Department of Mechanical and Energy Engineering, University of North Texas, Denton, TX, 76207, USA.
Department of Materials Science and Engineering, University of North Texas, Denton, TX, 76207, USA.
Sci Rep. 2020 Oct 20;10(1):17771. doi: 10.1038/s41598-020-74478-y.
Ecological, health and environmental concerns are driving the need for bio-resourced foams for the building industry. In this paper, we examine foams made from polylactic acid (PLA) and micro cellulose fibrils (MCF). To ensure no volatile organic compounds in the foam, supercritical CO (sc-CO) physical foaming of melt mixed systems was conducted. Mechanical and thermal conductivity properties were determined and applied to a net zero energy model house. The results showed that MCF had a concentration dependent impact on the foams. First structurally, the presence of MCF led to an initial increase followed by a decrease of open porosity, higher bulk density, lower expansion ratios and cell size. Differential Scanning Calorimetry and Scanning Electron Microscopy revealed that MCF decreased the glass transition of PLA allowing for a decrease in cell wall thickness when MCF was added. The mechanical performance initially increased with MCF and then decreased. This trend was mimicked by thermal insulation which initially improved. Biodegradation tests showed that the presence of cellulose in PLA improved the compostability of the foams. A maximum comparative mineralization of 95% was obtained for the PLA foam with 3 wt.% MCF when expressed as a fractional percentage of the pure cellulose reference. Energy simulations run on a model house showed that relative to an insulation of polyurethane, the bio-resourced foams led to no more than a 12% increase in heating and cooling. The energy efficiency of the foams was best at low MCF fractions.
生态、健康和环境问题推动了建筑行业对生物资源泡沫的需求。在本文中，我们研究了由聚乳酸（PLA）和微纤维素纤维（MCF）制成的泡沫。为了确保泡沫中没有挥发性有机化合物，采用超临界 CO（sc-CO）对熔融混合体系进行了物理发泡。测定了机械性能和热导率，并将其应用于零能耗模型房屋。结果表明，MCF 对泡沫有浓度依赖性的影响。首先在结构上，MCF 的存在导致开孔率先增加后减少、表观密度增大、膨胀比和细胞尺寸减小。差示扫描量热法和扫描电子显微镜表明，MCF 降低了 PLA 的玻璃化转变温度，当添加 MCF 时，允许细胞壁厚度减小。机械性能最初随 MCF 的增加而增加，然后减小。这种趋势与热绝缘相似，热绝缘最初有所改善。生物降解测试表明，PLA 中纤维素的存在提高了泡沫的可生物降解性。当以纯纤维素参考物的分数表示时，含有 3wt.% MCF 的 PLA 泡沫的最大比较矿化率达到 95%。对模型房屋进行的能源模拟表明，与聚氨酯绝缘相比，生物资源泡沫导致加热和冷却的增加不超过 12%。在 MCF 分数较低时，泡沫的能源效率最佳。
