Hard Coating Process

Hard coatings are a specially formulated treatment which are applied to plastic substrates in liquid form and cured, usually using heat or UV energy. They can be applied using many different methods such as spray, flow, roll or dip coating.

Hard coatings improve the surface performance of plastic materials, offering greater abrasion resistance (amongst many other benefits), giving very strong and versatile materials such as Polycarbonate a harder surface, enabling the material to be used in a wider variety of applications. This also means that the coated material(s) can last considerably longer, needing to be replaced less, therefore helping to cut down on a project’s carbon footprint.

 

Contents

1 Introduction

2 Main benefits of hard coating plastic

3 Applications

4 Thermally Cured Coatings and UV Cured Coatings

5 Environment

 

1. Introduction

Almost all hard coatings also offer increased chemical resistance to plastic materials, which are generally easily damaged by harsh chemicals.

Other properties can be included within hard coatings such as UV resistance, Anti-Microbial properties, Anti-Glare, Anti-Fog/Misting, Anti-Fouling/Graffiti, Anti-Static and even Electrical Shielding properties, as well as matte and textured finishes, etc.

The level of abrasion and chemical resistance can vary depending on the hard coating’s formulation. Some coatings offer a lower abrasion resistance but in doing so offer an extended life under external weathering conditions.

Hard coatings can be applied to many substrates such as Polycarbonate, PMMA, PET, PVC and PETg in sheet form or mouldings. They can also be applied to some printed (digital and screen) or painted surfaces.

Hard coatings provide multiple benefits, such as significantly better scratch resistance, weather resistance, and improved resistance to chemicals and solvents. In addition, coating helps to maintain colour, gloss, light transmission, and other physical properties of transparent plastic sheets.

 

2. Main Benefits Of Hard Coating Plastic

• Enhanced and long-term weatherability
• Improved resistance to scratches and abrasives
• Superior resistance to chemicals and solvents
• Excellent glazing protection
• Helps to extend a polymeric component’s durability and performance
• Maintains physical properties
• Material is easier to clean
• Contributes to safety and energy efficiency (lowering Carbon Footprint of projects).

 

3. Applications

Hard coatings are used on many different products in a wide variety of industries. Most common applications for hard coatings are:

• Automotive – Headlamps, internal surfaces, gear stick knobs, external pillar caps
• Aerospace – Internal cabin windows, internal coverings, foldable tables
• Rail – Headlamps, signal lenses, information display screens (internal and external)
• Road – Variable message signs, traffic light lenses and controls, noise barriers
• Electronics – Display screens, component covers
• Industry – Safety glazing, machine guards, roofing, etc.

The above applications are very much functional and allow plastics to perform better and last longer in everyday/harsh conditions.

There are many more instances where coatings allow for decorative finishes to be protected and therefore significantly extend the life of such products. These include, reverse printed splash backs, signage, point of sale, wall coverings, etc.

There are so many more products that benefit from hard coatings, the list is too long to cover everything.

 

4. Thermally Cured Coatings and UV Cured Coatings

Thermally cured coatings and UV cured coatings are commonly used in many industries, with most car headlamps in the world having one form of hard coating applied to them. Both technologies offer very similar end results – hard coatings with abrasion and chemical resistance. However, the chemistry behind both is very different.

Thermally cured coatings are applied to the substrate and then exposed to high temperatures for a period of time. This can be problematic with certain materials or thicknesses, where the heat required to cure the coating can warp the substrate.

UV cured coatings are applied to the substrate and then exposed to high levels of UV energy which cures the coating immediately. This process requires much lower temperatures offering greater versatility. UV curing is quicker, requires significantly lower levels of energy and a smaller footprint for machinery. Of the two methods, UV cured coatings are better for the environment.

Many sheet companies apply thermally cured coatings using the flow-coat method. Sheets are fixed into holders so that the material can be held in place whilst the coating is applied. For this reason, plastic sheets are produced over-sized and the edges are cut off. Whilst flow-coating offers a very good finish with low levels of inclusions, there is a high level of material waste during this process.

UV cured coating technology offers the option of a spray coating to sheet materials meaning that the sheet can be coated edge to edge, resulting in less waste.

There will always be applications where one technology or coating method is more beneficial than the other, however, UV cured coatings should be the favoured option for environmental reasons.

5. Environment

Plastic materials have an infinite amount of uses and benefit many people which is why they will continue to be used for many applications. Over time, untreated plastics degrade, especially outside due to UV exposure and weather conditions. Therefore, hard coatings that extend the life of plastic products are a great benefit.

One of the major benefits of plastics such as Polycarbonate or PMMA is that they are transparent, however, they scratch VERY easily, especially Polycarbonate. Displays, machine guards, screens, roofing, windows and lenses all very quickly become un-useable. But due to the abrasion resistance of hard coatings, such products have significantly harder surfaces and are therefore able to survive regular use over a much longer period of time.

Regularly, external displays, signs, bus shelters etc. are vandalised with graffiti. The excellent chemical resistance of hard coatings stops the spray paints from adhering to the plastic substrate permanently and allow for chemicals to be used in removal of the spray paint.

There are many instances where hard coatings are not used, meaning that plastic products must be regularly replaced. Some industries/manufacturers rely on such replacement business or after sales. For example, uncoated materials are used for many bus shelters or supermarket trolley parks, quickly becoming unsightly from vandalism or UV degradation and are therefore replaced often. This is clearly bad for the environment.

Hard coatings add a small additional cost to such products but extend their useful lives by many years, needing to be replaced much less often, ultimately reducing plastics use and cost. When hard coated material does need to be replaced it can be recycled just as easily as uncoated material.

 

Author

Mark Scott - Marketing Manager