Degradation of poly(l-lactide) under CO sub(2) laser treatment above the ablation threshold

In this paper, we present an analysis of changes in material properties in the heat affected zone HAZ induced by the CO sub(2) laser at the fluence well above the ablation threshold. The complexity of the processes of decomposition implies the need for simultaneous use of many selective analytical techniques which complement each other to give a full image of the changes. Introduced changes were characterized using Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC/SEC), X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Wettability (Contact Angle) measurement. It turns out that CO sub(2) laser processing of poly(l-lactide) mainly induces surface changes. However, oxidation of the surface was not observed. We recorded a bimodal distribution, a significant increase in polydispersity index and some reduction in the molecular weight. Infrared spectroscopy in turn revealed the existence of absorption bands, characteristic for the vinyl groups (RCHCH sub(2)). The appearance of these bands indicates that the decomposition of the polymer occurred, among others, by means of the cis-elimination reaction.