Flame Retardant, Heat Insulating Cellulose Aerogels from Waste Cotton Fabrics by in Situ Formation of Magnesium Hydroxide Nanoparticles in Cellulose Gel Nanostructures

Abstract

Cellulose aerogels with low density, high mechanical strength, and low thermal conductivity are promising candidates for environmentally friendly heat insulating materials. The application of cellulose aerogels as heat insulators in building and domestic appliances, however, is hampered by their highly flammable characteristics. In this work, flame retardant cellulose aerogels were fabricated from waste cotton fabrics by in situ synthesis of magnesium hydroxide nanoparticles (MH NPs) in cellulose gel nanostructures, followed by freeze-drying. Our results demonstrated that the threedimensionally nanoporous cellulose gel prepared from the NaOH/urea solution could serve as scaffold/template for the nonagglomerated growth of MH NPs. The prepared hybridized cellulose aerogels showed excellent flame retardancy, which could extinguish within 40 s. Meanwhile, the thermal conductivity of the composite aerogel increased moderately from 0.056 to 0.081 W m −1 k −1 as the specific surface area decreased slightly from 38.8 to 37.6 cm 2 g −1 , which indicated that the excellent heat insulating performance of cellulose aerogel was maintained. Because the concepts of the process are simple and biomass wastes are sustainable and readily available at low cost, the present approach is suitable for industrial scale production and has great potential in the future of green building materials.

Cellulose Aerogels for Thermal Insulation in Buildings: Trends and Challenges

“…Han et al [36] proposed an alternative approach to the conventional mixing of flame-retardant additives with cellulose nanofibrils, aiming to avoid additive agglomeration. The team used a three-dimensional nanoporous cellulose gel prepared by dissolution and coagulation of cellulose from an aqueous NaOH/urea solution as template for the growth of magnesium-hydroxide nanoparticles.…”

Research of aerogel in flame retardant field

“…Han等 [38] 利用废棉料在NaOH/尿素溶液中制备三维纳 图 2 PVA/MMT气凝胶总热释放量曲线(P指代PVA, M指代 MMT, APP下标代表PA-APP中PA的含量) [24] (网络版彩图) 表 2 PVA/MMT气凝胶的极限氧指数值以及垂直燃烧和锥形量热仪测试结果 [23] M2.5和M5分别代表5% PVA、1% MF、2.5% MF和5% MF) [25] (网络版彩图) 图 4 (a) CNT/PIA复合纤维; (b) CNT/PIA复合纤维横截面 的扫描电子显微镜图像 [30] (网络版彩图)…”

“…图 5 燃烧前(a)和燃烧10 s后(b)气凝胶的数码照片以及不 同含量氢氧化镁燃烧速度的柱状图(c) [38] (网络版彩图) 图 6 纯细胞纤维素气凝胶与PANI@BC气凝胶的燃烧现象 (a, b)和HRR曲线 (c) [39] (网络版彩图) 下, 未处理的气凝胶和处 理的气凝胶在第20秒和第60秒时的照片 [40] (网络版彩图) [44] (网络版彩图) Figure 8 The photos during vertical burning test [44] (color online).…”

Boron/nitrogen flame retardant additives cross‐linked cellulose nanofibril/montmorillonite aerogels toward super‐low flammability and improved mechanical properties

“…Flame resistance is another important property expected for porous CNF aerogels that are highly flammable in nature. Inorganic phases have been introduced by in situ formation, physical blending, or layer by layer on the surface to form a char that acted like a barrier preventing burning of the underlying substrate. A synergistic flame retardant effect was achieved via incorporating clay and flame retardant agents (FRAs) or phosphorylation of CNF .…”