Spreading Dynamics of Molten Polymer Drops on Glass Substrates

Abstract

Wetting dynamics drive numerous processes involving liquids in contact with solid substrates with a wide range of geometries. The spreading dynamics of organic liquids and liquid metals at, respectively, room temperature and >1000 °C have been studied extensively, both experimentally and numerically; however, almost no attention has been paid to the wetting behavior of molten drops of thermoplastic polymers, despite its importance, for example, in the processing of fiber-reinforced polymer composites. Indeed, the ability of classical theories of dynamic wetting, that is, the hydrodynamic and the molecular-kinetic theories, to model these complex liquids is unknown. We have therefore investigated the spreading dynamics on glass, over temperatures between 200 and 260 °C, of two thermoplastics: polypropylene (PP) and poly(vinylidene fluoride) (PVDF). PP and PVDF showed, respectively, the highest and lowest slip lengths due to their different interactions with the glass substrate. The jump lengths of PP and PVDF are comparable to their Kuhn segment lengths, suggesting that the wetting process of these polymers is mediated by segmental displacements. The present work not only provides evidence of the suitability of the classical models to model dynamic wetting of molten polymers but also advances our understanding of the wetting dynamics of molten thermoplastics at the liquid/solid interface.

Dynamic Wetting of Molten Polymers on Cellulosic Substrates: Model Prediction for Total and Partial Wetting

“…Figure 10 shows the results, indicating that for paraffin oil this law fits quite well the experimental data at different temperatures and at Ca < 2 • 10 −3 , allowing to obtain the coefficient of contact line friction ξ (Blake and De Coninck, 2002), shown in Table 5. The coefficient of contact line friction decreases as the temperature is increased, and then it is higher when the viscosity is higher, according to the literature (Zhang et al, 2017).…”

“…Some works using microfluidic techniques proved that, with partially wetting liquids, established models in literature are no longer valid (Wielhorski et al, 2012;Abdelwahed et al, 2014). A recent work studied molten polymers but in a spontaneous regime of drop spreading (Zhang et al, 2017). This procedure has been applied to rods or fibers with a large diameter (Zhang et al, 2019) but it turns out to be more difficult for thinner fibers (Hansen et al, 2017).…”

Temperature effect on dynamic wetting of cellulosic substrates by molten polymers for composite processing

“…Such liquids include hexadecane [25], dodecane [14], methanol [20], ethanol [20] and especially polydimethylsiloxane (PDMS) [17,23,26,14] due to ease of obtaining PDMS oils of different viscosities. One recent study considers wetting of molten thermoplastics [27], but still in a spontaneous drop spreading configuration on glass substrates, that could not represent forced dynamic wetting conditions on fibres during composite manufacturing [28].…”

The Optimization of Process Parameters and Characterization of High-Performance CF/PEEK Composites Prepared by Flexible CF/PEEK Plain Weave Fabrics

“…However, when the temperature rises continuously, the contact angle increases, indicating the gradual deterioration of the wettability, and at 380 °C, the contact angle is 93.3°, showing non-wettability at this condition. The contact angles are closely connected with the surface energy of melted PEEK and CFs, and the surface energy of PEEK differs with the changes of temperature [29], because CFs cannot change their shape when the surface energy of melted PEEK changes. Liquids can shrink or spread during the process to maintain the balance among gas, liquids (melted PEEK) and solids (CFs).…”