Many plastic components need to have a surface finish applied before use. This can act as a decorative layer, a protective layer, to smooth out surface defects, or to alter surface properties (for example, to enhance adhesion). If this surface effect is applied during the moulding process, it can reduce time, space, material and machinery requirements. It also allows processors to supply complete systems, rather than just moulded components. In-mould decoration techniques include the in-mould application of film, in-mould priming, in-mould labelling and the injection of paints into the mould.
In-mould decoration generally requires additional equipment, which can be expensive. Design is also critical for success. These factors need to be taken into consideration in corporate planning.
In-mould films are prepared by multi-layer extrusion or solvent casting. They can be single colour or highly patterned with detailed graphics. They are stretched across a mould prior to injection, compression or blow moulding to produce a variety of decorative effects. This technique allows for great design flexibility and permits increased customer personalisation of products such as cars and mobile phones. Changing design between moulds is as simple as changing a roll of film. Film preparation is also discussed in this review.
Coatings comprising thermoplastic, pseudo-thermoplastic and uncured thermosetting materials can be injected or extruded into a mould. Here they act as paints in compression injection moulding and co-injection moulding. An additional benefit is that in-mould painting can reduce the release of volatile organic compounds (VOCs) into the atmosphere, which is a common problem in paint shops.
In-mould labelling can eliminate the requirement for adhesive. In the first example of this practice, paper labels for ice cream container lids were inserted into the mould prior to injection. Labels can also be applied as film and made from the same plastic material as the component to facilitate bonding and create a continuous surface effect, i.e., the label becomes an integral part of the product.
These techniques have widespread use in the plastics industry and the marketplace is expanding. The car and mobile phone industries, packaging and toys are examples of key areas for growth.
Many new developments are taking place in this field. The indexed summaries of papers from the polymer library that are included with this review include a number of key patents. This reference section also provides a good indicator of the key companies involved in this area and the current applications of this technology.
The emphasis of this review is on practical applications of the techniques of in-mould decoration including advantages and disadvantages. This book provides an excellent source of information about a developing area of moulding, which will allow processors to add value to products and compete in the marketplace.
2. The Popularity of In-Mould Decoration
2.1 Customer Requirement
2.3 Environmental Legislation
2.4 A Strategic Decision
3. In-Mould Film Technologies
3.1 In-Mould Labelling
3.2 In-Mould Paint Films
3.2.1 The Structure of In-Mould Paint Films
3.2.2 Manufacturing Options
3.2.3 The Application of Paint Films in Moulding
3.2.4 Benefits of Using In-Mould Paint Films
3.2.5 Limitations of Using In-Mould Paint Films
3.3 In-Mould Textiles
3.4 In-Mould Decorating
4. Injection In-Mould Painting
4.2 Paint Formulations
4.2.1 The Base Plastics
4.3 Adhesion Technologies
4.3.1 Compatible Materials
4.3.3 Chemical Compatibilisation
4.4 Application Methods for Injection In-Mould Painting
4.4.1 Compression Injection Moulding
4.4.2 Simultaneous Co-Injection Moulding: Granular Injected Paint Technology (GIPT)
4.4.3 Moulded In Paint
5. On-Mould Painting
5.2 Coating Formulation
5.3 Application Methods
5.4 The Advantages and Limitations of On-Mould Painting
6. In-Mould Primer
6.2 In-Mould Priming of PP Using Simultaneous Co-Injection Moulding
6.3 In-Mould Priming of Composites
Abbreviations and Acronyms
Abstracts from the Polymer Library Databases
As a materials engineer, Jo Love has been researching in-mould decorating for five years. She is an expert in the development and use of the Granular Injected Paint Technology (GIPT), and has published papers and taught the principles of in-mould decorating internationally. Dr Goodship is a Senior Research Fellow with 14 years experience in industry and expertise in co-injection moulding technology. The authors are based at the Warwick Manufacturing Group in the Advanced Technology Centre at the University of Warwick, which has strong links to the automotive sector.