Thermal properties and kinetics of thermal decomposition of multiple recycled polypropylene

U radu je provedeno istraživanje utjecaja višestrukog recikliranja na degradaciju polipropilena (PP) budući da se široko primjenjuje zbog svojih dobrih svojstava te posljedično nastaju velike količine otpada, a potom i mikroplastike (MP) u okolišu. Reciklat PP dobiven je od tvrtke Poliplast d.d., koji je potom mehanički recikliran u četiri ciklusa, ekstrudiranjem, pri temperaturi od 200 °C. Uzorci su karakterizirani nakon svakog ciklusa recikliranja, kako bi se utvrdio stupanj degradacije i promjena svojstva PP. Karakterizacija je provedena: difuznom refleksnom spektroskopijom (DRS), određivanjem brzine protjecanja taljevine (MFR) te termogravimetrijskom analizom (TGA) iz koje je određena kinetika toplinske razgradnje primjenom Flynn-Wall-Ozawa (FWO) modela. Analiza rezultata dobivenih DRS, MFR i TGA tehnikama pokazuje da prilikom recikliranja uzoraka na povišenim temperaturama dolazi do blage razgradnje polipropilena.This paper investigates the impact of multiple recycling on the degradation of polypropylene (PP), since it is widely used due to its good properties, and as a result, large amounts of waste and then microplastics (MP) are generated in the environment. Recycled PP was obtained from the company Poliplast d.d., which was then mechanically recycled in four cycles, by extrusion, at a temperature of 200 °C. The samples were characterized after each recycling cycle, in order to determine the degree of degradation and change in PP properties. Characterization was performed by: diffuse reflection spectroscopy (DRS), determination of melt flow rate (MFR) and thermogravimetric analysis (TGA), from which the kinetics of thermal decomposition were determined using the Flynn-Wall-Ozawa (FWO) model. The analysis of the results obtained by DRS, MFR and TGA techniques shows that when samples are recycled at elevated temperatures, a slight degradation of polypropylene occurs