TY - JOUR
T1 - Macromolecular Insights into the Altered Mechanical Deformation Mechanisms of Non-Polyolefin Contaminated Polyolefins
AU - Demets, R.
AU - Grodent, M.
AU - Van Kets, K.
AU - De Meester, S.
AU - Ragaert, K.
N1 - Funding Information:
Funding: This research was supported by the DPI project #832 ‘Quality Model for Contaminated Recycled Polyolefins’ (QCORP). We also thank the Interreg 2 Seas program PlastiCity, which is co-funded by the European Regional Development Fund under subsidy contract no. 2S05-021 and the province of East Flanders.
Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2022/1/7
Y1 - 2022/1/7
N2 - Current recycling technologies rarely achieve 100% pure plastic fractions from a single polymer type. Often, sorted bales marked as containing a single polymer type in fact contain small amounts of other polymers as contaminants. Inevitably, this will affect the properties of the recycled plastic. This work focuses on understanding the changes in tensile deformation mechanism and the related mechanical properties of the four dominant types of polyolefin (PO) (linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP)), contaminated with three different non-polyolefin (NPO) polymers (polyamide-6 (PA-6), polyethylene terephthalate (PET), and polystyrene (PS)). Under the locally elevated stress state induced by the NPO phase, the weak interfacial adhesion typically provokes decohesion. The resulting microvoids, in turn, initiate shear yielding of the PO matrix. LLDPE, due to the linear structure and intercrystalline links, is well able to maintain high ductility when contaminated. LDPE shows deformation similar to the pure material, but with decreasing ductility as the amount of NPO increases. Addition of 20 wt% PA-6, PET, and PS causes a drop in strain at break of 79%, 63%, and 84%, respectively. The typical ductile necking of the high-crystalline HDPE and PP is strongly disturbed by the NPO phase, with a transition even to full brittle failure at high NPO concentration.
AB - Current recycling technologies rarely achieve 100% pure plastic fractions from a single polymer type. Often, sorted bales marked as containing a single polymer type in fact contain small amounts of other polymers as contaminants. Inevitably, this will affect the properties of the recycled plastic. This work focuses on understanding the changes in tensile deformation mechanism and the related mechanical properties of the four dominant types of polyolefin (PO) (linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP)), contaminated with three different non-polyolefin (NPO) polymers (polyamide-6 (PA-6), polyethylene terephthalate (PET), and polystyrene (PS)). Under the locally elevated stress state induced by the NPO phase, the weak interfacial adhesion typically provokes decohesion. The resulting microvoids, in turn, initiate shear yielding of the PO matrix. LLDPE, due to the linear structure and intercrystalline links, is well able to maintain high ductility when contaminated. LDPE shows deformation similar to the pure material, but with decreasing ductility as the amount of NPO increases. Addition of 20 wt% PA-6, PET, and PS causes a drop in strain at break of 79%, 63%, and 84%, respectively. The typical ductile necking of the high-crystalline HDPE and PP is strongly disturbed by the NPO phase, with a transition even to full brittle failure at high NPO concentration.
KW - immiscible polymer blends
KW - polyolefins
KW - deformation mechanisms
KW - commodity plastics
KW - mechanical recycling
KW - structure-property relationships
KW - IMMISCIBLE POLYMER BLENDS
KW - DOUBLE YIELD POINTS
KW - TENSILE DEFORMATION
KW - DISPERSED-PHASE
KW - MORPHOLOGY DEVELOPMENT
KW - MOLECULAR TOPOLOGY
KW - CRITICAL STRAINS
KW - PARTICLE-SIZE
KW - POLYETHYLENE
KW - BEHAVIOR
U2 - 10.3390/polym14020239
DO - 10.3390/polym14020239
M3 - Article
C2 - 35054644
SN - 2073-4360
VL - 14
JO - Polymers
JF - Polymers
IS - 2
M1 - 239
ER -