Chemical Treatment of Poly(lactic acid) Fibers to Enhance the Rate of Thermal Depolymerization

Abstract

When heated, poly(lactic acid) (PLA) fibers depolymerize in a controlled manner, making them potentially useful as sacrificial fibers for microchannel fabrication. Catalysts that increase PLA depolymerization rates are explored and methods to incorporate them into commercially available PLA fibers by a solvent mixture impregnating technique are tested. In the present study, the most active catalysts are identified that are capable of lowering the depolymerization temperature of modified PLA fibers by ca. 100 °C as compared to unmodified ones. Lower depolymerization temperatures allow PLA fibers to be removed from a fully cured epoxy thermoset resin without causing significant thermal damage to the epoxy. For 500 μm diameter PLA fibers, the optimized treatment involves soaking the fibers for 24 h in a solvent mixture containing 60% trifluoroethanol (TFE) and 40% H2O dispersed with 10 wt % tin(II) oxalate and subsequent air-drying of the fibers. PLA fibers treated with this procedure are completely removed when heated to 180 °C in vacuo for 20 h. The time evolution of catalytic depolymerization of PLA fiber is investigated by gel permeation chromatography (GPC). Channels fabricated by vaporization of sacrificial components (VaSC) are subsequently characterized by scanning electron microscopy (SEM) and X-ray microtomography (Micro CT) to show the presence of residual catalysts.

Thermal degradation mechanisms of epoxy composites filled with tin particles

“…5a and b shows that the true effect of tin on epoxy is to accelerate the thermal degradation of epoxy and this acceleration is dependent on the quantity of tin contained by epoxy. The reason for increase of the thermal degradation rate of epoxy is more probably the fine catalytic activity of tin which has been observed in tin-catalyzed depolymerization reactions [26,27]. However, the DTG peaks of epoxy/Sn composites are not affected by the subtraction of filler's mass [28] as can be seen in Fig.…”

Active Cooling of a Microvascular Shape Memory Alloy‐Polymer Matrix Composite Hybrid Material

“…[15][16][17] Here, we fabricate a vascular network into each phase of a bilayer nickel-titanium (NiTi)/glass fiber reinforced epoxy hybrid by the Vaporization of Sacrificial Components (VaSC) technique. [14,18,19] This hybrid material represents the bottom two layer of the proposed multilayer hybrid composite ( Figure 1). The effects of VaSC on material composition and phase transformation of the NiTi SMA are examined.…”

“…Methods for fabricating vascular networks into PMCs include integration of hollow glass fibers, [17,23,35] removal of a solid wire through either melt or manual extraction, [13,26,28] and VaSC. [14,18] Unlike other methods, which are restricted to straight channels with one-dimensional connectivity, sacrificial fibers used for VaSC allow for three-dimensional, interconnected architectures. [14] To create vascular networks in NiTi SMA, a new VaSC process was developed inspired by a technique initially demonstrated for titanium [36] and Ti-6Al-4V.…”

Sacrificial component fabrication for optimised production of micro-vascular polymer composite

“…The fibre treatment method previously used to prepare vascular composites is not fully described in literature [5]. For the initial experiments 500 µm PLA monofilament was rolled into loose coils and supported within a 3 litre Pyrex beaker on a steel wire nest.…”

“…The samples were prepared to compare PLA fibres developed through the solvent treatment method against those prepared through polymer extrusion with catalyst filler. The thermal degradation characteristics of treated PLA materials will have a serious implication on the efficiency of fibre removal as the most important event of thermal degradation of solvent treated fibres from literature is the onset of mass loss [5]. The lowest reported onset of thermal degradation from literature for PLA has been 180°C.…”