Nanostructuring Moves to Industrial Injection Moulding

Plastic performance is usually associated with what happens inside the material: its strength, flexibility, thermal stability or resistance to chemicals. But for many applications, what happens at the surface is just as important.

This is because modification of a polymer’s surface at even the nanoscale can change its properties without altering the material’s bulk characteristics. By creating nanoscale structures at the surface, properties such as hardness, wear resistance, conductivity, wettability, and resistance to chemicals can be added or enhanced. This allows existing polymers to take on new functions and perform in applications where conventional polymers may not be suitable.

What is nanotechnology?

The nanoscale refers to dimensions between roughly 1 and 100 nanometres, far smaller than anything visible to the naked eye. One nanometre is one millionth of a millimetre, meaning that a human hair is roughly 50,000–100,000 nanometres wide. At this tiny scale, materials can behave differently from the same materials at larger dimensions, opening up new possibilities for their use.

The breakthrough in nanoscale modification

Working at such a tiny scale is highly technical and, with current technology, takes a great deal of time. This has limited the ability of plastic manufacturers to adopt nanomodification processes.

But now, a development made by Czech nanotechnology specialists could help make the nanomodification of a plastic’s surface commonplace. The breakthrough was made with a laser technique to give the moulds used in the injection moulding process the required micro- and nanoscale textures practical for industry.

Published in August on the arXiv platform, the breakthrough was made at the HiLASE Centre of the Institute of Physics of the Czech Academy of Sciences, Czech Technical University in Prague, the Technical University of Liberec and Tomas Bata University in Zlín, in a study demonstrating a scalable way of giving injection-moulded plastics new characteristics, such as antibacterial, water-repellency, and improved adhesive properties.

This was achieved by combining ultrashort-pulse laser processes to give the moulds a nano-structured surface. Once the injection moulding process is complete, the finished polymer components made in the mould retain nanomodified surfaces to achieve tailored properties without the need for additional coatings or chemical treatments.

For example, testing of polypropylene and a non-optimised adhesive found that laser texturing of the surface produced up to a 30-fold increase in shear strength compared with the untreated material.

So far, the researchers have tested the technique with three widely used thermoplastics: polypropylene (PP), polyamide 66 (PA66) and acrylonitrile butadiene styrene (ABS), with polypropylene demonstrating the highest level of replication accuracy.

This approach has huge investment potential, as injection moulding is already widely used to manufacture large quantities of plastic components. If a nanoscale surface can be reliably transferred from the mould to the polymer, the additional functionality can effectively become part of the production process.

Making nanostructuring faster

Current technologies for creating highly precise structures with a laser can be relatively slow. This has limited the adoption of nanomodification processes, as injection mould production needs to be performed at an industrial scale. The new study addresses this problem by using different acceleration strategies for different types of structures.

For deeper microstructures, the researchers used an ultrashort-pulse fibre laser operating at a repetition rate of up to 1 MHz. This increased the speed of microhole drilling by up to 20 times.

For nanoscale structures, the team used a spatial light modulator to reshape the laser beam into a line rather than processing the surface point by point. This increased productivity for laser-induced periodic surface structures by around 35 times, with processing speeds exceeding 100 cm² per minute.

What can nanostructured plastics do?

The researchers then examined whether the structures transferred to the polymer actually produced useful changes in surface behaviour. Here they found that the textured polypropylene surfaces became more water-repellent than untreated polypropylene.

Even more striking were the antibacterial results obtained with structured PA66. Depending on the surface structure, bacterial retention was reduced by up to 99.8% for E. coli and approximately 90% for S. aureus compared with unstructured surfaces.

This is important for industry because the antibacterial effect does not depend on adding an antibacterial chemical or coating to the plastic. Instead, the physical structure of the surface itself has been changed, making it ideal for applications where long-term surface performance is important, such as medical devices. Additionally, polymers used in packaging and consumer products could also benefit from nanomodification by being given properties of added strength, electrical conductivity, or surface adhesion.

A Czech contribution to the future of nanotechnology

This latest research is another impressive example of the strength of nanotechnology research in Czechia. In bringing together expertise from leading Czech research institutions, the study also demonstrates how world-class nanotechnology can be translated into practical solutions for the plastics and polymer industry.

This breakthrough is similar to the research being conducted at Polymer Nano Centrum, where the focus is also on turning the potential of nanotechnology into practical solutions for industry.

Polymer Nano Centrum (who sponsor this webpage) works with manufacturers to develop and apply nanomodification techniques that can give existing polymers enhanced mechanical, thermal, electrical, and surface properties. Its work covers both the selection of suitable nanomaterials and the development of practical ways to incorporate them into polymer products and production processes.

The aim is not simply to demonstrate what is possible in a laboratory but to help manufacturers understand how nanotechnology can be applied to real polymer products. Using its own state-of-the-art research facility, the company helps manufacturers move from an initial concept through theoretical modelling and prototype production, and on to a tested nanomodified material.

As technologies such as laser surface structuring become faster and more suitable for industrial production, the opportunities for nanomodified polymers are likely to expand. As it does so, Czech nanotechnology research will be leading the way in creating polymers that are more functional, sustainable, and fit for the challenges of modern manufacturing.

To learn more about Polymer Nano Centrum's work and what nanotechnology can do for the manufacturing sector, visit Polymer Nano Centrum.

Photo credit: Pexels, Pexels, Magnific, & Polymer Nano Centrum