Thermal and Fire Behavior of a Bio-Based Epoxy/Silica Hybrid Cured with Methyl Nadic Anhydride

Abstract

Thermosetting polymers have been widely used in many industrial applications as adhesives, coatings and laminated materials, among others. Recently, bisphenol A (BPA) has been banned as raw material for polymeric products, due to its harmful impact on human health. On the other hand, the use of aromatic amines as curing agents confers excellent thermal, mechanical and flame retardant properties to the final product, although they are toxic and subject to governmental restrictions. In this context, sugar-derived diepoxy monomers and anhydrides represent a sustainable greener alternative to BPA and aromatic amines. Herein, we report an “in-situ” sol–gel synthesis, using as precursors tetraethylorthosilicate (TEOS) and aminopropyl triethoxysilane (APTS) to obtain bio-based epoxy/silica composites; in a first step, the APTS was left to react with 2,5-bis[(oxyran-2-ylmethoxy)methyl]furan (BOMF) or diglycidyl ether of bisphenol A (DGEBA)monomers, and silica particles were generated in the epoxy in a second step; both systems were cured with methyl nadic anhydride (MNA). Morphological investigation of the composites through transmission electron microscopy (TEM) demonstrated that the hybrid strategy allows a very fine distribution of silica nanoparticles (at nanometric level) to be achieved within a hybrid network structure for both the diepoxy monomers. Concerning the fire behavior, as assessed in vertical flame spread tests, the use of anhydride curing agent prevented melt dripping phenomena and provided high char-forming character to the bio-based epoxy systems and their phenyl analog. In addition, forced combustion tests showed that the use of anhydride hardener instead of aliphatic polyamine results in a remarkable decrease of heat release rate. An overall decrease of the smoke parameters, which is highly desirable in a context of greater fire safety was observed in the case of BOMF/MNA system. The experimental results suggest that the effect of silica nanoparticles on fire behavior appears to be related to their dispersion degree.

Structure and Bottom-up Formation Mechanism of Multisheet Silica-Based Nanoparticles Formed in an Epoxy Matrix through an In Situ Process

“… 4 − 6 Recently, the authors exploited the sol–gel chemistry to produce a silica/epoxy HOI with an inorganic content up to 6 wt %. 23 − 26 Two silica precursors were used: tetraethyl orthosilicate (TEOS) and (3-aminopropyl)-triethoxysilane (APTES). APTES also played the role of a coupling agent between silica and the epoxy matrix by allowing chemical reactions between the components.…”

“…Despite the very low silica content, the HOI exhibited an excellent fire behavior: absence of dripping during a vertical flame spread test, formation of a continuous and stable char, and a reduction in the heat release rate (HRR), down to 60% of the neat epoxy resin one. 23 − 26 …”

Polymer Adsorbents vs. Functionalized Oxides and Carbons: Particulate Morphology and Textural and SurfaceCharacteristics

“…Therefore, a set of methods could be used in parallel, such as direct (TEM, SEM) and indirect (probe adsorption, SAXS, NMR cryoporometry, DSC thermoporometry, etc.) methods [ 9 , 28 , 31 , 54 , 55 , 56 , 64 , 65 , 66 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 111 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 ]. More accurate results can be obtained if several methods are used in parallel (e.g., SAXS and adsorption).…”

“…Therefore, a set of methods could be used in parallel, such as direct (TEM, SEM) and indirect (probe adsorption, SAXS, NMR cryoporometry, DSC thermoporometry, etc.) methods [9,28,31,[54][55][56][64][65][66][74][75][76][77][78][79][80][81][82][83][84][85][86][87]111,[114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129][130]. More accurate results can be obtained if several methods are used in parallel (e.g., SAXS and adsorption).…”

Suitability and Sustainability of Anti-Graffiti Treatments on Natural Stone Materials

“…Consequently, it may be possible to affirm that E and NR are mainly based on epoxy resins as polymer binder systems. Moreover, the band at 1114 cm −1 is due to Si-O stretching and discloses the use of silica nanoparticles as fillers in both formulations [32,33]. For the E system, the band at 1188 cm −1 (in-plane CH deformations) suggests the presence of a silane agent, which may contain halo-atoms (X), since the band stretching at 690 cm −1 is normally ascribed to C-X groups [34].…”