In the multi-billion-dollar global leather industry New Zealand is a minnow but a local researcher has received recognition in an international award that will do much to help push local work on the textile further into the spotlight.
Yi (Ethan) Zhang, a researcher at the NZ Leather and Shoe Research Association in Palmerston North received a €1500 grant for his work into leather research from the International Union of Leather Technologists and Chemists Societies.
The formal description of his work, a mechanistic study on the effect of natural-artificial cross-links on tensile strength using small-angle neutron scattering, can be put more simply.
It aims to determine what makes leather stronger once it has been treated in the tanning process.
At the core of Zhang’s work is a study into cross-links that act as a bridge between collagen molecules in leather.
“Some of these will occur naturally in the structure but some are added during the tanning process by the compounds used.
“The technique uses isotopes which can be measured, identifying the position of the cross-links and also determine which cross-link structures, either in the leather or from the process, have the best level of strength.”
A key product used in the tanning process is chromium sulphate, which increases the strength of leather cross-links.
“It also adds a high thermal stability to leather but there are environmental issues that go with using it in the process. Our research aims to better understand the hows and whys of leather cross-links and the way they affect the strength of leather with chromium sulphate use.
“Ultimately, we are hoping we can determine what the optimal level of chromium sulphate is to use so that it is not over-used in the tanning process.”
The researchers also hope their work will lead to the development of new tanning agents that incorporate the cross-linking chemistry in a more environmentally friendly manner.
Chromium sulphate is generally regarded as safe, as the cross-links are fixed in the leather matrix. However, if it leaches out in soluble forms it could be oxidized to hexavalent chromium and potentially lead to health concerns.
Zhang said related work of the research group is already discovering some interesting aspects during thermal denaturation of collagen in leather and that not using so much chromium can still achieve the same level of leather quality in the process.
“The challenge for us as researchers is that we are trying to find out why the compounds work, something that has never really been fully understood.”
Other work has included studying collagen, the main structural protein in the connective tissue of animals and humans and, by default, in skin and leather.
It is the most abundant protein in mammals, accounting for 25-35% of the body’s whole protein content.
“Collagen has broad applications in medical areas including drug delivery and wound healing.
“We hope our fundamental research will increase our knowledge of collagen structures, their extraction and their application across a wide range of fields.”
Zhang said increased pressure on the tanning industry to clean up its environmental footprint is increasingly focused on solving the problems from the source, while also trying to improve the functionality of leather as a product.
“We are also looking at a way to improve the traceability of leather.
“NZ leather generally is regarded as very good quality and there is still a lot of potential there for us to build on that.”
Researchers putting value back into pelts
Richard Rennie
AS WOOL continues to struggle another by-product of the buoyant sheep meat market could provide farmers with a valuable boost to farm incomes, should the industry decide to take a lead on its future.
Pelts are a much maligned part of the income equation for farmers, often relegated to an average payment that makes no allowance for the variation in quality that inevitably exists.
But Leather and Shoe Research Association director Geoff Holmes is adamant changes in consumer demands, New Zealand’s inherently high-quality pelts and the product’s natural qualities could see things change.
Despite being around for 82 years the association is a relatively low-profile research organisation that works closely with the leather industry, being commissioned for testing services and research projects.
But it is also increasingly reaching back down the supply chain to help understand and influence the quality of pelts farmers provide the industry, essentially as a raw material.
“We have supported research on the fringes of the FarmiQ programme which has meant we have been able to access information from two mobs with very good genetic profiles. In one flock 60% of the skins were suitable for high grade shoe leather.”
The work with FarmiQ has identified how breeding traits of weaner and carcase weights deliver a strong heritability correlation to skin quality.
“By committing to this big project there is huge potential to identify those traits and deliver value back to farmers.”
He siggests the industry reconsider an updated version of the Quality Enhancement Project, a bar-coded tagging system tested in Hawke’s Bay about 25 years ago.
NZ lamb pelts are part processed for sale on the commodity market then processed into leather offshore, nowadays largely in India and China.
“It is a very dynamic market with a lot of downward pressure on prices over the years and demand is slower in the fashion sector.
“The footwear market is where more stable growth prospects lie for NZ leather from lamb pelts, given that market is not as fashion-driven as the leather garment market.”
The association is working with a processor and two local shoe companies on treatment and processing of NZ pelts for local manufacture into final products.
But the good quality of the pelts supplied by NZ might just be a starting point for final leather products seeking traceability and provenance in an industry facing greater pressure to clean up its environmental practices.
Traceability falls into the association’s research brief, with work being done looking at how to identify leather from its source, including isotope profiling.
“With a strong identity to NZ products there are customers in countries who would prefer to buy in NZ, compared to some of the alternatives available.”
Lifecycle analysis is also coming onto the radar as more consumers want to know what happens to their product when it reaches the end of its useable life.
More than three million tonnes of micro-plastic fibres end up in the world’s oceans from synthetics as they are washed or discarded.
However, the natural fibre sector is not immune to environmental impacts, with big demands on chemical inputs and water use from leather, cotton and silk processors.
“We are just starting work with Massey University’s lifecycle management unit, studying leather biodegradability, among other technologies, for improved sustainability and it’s something that may lead to an environmental mark for the leather sector.”
