Abstract
Antioxidant-rich agro-wastes such as grape pomace waste (GW), turmeric shavings and waste, coffee grounds, and orange peel waste are used as-received for the first time as thermo-oxidative stabilizers for polymer. Relative to neat low density polyethylene (LDPE), a well-dispersed hybrid made by solid-state shear pulverization with 4 wt % GW results in 62 and 44 °C increases in temperatures corresponding to 10 and 20% mass loss in air (T10% and T20%), respectively. Such enhancements are superior to those obtained by adding 1 wt % synthetic antioxidant Irganox I1010 to LDPE by melt mixing. Relative to neat LDPE, hybrids with well-dispersed agro-waste exhibit enhanced Young's modulus, equal or enhanced tensile strength, and relatively small reduction in elongation at break. Reprocessing or recycling sometimes leads to enhanced antioxidant activity: relative to a hybrid before melt extrusion, 92/8 wt% LDPE/TW exhibits major increases in T10% and T20% after two and six melt extrusion passes, which is consistent with formation of transformation products with improved antioxidant activity during multiple high-temperature reprocessing cycles. Natural antioxidants are effective in suppressing LDPE chain scission and branching. After ten extrusion passes, neat LDPE exhibits a 16% increase in zero-shear viscosity and reduction in elongation at break from 500% to 280%, whereas hybrids with agro-waste have zero-shear viscosity and elongation at break values close to those of unprocessed hybrids. Isothermal shear flow measurements also show the effectiveness of natural antioxidant in stabilizing LDPE: hybrids exhibit no sign of chain branching during 3000 s of melt flow at 200 °C whereas neat LDPE branches after ∼500 s.
Original language | English (US) |
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Pages (from-to) | 881-889 |
Number of pages | 9 |
Journal | ACS Sustainable Chemistry and Engineering |
Volume | 4 |
Issue number | 3 |
DOIs | |
State | Published - Mar 7 2016 |
Keywords
- Extrusion
- Mechanical properties
- Polymer degradation
- Solid-state shear pulverization
- Thermoxidative stability
ASJC Scopus subject areas
- General Chemistry
- Environmental Chemistry
- General Chemical Engineering
- Renewable Energy, Sustainability and the Environment