Extruded-Calendered Sheets of Fully Recycled PP/Opaque PET Blends: Mechanical and Fracture Behaviour

Abstract

This work presents the experimental results of the mechanical and fracture behaviour of three polymeric blends prepared from two recycled plastics, namely polypropylene and opaque poly (ethylene terephthalate), where the second one acted as a reinforcement phase. The raw materials were two commercial degrees of recycled post-consumer waste, i.e., rPP and rPET-O. Sheets were manufactured by a semi-industrial extrusion-calendering process. The mechanical and fracture behaviours of manufactured sheets were analyzed via tensile tests and the essential work of fracture approach. SEM micrographics of cryofractured sheets revelated the development of in situ rPP/rPET-O microfibrillar composites when 30 wt.% of rPET-O was added. It was observed that the yield stress was not affected with the addition of rPET-O. However, the microfibrillar structure increased the Young’s modulus by more than a third compared with rPP, fulfilling the longitudinal value predicted by the additive rule of mixtures. Regarding the EWF analysis, the resistance to crack initiation was highly influenced by the resistance to its propagation owing to morphology-related instabilities during tearing. To analyze the initiation stage, a partition energy method was successfully applied by splitting the total work of fracture into two specific energetic contributions, namely initiation and propagation. The results revelated that the specific essential initiation-related work of fracture was mainly affected by rPET-O phase. Remarkably, its value was significantly improved by a factor of three with the microfibrillar structure of rPET-O phase. The results allowed the exploration of the potential ability of manufacturing in situ MFCs without a “precursor” morphology, providing an economical way to promote the recycling rate of PET-O, as this material is being discarded from current recycling processes.

Implications of the Circular Economy in the Context of Plastic Recycling: The Case Study of Opaque PET

“…Additionally, and considering the possibility of increasing this TiO 2 content, a mixture with a global content of 4% w / w of TiO 2 was evaluated to compare its performance. Details of this study could be found in [ 18 , 19 ].…”

“…This effect is caused by the TiO 2 sub-micron particle cavitation, which allows a significant release of local triaxiality, promoting plastic the premature plastic tearing of the PET matrix [ 17 ]. Thus, one of the upgrading pathways proposed considered in this case study was to explore the use of r-O-PET as a reinforcement for recycled polypropylene (r-PP) matrix, inducing a microfibrillation of the PET phase during processing that acts as reinforcing fibres, under the manufacturing philosophy of in situ microfibrilated composites (MFC) [ 18 ]. According to his study, the blend composition that offers the best balance of mechanical properties and fracture behaviour of the MCM produced is the one with 20% w / w of r-O-PET.…”

A Brief Overview of Polymers Science and Technology, in Spain

“…Polyamide powders functionalized with nanosilica for wear resistence applications [30] Ángel Alvaredo-Atienza Juan P. Fernández-Blázquez Fabrication and characterization of PEEK/PEI multilayer composites by alternate layer stacking [31] David Loaeza Orlando Santana Pérez, Maria Lluïsa Maspoch Polymeric blends prepared from two recycled plastics, polypropylene and opaque poly(ethylene terephthalate), acting as reinforcement [32] Vanessa García Vanessa García-Martínez, Alejandro Ureña…”

Melt processing behaviour and structure development in recycled PP blends with recycled PET

“…Such reinforcement increases the fatigue life of this blend eightfold. 10 Waste PET fabric acts as a reinforcement in the adhesive layer for improving the flexural properties of a bi-layer laminate bonded with rPP based adhesive. 11,12…”

“…Such reinforcement increases the fatigue life of this blend eightfold. 10 Waste PET fabric acts as a reinforcement in the adhesive layer for improving the flexural properties of a bi-layer laminate bonded with rPP based adhesive. 11,12 Moisture absorption capacity of rPP/rPET blend is lesser than the rPet alone and the compatibilized rPP/rPET blend.…”