Superhydrophobic injection moulding products thanks to laser texturing

The demand for extra functionality on components is increasing. Texturing can be applied to plastic surfaces for example, which often proves to be a long-lasting, cheap and rapid solution. Sirris and KU Leuven have been able to create a superhydrophobic surface by introducing a cavity pattern to a mould insert and then using it in injection moulding trials. The technology permits the quick and efficient application of complex structures without the need for heating. 

Many industrial sectors are demanding that components and consumer goods are given extra functionality. This could include superhydrophobic surfaces with potentially self-cleaning properties, or metal engineering products with specific friction coefficients. These can be achieved by texturing the surface of such products for example. For example certain surface structures can cause the contact angle of water to be raised, or light to be scattered, or to have increased, lowered or controlled levels of friction. The advantage of applying functionality this way is that the texturing is usually long-lasting and in specific cases very cheap and quick to apply.

Injection moulding

One of the most interesting ways of doing this is by using traditional injection moulding. The mould or insert surface is given the negative of the desired structure. During the injection moulding process the polymer in the texture is pressed and takes the pattern from the surface of the mould. This can be done without making the injection moulding process slower or less efficient.

Sirris and the Plastics department at KU Leuven at Diepenbeek Campus have together already been able to create the first superhydrophobic surface by introducing a cavity pattern to a mould insert and then using it in injection moulding trials. The cavities have a diameter and depth of just a few microns and are applied using a femtosecond laser. This technology enables the quick and efficient application of complex structures without the need for heating. Because it is not necessary to heat the material, there are no melt zones or breaks that would otherwise weaken the mould.

Polypropylene

The injection moulding tests were carried out using PP as the basic material. Polypropylene is a widely used plastic with applications in the packaging, automotive, and consumer products sectors for example, which is all thanks to its low cost and excellent properties. By applying micro-pillars to the surface of PP by way of injection moulding in a laser textured mould, the contact angle with water was raised to above 140°, where the normal contact angle of unstructured PP is around 100°. This opens the door for packaging that can be emptied better and that reduces waste, or for self-cleaning bicycles and vehicle components.

Over the coming months Sirris will continue with its research into the relationship between laser parameters, geometry and functionality, specifically for injection moulding processes.

Would you like to know more about this technology? Contact us now!

Tags: