Abstract
The research undertaken in this work is one of the examples of the engineering of modern polymer materials. This manuscript presents studies on the gelation process which might occur during the synthesis of epoxy resin using the modified vegetable oil via the epoxy fusion process conducted in bulk. Based on obtained results we determined rheological parameters related to the properties of reacting mixture during the polyaddition process, especially before and after occurring the phenomenon of gelation (via (1) theoretical determination of the gel point using the degree of conversion of reactants before occurring the gelation process of reacting mixture and (2) experimentally—the dynamic mechanical properties such as storage modulus, G′; loss modulus, G″; and loss tangent, tg δ). Theoretical investigations show that for both systems: epoxidized soybean oil and bisphenol A (ESBO_BPA), as well as the hydroxylated soybean oil and low molecular weight epoxy resin (SMEG_EPR), theoretical values of the degree of conversion at the gel point are characterized by similar values (ESBO_BPA: xgel-theoretical = 0.620, xgel-theoretical = 0.620 and SMEG_EPR: xgel-theoretical = 0.614, xgel-experiment = 0.630, respectively), while the one determined based on the initial assumptions are greater than the above-mentioned (ESBO_BPA: xgel-assumed = 0.696 and SMEG_EPR: xgel-assumed = 0.667). Moreover, experimental studies in the viscoelastic fluid stage showed that the SMEG_EPR system is characterized by lower values of G′ and G″, which indicates lower elasticity and lower viscosity than the epoxidized derivative. It was found that alike during the conventional polyaddition reaction, both systems initially are homogeneous liquids of increasing viscosity. Wherein gradual increase in viscosity of the reaction mixture is related to the fusion of oligomer molecules and the formation of higher molecular weight products. In the critical stage of the process, known as the gelation point, the reaction mixture converts into the solid form, containing an insoluble cross-linked polymer.
Highlights
Epoxy resins as one of the commonly used thermosets are typically applied as adhesives in various applications, e.g., in the aerospace industry [1], surface coatings [2], construction composite materials [3], automotive and ship industries [4], packaging materials for electronic devices, as well as in medicine [5] or home fields
One of them is the application of renewable resources for the synthesis and modification of epoxy resins
We report studies on the rheological behavior of a reacting mixture in the epoxy fusion process carried out using the following: (i) biobased monomers, as well as (ii) monomers of functionality greater than 2: epoxidized soybean oil and bisphenol A (BPA) or hydroxylated soybean oil and low molecular weight epoxy resin when approaching the gelling point
Summary
Epoxy resins as one of the commonly used thermosets are typically applied as adhesives in various applications, e.g., in the aerospace industry [1], surface coatings [2], construction composite materials [3], automotive and ship industries [4], packaging materials for electronic devices, as well as in medicine [5] or home fields. G00 and the intermediate frequency reflect the complexity of network structure for polymer without chemical cross-linking—the smaller the value is, the more complicated the network structure [45,46] In this manuscript, we report studies on the rheological behavior of a reacting mixture in the epoxy fusion process carried out using the following: (i) biobased monomers (modified soybean oil), as well as (ii) monomers of functionality greater than 2: epoxidized soybean oil (functionality, fESBO = 3.6) and BPA or hydroxylated soybean oil (functionality, fSMEG = 3.65) and low molecular weight epoxy resin (functionality equal 2) when approaching the gelling point. We were trying to apply the rheological investigations as a relatively simple tool for the estimation of the most optimal time for conducting such polyaddition process to obtain the final product of the highest possible average-molecular weight but still in the processable form
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
