The start of ageing, long before it shows
Sunlight, artificial light and heat damage textiles through reactions in which radicals are formed. They weaken the fibre, turn it yellow, and make dyes and pigments fade. EPR (electron paramagnetic resonance) sees the radicals themselves, directly in the solid fibre. It shows when the damage begins, how fast it proceeds, and how well a fibre, a dye or a protective treatment holds it back.
Where it is used
- Natural fibres such as cotton, wool and silk
- Polyester, nylon, polypropylene and other manufactured fibres
- Dyed, printed and pigmented yarns and fabrics
- Fibres with delustrants, UV absorbers, stabilisers or other finishing agents
- Outdoor, technical and protective textiles
Typical tasks are comparing dyes and pigments for their stability in light, measuring the efficiency of an anti-UV treatment, studying what heat setting or a heat treatment does, and finding the cause of yellowing, fading or loss of strength.
Expose in steps, measure the radicals
A small piece of fibre or fabric is exposed to UV light or heat in controlled steps, and the radical signal is recorded after each step. The signal of each sample is compared with that of a reference of known spin number. Because the fibre is measured as it is, the same piece can be exposed and measured again.
In many systems, radicals appear before the colour changes, so EPR can give an early indication of which dye or fibre will fade first. How early depends on the system, and it has to be established for your own materials.
How well does the protection work, and how long does it last
Anti-UV treatments, such as UV absorbers, stabilisers, coatings and finishes, are meant to stop the radicals from forming. That is what EPR measures. The same fibre is exposed with and without the treatment, and the radical signal after the same exposure is compared: the fewer the radicals, the better the protection.
Because the measurement is non-destructive, the protection can also be followed through the life of the textile: after washing, after wear or after a period outdoors. This shows whether a treatment lasts, which is often the question that matters most to the customer.
Standard UV-protection tests measure how much UV passes through a fabric to the skin. EPR looks at a different question: how well the fibre and its dye are protected from damage. The two complement each other.
What it adds
- Sees the radicals directly and selectively, in the solid fibre
- An early warning, long before the colour changes or the fibre weakens
- Compares many dyes, fibres and treatments in a short time
- Also detects traces of paramagnetic metals, such as iron or copper, that speed up degradation
- Benchtop instruments make the technique practical in a textile laboratory
Points that matter in practice
- EPR measures radicals. It does not measure colour. Relate the results to your usual colourfastness and strength tests, such as those of the ISO 105 series, so that the link is established for your own materials
- Some dyes and metal-containing pigments are paramagnetic and give their own signals. Always measure an undyed reference and the unexposed sample as well
- Radicals can decay in storage, so keep the time between the exposure and the measurement the same
- Degradation often starts at the surface of a fibre. Compare samples of the same form and thickness
- Condition the samples in the same way before measuring, since water on the fibres is hard to control
- EPR complements the standard tests. It does not replace them
From your fibres to a routine method
Send or bring representative samples. MSY Consulting runs feasibility measurements, plans the exposure steps and the references with you, helps you relate the results to your colourfastness tests, and trains your team until the method is part of your routine.
Let's talk about your application
Send an email describing your instrument and your application, and you will get a reply.
contact@msyconsulting.euMSY CONSULTING SAS · Wissembourg, France · LinkedIn