Evaluating the Ability of Additively Manufactured Polyester Blends to Thermally Recover from Organic Chemical Exposure

The work presented here sought to understand if damage induced to polymeric materials by chemical exposure could be mitigated by thermal annealing. This concept has not been widely explored in literature. Here, two polymer blends with known shape memory properties and documented thermal process for shape recovery; a binary blend of equal parts by mass polycaprolactone (PCL)/thermoplastic urethane (TPU), and a ternary mixture of equal parts by mass polycaprolactone (PCL), thermoplastic urethane (TPU), and polylactic acid (PLA) were subjected to chemical exposure to either ethyl acetate or heated acetic acid for a duration of 7 days. The specimens were fabricated by fused filament fabrication (FFF) in two different raster orientations. Swell testing revealed a dependence on raster orientation for solvent uptake. Characterization of the chemical bonds by FTIR-ATR revealed the acetic acid exposure to be more damaging in terms of breaking of chemical bonds and that thermal recovery reforms some bonds. Analysis of tensile test results with Tukey-Kramer Honestly Significant Difference revealed thermally annealing specimens after chemical exposure could recover mechanical properties to a level similar to specimens that were not exposed. Analysis by scanning electron microscopy revealed that the chemical attack was concentrated at the print raster interface, leading to delamination between the print rasters. Analysis by way of DMA revealed that chemical exposure lowered the max tan δ value, but not the temperature at which this parameter was reached as compared to control specimens. This work demonstrates that thermally induced recovery can heal chemical damage to polymer materials, offering a route to extend the life of plastic parts and reduce polymer waste.