Search results for "Thermoset"

Absorption kinetics and swelling stresses in hydrothermally aged epoxies investigated by photoelastic image analysis

2015

Abstract The present work proposes an experimental optical methodology able to measure the transient swelling stresses induced by the water uptake ageing of polymers. In particular, the work describes the implementation of a Photoelastic technique to quantify internal stresses arising during the hydrothermal ageing of cast epoxy samples. The material investigated is a model DGEBA/DDS epoxy system. Curing and post-curing cycles have been optimised in order to obtain a fully cured, high T g , and completely stress free initial condition. Rectangular beam samples were then left in a hydrothermal bath at 90 °C, and regularly monitored by gravimetric and photoelastic analyses. The quantitative e…

A review on basalt fibre and its composites

2015

Abstract In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as po…

Interfacial shear strength of flax fibers in thermoset resins evaluated via tensile tests of UD composites

2012

Abstract A method of interfacial shear strength evaluation, based on the length distribution of fibers pulled out from the tensile fracture surface of an oriented flax-reinforced composite, is applied to composites with vinyl ester and acrylated epoxidized soy oil resin matrices. Two approaches for characterizing the strength of fibers with modified Weibull distribution, fiber fragmentation tests and fiber tension tests, are compared in the analysis of pull-out data. Interfacial shear strength is found to increase by a few percent when loading rate is increased from 1.33% to 8%/min.

Design and synthesis of biobased epoxy thermosets from biorenewable resources

2017

International audience; Biobased diepoxy synthons derived from isoeugenol, eugenol or resorcinol (DGE-isoEu, DGE-Eu and DGER, respectively) have been used as epoxy monomers in replacement of the diglycidyl ether of bisphenol A (DGEBA). Their curing with six different biobased anhydride hardeners leads to fully biobased epoxy thermosets. These materials exhibit interesting thermal and mechanical properties comparable to those obtained with conventional petrosourced DGEBA-based epoxy resins cured in similar conditions. In particular, a high Tg in the range of 90–130 °C and instantaneous moduli higher than 4.3 GPa have been recorded. These good performances are very encouraging, making these n…

Dielectric spectroscopy of novel thiol-ene/epoxy thermosets obtained from allyl-modified hyperbranched poly (ethyleneimine) and diglycidylether of bi…

2019

[EN] Dielectric Thermal Analysis (DETA) of a series of new thermoset obtained by click chemistry was performed. The new thermosets were obtained by a dual-curing process consisting in a first photochemical thiol-ene, followed by a thermal thiol-epoxy starting from an allyl-terminated hyperbranched poly(ethyleneimine) (HBPEI) and different proportions of diglycidylether of bisphenol A (DGEBA) and the corresponding stoichiometric proportions of pentaerythritol tetrakis (3-mercaptopropionate, PETMP). The dielectric behaviour was obtained experimentally supressing the conductive effects. Two sub-Tg intramolecular non-cooperative gamma and beta relaxations and an intermolecular cooperative alpha…

Biobased Epoxy Resin by Electrochemical Modification of Tall Oil Fatty Acids

2019

A biobased epoxy resin was prepared from tall oil fatty acids (TOFAs), a byproduct of the pulping industry. As free carboxylic acids compromise resin stability, TOFA was subjected to non-Kolbe decarboxylation to give alkenes upon loss of CO2. Thereby, the degree of unsaturation is significantly increased. This electrosynthetic protocol using an undivided cell setup and inexpensive graphite electrodes in a galvanostatic operation mode was scaled to a 1.5 L reactor, making use of electric current as a green and waste-free reagent. Simple, cost-efficient epoxidation using oxone subsequently gives an epoxy resin of low viscosity. Curing with anhydrides yields thermoset materials. Dynamic mechan…

2020

Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates for the replacement of DGEBA. This article presents an effective and eco-friendly way to prepare epoxy resin derived from isoeugenol (BioIgenox), making its upscale possible. BioIgenox has been totally characterized by NMR, FTIR, MS and elemental analyses. Curing of BioIgenox and camphoric anhydride with varying epoxide function/anhydride molar ratios has allowed determining an optimum ratio near 1/0.9 based on DMA and DSC analyses a…

Electrical Aging Tests on Enameled Wire Exposed to Gamma Irradiation

2011

Modelling of phase transitions and residual thermal stress of CTBN rubber modified epoxy resins during a pultrusion process

2007

Abstract The implicit finite difference and fourth order Runge-Kutta method are used both to solve the heat transfer problem in the pultrusion reaction and to calculate the temperature and conversion distributions within a thermoset composite profile. The aim of our work is to study the influence of a rubbery phase added to the epoxy matrix in production conditions. The results have shown that the rubber modified systems have a low exothermic temperature peak value, so that neither the amount of cured resin nor the final product properties are limited. First of all we will show that the phase transition (gelation and vitrification) zones within the die change as the amount of rubber varies …

Contribution to the development of 100% bio-based composites : synthesis of bio-based polyepoxides, supercritical CO2 treatment of hemp fibers and im…

2018

This thesis contributes to the development of 100% bio-based hemp/epoxy composites. Current environmental issues favor the emergence of materials derived from renewable resources such as plant fibres and a wide range of bio-based building-blocks, source of epoxy prepolymers in particular. An intensive investigation of the two constituents (hemp fibres and polyepoxidic matrix) is carried out before the composites manufacturing. Supercritical CO2 treatment is applied to hemp fibres used as reinforcement in composite materials. This treatment, not optimized, leads to better individualization as well as a decrease in the hygroscopic power of the fibres. These aspects, which are essential in ord…