Low-pressure plasma treatment applied to polymeric materials for a sustainable footwear industry

Abstract

In this paper INESCOP proposes the improvement of the bonding of footwear soling materials using the low-pressure plasma surface treatment as a non-polluting and resource-efficient technology by means of adhesive bonds, with a reactive hot melt polyurethane adhesive, as a more sustainable alternative to current chemical surface treatments such as halogenation. More precisely, low-pressure plasma is capable of cleaning and removing all impurities, such as oxides, oils and fats on material surface. Then, it is activated by producing new chemicals species on the top layer of the substrate. Thus, the materials’ surface acquires new surface functionalities, improving the compatibility adhesive-substrate and, therefore their adhesion properties. Furthermore, in this work the surface modifications produced in these materials of different polymeric nature have been optimised to increase their roughness, wettability, adhesive properties, etc., and have been validated through various experimental characterisation techniques. As a result, the samples treated with plasma meet the adhesion requirements for footwear materials. As a result, low-pressure plasma treatment has desmonstrated to be a green, alternative, and sustainable technology in line with European policies on circular economy, which enhances material surface properties by improving the adhesion bonding process.

Organosilicon-Based Plasma Nanocoating on Crust Leather for Water-Repellent Footwear

“…However, few authors have studied the plasma polymerisation process of different organosilicon compounds, such as HMDSO on leather and synthetic materials [ 30 ], for the development of hydrophobic coatings [ 31 , 32 , 33 , 34 ]. Previous work by the authors showed preliminary evidence of the use and optimisation of plasma technology [ 35 , 36 , 37 ] with enhanced hydrophobicity at high water contact angles in leather for footwear applications [ 38 , 39 ].…”

Cleaner technologies to minimise the environmental footprint of the footwear bonding process

“…The most used plasma technologies so far are low-pressure and atmospheric pressure systems. 21 Recent research works have demonstrated the enhancement of the adhesion properties of different polymeric materials, 22,23 used to produce soles, such as styrene-butadiene-styrene (SBS), 24 styrenebutadiene vulcanised (SBR), [25][26][27] nitrile butadiene rubber (NBR) 28 and ethylene vinyl acetate foams (EVA) 29 with different types of polyurethane adhesives such as solvent-based (PU), waterborne polyurethane adhesives (ADPU) and HMPUR adhesives after applying different plasma treatments either at atmospheric pressure or low-pressure. 30 In this study, reactive polyurethane hot melt adhesives were synthesised from a CO 2 -based polyol to obtain a moisture curing NCO-terminated prepolymer whose properties were characterised by different experimental techniques.…”

“…Recent research works have demonstrated the enhancement of the adhesion properties of different polymeric materials, 22,23 used to produce soles, such as styrene-butadiene-styrene (SBS), 24 styrene-butadiene vulcanised (SBR), 25–27 nitrile butadiene rubber (NBR) 28 and ethylene vinyl acetate foams (EVA) 29 with different types of polyurethane adhesives such as solvent-based (PU), waterborne polyurethane adhesives (ADPU) and HMPUR adhesives after applying different plasma treatments either at atmospheric pressure or low-pressure. 30…”