Highly Efficient Flame Retardant Hybrid Composites Based on Calcium Alginate/Nano-Calcium Borate

Abstract

Hybrid composites with low flammability based on renewable calcium alginate and nano-calcium borate were fabricated using an in situ method through a simple, eco-friendly vacuum drying process. The composites were characterized by X-ray diffractometry (XRD), Fourier transform infrared spectrum (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The combustion behavior and flammability of the composites were assessed by using the limiting oxygen index (LOI) and cone calorimetry (CONE) tests. The composites showed excellent thermal stability and achieved nonflammability with an LOI higher than 60. Pyrolysis was investigated using pyrolysis–gas chromatography–mass spectrometry (Py-GC-MS) and the results showed that fewer sorts of cracking products were produced from the hybrid composites compared with the calcium alginate. A possible thermal degradation mechanism of composites was proposed based on the experimental data. The combined results indicate that the calcium borate had a nano-effect, accumulating more freely in the hybrid composites and contributing significantly to both the solid phase and gas phase, resulting in an efficient improvement in the flame retardancy of the composites. Our study provides a novel material with promising potentiality for flame retardant applications.

Morphology and Thermal Properties of Calcium Alginate/Reduced Graphene Oxide Composites

“…As a hydrophilic and soluble marine polysaccharide macromolecule [1,2], sodium alginate (NaAlg) can form a cross-linked network by interacting with multivalent cations [3] and improve their water and mechanical resistance, barrier properties, cohesion and rigidity [4,5,6]. Due to its biocompatibility, non-toxicity [7], low cost, and the ability to achieve functional gel through the addition of polyvalent cations, NaAlg has been developed for many applicable purposes [8,9,10,11,12].…”

A Novel Inherently Flame-Retardant Composite Based on Zinc Alginate/Nano-Cu2O

“…A series of characteristic absorption peaks were observed, of which 3240 cm −1 (O–H stretching vibration), 2923 cm −1 (–CH 2 ), 1584 cm −1 (C=O stretching vibration) [29], 1429 cm −1 (symmetric and asymmetric vibrations of –COO), 1029 and 914 cm −1 (symmetric and asymmetric vibrations of C–O–C), respectively. No significant differences between the infrared peaks of ZnAlg/Cu 2 O and ZnAlg can be noticed, indicating that the addition of Cu 2 O did not break the structure of ZnAlg [30,31].…”

“…The thermal stability of the materials was tested in the air as well as the nitrogen atmosphere, and the results show both materials had similar degradation trends. It can be observed from Figure 4a,b that, under air, from the start of heating to 200 °C, there was about 18% weight loss, which was caused by evaporation of free water and crystal water in the materials, suggesting high natural moisture regain of the materials [31]. From 200 to 450 °C, the masses of ZnAlg/Cu 2 O and ZnAlg were dropped sharply, which was mainly due to the cleavage of glycosidic bonds in the alginate, as well as decarboxylation and decarbonylation [32].…”

An Alginate Hybrid Sponge with High Thermal Stability: Its Flame Retardant Properties and Mechanism

“…LOI represents the minimum percentage of oxygen required for the combustion of samples in an oxygen-nitrogen atmosphere and is commonly used for the evaluation of the flammability and flame retardancy of polymeric materials in the same conditions [34,35]. A higher value of LOI reflects a better flame retardancy of the tested samples.…”