Abstract
One of the approaches to prolong the service lifespan of polymeric material is the development of self-healing ability by means of embedded microcapsules containing a healing agent. In this work, poly(melamine-urea-formaldehyde) (PMUF) microcapsules containing a palm oil-based alkyd were produced by polymerization of melamine resin, urea and formaldehyde that encapsulated droplets of the suspended alkyd particles. A series of spherical and free-flowing microcapsules were obtained. The chemical properties of core and shell materials were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance spectroscopy (1H-NMR). Differential scanning calorimetry (DSC) analysis showed a glass transition around −15 °C due to the alkyd, and a melting temperature at around 200 °C due to the shell. Thermogravimetric analysis (TGA) results showed that the core and shell thermally degraded within the temperature range of 200–600 °C. Field emission scanning electron microscope (FESEM) examination of the ruptured microcapsule showed smooth inner and rough outer surfaces of the shell. Flexural strength and microhardness (Vickers) of the cured epoxy compound were not affected with the incorporation of 1%–3% of the microcapsules. The viability of the healing reactions was demonstrated by blending small amounts of alkyd with epoxy and hardener at different ratios. The blends could readily cure to non-sticky hard solids at room temperature and the reactions could be verified by ATR-FTIR.
Highlights
The failure of a structural polymer begins from cracks within the materials
Results and Discussion and hardener at different ratios and cured at room temperature for 24 h and the samples were analyzed by ATR-FTIR
The selected palm oil-based alkyd has been successfully encapsulated by the PMUF resin to produce free-flowing microcapsules with good yield
Summary
The failure of a structural polymer begins from cracks within the materials. Continuous efforts are being made to overcome the damages of the cracks by integrating self-healing ability to the material. (PUF) resin by mixing urea with melamine-formaldehyde pre-polymer forming poly(melamineurea-formaldehyde) (PMUF) for encapsulating 5-ethylidene-2-norbornene (ENB) and its crosslinking agent. Nesterova and co-researchers [10] have prepared microcapsules of epoxy resins, DCPD, linseed oil and alkylglycidyl ether using both PUF and PMUF resins They had reported that PMUF shells were more stable and had produced higher yield. This observation has led us to the idea of using the alkyd for self-healing application in epoxy matrix. We have encapsulated the selected palm oil-based alkyd using urea, melamine resin and formaldehyde. The yield has improved and the microcapsules were more robust compared to our previous work using urea-formaldehyde [22]
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