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A new family of thermoplastic-metal composites, Polymetals, are poised to replace lead and other high-gravity metallics. Potential uses include radiation shielding for nuclear medicine, medical imaging, and radiation therapy; weighting and ballast applications for industrial machinery, sporting goods, and instrumentation; and nontoxic projectile inserts for small-caliber ammunition.
The high-density composite, called Ecomass, consists of powdered tungsten dispersed in a thermo-plastic matrix. The composite provides a high level of radiation shielding and dense mass comparable to lead without the negative health effects and environ-mental concerns over toxicity. Currently, eight Eco-mass compounds are commercially available, ranging in specific gravity from 6.0 to 11.0 gm/cc. A special radiation-shielding formulation is said to provide shielding efficiency comparable to lead with approximately only two-thirds the density.
Another resin system crosses the Atlantic after a successful 15-yr run in Europe. Forprene, a thermo-plastic vulcanate (TPV) elastomer, expands M.A. Hanna's Co., Cleveland, portfolio of thermoplastic elastomers (TPEs). The Forprene TPV compounds consist of a polyolefin phase with a cross-linked ethylene-propylene-diene monomer (EPDM) rubber phase dispersed throughout. The TPV has rubberlike properties such as softness, elastic memory, and flexibility, but is melt processible.
The Forprene product line covers a broad hardness range extending from Shore 35A to 60D. Resins are tailored for injection and blow molding, extrusion, and calendering. Special grades are stabilized against heat, copper, and UV degradation, while others are flame resistant, high-flow, and antifogging.
Hanna also debuts a new line of thermally conductive composites under the Edgetek family of high-performance compounds. Called Therma-tech they sport a high coefficient of thermal conductivity and target thermal management applications. Custom-molded heat sinks on circuit boards, and innovative heat exchangers in appliances, telecommunication devices, business machines, and other related industrial equipment are possible.
The easily recyclable compounds are designed to replace metal and nonrecyclable metallized plastics in shrouds, heat sinks, thermostats, heat exchangers, and radiant heating coils. Thermal qualities are said to rival those of commonly used metals such as steel, tin, and aluminum. Other formulations combine both thermal and electrical conductivity, permitting both heat dissipation and electrical management in a single part.
Typical mechanical properties of standard-grade Forprene TPV | |||||||
PROPERTY | TEST METHOD | A35 | A45 | A55 | A65 | A75 | A85 |
Hardness @15 sec, Shore A | ASTM D 2240 | 38 | 47 | 57 | 67 | 77 | 87 |
Tensile strength, psi | ASTM D 412-C | 580 | 754 | 811 | 956 | 1,160 | 1,594 |
Elongation at break, % | ASTM D 412-C | 550 | 500 | 450 | 450 | 460 | 510 |
Modulus at 100%, psi | ASTM D 412-C | 145 | 203 | 246 | 333 | 449 | 652 |
Modulus at 300%, psi | ASTM D 412-C | 304 | 377 | 464 | 565 | 623 | 870 |
Typical physical properties of Ecomass NJ-96TP/000 | ||
PHYSICAL PROPERTY | TEST | NJ-96TP/000 |
Density, gm/cm 3 | D-792 | 11.0 |
Melt point, °F | D-789 | 351 |
Flexural modulus, psi | D-790 | 790,000 |
Tensile strength, psi | D-638 | 6,000 |
Ultimate elongation, % | D-638 | < 1.0 |
Deflection temperature @264 psi, °F | D-648 | 311 |
(High-density thermoplastic, nontoxic alternative to lead) |
Preliminary mechanical properties of Therma-Tech composites | |||
PROPERTY | TEST METHOD | LC-6000 TC (Thermally conductive liquid-crystal polymer, LCP) | NY-4515 TC (Thermally conductive nylon 6) |
Tensile strength, psi | D638 | 15,100 | 15,544 |
Tensile elongation, % | D638 | 0.9 | 0.53 |
Tensile modulus, psi | D638 | 5,400,000 | 75.520 |
Flexural strength, psi | D790 | 2,600 | 27,150 |
Flexural modulus, psi | D790 | 4,300,000 | 29,785 |
M.A. Hanna Co., 200 Public Square, Suite 36-5000, Cleveland, OH 44114, (216) 589-4000, www.mahanna.com