What kind of dye is best to use for plastic materials?

Name: Cathy

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Dye polyester, acetate, or acrylic

Country or region: USA

Message: What kind of dye is best to use for plastic materials?

Plastics vary a lot. Different plastics are made from entirely different materials. This means that completely different dyes must be used, depending on what plastic you have.

A plastic item that is made of nylon, a common material for making frisbee discs, can best be dyed by heating it in water to which an Acid Dye has been added, as well as a mild acid such as vinegar to attain a particular pH. Nylon dyes very well with acid dyes, whether it is nylon that has been woven into textile fibers or solid nylon plastic. All-purpose dyes contain one type of acid dye, the Strong Acid or Acid Leveling type. Better results may be obtained by using a superior acid dye, such as the metal complex (also known as premetallized) acid dyes. It is best to keep the dyebath around 185°F; higher temperatures might warp the shape of the nylon, or damage nylon fabric, but lower temperatures will not work as well in aiding the dye to bond to the fiber. For more information see my page, "How to dye nylon or polyamide".

Polyurethane, another common material for making frisbee discs, can also be dyed with acid dyes, but it can be damaged more easily by high heat. The spandex that gives stretch to our clothing is made out of polyurethane, but it is apt to lose its shape if heated above 140°F (60°C). Polyurethane is also commonly used to make foam materials, such as the padding used in furniture cushion. The 1:2 metal complex acid dyes are the best choice for dyeing polyurethane. In the case of fabrics made from spandex blends, it is best to dye at the lowest temperature that will work, never exceeding 140°F; it works quite well, in most cases, to dye only the other fibers in the blend, ignoring the spandex fibers altogether. For more information, see my page, "How to Dye Spandex", as well as the forum discussions on "Dyed Golf Discs", in the Dye Forum.

Polyester cannot be dyed with any of the dyes listed above, nor with any other dye you are likely to have encountered before now. Polyester can be dyed only with dyes from the class called Disperse dyes. See "Dyeing Polyester with Disperse Dyes". Acid dyes do not attach to polyester. The disperse dye process requires high heat, preferably above boiling temperatures (212°F or 100°C). Temperatures below boiling are quite disappointing. Nylon can be dyed with disperse dyes, but acid dyes are more resistant to washing on nylon. Disperse dyes are also the dye of choice for other synthetic materials such as acrylic and acetate. Polyester is widely used in textile fibers, but also in some resin materials and in the reinforcing resin for fiberglass. Polyester can be made from plastics that are marked with the recycle numbers 2, 4, or 1, so the same dyes that are used for polyester would probably be your best bet for any of these plastics.

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Acrylics can be dyed not only with disperse dyes, which are the best and safest choice for home use; they can also be dyed with dyes from a class called Basic Dyes, or cationic dyes. Acrylic plastics may not be not quite the same as the acrylonitrile used in acrylic fibers, so it's possible not all acrylic plastics will dye equally well with basic dyes. Basic dyes are unpleasant to work with, unless you have a properly safety-equipped laboratory; when used at home, they tend to badly stain everything they come in contact with, and some of them are possible carcinogens which I do not like to recommend for use by people who are not trained in laboratory safety procedures. See "Dyeing Acrylic with Basic Dye".

There are other plastics which simply cannot be dyed at home. Some plastics must be dyed while they are still in the liquid form. For example, polypropylene, marked with the recycle logo number 5, is used to make water bottles and also to make some performance sports clothing and stain-resistant carpeting and upholstery material, such as Herculon or Olefin. No matter what color your polypropylene object may be, you will not be able to dye it. It repels water sufficiently that it is unlikely you will even be able to paint a polypropylene material, unless you use a a special paint called Krylon Fusion for Plastics.

Before tackling any large or expensive project, be sure to do a small-scale test of trying to dye your plastic material with the recommended dye, to see how well your results come out. If you do not know what material your plastic is made of, you might try dyeing it as though it is nylon, first, since that is the easiest sort of plastic to dye, and proceed to try other dyes for other types of plastics if that does not work. For heating the dye with your plastic, use a large stainless steel cooking pot that you plan to never again use for food. You will also need a thermometer that you won't be reusing for cooking, in order to maintain your dyebath at the correct temperature for the required period of time.

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Posted: Friday - July 23, 2010 at 08:29 AM

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What kind of dye is best to use for plastic materials?

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