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Foamed lignin-silicone bio-composites by extrusion and then compression molding

机译：发泡木质素-有机硅复合材料，先挤出再压缩成型

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The use of lignin, one of the most abundant natural products, has not gained wide use as a feedstock due to the difficulty of processing it. We have developed a simple route to produce lignin-silicone composite foams via first extrusion and then compression molding. The formulation consists of raw lignin particles, suitable mixtures of hydrosilanes, and a catalyst B(C6F5)(3). In order to balance the reaction rates between extrusion and molding, as well as to find other optimized conditions for producing foamed structures, a series of optimizations established that a uniform, closed cell lignin-silicone foam was most effectively made by extrusion at room temperature followed by molding at elevated temperatures under pressure for up to 5 minutes. The morphology and uniformity of the foamed structure depended on many factors, including the quantity of lignin, the catalyst, the crosslinking silicone PHMS, the molecular weight of the spacer silicone H-PDMS-H, and the molding temperature. The content of lignin, acting as both a reinforcing filler and a crosslinker (chemically bonded to the siloxane network), could be varied over a wide range from 25 to 55%. The mechanical performance of the lignin-silicone foam was characterized using DMA and tensile tests (tensile strength up to 0.42 MPa, break-at-elongation up to 249%). The strength of the foam was improved by post-curing at 140 degrees C. Although the lignin-silicone foam loses some elasticity after post-curing, it maintains reasonable stability even after heating to 300 degrees C for 12 h. This processing method for lignin-based bio-composites provides new opportunities for better utilization of lignin in silicones and more broadly in organic materials.
机译：木质素是最丰富的天然产物之一，由于难以加工，因此尚未广泛用作原料。我们已经开发出一种简单的方法，通过首先挤出然后压模来生产木质素-硅氧烷复合泡沫。该配方由原始木质素颗粒，合适的氢硅烷混合物和催化剂B（C6F5）（3）组成。为了平衡挤出和成型之间的反应速率，并找到生产泡沫结构的其他优化条件，一系列优化确定了均匀，闭孔的木质素-有机硅泡沫最有效的方法是在室温下挤出通过在高温高压下模塑最多5分钟。泡沫结构的形态和均匀性取决于许多因素，包括木质素的量，催化剂，交联硅酮PHMS，间隔基硅酮H-PDMS-H的分子量以及成型温度。用作增强填料和交联剂（化学键合到硅氧烷网络）的木质素含量可以在25％至55％的宽范围内变化。木质素-硅氧烷泡沫的机械性能使用DMA和拉伸测试进行了表征（拉伸强度高达0.42 MPa，断裂伸长率高达249％）。通过在140摄氏度下进行后固化可以提高泡沫的强度。虽然木质素-硅树脂泡沫在后固化后会失去一些弹性，但即使在300摄氏度下加热12小时也可以保持合理的稳定性。这种基于木质素的生物复合材料的加工方法为更好地利用有机硅中的木质素以及更广泛地用于有机材料中提供了新的机会。

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