Blends rheological properties of copolymer polypropylene/recycled polypropylene from industrial containers

ABSTRACT

In this study, blends of copolymer polypropylene (PP_Cop /recycled polypropylene (PPRec) from industrial containers after consumption were evaluated in three different ratios (80:20, 60:40 and 40:60 wt.%). The blends were evaluated by melt flow index, torque rheometry and rheology in a dynamic oscillatory regime. The results from the melt flow index indicated that the blending of recycled material with PP_Cop causes a decrease in the molecular weight as compared to PP_Cop. By torque rheometry, it was verified that the blends showed improved processability in relation to PP_Cop. Also, the blends showed stability throughout the processing, indicating absence of degradation due to the process conditions used. By the dynamic-oscillatory regime tests, it was observed that, at low frequencies (<1 rad/s), the PP_Cop and the blends (PP_Cop / PP_Rec) demonstrated a Newtonian fluid behavior, whereas, at frequencies greater than 1 rad/s, a pseudoplastic fluid behavior was observed. The values of the intersection points (G ‘= G”) of the storage modulus curves (G’) and loss modulus (G’), as a function of the angular frequency (ω) indicated that the blends showed a reduction of the molecular weight, which was more pronounced in the composition containing 60% PP_Rec. The rheological results of the PP_Cop / PP_Rec blends were of great relevance, since they allowed the analysis of the blends behavior containing recycled material.

Keywords
polypropylene; recycled polypropylene; polymer blends; rheology