Enhancement of thermal conductivity of PEG-PPG-based waterborne polyurethane coating by incorporating ordered polyethylene glycol fragment

With the respect to research the effects of polyethylene glycol (PEG, M-w = 1000), an ordered hydrophilic fragment, on thermal conductivity of waterborne polyurethane coatings (WPUCs), the PEG-polypropylene glycol (PPG, M-w = 2000)-based WPUCs (PEG-PPG-based WPUCs) were synthesized with different combinations of PEG and 2,2-bis(hydroxymethyl)propionic acid (DMPA). The total amount of hydrophilic agent was fixed. Experiment found that the PEG-PPG-based WPUC synthesized with 13% PEG and 2% DMPA showed a highest thermal conductivity (similar to 0.675 W/m.K). The phase separation, crystallinity and thermal conductivity were increased with the increasing of PEG. A number of characterizations were carried out through FTIR, TG, DSC, DMA, AFM and XRD to study the association of chemical structures and thermal conductivity at the basis of multiple combinations. The results showed that the ordered PEG fragments incorporated into WPUCs could increase the crystallinity and thermal conductivity, which was owing to the more ordered structures formed in hard phase and soft phase, and that facilitated the phonon propagation in free pathways, as a result.