Radiation sterilizable

The protection of polymers against high doses (20 - 1000 kGy) requires efficient additives preventing and/or stopping chain reaction type oxidative degradation. Primary and secondary antioxidants work well here in synergy. Commercial raw materials are available for radiation-sterilizable medical devices made out of polyolefins and other thermoplastics. Similarly, polymer compounds of suitable formulae are offered commercially for high-dose applications of polymers in nuclear installations. 

Table 2 Vicat Softening Temperatures of Radiation-Sterilizable Medical Grade Molding Polymers...

Radiation-sterilizable, segmented copolyester made by end-grafting radiostable aromatic prepolymers with glycolide... 

In order to improve the handling properties, copolymerization with p-dioxanone wasattempted (Koelmel etal, 1985 1991).These copolymers, like their PGA analogs, were also found to be radiation sterilizable with little loss of physical properties (Koelmel etal, 1985 1991). 

Even after irradiation, significant strength was retained out to four weeks postimplantation. The absorption data indicate that absorption occurs at least as fast as PDS. Thus, these systems can provide radiation sterilizable absorbable monofilament sutures with good handling properties. 

As the economy picks up in Europe, the eonstruetion industry should offer interesting growth opportunities for PP in carpets as well as woven and nonwoven geotextiles. In the medical industry, PP will get a boost, as radiation sterilizable grades become available. 

PC—copolyester better processibihty, hydrolytic, and gamma radiation resistance than PC sterilizable apphcations 43,109... 

EVOHs are convenient for food contact, have a good UV behaviour, are sterilizable by radiation and are transparent or translucent. 

Radiation doses up to 108 r. have little effect on tensile strength or other properties at room temperature. Gas permeability is also unaffected. A most striking and useful development is the increased strength above 100°C. of polymers treated with about 107 r. The polymer will withstand 100 to 400 lb./sq. in. at these temperatures, which is sufficient to permit containers to support their own weight. This has opened up new markets for polyethylene as a material for heat-sterilizable containers, pipe liners, motor winding material, corrosion-resistant gaskets, etc. 

Commercial PCTG/PC blends (Ektar DA series, Eastman Kodak) have been used in lawn and garden equipment, floor care appliance parts, sterilizable medical equipment, etc., where their combination of clarity, toughness, chemical resistance, heat resistance, UV and gamma radiation resistance have been well utilized. Molded parts... 

Medical applications of PP such as disposable syringes, hospital trays, and labware are contingent on sterilizability, either autoclaving or radiation. Disposable syringes that are sterilized by radiation require special formulations to prevent discoloration (yellowing) or brittleness as a consequence of degradation and cross-linking. 

Polymers used in nontoxic sterilizable items, such as tubing, artificial organs, and wound coverings, must be able to withstand sterilization by ethylene oxide, steam autoclave, or gamma radiation. For medical products sterilized by gamma irradiation, only plastics that do not degrade or discolor on exposure to radiation, such as polyester and polycarbonates, can be used. 

Biocompatibility Noncarcinogenesis, nonpyrogenicity, nontoxicity, and nonallergic response Sterilizability Autoclave, dry heating, ethylenoxide gas, and radiation... 

Sterilizability is of essential importance when the pol5mier is used in medical applications. Steam sterilization is preferred over chemical sterilization and radiation sterilization. Steam sterilization consists of a treatment of the membrane with superheated steam of >110°C for 30 min. Steam sterilizable membranes include poly(ether imide), PES and poly-(vinylidene fluoride). 

The growing importance of medical plastics has allowed POs to step outside their traditional low-cost roles and serve in life-and-death situations. However, their use in medical components is complicated by the degree to which they can resist various sterilization methods, including those that use damaging radiation. At the same time, more heat-sterilizable food packaging also requires POs that resist hot retort treatments. 

III. Sterilizability Radiation ( ray and eiectron beam), Ethyiene oxide gas, Autociave, Dry heating... 

There are additional applications with similar requirements which can be a fit for PPE/PS blends. Clinical diagnostics and labware applications such as connectors, fittings, and filtration housings require radiation/autoclave sterilizability and chemical resistance. 

However for intermediate compositions (32-50% in CHDM) they formed homogeneous mixtures above an upper critical solution temperature (UCST) that rendered a miscible metastable phase upon quenching. A thermodynamic analysis of the USCT-type behavior demonstrated that the bare interaction energy for each pair of blends, was positive and increased with the content of 1,4-CHDM units in the copolymer (140). Commercial PEj.C -T/ PC blends (Ektar DA series, Eastman Kodak) have been used in lawn and garden equipment, floor care appliance parts, sterilizable medical equipment, etc. In these applications, a beneficial combination of clarity, toughness, chemical resistance, heat, UV and gamma radiation resistance has been profited. Molded parts made of these blends generally showed excellent surface finish and hence molded-in-color could be used (141). 

Also, since the practice of sterilization of biomedical devices by ethylene oxide is diminishing due to concerns for the environment, along with health and safety factors, it may also be necessaiy for future biomedical devices to be irradiation sterilizable (i.e., Cobalt/gamma, E-beam). From work at Ethicon on polymers with aromatic substituents in the backbone (4a, b), it is believed that aromatic groups lead to an enhancement in the radiation stability of a polymer. 

Sterilizability of biomedical polymers is an important aspect of the properties because polymers have lower thermal and chemical stability than other materials such as ceramics and metals, consequently, they are also more difficult to sterilize using conventional techniques. Commonly used sterilization techniques are dry heat, autoclaving, radiation, and ethylene oxide gas [ Block, 1977]. 

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