Dye-sublimation technology finds commercial use

Edited by the Engineeringtalk editorial team Dec 12, 2005

The first application of a new dye-sublimation technology for decorating complex-shaped plastics parts moulded from semicrystalline engineering polymers is about to go commercial.

The first application of DuPont Engineering Polymers' new dye-sublimation technology for decorating complex-shaped plastics parts moulded from semicrystalline engineering polymers is about to go commercial.

Tefal's Color Click electric kettle, whose outer shell is made of DuPont Crastin PBT polyester resin and decorated with different colours and patterns by means of dye sublimation, will be in the shops by Christmas.

"This economic, efficient way to apply sophisticated multicolour images, photographs or patterns onto three-dimensional plastics substrates of complex shape opens new ways for manufacturers to enhance their products' aesthetic appeal", says Christophe Chervin, Development Specialist at DuPont's European Technical Centre in Geneva, Switzerland.

Sublimation is a process whereby a solid substance is converted into gas without passing through an intermediate liquid phase.

Many industries use dye sublimation to transfer images or patterns from a carrier onto a variety of substrates, including textiles, by means of heat and pressure.

Decoration of plastics by sublimation is not new.

However, its use was until now limited to surfaces of simple geometric shape: flat or cylindrical parts.

This was because conventional dye carriers - paper or plastic film - cannot be applied smoothly onto complex shapes.

Stretchable dye carriers overcome this difficulty, but often produce blurred results, especially over tight curves and sharp edges.

Now DuPont's new process uses a patented dye-carrier which adheres smoothly onto 3D curved parts and complex geometries without wrinkling, producing high-precision patterns.

On semicrystalline plastics, such as DuPont Crastin, DuPont Delrin, DuPont Hytrel, DuPont Rynite and DuPont Zytel, sublimated dyes penetrate into the material to a depth of between 0.2 and 0.3mm.

This makes the decoration highly resistant to wear, scratches and abrasion.

On amorphous plastics, such as ABS and polycarbonate, the dye does not penetrate and can be scratched off easily.

In Tefal's patented design, the Color Click kettle has a removable two-part outer shell which is curved in three dimensions.

Various models are decorated with different colours and patterns by means of dye sublimation.

"These interchangeable shells give the Color Click kettle greater aesthetic appeal", explains Christian Dupuy, Product Manager at Tefal.

"The user can change these shells at will, to suit the mood of the moment".

"The kettle is sold with one or two pairs of shells, depending on the country of sale; further pairs of shells, with different colours, designs and textures, are sold separately".

The shells, made of DuPont Crastin PBT, have a high-gloss surface.

Sublimation produces a permanent image on this material, Dupuy says; the pattern remains sharp, the colours are not affected by the kettle's heat and the surface is resistant to scratching and abrasion.

Sublimation can produce an almost unlimited range of effects on plastics, such as wood, marble, or lace; the surface can be glossy or grainy, the colours light or dark.

"As a way to add value to plastics parts, the process has great potential in many industries", adds Chervin.

"In the clothing industry, for example, zippers can be coloured and patterned, to go with the rest of the garment; in the cosmetics and furniture industries, possibilities are limitless".

DuPont developed the 3D sublimation process for semicrystalline plastics in partnership with Pacific Colour, of Lons-le-Saunier, France, for the sublimation printing of the Tefal kettle shells, and with Sublistatic International, of Henin-Beaumont, France, for the printing of the dye-carrier.