Adding colour during the moulding process

Because polymers are synthetically produced, colour can be introduced in the creation of the polymers. Polymers are self- finishing as they take the surface of the mould they are made in. With sheet materials this is often a perfectly smooth mirror-like finish, but they can also be textures to give a frosted look or any other texture that is also in the mould.

They are also self coloured.

Two injection moulds

One mould is made for the product , such as a toothbrush body, and one mould for the grip areas. The toothbrush is injection moulded in one material such as Polypropylene, then the product is moved to a second mould where the grip is injection moulded on to the body using a TPE.

Twin shot injection moulding

This process uses an injection moulding machine with a mould designed to produce the product in one cycle. The mould has two separate component cavities which can be rotated through 180 degrees so the line up with the twin injection points.

It is a continuous cycle as one part is being overmoulded while another part is being made in the first mould cavity.

Cellulose and acrylic paints

Paints provide colour and sometimes a textured finish to metals. They can also provide a barrier against corrosion for metals such as Steel and Iron. The surface of the metal must be cleaned, de-greased and primed for the paint to adhere to the surface properly. To get a full, rich colour an undercoat is often applied before the colour and, in the case of cars and other shiny products, a clear lacquer may be applied over the paint layer.

Electroplating

This involves using a metal to coat a (usually) cheaper metal to provide a protective layer and enhance the aesthetic qualities of the material. For example, teapots can be silver plated and cheaper jewellery can be gold plated.

The metal product is submerged in a solution containing tiny particles of the donor (plating) metal. As the current is applied, the product attracts the donor metal and the product is electroplated.

Polymer dip coating

This is used on a variety of products such as wire coat hangars and outdoor equipment. The metal is heated then the hot product is dipped into a tank of fine polymer powder which has air blown into it to ensure even distribution of the powder. The hot metal melts the powder giving a tight fitting and even polymer finish.

Metal dip coating

Metal can also be dipped into other metals for coating. In this case the product is dipped into a tank of molten plating metal. This process is often used for inexpensive metals such as low carbon Steels primarily to provide a barrier against corrosion.

Products can be Tin plated (food cans) or Zinc plated (known as Galvanizing) which is used to produce car bodies, buckets, screws, hinges and much more.

Powder coating

This process gives a much better finish than dip coating. A negatively charged product is sprayed with positively charged polymer powder so it sticks to it like a fine dust. It then passes through an oven which bakes the fine layer of powder into an even coat of polymer. Used to coat chair and table legs as well as many domestic metal products such as fridges and washing machines.

Varnishing

Metal varnishing is a method used to provide a clear surface finish to metals that will also provide some resistance to corrosion. They would be applied exactly the same as a paint or spray. Varnish is effectively paint without any pigment leaving it completely clear. A clear lacquer could also be used for a finer finish.

Sealants

Metal sealants are tough polymer based sealant coatings that protect polished surfaces from decay and tarnishing. Silicon based sealants are often used in the automotive industries as an additional bodywork barrier against weathering and rust. It is generally applied with a cloth or machine pad to produce a film that is then left to cure for 15 mins. then buffed to a shine.