Study of microplastics with semicrystalline and amorphous structure identification by TGA and DSC.

The potential of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to identify, distinguish among the most relevant microplastics, and quantification, has been studied, including semicrystalline polymers (polypropylene (PP), polyamide (PA), high density polyethylene (HDPE), low density polyethylene (LDPE) and polyethylene terephthalate (PET)) and amorphous polymers (polystyrene (PS) and Polyvinyl Chloride (PVC)). The identification has been carried out by analyzing the decomposition, melting and glass transition temperatures. Both amorphous polymers (PVC and PS) can be properly identified by DSC using the glass transition temperature. Semicrystalline polymers, PA, PET, PP, HDPE and LDPE can be identified by using the melting temperature without the interference of other polymers, neither semicrystalline nor amorphous. The main limitation of the evaluated techniques is to distinguish between the semicrystalline polymer LDPE and the amorphous PS, as LDPE melting temperatures overlap with PS glass transition temperature, and this parameter would be useful only if one of these two polymers is present in the sample to be analyzed, since interference with other polymers (PA, PP, PET, LDPE, PVC and PS) do not exist. If both LDPE and PS are present in the sample, the best but not ideal option would be to analyze the decomposition temperature curves, since overlapping is weak in this case.