Percorrer por autor "Santos, Palloma Carvalho dos"
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- Development of bio- and eco-composites for the footwear industryPublication . Santos, Palloma Carvalho dos; Fernandes, Isabel P.; Ribeiro, J.E.; Pietrobelli, Juliana Martins Teixeira; Barreiro, M.F.Cork composites are often used in several applications including footwear components. The traditional agglomeration process uses a reactive polyurethane-based binder (containing TDI), generating composites with low flexibility and poor water absorption/desorption characteristics, resulting in products with low comfort properties. Furthermore, the presence of TDI, is another important drawback due to its high toxicity. Therefore, the present work is devoted to the development of cork composites, where the TDI-based binder was replaced by an aqueous PUD reinforced with Melissa officinalis L. extract. Cork-composites were produced using different adhesive/cork ratios, and characterized in terms of dimensional stability, water absorption/desorption properties, and mechanical behavior. After the selection of the best adhesive content, composites reinforced with sugarcane bagasse, malt bagasse, coconut fibers, and chia seeds were also produced and characterized.
- Development of bio- and eco-composites for the footwear industryPublication . Santos, Palloma Carvalho dos; Barreiro, M.F.; Pietrobelli, Juliana Martins TeixeiraThe evolution of consumers' environmental awareness, allied to the demand for bio-products, is considered a challenge for the footwear sector. In this context, the development of novel composites, based on natural materials and by adopting green productive processes, is an area of great interest. Based on this motivation, the present work aims to develop cork composites where the toxic TDI-based binder traditionally used for cork agglomeration, is substituted by an aqueous water-based polyurethane adhesive reinforced with Melissa officinalis L. extract. The work was divided into three stages. The first one was dedicated to the synthesis of water-based polyurethane adhesives (PUD) following a modified pre-polymer method. Three adhesives were produced, namely a formulation with no added extract, and two formulations incorporating Melissa officinalis L. hydrophilic extract, at contents of 3 and 5% (w/w, prepolymer-basis). In the second stage of this study, based cork composites were produced using adhesives at contents of 20, 30 and 40% (w/w, cork-basis, adhesive weight based on its solids content). The final stage comprised the production of cork composites (30% of adhesives content of the three formulations were used) added with biomass residues (sugarcane bagasse (CA), malt bagasse (MA), coconut fibers (CO) and chia seeds (CH)) at contents of 5 and 10% (w/w, cork-basis). The obtained results pointed out for the viability of using PUDs to substitute the traditionally used TDI-based binders, which also added several advantages. Namely, a remarkable increment of the water absorption capacity was identified, particularly when the adhesives were incorporated with the extract. It was observed that all the produced composites fulfill the imposed value of 70 mg/cm2. For the water desorption capacity, and with the exception of the composite produced with the adhesive added with 5% of extract at a content of 20%, all of the adhesives were below to the limit of 80%. This means that the adhesive hydrophilic nature lead to an increase of the composite drying time. Regarding the dimensional stability, almost all the produced composites presented shrinkage lower or close to 2%. The results evidenced also the increasing of film’s flexibility due to the extract incorporation. In a general way, the adding of biomasses results in the decrease of both water adsorption and desorption properties, even very close to the corresponding base-composites. Concerning shrinkage values, and flexibility, better results were generally achieved. Namely, in terms of flexibility, the biomasses conducting to the best results were CA, CO or CH at contents of 5% combined with the PU3C adhesive at a content of 30%.