Gonçalves Bárbara Maria Mateus, Camillo Mayara de Oliveira, Oliveira Michel Picanço, Carreira Lilian Gasparelli, Moulin Jordão Cabral, Fantuzzi Neto Humberto, de Oliveira Bárbara Ferreira, Pereira Artur Camposo, Monteiro Sergio Neves
Forest and Wood Sciences Department, Federal University of Espírito Santo, Jeronimo Monteiro, Vitória 29550-000, Brazil.
Rural Engineering Department, Federal University of Espírito Santo, Alto Universitário, sn., Alegre 29500-000, Brazil.
Polymers (Basel). 2021 Oct 7;13(19):3428. doi: 10.3390/polym13193428.
Natural lignocellulose fibers have been extensively investigated and applied as a reinforcement of polymer composites in industrial applications from food packing to automotive parts. Among the advantages of natural fibers stands their relatively low cost and sustainable characteristics. These are accentuated in the case of residual fibers such as those obtained from coffee husks, an agribusiness waste, usually burnt or disposed into the environment. As composite reinforcement, hydrophilic natural fibers display adhesion problems to the most hydrophobic polymer matrices. This adhesion might be improved with distinct types of fibers surface treatments. In the present work, the effectiveness of three surface treatments applied to coffee husk fiber wastes (CHFW) were investigated, aiming to improve the tensile performance of castor oil-based polyurethane (COPU) biocomposites. The effects of treatments associated with (i) chemical with sodium hydroxide, (ii) physical by temperature and pressure and hydrothermic treatment, and (iii) biological by fermentation with fungus were evaluated by means of Fourier transformed infrared spectroscopy, X-ray diffraction, thermal analyses and morphology by scanning electron microscopy for different concentration of NaOH, different hydrothermic times at 121 °C/98 kPa and exposition to . The most effective treatment was the hydrothermal one at 121 °C and 98.06 kPa for 30 min. Preliminary tensile tests were performed in COPU biocomposites reinforced with 20% CHFWs subjected to the optimized conditions for each distinct type of treatment. The results indicated that the hydrothermal treatment promoted significant enhancement in the fiber/matrix interfacial bond, increasing the tensile strength up to 60% compared to COPU reinforced with in natura CHFWs fibers. It is important to mention that these composites can be applied as plastic wood for household items' internal parts and in the automobile industry.
天然木质纤维素纤维已得到广泛研究，并作为聚合物复合材料的增强材料应用于从食品包装到汽车零部件等工业领域。天然纤维的优点包括成本相对较低和可持续性强。对于诸如咖啡壳等残余纤维而言，这些优点更为突出，咖啡壳是一种农业废弃物，通常被焚烧或排放到环境中。作为复合材料增强材料，亲水性天然纤维与大多数疏水性聚合物基体存在粘结问题。通过不同类型的纤维表面处理可以改善这种粘结。在本工作中，研究了三种应用于咖啡壳纤维废料（CHFW）的表面处理方法的有效性，旨在提高蓖麻油基聚氨酯（COPU）生物复合材料的拉伸性能。通过傅里叶变换红外光谱、X射线衍射、热分析以及扫描电子显微镜观察不同浓度氢氧化钠、121℃/98kPa下不同水热时间以及暴露于真菌发酵等条件下的形态，评估了（i）用氢氧化钠进行化学处理、（ii）通过温度和压力以及水热处理进行物理处理、（iii）用真菌进行生物发酵处理的效果。最有效的处理方法是在121℃和98.06kPa下进行30分钟的水热处理。对经过每种不同处理类型的优化条件处理的、含有20%CHFWs增强的COPU生物复合材料进行了初步拉伸试验。结果表明，水热处理显著增强了纤维/基体界面粘结，与用天然CHFWs纤维增强的COPU相比，拉伸强度提高了60%。需要指出的是，这些复合材料可用于制造家居用品内部部件的塑木以及汽车工业。
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