A new 100% bio-based thermosetting coating system was developed from epoxidized sucrose soyate crosslinked with blocked bio-based dicarboxylic acids. A solvent-free, green method was used to block the carboxylic acid groups and render the acids miscible with the epoxy resin. The thermal reversibility of this blocking allowed for the formulation of epoxy-acid thermoset coatings that are 100% bio-based. This was possible due to the volatility of the vinyl ethers under curing conditions. These systems have good adhesion to metal substrates and perform well under chemical and physical stress. Additionally, the hardness of the coating system is dependent on the chain length of the diacid used, making it tunable.
Ultraviolet-curable nanocomposites containing organically modified nanoclays were prepared to serve as barrier coatings against oxygen and water permeation. A novel in situ synthesis technique was used to produce well-dispersed clays in an unsaturated polyester polymer before crosslinking. The in situ dispersion route was compared with nanocomposites prepared by mixing and sonication for several levels of nanoclay loading (1, 2, 5, and 10 wt %). The comparison of nanocomposite properties prepared from each processing method demonstrated that the in situ preparation technique led to better clay disper-sion as verified by transmission electron microscopy. The in situ route for nanoclay dispersion produced nanocomposites with lower water vapor transmission and permeability compared with the sonicated dispersion method. The impact on cure characteristics, mechanical properties, thermal stability, and optical clarity of the nanocomposites were also compared.
The potential of nanoclay organic modifiers to induce plasticizing effects in resin and coatings systems was studied. In previous work, it was found that while low amounts of incorporation of organomodified clays significantly improved the physical and mechanical properties of a ultraviolet (UV)-curable nanocomposite, further increasing the organomodified clay content could result in the reduction of properties. To investigate the potential impact of the organic modifier composition and concentration on polymer properties, a series of experiments were carried out using only the organic modifier. Methyl, tallow, bis-2-hydroxyethyl ammonium (MTEtOH), the organic modifier used in montmorillonite clay Cloisite V R 30B, was dispersed with precursor polyester oligomers at 1-10 wt % through an in situ synthesis process and via sonication, and UV-curable coatings were prepared from these MTEtOH-containing resins. The organic modifier cetyltrimethylammonium bromide (CTAB) was also studied to examine the impact of the organic modifier structure. According to differential scanning calorimetry, small decreases in the glass transition temperatures (T g ) of the MTEtOH-containing polyesters were observed, but CTAB-containing polyesters had small T g increases. Polyester molecular weight and viscosity were also affected by both the structure of the organic modifier as well as its concentration. The mechanical performance of the UV-curable coatings diminished with increased MTEtOH concentration for the films containing the organic modifier compared to a control film. Furthermore, the crosslink density was found to reduce $ 50% with increased MTEtOH loading into the UV-curable films. The cure characteristics, thermal stability, and optical clarity were also studied.
A novel in situ intercalative polymerization technique was used to disperse clay mineral in a precursor resin for use in UV curing by performing an in situ ion exchange reaction during polyesterification. Unmodified montmorillonite (MMT) was added to a reaction mixture composed of monomers and methyl, tallow, bis‐2‐hydroxyethyl ammonium (MTEtOH) during the synthesis of unsaturated polyesters to create resins containing highly dispersed, organically modified MMT. UV‐curable clay–polymer nanocomposite (CPN) films were then prepared utilizing donor–acceptor chemistry through reactions of the unsaturated polyester resin with triethylene glycol divinyl ether. Functional group conversion improved up to 15% by the incorporation of clay mineral into the polymer matrix through the in situ polymerization method. The CPNs also had improved barrier, mechanical, and thermal properties over a control film containing no clay mineral. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42601.
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