The goal of this paper was to establish a metric, which we refer to as the resilience parameter, to evaluate the ability of a material to retain tensile strength after damage recovery for shape memory polymer (SMP) systems. In this work, three SMP blends created for the additive manufacturing process of fused filament fabrication (FFF) were characterized. The three polymer systems examined in this study were 50/50 by weight binary blends of the following constituents: (1) polylactic acid (PLA) and maleated styrene-ethylene-butylene-styrene (SEBS-g-MA); (2) acrylonitrile butadiene styrene (ABS) and SEBS-g-MA); and (3) PLA and thermoplastic polyurethane (TPU). The blends were melt compounded and specimens were fabricated by way of FFF and injection molding (IM). The effect of shape memory recovery from varying amounts of initial tensile deformation on the mechanical properties of each blend, in both additively manufactured and injection molded forms, was characterized in terms of the change in tensile strength vs. the amount of deformation the specimens recovered from. The findings of this research indicated a sensitivity to manufacturing method for the PLA/TPU blend, which showed an increase in strength with increasing deformation recovery for the injection molded samples, which indicates this blend had excellent resilience. The ABS/SEBS blend showed no change in strength with the amount of deformation recovery, indicating that this blend had good resilience. The PLA/SEBS showed a decrease in strength with an increasing amount of initial deformation, indicating that this blend had poor resilience. The premise behind the development of this parameter is to promote and aid the notion that increased use of shape memory and self-healing polymers could be a strategy for mitigating plastic waste in the environment.
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Bypassing energy barriers in fiber-polymer torrefaction
The amount of waste generation has been increasing with a significant amount being
landfilled. These non-recyclable wastes contain large number of fiber and plastic wastes
which can be treated with thermal processes to turn them into energy sources since they
have high calorific values, are abundant and usually tipping fees are paid to handle them.
This paper studied the torrefaction of non-recyclable paper (fiber) wastes, mixed plastic
wastes (MPW) and their blends at different ratios in the temperature range of 250–400°C
through thermogravimetric analysis (TGA). The solid residues after the experiments were
analyzed by nuclear magnetic resonance (NMR) spectroscopy. Significant synergy
between fiber and MPW were observed at the range 250–300°C, showing both
increase in the reaction rate as well as the overall mass loss. At 250°C, the maximum
mass loss rate was more than two times higher and the mass loss at the end of the
experiments were also much higher compared to the expected results. In addition, synergy
was weakened with an increase of temperature, disappearing at 400°C. The existence of
such interactions between fiber and plastic wastes indicates that the natural energy
barriers during the individual torrefaction in paper waste or plastic waste could be
bypassed, and the torrefaction of fiber and plastic blend can be achieved at lower
temperatures and/or shorter residence times. The MPW and fiber wastes were also
compounded by extrusion (to produce pellets) at 220°C with different blend ratios. The
fiber-MPW pellets from extrusion were characterized by IR spectroscopy, rheology,
thermal analysis and flexural properties and showed significant chemical changes from
the non-extruded blends at the same ratios. From IR characterization, it was found that
there was significant increase in hydroxyl (OH) group on account of the carbonyl (C O)
and etheric (C-O-C) groups. The interaction between paper and MPW can be attributed to
the plastic polymers acting as a hydrogen donor during the reactive extrusion process.
Synergistic effects were also found from mechanical and rheological properties.
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- Award ID(s):
- 1827364
- NSF-PAR ID:
- 10280504
- Date Published:
- Journal Name:
- Frontiers in energy research
- Volume:
- 9
- ISSN:
- 2296-598X
- Page Range / eLocation ID:
- 643371
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Polymer compatibilization plays a critical role in achieving polymer blends with favorable mechanical properties and enabling efficient recycling of mixed plastic wastes. Nonetheless, traditional compatibilization methods often require tailored designs based on the specific chemical compositions of the blends. In this study, we propose a new approach for compatibilizing polymer blends using a dynamically crosslinked polymer network, known as vitrimers. By adding a relatively small amount (1–5 w/w%) of a vitrimer made of siloxane‐crosslinked high‐density polyethylene (HDPE), we successfully compatibilized unmodified HDPE and isotactic polypropylene (iPP). The vitrimer‐compatibilized blend exhibited enhanced elongation at break (120 %) and smaller iPP domain sizes (0.4 μm) compared to the control blend (22 % elongation at break, 0.9 μm iPP droplet size). Moreover, the vitrimer‐compatibilized blend showed significantly improved microphase stability during annealing at 180 °C. This straightforward method shows promise for applications across various polymer blend systems.
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Abstract Polymer compatibilization plays a critical role in achieving polymer blends with favorable mechanical properties and enabling efficient recycling of mixed plastic wastes. Nonetheless, traditional compatibilization methods often require tailored designs based on the specific chemical compositions of the blends. In this study, we propose a new approach for compatibilizing polymer blends using a dynamically crosslinked polymer network, known as vitrimers. By adding a relatively small amount (1–5 w/w%) of a vitrimer made of siloxane‐crosslinked high‐density polyethylene (HDPE), we successfully compatibilized unmodified HDPE and isotactic polypropylene (iPP). The vitrimer‐compatibilized blend exhibited enhanced elongation at break (120 %) and smaller iPP domain sizes (0.4 μm) compared to the control blend (22 % elongation at break, 0.9 μm iPP droplet size). Moreover, the vitrimer‐compatibilized blend showed significantly improved microphase stability during annealing at 180 °C. This straightforward method shows promise for applications across various polymer blend systems.
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Polymer blend compatibilization is an attractive solution for mechanical recycling of mixed plastic waste because it can result in tough blends. In this work, hydroxy-telechelic polyethylene (HOPEOH) reactive additives were used to compatibilize blends of polyethylene terephthalate (PET) and linear low-density polyethylene (LLDPE). HOPEOH additives were synthesized with molar masses of 1–20 kg/mol by ring-opening metathesis polymerization of cyclooctene followed by catalytic hydrogenation. Melt-compounded blends containing 0.5 wt % HOPEOH displayed reduced dispersed phase LLDPE particle sizes with ductilities comparable to virgin PET and almost seven times greater than neat blends, regardless of additive molar mass. In contrast, analogous blends containing monohydroxy PE additives of comparable molar masses did not result in compatibilization even at 2 wt % loading. The results strongly suggest that both hydroxy ends of HOPEOH undergo transesterification reactions during melt mixing with PET to form predominantly PET–PE–PET triblock copolymers at the interface of the dispersed and matrix phases. We hypothesize that the triblock copolymer compatibilizers localized at the interface form trapped entanglements of the PE midblocks with nearby LLDPE homopolymer chains by a hook-and-clasp mechanism. Finally, HOPEOH compounds were able to efficiently compatibilize blends derived solely from postconsumer PET and PE bottles and film, suggesting their industrial applicability.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi: 10.3389/fenrg.2021.643371
