Abstract
This work provides an experimental analysis regarding the fracture behavior of recycled opaque PET (rPET-O) containing titanium dioxide (TiO2) under plane stress conditions. For this purpose, a commercially post-consumer transparent colored/opaque PET flakes mix was processed using a semi-industrial extrusion calendering process. The manufactured rPET-O sheets had a TiO2 content of 1.45 wt.%. The mechanical and fracture properties of unaged and physically aged (1 year) samples were determined through uniaxial tensile experiments and the Essential Work of Fracture (EWF) methodology, respectively, and were compared to those of recycled transparent PET (rPET-T). Under tensile loading, independently of the aging time, rPET-O samples exhibited similar mechanical behavior as rPET-T up to the yield point. The main differences remained in the post-yielding region. The presence of TiO2 particles allowed reducing the strain energy density up to neck formation in aged samples. Regarding the EWF analysis, it is argued that the energy consumed up to the onset of crack propagation (we) for rPET-T was mainly dependent of the molecular mobility. That is, the we value decreased by 26% when rPET-T was physically aged. Interestingly, we values remained independent of the aging time for rPET-O. In fact, it was highlighted that before crack propagation, the EWF response was principally governed by matrix cavitation ahead of the crack tip, which allowed a significant release of the triaxial stress state independently of the molecular mobility. This property enabled rPET-O to exhibit a resistance to crack initiation 17% higher as compared to rPET-T when the material was physically aged. Finally, independently of the aging time, rPET-O exhibited a resistance to crack growth approximately 21% larger than rPET-T due to matrix fibrillation in large scale deformation.
Highlights
According to recent statistics compiled by plastic Europe, in 2018, the packaging industry made up 39.9% of the total European plastics demand, representing the largest end-use plastic market with 20.4 million tons
It was highlighted that before crack propagation, the Essential Work of Fracture (EWF) response was principally governed by matrix cavitation ahead of the crack tip, which allowed a significant release of the triaxial stress state independently of the molecular mobility
Parameter seemed to remain unaffected in rPET-O. This result highlighted that prior to crack propagation, the EWF response of rPET-O was principally governed by mat1r3ixofc1a6vitation ahead of the crack tip, which allowed a significant release of the triaxial stress state independently of the molecular mobility
Summary
According to recent statistics compiled by plastic Europe, in 2018, the packaging industry made up 39.9% of the total European plastics demand, representing the largest end-use plastic market with 20.4 million tons. This was argued by the large-scale yielding ahead of the crack tip prior to crack propagation This concept postulates that the total work of fracture (Wf) dissipated in a pre-cracked body could be split into two additive terms; the essential work required to generate a new free surface during loading (We) and the non-essential or plastic work consumed by various deformation mechanism in the plastic zone surrounding the crack propagation plane (Wp) [11,12]. The main purpose of the present work is an experimental study regarding the impact of TiO2 on the crack propagation processes in post-consumer PET bottle waste. Where ∆Hm is the melting enthalpy (J·g−1), ∆Hcc the cold crystallization enthalpy (J·g−1), ∆Hmo the melting enthalpy for a 100% crystalline PET (140 J·g−1 [24,25]), and ∅PET the weight fraction of PET
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
