Flame retardant effect of lignin/carbon nanotubes/potassium carbonate composite coatings on cotton roving

Damian Łukawski,Wojciech Grześkowiak,Małgorzata Widelicka,Alina Dudkowiak,Filip Lisiecki,Agnieszka Lekawa-Raus

doi:10.1007/s10570-020-03270-y

Abstract

A new composite flame retardant coating for cotton roving has been investigated. The proposed coating comprises natural lignin, pure carbon allotrope carbon nanotubes (CNTs) and non-toxic potassium carbonate (K2CO3). The series of complementary experiments, including thermogravimetric analysis, vertical burning in fire tube, limiting oxygen index (LOI) measurement and combustion in mass loss calorimeter enabled the formulation of an optimum composition including aqueous suspension with 1 wt% of CNTs, 1 wt% lignin (L) as well as 1 wt% of K2CO3. Applying L/CNT/K2CO3 on cotton roving increased LOI from 17.1 to 38.5%, decreased final mass loss and temperature during vertical burning from 100 to 78% and 457 to 190 °C, respectively. Moreover, peak heat release rate and total heat released dropped from 97.5 to 70.4 kW/m2 and from 4.2 to 1.6 MJ/m2, respectively . The above experiments supported by scanning electron microscopy and Raman spectroscopy allowed also the explanation of the complementary mechanisms responsible for the overall fire retardant effect.

Highlights

Cellulose, the main compound of cotton fibers, is the most abundant biopolymer largely used for environmental protection, water treatment, biomedical applications, food packaging, textile industry, civil engineering and others (Vroman and Tighzert 2009).Cellulose is composed of two anhydroglucose rings (C6H10O5)n with linear homopolymer of glucopyranose residues connected by b-1,4-glycosidic bond
In our previous studies we showed that carbon nanomaterials, including carbon nanotubes (CNTs) may be successfully composited with wood chips (Łukawski et al 2019) showing slight flame retardant effect and can create superhydrophobic coatings of wood and cotton (Łukawski et al 2018a, b)
We propose the use of CNT/lignin based coatings on cotton as flame retardant agents

Summary

Introduction

The main compound of cotton fibers, is the most abundant biopolymer largely used for environmental protection, water treatment, biomedical applications, food packaging, textile industry, civil engineering and others (Vroman and Tighzert 2009). Cellulose is composed of two anhydroglucose rings (C6H10O5)n with linear homopolymer of glucopyranose residues connected by b-1,4-glycosidic bond. The combustion of cellulose begins with its pyrolysis (Shen et al 2011). At low temperature the initial process is delayed, which leads to a reduction in the degree of polymerization and formation of active cellulose (Shen and Gu 2009). High temperature pyrolysis of cellulose is developed through two competitive degradation reactions: the first one is the formation of char and gas, and second one is leads mostly to formation of tars. In the presence of oxygen the volatile gases, resulting from pyrolysis, ignite starting the rapid combustion (White and Nordheim 1992)

Results

Discussion

Conclusion