New acrylics & elastomers for medical applications.

High-clarity acrylics and new silicone and thermoplastic elastomers highlighted the new material entries at June's Medical Design & Manufacturing East '93 show in New York. New adhesives for plastics also were introduced at the show.

NEW ACRYLIC GRADES

A pair of new rubber-modified acrylic compounds designed for high-clarity medical packaging and molded parts was brought out by Cyro Industries, Mt. Arlington, N.J. The two new grades in Cyro's XT "multipolymer" range are X800RG and X800RH, which are said to offer reduced haze and higher clarity than Cyro's XT 375 medical packaging resin, while matching or exceeding its mechanical properties. The new pair is offered for injection molding and sheet extrusion for thermoforming. X800RG, with a haze of 7.5%, is the higher clarity grade; X800RH has a haze of 12%. The latter offers easier trimming of thermoformed parts. This is due to the improved ductility of the material (compared with previous XT compounds), which results in a decrease in burrs and "angel hairs" during trimming. Both grades reportedly can be used in injection tooling built for ABS and PVC, and both can withstand ethylene oxide and gamma sterilization techniques used for medical packaging.

Both grades have a specific gravity of 1.11, HDT at 264 psi of 180 F, mold shrinkage of 0.004 to 0.007 in./in., and light transmission of 88%. X800RG has a melt-flow rate of 14 g/10 min, tensile strength of 6300 psi, flexural modulus of 320,000 psi, and elongation at break of 5.5%. X800RH has a melt-flow rate of 8 g/10 min, tensile strength of 5500 psi, flex modulus of 290,000 psi, and elongation at break of 8.3%. (30)

ICI Acrylics Inc., St. Louis, extended its line of medical resins with its new Perspex CP-61 UVT-N. The new grade is a high-flow, high-clarity acrylic formulated for reduced mold plate-out while offering superior optical properties required for blood-analysis devices. The new grade has a light transmission of 92%. Melt-flow rate is 5.9 g/10 rain, Vicat softening point is 225 F, tensile strength is 9900 psi, and an elongation at break is 3.77%. (31)

MEDICAL ELASTOMERS

Dow Coming Corp., Midland, Mich., recently commercialized Silastic 7-6860 medical-grade liquid silicone rubber for injection molding, which features a high durometer (60 Shore A) and reportedly superior tear strength. This product was still developmental when first announced at last year's show. The two-part silicone rubber offers high clarity, tensile strength of 1300 psi, and tear strength of 275 ppi (die B). The company says it will commercialize 30 and 40 Shore A grades of this LSR later this year. (32)

Dow Corning also announced that next year it will restructure its medical silicone product line to reflect the evolving globalization of medical and pharmaceutical markets. The company plans to offer new custom product lines in silicone rubber that conform to international testing and quality standards, such as ISO 9000, as well as regional standards, such as the Japanese and European Pharmacopoeias.

A new addition to the Santo-prene olefinic TP elastomer line was unveiled by Advanced Elastomer Systems L.P., St. Louis. Santoprene 281-45 has 45 Shore A and is designed for both injection molding and extrusion. This soft grade is a candidate to replace silicone and natural-rubber medical parts such as rings, stoppers, fittings and plunger tips used in syringes and blood tubing. (33)

A new styrenic TP elastomer compound was introduced by the Plastics Div. of Teknor Apex Co., Pawtucket, R.I. Tekron 5000-45NT compound is based on Kraton G from Shell Chemical Co., Houston. It has a specific gravity of 0.91, 45 Shore A durometer, tensile strength of 1300 psi, and elongation of 860%. (34)

ADHESIVES FOR PLASTICS

Loctite Corp., Newington, Conn., introduced five new acrylic-based, solvent-free, single-component adhesives for polycarbonate and PVC. The five grades all are uv-curable (2- to 30-sec cure times), offer high flexibility (exceeding 200% elongation), and can withstand repeated standard medical sterilization procedures, the company says.

Loctite #3211 and #3201 are designed for PC components such as filters and blood oxygenators, while Loctite #3321, #3311, and #3301 are for flexible and rigid PVC materials. (35)