Why NMR Beats Wet Chemical Analysis of Liquid Coatings
The textile industry is one of the largest in the world. Encompassing sprawling global supply chains and an almost unlimited variety of products, reliability and speed can be the difference between profitability and significant losses.
An important part of the industrial textile process is the use of liquid coatings to control and modify the behaviour of fibres. These liquid coatings are carefully formulated products, often combining many components.
Constant attention is needed to check that the correct amount of liquid coating is applied to ensure efficient and profitable fibre, yarn, and fabric processing. This means that in a busy manufacturing facility, potentially hundreds of samples need to be measured each day.
The Problem with Traditional Methods
The traditional wet chemistry (solvent extraction) method has many features that make it unattractive in an industrial environment. It is time consuming, requires skilled operators and makes use of flammable and hazardous solvents.
This not only leads to higher running costs, but also means that the consistency of results depends a great deal on the skill of the individual operator. Disposing of the solvents used in an environmentally acceptable way can also be costly.
The Benefits of Nuclear Magnetic Resonance
The use of Nuclear Magnetic Resonance (NMR) analysers means that no solvent extraction is required and the instrument needs only a benchtop in a reasonably clean and stable-temperature environment. - No fume cupboard is required.
Measurements can be carried out by process operators with minimal training, creating results that are consistent and operator-independent. Measurement is fast, allowing hundreds of samples to be measured each day.
NMR analysers can distinguish between the hydrogen signal from solids (such as fibre, yarn, textile or nonwoven fabric) and liquids (such as an oil-based coating). They can (with a different sample holder, commonly known as a probe) also measure fluorine based liquid coatings.
An enormous and ever-expanding range of fibre types are available. A similarly broad range of liquid coatings has been developed, each tailored for use with particular fibres, and often specifically developed to optimise the fibre properties for a particular use or application. NMR methods are being developed to meet the requirements of those products. Thus NMR methods can be applied to a variety of products including, but not exclusively, yarn, monofilaments, staple fibre, textiles and non-wovens.
Ease of use
Making a measurement of liquid coating level by NMR is a very simple process. A sample is taken from the production line and then inserted into the instrument. Measurement time is usually 1 minute per sample. (This may be longer for very low concentrations, < 0.3%.)
Once the initial calibration has been set up, calibration maintenance can be accomplished using Calibration Maintenance Standards (CMSs). The CMSs can be periodically used to correct for any slight drifts in the instrument, without needing to measure a new set of reference samples. They are stable over very long periods, and can be used to maintain the highest performance with minimum effort.
Concentrations as low as 0.05% liquid coating have been measured by NMR using the weighing method; there is no upper limit to the concentration that can be measured. Samples must be dried prior to testing if moisture is in excess of 10%, but this is rarely the case with synthetic fibres.
The MQC+ method
Oxford Instruments’ MQC+ analysers give operators cutting edge benchtop NMR today. As a solution for the textile industry, it is much faster than wet chemical analysis methods, enabling measurement of a large number of samples in a non-destructive way.
NMR is an attractive, accurate, fast, reliable and easy-to-use technique for the measurement of liquid coating levels in the textile industry. It is already widely accepted, and makes a meaningful contribution to the most efficient operation of a fibre or textile plant. By guaranteeing results in seconds with little user training, MQC+ is the right tool for operators that need pinpoint accuracy quickly and reliably.
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