Curing Kinetics and Thermal Stability of Epoxy Composites Containing Newly Obtained Nano-Scale Aluminum Hypophosphite (AlPO₂)

• Main Authors: Farimah Tikhani, Shahab Moghari, Maryam Jouyandeh, Fouad Laoutid, Henri Vahabi, Mohammad Reza Saeb, Philippe Dubois
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Polymers
• Subjects: <i>cure index</i>; epoxy nanocomposite; nano-scale aluminum hypophosphite; cure kinetics; thermosetting resins
• Online Access: https://www.mdpi.com/2073-4360/12/3/644

For the first time, nano-scale aluminum hypophosphite (AlPO₂) was simply obtained in a two-step milling process and applied in preparation of epoxy nanocomposites varying concentration (0.1, 0.3, and 0.5 wt.% based on resin weight). Studying the cure kinetics and thermal stability of these nanocomposites would pave the way toward the design of high-performance nanocomposites for special applications. Scanning electron microscopy (SEM) and transmittance electron microscopy (TEM) revealed AlPO₂ particles having domains less than 60 nm with high potential for agglomeration. <i>Excellent</i> (at heating rate of 5 &#176;C/min) and <i>Good</i> (at heating rates of 10, 15 and 20 &#176;C/min) cure states were detected for nanocomposites under nonisothermal differential scanning calorimetry (DSC). While the dimensionless curing temperature interval (&#916;<i>T</i>*) was almost equal for epoxy/AlPO₂ nanocomposites, dimensionless heat release (&#916;<i>H</i>*) changed by densification of polymeric network. Quantitative cure analysis based on isoconversional <i>Friedman</i> and <i>Kissinger</i> methods gave rise to the kinetic parameters such as activation energy and the order of reaction as well as frequency factor. Variation of glass transition temperature (<i>T_g</i>) was monitored to explain the molecular interaction in the system, where <i>T_g</i> increased from 73.2 &#176;C for neat epoxy to just 79.5 &#176;C for the system containing 0.1 wt.% AlPO₂. Moreover, thermogravimetric analysis (TGA) showed that nanocomposites were thermally stable.