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Design engineering |
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Why are two sets of property data shown in nylon data sheets? |
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Most nylon manufacturers publish "as-molded" (or "dry-as-molded") and "conditioned" property values. As-molded properties represent the properties of parts as they come out of the mold. These parts begin absorbing moisture from the atmosphere immediately. The amount of moisture in the parts is a function of time since molding and the temperature and humidity of the atmosphere to which the parts are exposed. The parts will eventually achieve an equilibrium moisture content based on the temperature and humidity. Conditioned properties are those of the parts after this equilibrium moisture content is achieved. The data sheet should say what these conditions are, and most manufacturers use the standard ASTM laboratory conditions of 73 °F (23 °C) and 50 % relative humidity.
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Processing technology |
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Can the conditioning process of nylon be sped up? |
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There are several methods to decrease the amount of time until a part is conditioned. These include humidity chambers, packaging in PE bags containing some water, storage in cold or hot water, and exposure to saturated steam. All methods have advantages and disadvantages. Further information is available from nylon suppliers.
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How long does it take nylon to become conditioned? |
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The rate of moisture uptake is dependent upon temperature and humidity. Time to equilibrium also depends upon part thickness. A part exposed to the standard laboratory atmosphere of 73 °F (23 °C) and 50 % relative humidity can take months to reach equilibrium. Under tropical climate conditions of 104 °F (40 °C) and 95 % humidity, it could take a few days or weeks. In boiling water, time is measured in hours or minutes.
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How should nylon be dried? |
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Most manufacturers supply nylon in moisture-resistant packaging, with a moisture content of 0.2 % or less. If the packaging is unopened and undamaged, it should be ready to process if transferred to the molding machine with minimal contact with the atmosphere. Most molders prefer to load the material into a hopper dryer for an added margin of safety. The hopper dryer must be a dehumidifying dryer. Air temperatures less than 180 °F (80 °C) are recommended to prevent yellowing of the pellets. Reground material and pellets from open containers need to be dried to below 0.2 % (or even less, depending upon the manufacturers' recommendation). Without knowing the initial moisture content, a drying time cannot be established that gives any certainty.
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Is moisture absorption by nylon reversible? |
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Yes. The moisture content of a nylon part is a function of temperature and humidity, and the time spent under those conditions. The amount of moisture in the part is constantly changing by small amounts as temperature or humidity changes. The rate at which this occurs is usually slow.
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Products |
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Are there any clear grades of Durethan® nylon? |
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Are there any grades that can be used for medical applications requiring biocompatibility? |
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Can nylon 6 and nylon 66 be used interchangeably? |
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In many cases these two nylons can be substituted for each other. Each resin, though, has some advantages in particular situations. Nylon 66 has a higher melting point, so the heat distortion temperature is higher than for nylon 6. However, the long-term heat stability of the two resins is similar. Nylon 6 is incompatible with antifreeze solutions, but nylon 66 has long been used in radiator applications. Nylon 66 absorbs less moisture than nylon 6, so the properties after conditioning do not change as much. Nylon 6 is considered to have a better surface quality and higher impact strength.
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Sales & Services |
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How can I get a Material Safety Data Sheet (MSDS) for a specific product? |
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You can request a Material Safety Data Sheet (MSDS) by sending us an email at Contact Us.
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