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Open AccessArticle

Hybrid Silica‐Phytic Acid Coatings: Effect on the Thermal Stability and Flame Retardancy of Cotton

1
Department of Applied Science and Technology, Local INSTM Unit, Viale Teresa Michel 5, 15121 Alessandria, Italy
2
Institute of Physics of Materials of the Czech Republic, Brittle Fracture Group, Žižkova 22, 61662 Brno, Czechia
3
CEITEC—Central European Institute of Technology, Masaryk University, Kamenice 5/4A, 62500 Brno, Czechia
*
Author to whom correspondence should be addressed.
Polymers 2019, 11(10), 1664; https://doi.org/10.3390/polym11101664
Received: 29 August 2019 / Revised: 10 October 2019 / Accepted: 11 October 2019 / Published: 12 October 2019
(This article belongs to the Section Polymer Analysis)
New hybrid sol–gel coatings based on tetraethoxysilane (TEOS) and phytic acid (PA) were designed and applied to cotton; the flame-retardant properties of the treated fabrics were thoroughly investigated by means of flame-spread and forced-combustion tests. The first goal was to identify the TEOS:PA weight ratio that allowed the achievement of the best flame-retardant properties, with the lowest final dry add-on on the fabrics. Therefore, different TEOS:PA sols were prepared and applied to cotton, and the resulting coated fabrics were thoroughly investigated. In particular, solid-state NMR spectroscopy was exploited for assessing the condensation degree during the sol–gel process, even for evaluating the occurrence of possible reactions between phytic acid and the cellulosic substrate or the alkoxy precursor. It was found that a total dry add-on of 16 wt. % together with 70:30 TEOS:PA weight ratio provided cotton with self-extinction, as clearly indicated by flame-spread tests. This formulation was further investigated in forced-combustion tests: a significant reduction of heat release rate (HRR), of the peak of HRR, and of total heat release (THR) was found, together with a remarkable increase of the residues after the test. Unfortunately, the treated fabrics were not resistant to washing cycles, as they significantly lost their flame-retardant properties, consequently to the partial removal of the deposited hybrid coatings.
Keywords: sol–gel processes; flame retardancy; cotton; phytic acid; solid state NMR spectroscopy; thermal stability; durability sol–gel processes; flame retardancy; cotton; phytic acid; solid state NMR spectroscopy; thermal stability; durability
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MDPI and ACS Style

Barbalini, M.; Bertolla, L.; Toušek, J.; Malucelli, G. Hybrid Silica‐Phytic Acid Coatings: Effect on the Thermal Stability and Flame Retardancy of Cotton. Polymers 2019, 11, 1664.

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