of stiffness and heat-sealing problems of cross-plastics laminated films led him to the miniflute development, he says. Rasmussen is licensing the technology and will not produce the film himself. Markets include industrial bags, tarpaulins, standup pouches, and diaper film. O-B R Enterprise, Walchwil, Switzerland; +41 41 758 1677; www.xf-plasticfilms.com

NEC Succeeds in development of flame resistant bio-plastic

NEC Corp. (Tokyo) has developed flame-retardant biodegradable polylactic acid (PLA) resin rated at UL94 5V and UL94 V-0/1.6mm that does not contain halogenated phosphorus-based flame retardants. The flame retardant is a special metal hydroxide that absorbs heat during ignition.

The material''s heat resistance, processability, and strength are said to be comparable to those of fiber-reinforced polycarbonate. Impact strength, for example, is 65 J/m compared to 50 for PC. The physical properties of the bioplastic are enhanced by use of special additives.

General electronic products such as personal computers and TVs require standards higher than V-1. Special products that generate heat at high temperature, such as projectors, require a UL rating of 5V. NEC plans to start using the bioplastic in its electronic products within two years. NEC Corp., Tokyo, Japan; www.nec.co.jp/eco/en/index.html

POLYURETHANES Back to school with polyurethanes

The "Secundo" classroom chair, made by Marko GmbH in Ludinghausen, Germany, has a seat shell reaction injection molded in Baydur 110 microcellular polyurethane from Bayer MaterialScience—a material Bayer says combines the necessary flexibility with a high degree of stability and design freedom. It is also strong enough to withstand the sort of rough treatment school kids dish out these days.

Experts estimate that more than 60% of all schoolchildren already suffer from posture damage in elementary school (although that may also be connected with the weight of books they have to carry around, as well as the way they sit). Bayer says one solution would be chairs that reduce stress on the back, provide dynamic support to the lumbar vertebrae, and allow a variety of sitting positions to be adopted—which is what the Secundo does, with its cantilevered design.

The shell is made for Marko by Ilpo Divisione Integrali SpA, Osteria Grande, Italy, and mounted on a tubular steel base. The material is resistant to most cleaning agents, highly break resistant, nonsplintering when it finally does break, and can be produced in any color. Bayer Material Science, Leverkusen, Germany; +49 221 9902 160; www.bayermaterialscience.com

RESINS/COMPOUNDS Soft TPOs

Engage polyolefin elastomers'' U.K. compounder, AEI Compounds, cooperated with DuPont Dow Elastomers to develop what it says are innovative specialty compounds using reaction compounding technology.

The compounds have enhanced thermal, abrasion, and mechanical toughness for applications such as flexible cable insulation and sheathing; automotive flooring and profiles made via blowmolding; calendering; sheet extrusion; injection over-molding; and slush molding. First grades are CT03-77A, a translucent material with high resistance to abrasion and stress whitening for extruding or calendering into automotive profiles or sheets for automotive flooring and CT03-77B, which is grafted to enable parts to be painted without priming, while adhering to polar substrates. AEI Compounds Ltd., Gravesend, England; +44 1474 564466; www.aeicompounds.com

Acetal water temperature indicator stops scalding

Heliote is a device that fits onto water taps to stop children (in particular) getting scalded when using kitchen and bathroom hot water taps. It incorporates a heart-shaped propeller, inside a clear chamber, that turns from purple to pink when the water is 39C or hotter. The propeller is made of DuPont''s Delrin acetal resin.

Heliote is made by Enviro-Developpement, Chatellerault. CEO and owner David Cottereau says the company selected Delrin for its high resistance to rapid hot- and cold-water temperature changes and pressure.

The device was also designed to keep tap water flow levels down to between 3 and 7 l/minute, compared to standard average flows of around 12. It has won numerous French industrial design prizes since its November 2001 launch. DuPont de Nemours International SA, Geneva, Switzerland; +41 227175111; plastics.dupont.com

Additives Laser additive aids marking

The quality of Nd:YAG laser markings on moldings can reportedly be improved with additive masterbatches that are said to be the first to allow sharp laser marking of a wide variety of transparent polymers without loss of clarity. The 756-brand products are neutral in color and require dosage of 2% to 3%. They have German BgVV food contact approval. Gabriel-Chemie, Gumpoldskirchen, Austria; +43 2252 63630; www.gabriel-chemie.com