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Compatibility with cleaning agents and disinfectants is an important consideration when selecting materials for healthcare applications. Chemical resistance varies considerably among plastics and is largely dependent on molecular structure. Other factors can also influence performance, such as:
| Temperature |
Ranging from room temperature for non-sterilized devices up to 134°C for steam-sterilized devices
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| Exposure Time |
As short as a couple of minutes for hypochlorites and as long as 10 hours for glutaraldehydes |
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| Type of Reagent |
Commonly used reagents include hypochlorites, quaternary ammonium chloride compounds (QUATs), phenolics and glutaraldehydes |
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Reagent
Concentration |
From a few hundred ppm for hypochlorites up to 10% for QUATs
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Solvay’s healthcare plastics typically exhibit good chemical resistance, especially to aqueous systems including acids and bases. This allows them to withstand strong solutions of aqueous caustic solutions like sodium hydroxide, which has become one of the preferred methods for sterilization against Creutzfeldt-Jakob disease.
Ingredients are often added to cleaners and disinfectants to improve surface wetting and reduce evaporation. Our experience has shown that these chemicals can have a more detrimental affect on plastics than cleaners and disinfectants by themselves. This is primarily due to improper dilution or insufficient rinsing. Be sure to follow the manufacturer’s instructions to optimize the performance of the plastic.
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Stress on the Fabricated Part
Stress can be caused by an external load applied during use or by a residual internal stress in the molded part due to processing. Residual stress can be minimized by adjusting processing conditions. It’s important to be familiar with a material’s performance under unstressed and stressed conditions as some reagents having no effect on unstressed plastics can cause cracking when stressed.
A recent study evaluated the chemical compatibility of sulfone polymers and their resistance to environmental stress cracking when exposed to a variety of selected chemicals, including:
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- medical reagents
- common disinfectants
- high-performance greases
- anti-spotting agents
- inorganic reagents
- organic reagents
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| Results show that Radel® PPSU provides the best resistance of all sulfone polymers tested and Udel® PSU offers good resistance to many of these materials. Glass fiber reinforced grades deflect less (have lower strain) than unreinforced grades and provide better resistance to environmental stress cracking.
Since each application has unique performance and design criteria, it’s important to evaluate a material under conditions that best simulate the function of the component or system in its intended use. This includes cleaning and disinfection followed by sterilization in order to assess their cumulative effect on the material.
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