Depth Analysis of Polymer Degradation by MALDI-TOF-MS

Analysis near the surface is crucial for researching the degradation process, since degradation begins with on external stimulation, such as light and heat. Poly (butylene tere:phthalate) (PBT) is an engineering plastic with a good balance of mechanical and electrical properties, widely used in automobile components, such as connectors. We report here on a technique to analyze the depth profile of degradation products using matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), formed the upon thermal aging of PBT. Pristine and aged sample pieces were shaved into thin films by a microtome for MALDI-TOF-MS analysis of the depth profile. The tensile strength was drastically reduced and the COOH/COOH end-group was increased for bulk samples after aging at 180 degrees C for 200 hours. The degradation proceeds via thermo-oxidation pathway mainly because of the appearance of the (CH2)(3)-COOH/COOH end group in the layers shallower than 155 gm. It was suggested that the decomposition into low-molecular-weight products in the layers shallower than 155 mu m affected the decrease in tensile strength. The MALDI-TOF-MS would be useful for the analysis of the degradation process in depth profile.