Decapsulation constitutes the critical initial phase in the recycling of waste photovoltaic (PV) laminated modules. Wet decapsulation has emerged as a prominent research focus. However, the underlying removal mechanisms of ethylene-vinyl acetate (EVA) encapsulants remain insufficiently characterized, and the optimal solvent has not been selected. This article introduces a green alternative solvent terpinolene to decapsulate waste PV laminated modules. The decapsulation parameters were optimized. The waste PV laminated modules could be completely decapsulated under the identified optimal conditions: 2 cm × 2 cm specimens treated with 90 wt% terpinolene solvent under 800 W ultrasound agitation for 55 min. This study reveals the decapsulation mechanism: the ultrasonic field caused the water and terpinolene to produce O· and groups containing methylene radicals. The free radicals approached the directional C-C and C-O bonds in the bridging structure and the directional C-C bonds in the backbones of EVA and oxidized them to make them interrupt and to be grafted. EVA molecules were broken into multiple and smaller organic molecules, resulting in a swelling effect and loss of viscosity, thus prompting the laminated modules to decapsulate. We report for the first time the use of the green solvent terpinolene coupled to ultrasonic efficiently decapsulating waste photovoltaic laminated modules. And this study pioneers the discovery of the infinite swelling induced by terpinolene-mediated radical reactions in PV EVA encapsulants. It provides scientific information and key technologies for the decapsulating of waste PV laminated modules, the recycling of materials and the closed-loop development of PV industry.
Developing a simple and efficient heterogeneous catalyst for the cycloaddition of epoxides with CO2 under atmospheric pressure and cocatalyst-/metal-/solvent-free conditions remains a great challenge. Herein, poly(ionic liquid)s (P-[VRIm]Br-crosslinker-x) with unique adsorption-swelling ability toward epoxides are designed and facilely synthesized via free radical polymerization in water. The adsorption-swelling of epoxides by P-[VRIm]Br-crosslinker-x is controllable, reversible, and widespread, resulting from the strong interactions between the poly(ionic liquid)s and epoxide molecules, especially the hydrogen-bonding interaction. Superior CO2 cycloaddition is realized in the P-[VRIm]Br-crosslinker-x catalyst through the adsorption-swelling effect. Specifically, P-[VC6Im]Br-C8-5% with 54.1 mmol g−1 adsorption-swelling ability toward styrene oxide achieves 89.3% yield and >99% selectivity in the cycloaddition of styrene oxide with CO2 to styrene carbonate under mild conditions (1 atm, 80 °C) without cocatalyst/metal/solvent consumption. Moreover, P-[VC6Im]Br-C8-5% can be easily recovered by deswelling, and shows good reusability and stability after five cycles for a total of 180 h. The adsorption-swelling property of P-[VRIm]Br-crosslinker-x to epoxides not only prompts the active centers to be fully exposed to the reactants but also induces the enrichment of epoxides during the whole catalytic process, thus accelerating the CO2 cycloaddition reaction rate. This work furnishes new insights for improving the activity of CO2 cycloaddition and would guide the design of efficient poly(ionic liquid) catalysts for atmospheric CO2 conversion.
Tao Xiang,Jiao Wang,Lianghao Jia,Pan Wang,Shaobing Zhou
Two-way shape-memory polymers (2W-SMPs) have gained much attention due to their great potential in smart actuators, soft robotics, and artificial muscles. However, the application of 2W-SMPs is always limited by the complex fabrication process and strict triggering conditions. In this work, we propose that water-triggered 2W-SMPs can be facilely fabricated by one-step free radical polymerization of vinyl-ended 6-arm poly(ethylene glycol)-poly(ε-caprolactone) and vinyl-ended Pluronic F127. The crosslinked networks show a programmable and reversible water-triggered two-way shape-memory effect (2W-SME) based on two independent crystalline domains, with the highest angle reversibility of 45.2%. Due to the asymmetrical swelling induced by the asymmetrical cross-section chemical structure formed in the fabrication process, spontaneous bending behavior is observed, further enhancing the 2W-SME. In addition, the networks with 60% Pluronic F127 can be applied as a soft gripper and water level monitor, which exhibits programmable deformation. Therefore, a convenient and effective strategy is proposed to fabricate 2W-SMPs, which can be extended to other polymers to obtain water-triggered 2W-SMPs.
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