Vatrootporni kompoziti na bazi fosfatnih estara kraft lignina i poliesterske smole - ekološki prihvatljiv materijal za sisteme termičke zaštite raketnih goriva

Jelena Rusmirović,Saša Brzić,Aleksandar Marinković,Vesna Lukić,Marica Bogosavljević,Tihomir Kovačević,Tatjana Stevanović

doi:10.5937/str1901016r

Abstract

Presented study was aimed to investigate the influence of surface functionalization of the industrial kraft lignin (KL) on mechanical and thermal properties of high-performance and fireproof composites based on unsaturated polyester (UPe) resin. In order to improve flame retardant properties, surface of the KL was modified by phosphorylation method in two-step process. First, direct grafting of phosphorus chloride on KL phenolic hydroxyl groups was performed and phosphoric acid ester of KL was formed. In the second step, phosphor ester of KL was recovered by precipitation in cooled isopropyl alcohol and the final obtained product, phosphorylated industrial kraft lignin with methyl terminal groups (KLP) was obtained. KLP mass contents in UPe based composites varied from 0.5 wt.% to 5.0 wt.%. Structural characterization was done via Fourier Transform-Infrared Spectroscopy (FT-IR). The effects of KLP surface functionalization and KLP mass contents on the UPe tensile properties were studied. Tensile strength (σ), elongation (ε) and Young's modulus of elasticity (E) and Shore A (Sh A) hardness of the UPe/KLP composites were analyzed in relation to the structure of KLP modification. Tensile testing results showed an increase in σ of 31 % for UPe/KL sample with 1.0 wt.% KL particles compared to the bare UPe matrix. The origin and cause of fracture that occurred during uniaxial tensile testing were analyzed using stereo microscopy. The obtained composites were tested on fire retardant properties in accordance with the standard test method UL-94V, and composites with 5.0 wt.% loaded KLP achieved V-1 category.

Highlights

MATERIALS for thermal protection systems (TPS) of rocket propellants (RP) play fundamental role for aerospace and military industries [1,2]
The results indicate that Energy absorption (EA) of the unsaturated polyester (UPe)/kraft lignin (KL) based composites increases with KL loading
This study explored the valorization of industrial kraft lignin as flame retardant additive in unsaturated polyester resin based on products of catalytic depolymeriyzation of waste poly(ethylene terephthalate) (PET)

Summary

Introduction

MATERIALS for thermal protection systems (TPS) of rocket propellants (RP) play fundamental role for aerospace and military industries [1,2]. TPS materials are classified in two classes, non-ablative and ablative TPS, according to the mechanism of dissipation of kinetic energy [1]. Polymer ablatives (PA) represent high performance materials used in ablative TPS which have high heat shock resistance, low density, good mechanical strength and thermal insulation capabilities [1]. As ablative polymer matrix of TPS material, UPe has to satisfy the prescribed physical, 1) Military Technical Institute (VTI), Ratka Resanovića 1, 11132 Belgrade, SERBIA 2) University of Belgrade, Faculty of Technology and Metallurgy, Karnegijeva 4, 11120 Belgrade, SERBIA 3) Département des sciences du bois et de la forêt, Université Laval, Québec, CANADA

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