Environmental and Durability Perspective of the Use of Curaua Fiber Treated in Mortars

The use of natural lignocellulosic fibers(NLFs)as a reinforcement mechanism for cementitious composites,such as mortar,has been investigated in the last decades.However,their application has often been restricted to technological evaluation research.A NLF with great potential the curaua,which after treatment with NaOH solution,proved to be technologically feasible for mortars reinforcement based on cement and lime.The objective of this research was the comparative evaluation between a traditional mortar,based on cement and lime,with 1:1:6:0.8 ratio of cement:lime:sand:water,and a modified mortar with addition of 2 wt.%treated curaua fiber in cement mass by evaluating environmental and durability aspects.After a curing time for 28 days,environmental assessments were carried out and durability methodologies were evaluated.The tests performed were:(i)attack by chlorides and sulfate,(ii)the wetting and drying cycles,and(iii)slake durability test.The results showed that the mortar with the addition of curaua fiber presented a similar behavior to the reference mixture,both in terms of environmental and durability aspects.This modified mortar is able to be used in internal and external environments,the latter with some conditions.Besides,it also contributes to the promotion of sustainable use of curaua fiber.

乌拉草纤维的超声波辅助碱氧-浴法提取工艺优化

为了提取一种新型植物纤维-乌拉草纤维并研究其性能,采用超声波-碱氧-浴法从乌拉草秸秆中提取乌拉草纤维,用多指标正交试验方法对超声波时间,碱煮时间,碱用量和双氧水用量进行优化设计,并通过对直径,断裂强度,回潮率3个指标的综合分析评价确定最佳提取工艺,对处理后的乌拉草纤维进行基本性能测试及保暖、抗菌效果测试。结果表明:最佳工艺参数为:超声波时间为70min;碱氧-浴时间为100min;0.75L溶液中碱质量浓度为8g/L;双氧水质量浓度为12g/L。采用最优工艺所提取的乌拉草纤维平均直径、长度、断裂强度及回潮率分别为47.19μm、152.59mm、2.03×104MPa和15.33%,与苎麻纤维性能相似,可满足可纺性要求。并有一定的保暖性和优良的抑菌效果。

乌拉草纤维热解及其产物挥发性有机物特性分析

为探究乌拉草纤维的热解性能及其在热解过程中挥发性有机物释放情况,基于傅里叶红外光谱仪及同步热分析质谱联用系统对乌拉草纤维及汉麻纤维的主要化学成分进行分析,探究其热分解过程,采用Coats-Redfern法进行热动力学计算,并对其热分解过程中挥发性有机物释放进行检测。研究结果发现,乌拉草纤维与汉麻纤维主要成分相似,以纤维素、半纤维素、木质素为主。其热分解过程可依次分为水分挥发失重、半纤维素热解、纤维素及木质素热解3个主要阶段,并可用半纤维素热解、纤维素热解、木质素热解3个独立的一级反应描述,纤维素与木质素热解阶段反应活化能较高,热解过程与汉麻纤维热分解过程相似。在乌拉草纤维热解过程中,除H2O、CO2气体释放以外,同时释放少量甲醛等挥发性有机物。研究结果为乌拉草纤维实际应用中阻燃及环保问题的考虑提供参考。

乌拉草超声波预处理脱胶工艺

以乌拉草根部为研究对象,探讨采用物理-化学联合脱胶方法提取乌拉草纤维的工艺。将残胶率作为考查指标,对脱胶工艺中超声波预处理时间、氢氧化钠用量、过氧化氢用量以及碱煮时间等因素进行优化,确定乌拉草脱胶工艺。结果表明:当超声波预处理时间为25 min,超声波处理温度为40℃,碱液质量浓度14g/L,过氧化氢质量浓度8g/L,碱煮时间2.5 h,a氧化氢处理时间为1.5 h时,残胶率较低,为9.1%。

乌拉草纤维联合脱胶工艺优化

采用物理-生化联合脱胶法制取乌拉草纤维,用多指标正交试验方法对酶反应时间、酶制剂浓度、碱氧一浴时间、NaOH溶液浓度、H_2O_2溶液浓度等因素进行优化,由多个指标的综合评价确定最佳工艺条件,并对脱胶后的乌拉草纤维进行基本性能测试。联合脱胶的优化工艺条件为:酶反应时间10 min,酶制剂质量浓度12 g/L,碱氧一浴时间100 min,NaOH溶液质量浓度8 g/L,H_2O_2溶液质量浓度8 g/L。制取的乌拉草纤维长度为66.2～89.3 mm,直径为63～70μm,断裂强度为275.3×10^(-6)～285.8×10^(-6)MPa,回潮率为7.8%～9.2%。