Effect of surface treatment on the durability of plastics
How does surface treatment affect plastics? More about surface energy, activation, pre-treatment and suitable processes.
The durability of plastics is largely determined by their chemical and physical properties. In addition to the intrinsic material characteristics, surface treatment plays a central role. Through targeted processes, plastics can be made more resistant to mechanical stress, chemical influences,
, abrasion, temperature influences and moisture.
Optimising the surface not only influences the service life of the material, but also its possible applications in industrial applications,
, construction and high-performance applications such as
.
Surface treatments serve not only to improve resistance, but also functionality. This includes controlling wettability, increasing the adhesion of coatings, reducing friction or improving optical properties. The choice of treatment method depends on the type of plastic, the specific operating conditions and the desired functional properties.
Materials in plastics and their reaction to surface treatments
Different types of plastic react differently to surface treatments. Thermoplastics such as
or
exhibit only limited adhesion due to their low surface energy, while engineering thermoplastics such as
,
,
or PPS can be modified more effectively. Thermoset
, fibre-reinforced composites or polymer blends also require specific treatment methods in order to optimise their functionality.
| Plastic type | Typical surface treatment | Effect on durability |
|---|---|---|
| Polyethylene (PE) | Plasma treatment, flame treatment, laser activation | Increases adhesion of paints, adhesives and coatings, improves UV resistance |
| Polypropylene (PP) | Corona or plasma treatment, UV oxidation | Improves wettability and adhesion, reduces cracking and stress cracks |
| Polyamide (PA) | Sandblasting, chemical etching, nanocoating | Optimises surface energy, improves coating absorption, increases abrasion resistance |
| Polyoxymethylene (POM) | Surface activation, primer, plasma coating | Increases abrasion resistance, reduces cracking, extends service life |
| PEEK | Plasma, coatings, corrosion protection layers | Improves chemical resistance, UV stability and thermal resistance |
| PC/ABS | Polishing, primer, protective lacquers | Reduces stress cracks, improves chemical resistance, increases impact strength |
| fibre-reinforced composites | Etching, blasting, coatings | Optimises composite adhesion, increases mechanical strength and wear resistance |
Types of surface treatment
Physical processes
Physical processes change the surface structure by introducing energy without changing the chemical composition of the material. These include processes such as
plasma treatment
, corona treatment
or
UV irradiation
. In plasma treatment, the molecules on the surface are activated by ionised gases, which considerably improves wettability. This treatment is particularly suitable for plastics with low surface energy, as it significantly increases the adhesion of paints, lacquers or adhesives.
Corona treatment uses electrical discharge to create a highly active surface, which ensures optimum printing and adhesive properties, especially for films and thin plastic layers. UV irradiation is used to promote cross-linking processes on the surface, thereby increasing the curing and chemical stability of the plastic surface. Laser activation also falls into this area, in which precise micro- and nanostructures are created in order to specifically improve adhesion and tribological properties.
Chemical processes
Chemical surface treatments change the molecular structure of the plastic surface in order to increase functionality and resistance. Methods such as etching, oxidising or the use of primers increase the surface energy and thus enable better adhesion of coatings and adhesives. Chemical treatment can also increase abrasion resistance and make the plastic more resistant to aggressive chemicals.
Nanocoatings are increasingly being used to achieve additional properties such as UV protection, antibacterial action or self-healing functions. These processes make it possible to adapt the surface specifically to the requirements of the respective area of application, thereby significantly extending the service life of the components.
Mechanical processes
Mechanical processes influence the surface structure through physical change such as material removal, smoothing or structuring. These include blasting, polishing, grinding or embossing. Blasting processes, in which sand, glass beads or ceramic are used, increase the roughness of the surface and improve the mechanical adhesion of coatings or adhesives.
Polishing and grinding reduce surface roughness, minimise stress cracks and improve optical quality. Embossing and milling create targeted structures on the surface that are optimised for special tribological requirements such as friction reduction or improved wear resistance. Mechanical processes are often used in combination with physical or chemical treatments in order to maximise the overall performance of the plastic surface.
Surface energy in plastics
Surface energy in plastics describes how well a surface can be wetted by liquids. It is a decisive factor for the bonding, painting, printing or coating of plastic components. The higher the surface energy of a material, the better adhesives, paints or coatings can adhere to the surface. With low surface energy, on the other hand, liquids often bead off, which makes adhesion considerably more difficult.
Particularly non-polar plastics such as polyethylene (PE), polypropylene (PP) or PTFE have a low surface energy and are therefore considered difficult to bond or paint. Materials such as ABS, polycarbonate (PC) or PMMA, by contrast, have a higher surface energy and can in many cases be further processed without extensive pre-treatment.
An important measure of wettability is the so-called contact angle. The smaller the contact angle of a liquid droplet on the plastic surface, the better the liquid spreads and the higher the adhesion. For this reason, the surface energy is often specifically increased before many manufacturing processes by methods such as plasma, corona or flame treatment.
Knowledge of the surface energy is of great importance, particularly when selecting suitable manufacturing processes. It helps to avoid adhesion problems at an early stage and to ensure permanently reliable bonds between plastic surfaces and adhesives, lacquers or coatings.
Surface activation of plastics
The surface activation of plastics serves to specifically change the surface properties of a material. The aim is to increase the surface energy and thereby improve the wettability and the adhesion of adhesives, lacquers, printing inks or coatings. Particularly in the case of plastics with low surface energy such as PE (polyethylene), PP (polypropylene) or PTFE, surface activation is often a prerequisite for a permanently reliable bond.
Depending on the plastic and application, different processes are used. The most commonly used methods include plasma treatment, corona treatment and flame treatment. In these, the uppermost molecular layers of the plastic are specifically changed without influencing the mechanical properties of the component. This activation creates polar groups on the surface, which allows adhesives and coatings to adhere considerably better.
Which method is suitable depends on the respective material, the component geometry and the later area of application. While corona treatment is used primarily for films and sheets, plasma treatment is also suitable for complex-shaped components. Flame treatment is often used for larger plastic parts and also enables a considerable improvement in adhesive strength.
A professionally performed surface activation of plastics increases process reliability in further processing and helps to achieve long-lasting bonding, painting or printing results. It is therefore an important step before the actual surface treatment in many industrial applications.
Influence on durability
The
durability of plastics
is decisively determined by the surface condition. A carefully treated surface resists mechanical stress, abrasion and cracking better, which significantly extends the service life of the components. Chemical surface modifications increase resistance to aggressive media such as solvents, oils or cleaning agents, while physical and mechanical processes optimise surface roughness and friction properties in such a way that wear is reduced and the structure remains stable in its integrity.
In addition, resistance to UV radiation and weathering can be increased by special coatings, so that discolouration, material embrittlement and cracking are minimised. In medical or food technology applications, surface treatments additionally improve the hygienic properties by applying antibacterial coatings that prevent the formation of germs.
By combining different processes, the overall performance of the plastic is maximised, which leads to a significantly extended service life and higher functional reliability, particularly in heavily loaded components in
, construction,
,
and aerospace.
Which plastics require surface treatment?
Whether a surface treatment of plastics is required depends primarily on the surface energy of the respective material and the requirements of the later application. Particularly when bonding, painting, printing or coating, suitable pre-treatment is often decisive for a permanently high adhesive strength.
Plastics with low surface energy often require surface activation. These include primarily polyethylene (PE), polypropylene (PP) and PTFE. These materials are chemically very resistant and have excellent sliding properties, but are difficult to bond or coat without pre-treatment. Processes such as plasma, corona or flame treatment improve wettability and create the conditions for reliable further processing.
Materials such as POM (polyoxymethylene) or PBT (polybutylene terephthalate) can also benefit from surface treatment depending on the application, particularly where high demands are placed on adhesion.
Plastics with higher surface energy, for example ABS, polycarbonate (PC), PMMA, PVC or PET, can often be painted or bonded without extensive pre-treatment. Nevertheless, careful cleaning or surface activation can also increase process reliability in these materials and further improve the quality of the bond.
Which surface treatment is sensible in an individual case depends not only on the material but also on the adhesive used, the coating, the ambient conditions and the later load on the component. A pre-treatment tailored to the material and application contributes significantly to a long-lasting and reliable bond.
Industrial applications
Surface treatments are used in all industries in which plastic components must meet high requirements:
- Automotive industry: bumpers, interior trim and technical housings benefit from improved adhesion for paints as well as increased UV and chemical resistance.
- Medical technology: instruments, housings and sterilisable components are treated in order to ensure cleaning resistance and durability under sterilisation conditions.
- Construction industry: window profiles, pipes and seals are protected in order to withstand weathering and UV radiation.
- Electronics industry: housings, circuit boards and connectors gain better adhesion for paints and adhesives through surface activation and thus increase their mechanical stability.
- Aerospace: lightweight components and composite materials are treated in order to withstand extreme temperatures and mechanical stress.
Future prospects and innovations
Research in the field of surface treatments of plastics is developing rapidly, with the focus increasingly on sustainable, resource-saving and energy-efficient processes. Modern plasma technologies enable activation of the plastic surface without the use of solvents, thereby reducing both environmental impact and production effort. Laser and nanostructuring make it possible to specifically create micro- and nanostructures that optimise the adhesion of coatings, improve friction properties and increase wear resistance.
In addition, bioactive and self-healing coatings are being researched that detect and repair micro-cracks, thereby extending the service life of components and reducing maintenance intervals. Smart coatings that react to environmental influences and dynamically adapt their properties open up new possibilities for the use of plastics in demanding and extreme environments. The integration of these processes into digital manufacturing chains, particularly in additive manufacturing processes such as
, enables the production of customised, long-lasting and functionally optimised plastic components.
Future innovations will also automate the combination of several processes and align surface modification even more precisely with the respective application, which promises a previously unattained performance capability of plastic components.
In summary
Surface treatments are a decisive factor for the longevity, functionality and safety of plastic components. The targeted combination of physical, chemical and mechanical processes reduces wear, minimises cracking, protects against chemical attack and increases resistance to weathering.
The continuous further development of technologies such as plasma, laser and nanostructuring, bioactive coatings and smart coatings enables ever more precise adaptation to the specific requirements of industry, medical technology, construction, the automotive and aerospace industries.
These innovations not only contribute to improving material durability, but also open up completely new possible applications, increase the performance and efficiency of plastic components and lead in the long term to sustainable, resource-saving solutions in the production and use of plastic products.
FAQ
What is the main purpose of a surface treatment for plastics?
Surface treatment serves to improve the durability, resistance and functionality of plastics by optimising the mechanical, chemical and physical properties of the surface.
What types of surface treatment are there?
The common processes can be divided into physical, chemical and mechanical treatments, including plasma treatment, corona treatment, UV irradiation, etching, primer, blasting, polishing, grinding and embossing.
How does surface treatment influence the durability of plastics?
Surface modifications reduce abrasion, cracking and chemical attack, increase resistance to UV radiation and weathering and improve the hygienic properties in medical or food technology applications.
Which industries benefit particularly from surface treatments?
These processes are particularly relevant in the automotive industry, medical technology, the construction industry, electronics and aerospace, where there are high requirements for durability, resistance and functionality.
What future developments can be expected in surface treatments?
Forward-looking developments include energy-efficient plasma technologies, laser and nanostructuring, bioactive and self-healing coatings as well as smart coatings that react dynamically to environmental influences. In addition, integration into digital manufacturing chains is becoming increasingly important.
