Proteins like collagen found in leather waste are synergists for conventional flame retardants in polymers like poly(ethylene-co-vinyl acetate) (EVA)
Source: BAM, division Technical Properties of Polymeric Materials
Nature knows no waste. In contrast, the worldwide leather production, estimated at 15 megatons per year, leads to enormous amounts of waste. Mexico is among the top-10 most leather producing countries next to China, Brazil, and Russia, and leather waste presents a considerable economic and ecological problem there, as it is discarded either via landfill or incineration. The polymer industry also faces an ecological dilemma as consumers long for more sustainable products that do not sacrifice material properties or safety aspects like flame retardancy. These two topics, sustainable polymers and Mexican industrial leather waste, find an overlap in an innovative project between BAM and the Mexican research institute CIATEC, that investigates the possibility of “upcycling” leather waste as multifunctional fillers for polymers.
Within the scope of a cooperative project with Mexican scientists, the use of leather waste as a filler for conventional polymers from the cable industry was investigated, particularly their use as flame retardant adjuvants. Previous investigations of keratin and agave fibers showed that these bio-fillers not only replaced polymer content in composites, but also improved their flame retardant properties.
The results illustrated that leather waste has a synergistic effect with conventional phosphorus flame retardants in poly(ethylene-co-vinyl acetate) (EVA) polymers. Samples containing 10 percentage by weight leather waste and 20 percentage by weight flame retardant exhibited lower fire loads and better fire performance than samples without leather waste containing 30 percentage by weight flame retardant. EVA melts at elevated temperatures, but the composites formed a carbonaceous residue during the burning process which acted as a protective layer, preventing heat transfer to and mass flux from the material. Structural proteins like collagen from leather waste react with the decomposing flame retardant and matrix during fire tests.
The presented paper of the month, titled “Waste not, want not: The use of leather waste in flame retarded EVA” offers an innovative approach aimed toward a circular economy, and it shows that wastes from leather industries can also be building blocks of flame retardant, more sustainable polymers.
Waste not, want not: The use of leather waste in flame retarded EVA
A. Battig, G. Sanchez-Olivares, D. Rockel, M. Maldonado-Santoyo, B. Schartel
published in Materials & Design, Vol. 201, 110100, 2021
BAM, division Technical Properties of Polymeric Materials