Sustainable Polymer & Energy Open Access

Recent Progress in Modification and Preparations of the Promising Biodegradable Plastics: Polylactide and Poly(butylene adipate-co-terephthalate)

The acquisition of high-performance biodegradable plastics is of great significance in addressing the problem of environmental pollution of plastics. Polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are the most promising biodegradable polymers and have excellent functional properties. However, low elongation at break and impact strength of PLA and low tensile modulus and flexural strength of PBAT hinder their application. A large number of studies focus on improving the performance of PLA and PBAT and broadening their applications. In terms of polymer modification, this paper summarized recent progresses in both chemical and physical modification methods for PLA and PBAT, respectively. The properties of PLA can be improved by co-polymerization, grafting, cross-linking and blending. The properties of PBAT can be improved mainly through blending with other degradable polymers, natural macromolecules and inorganic materials. This review can provide the reference and ideas for the modification of biomass-based biodegradable plastics like PLA and fossil-based biodegradable plastics like PBAT.

Ultra-thin Solid Electrolyte in Lithium-ion Batteries

Safety concern of lithium-ion battery, attributed to using volatile and flammable liquid electrolytes, could be addressed by using solid electrolytes. Solid electrolytes including inorganic solid electrolytes, polymer solid electrolytes and organic/inorganic composite electrolytes have the common drawbacks in low ion-conductivity. Much efforts have been devoted to increase the specific ion conductivity, especially for inorganic solid electrolyte whose intrinsic conductivity are close to liquid electrolyte. However, most solid-state electrolyte membranes in lithium-ion batteries are thick, resulting in long ion-conduction pathway, low energy density and high cost. In this review, the advantages and disadvantages of different kinds of solid electrolytes were analyzed, and the promising strategies of ultra-thin solid electrolyte preparation are summarized and prospected. Applying organic-inorganic composite, continuous phase enhancement and in situ integration have been devoted to reduce thickness of electrolyte membrane and improve battery performance. On the basis of the technical requirement of lithium-ion batteries, this review aims to provide a guidance in terms of rational design and synthesis of ultra-thin solid electrolytes for further research that addresses the safety issues and improves cycling performance of batteries.

Metal-Free Lewis Pair Catalysts for a One-Pot Terpolymerization of Propylene Oxide, ʟ-Lactide and CO₂

Multiblock and di-/tri-block copolymers are successfully synthesized for the first time via the metal-free terpolymerization of propylene oxide (PO), ʟ-lactide (LA) and CO₂ in one-pot/one-step and one-pot/two-step protocols respectively. Firstly, triethyl borane (TEB) and bis(triphenylphosphine)iminium chloride (PPNCl) Lewis pair is employed in the ring-opening polymerization of LA, wherein the catalytic efficiency is significantly correlated to the TEB/PPNCl feed ratio. Next, a series of TEB/base pairs are selected to synthesize the PO/LA/CO₂ terpolymer (PPCLA) in one-pot/one-step strategy. In PPCLA synthesis, LA exhibits the fastest reaction rate but the severe transesterification is almost unavoidable, resulting in low molecular weight products. In order to prepare high-molecular-weight terpolymers, a one-pot/two-step methodology has to be applied. By this method, the copolymerization of PO/CO₂ proceeds first to form poly(propylene carbonate) (PPC) macroinitiators, which triggers the polymerization of LA to polylactide (PLA), leading to PLA-PPC or PLA-PPC-PLA block copolymers. The synthesized PLA-PPC-PLA block copolymers display an improved thermal stability compared with PPC.

Green Composites Using Naturally Occurring Fibers: A Comprehensive Review

Depletion of non-renewable resources and health hazards of petroleum-based polymers and plastics has enforced the development of eco-friendly materials. The use of conventional plastics has to be minimized and can be replaced with environmentally friendly and sustainable bio-based polymers or biopolymers due to extensive environmental impact. A major share of petroleum-based polymers is used for polymeric composites with research focus on green composites and biocomposites containing renewable/bioderived matrix polymer and fillers from naturally occurring fibers. Biocomposites hold great promise to replace petroleum-based polymer composites owing to their lower cost, non-toxicity, abundance of raw material, renewability, and high specific strength. All these merits of biocomposites have led to an increment in the development of new biocomposites with enhanced properties, wide applicability and ever demanding criteria. The recently published review studies detailed the raw materials used, fabrication techniques, characterization, and applications including biodegradation and rheological studies performed in recent years. This review covers all the important properties of biocomposites along with detailed description of synthesis, properties, characterizations and applicability of these green composites in several areas. The review also focuses on their raw materials, types, recent biocomposites, processing techniques, characterizations, applications, and current challenges with future aspects.

Waterborne Polyurethane Dispersion Synthesized from CO₂ Based Poly (Ethylene Carbonate) Diol with High Performance

CO₂-based aliphatic polycarbonates (APCs) are not widely commercialized due to the poor performance and high cost, compared to the traditional synthetic materials. In this paper, poly(ethylene carbonate) diol (PECD) was synthesized from CO₂ and ethylene oxide (EO), and the comprehensive properties were characterized. Furthermore, the preparation and properties of waterborne polyurethane dispersion (WPU) derived from PECD were studied. The result showed that PECD had high reactivity, narrow molecular weight distribution index and excellent thermal stability. The obtained WPU exhibited superior tensile performance, adhesion properties and surface hardness. Due to the low cost of EO and CO₂, PECD is expected to be widely used in the preparation of polyurethanes.

Sustainable Polymer & Energy: A New Open-Access Journal to Share Your Research on Sustainable Polymer and Advanced Energy Materials

Review on Multi-Functional Separator for Li-S Batteries

Because lithium-ion batteries are not able to meet increasing demand for capacity density and power density, lithium metal batteries are given great expectations as the next generation of rechargeable batteries. As one of lithium metal batteries, lithium-sulfur (Li-S) batteries have attracted extensive attention because of their ultrahigh capacity density (1675 mAh g⁻¹) and low cost of sulfur. In order to overcome problems of active material attenuation, dendritic growth and volume expansion caused by the shuttle effect in Li-S batteries, researchers have adopted several methods such as adding electrolyte additives, electrode modification and separator modification. Among them, separator modification shows significant advantages in inhibiting the shuttle effect of lithium polysulfides. This paper reviews research progress of inhibiting the shuttle effect of Li-S batteries by separator modification in recent years, including direct design of new type separator and physical/chemical modification of separator surface. Through extensive reading and summarizing research results of separator modification of Li-S batteries, we give the possible development direction of Li-S batteries at the end of the paper.

Transparent, Hydrolysable and Flame Retarded Bio-based Epoxy Resins via Catalyst-free Polymerization of Triglycidyl Isocyanurate and Aliphatic Diacids

In this study, transparent and hydrolysable intrinsic flame retarded epoxy resins were synthesized successfully by melting polymerization without any catalyst, simply from bio-based triglycidyl isocyanurate and aliphatic diacids. Due to the possibility of transesterification along with the ring-opening reaction, the most suitable feed ratio of [COOH]/[epoxy] is found to be 60%. By changing the carbon number of diacid from 8 to 12, ER08-60, ER10-60 and ER12-60 were synthesized. The flame retardancy of ER08-60 is found to be excellent, with a UL-94 rating at V-0 and a LOI value at 27.6%. It is revealed from this study that upon heating isocyanurate ring decomposes first and CO₂ released prevents the contact of materials with oxygen, thus preventing further combustion. The tensile strength and bending strength of ER08-60 can reach 86.6 MPa and 75.4 MPa, respectively. Additionally, all epoxy resins are able to hydrolyze quickly in both acid and alkaline solutions. It is worth to mention that these epoxy resins are transparent, with a transmittance of around 85%.

Anion Exchange Membrane Reinforced with Polyethylene Substrate for Alkaline Fuel Cell Applications

To enhance mechanical robustness of our in-house anion exchange membrane (QPAF-4), the reinforcement technique was applied using ozone-treated, porous polyethylene (PE) thin film (Toray SETELA) as a substrate. Homogenous and flexible reinforced membranes (QPAF-4-PE, 15–20 µm thick) were obtained by bar-coating method. The cross-sectional SEM image and EDS analysis revealed triple-layered (sandwich-like) structure without detectable pinholes. The QPAF-4-PE with ion exchange capacity (IEC) of 1.48 meq·g⁻¹ exhibited lower water uptake (15 wt% at 90% relative humidity) and slightly lower hydroxide ion conductivity (71 mS·cm⁻¹ at 80 ℃) than those of the pristine QPAF-4 (IEC = 1.84 meq·g⁻¹, 25 wt% water uptake and 82 mS·cm⁻¹ of the conductivity). The reinforced QPAF-4-PE exhibited slightly higher viscoelasticity (particularly, in MD direction) due to the suppressed water absorbability. Furthermore, the elongation at break increased by 9.8% in TD direction and 6.3% in MD direction. An H₂/O₂ fuel cell using QPAF-4-PE as membrane was investigated at different back-pressure, in which the cell with 100 kPa back-pressure onto the cathode side only achieved the maximum performance (176 mW·cm−2 at current density of 364 mA·cm⁻²) and the longest durability for (>200 h) at a constant current density of 100 mA·cm⁻² maintaining 0.43 V of the cell voltage (67% remaining). The durability was eight times longer than that with ambient pressure and two times longer than that with back-pressure on both sides.

Creating Shape Memory Polymers from Biobased Resources

Developing polymer materials from biomass is a promising pathway to address serious environmental and resource issues. To date, a series of biobased general polymer materials have been successfully industrialized. However, exploring highly valuable functional polymers and intelligent polymer materials from biomass, such as shape memory polymers (SMPs) and self-healing materials, is still a great challenge. The present review intends to bridge a sustainable pathway for the creation of SMPs from biobased resources. Thus, we first recall some backgrounds of the design principle of SMPs and highlight the biobased monomers or building blocks for SMPs, and then we focus on the main varieties of biobased SMPs to clarify their fabricating approaches, functionalizing strategies, new manufacturing methods and the application potential.

Metal-Free Lewis Pair Catalysts for a One-Pot Terpolymerization of Propylene Oxide, ʟ-Lactide and CO₂

Multiblock and di-/tri-block copolymers are successfully synthesized for the first time via the metal-free terpolymerization of propylene oxide (PO), ʟ-lactide (LA) and CO₂ in one-pot/one-step and one-pot/two-step protocols respectively. Firstly, triethyl borane (TEB) and bis(triphenylphosphine)iminium chloride (PPNCl) Lewis pair is employed in the ring-opening polymerization of LA, wherein the catalytic efficiency is significantly correlated to the TEB/PPNCl feed ratio. Next, a series of TEB/base pairs are selected to synthesize the PO/LA/CO₂ terpolymer (PPCLA) in one-pot/one-step strategy. In PPCLA synthesis, LA exhibits the fastest reaction rate but the severe transesterification is almost unavoidable, resulting in low molecular weight products. In order to prepare high-molecular-weight terpolymers, a one-pot/two-step methodology has to be applied. By this method, the copolymerization of PO/CO₂ proceeds first to form poly(propylene carbonate) (PPC) macroinitiators, which triggers the polymerization of LA to polylactide (PLA), leading to PLA-PPC or PLA-PPC-PLA block copolymers. The synthesized PLA-PPC-PLA block copolymers display an improved thermal stability compared with PPC.utf-8

Recent Progress in Modification and Preparations of the Promising Biodegradable Plastics: Polylactide and Poly(butylene adipate-co-terephthalate)

The acquisition of high-performance biodegradable plastics is of great significance in addressing the problem of environmental pollution of plastics. Polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are the most promising biodegradable polymers and have excellent functional properties. However, low elongation at break and impact strength of PLA and low tensile modulus and flexural strength of PBAT hinder their application. A large number of studies focus on improving the performance of PLA and PBAT and broadening their applications. In terms of polymer modification, this paper summarized recent progresses in both chemical and physical modification methods for PLA and PBAT, respectively. The properties of PLA can be improved by co-polymerization, grafting, cross-linking and blending. The properties of PBAT can be improved mainly through blending with other degradable polymers, natural macromolecules and inorganic materials. This review can provide the reference and ideas for the modification of biomass-based biodegradable plastics like PLA and fossil-based biodegradable plastics like PBAT.utf-8

Sustainable Polymer & Energy: A New Open-Access Journal to Share Your Research on Sustainable Polymer and Advanced Energy Materials

Waterborne Polyurethane Dispersion Synthesized from CO₂ Based Poly (Ethylene Carbonate) Diol with High Performance

CO₂-based aliphatic polycarbonates (APCs) are not widely commercialized due to the poor performance and high cost, compared to the traditional synthetic materials. In this paper, poly(ethylene carbonate) diol (PECD) was synthesized from CO₂ and ethylene oxide (EO), and the comprehensive properties were characterized. Furthermore, the preparation and properties of waterborne polyurethane dispersion (WPU) derived from PECD were studied. The result showed that PECD had high reactivity, narrow molecular weight distribution index and excellent thermal stability. The obtained WPU exhibited superior tensile performance, adhesion properties and surface hardness. Due to the low cost of EO and CO₂, PECD is expected to be widely used in the preparation of polyurethanes.utf-8

Review on Multi-Functional Separator for Li-S Batteries

Because lithium-ion batteries are not able to meet increasing demand for capacity density and power density, lithium metal batteries are given great expectations as the next generation of rechargeable batteries. As one of lithium metal batteries, lithium-sulfur (Li-S) batteries have attracted extensive attention because of their ultrahigh capacity density (1675 mAh g⁻¹) and low cost of sulfur. In order to overcome problems of active material attenuation, dendritic growth and volume expansion caused by the shuttle effect in Li-S batteries, researchers have adopted several methods such as adding electrolyte additives, electrode modification and separator modification. Among them, separator modification shows significant advantages in inhibiting the shuttle effect of lithium polysulfides. This paper reviews research progress of inhibiting the shuttle effect of Li-S batteries by separator modification in recent years, including direct design of new type separator and physical/chemical modification of separator surface. Through extensive reading and summarizing research results of separator modification of Li-S batteries, we give the possible development direction of Li-S batteries at the end of the paper.utf-8

Ultra-thin Solid Electrolyte in Lithium-ion Batteries

Safety concern of lithium-ion battery, attributed to using volatile and flammable liquid electrolytes, could be addressed by using solid electrolytes. Solid electrolytes including inorganic solid electrolytes, polymer solid electrolytes and organic/inorganic composite electrolytes have the common drawbacks in low ion-conductivity. Much efforts have been devoted to increase the specific ion conductivity, especially for inorganic solid electrolyte whose intrinsic conductivity are close to liquid electrolyte. However, most solid-state electrolyte membranes in lithium-ion batteries are thick, resulting in long ion-conduction pathway, low energy density and high cost. In this review, the advantages and disadvantages of different kinds of solid electrolytes were analyzed, and the promising strategies of ultra-thin solid electrolyte preparation are summarized and prospected. Applying organic-inorganic composite, continuous phase enhancement and in situ integration have been devoted to reduce thickness of electrolyte membrane and improve battery performance. On the basis of the technical requirement of lithium-ion batteries, this review aims to provide a guidance in terms of rational design and synthesis of ultra-thin solid electrolytes for further research that addresses the safety issues and improves cycling performance of batteries.utf-8

Green Composites Using Naturally Occurring Fibers: A Comprehensive Review

Depletion of non-renewable resources and health hazards of petroleum-based polymers and plastics has enforced the development of eco-friendly materials. The use of conventional plastics has to be minimized and can be replaced with environmentally friendly and sustainable bio-based polymers or biopolymers due to extensive environmental impact. A major share of petroleum-based polymers is used for polymeric composites with research focus on green composites and biocomposites containing renewable/bioderived matrix polymer and fillers from naturally occurring fibers. Biocomposites hold great promise to replace petroleum-based polymer composites owing to their lower cost, non-toxicity, abundance of raw material, renewability, and high specific strength. All these merits of biocomposites have led to an increment in the development of new biocomposites with enhanced properties, wide applicability and ever demanding criteria. The recently published review studies detailed the raw materials used, fabrication techniques, characterization, and applications including biodegradation and rheological studies performed in recent years. This review covers all the important properties of biocomposites along with detailed description of synthesis, properties, characterizations and applicability of these green composites in several areas. The review also focuses on their raw materials, types, recent biocomposites, processing techniques, characterizations, applications, and current challenges with future aspects.utf-8

Transparent, Hydrolysable and Flame Retarded Bio-based Epoxy Resins via Catalyst-free Polymerization of Triglycidyl Isocyanurate and Aliphatic Diacids

In this study, transparent and hydrolysable intrinsic flame retarded epoxy resins were synthesized successfully by melting polymerization without any catalyst, simply from bio-based triglycidyl isocyanurate and aliphatic diacids. Due to the possibility of transesterification along with the ring-opening reaction, the most suitable feed ratio of [COOH]/[epoxy] is found to be 60%. By changing the carbon number of diacid from 8 to 12, ER08-60, ER10-60 and ER12-60 were synthesized. The flame retardancy of ER08-60 is found to be excellent, with a UL-94 rating at V-0 and a LOI value at 27.6%. It is revealed from this study that upon heating isocyanurate ring decomposes first and CO₂ released prevents the contact of materials with oxygen, thus preventing further combustion. The tensile strength and bending strength of ER08-60 can reach 86.6 MPa and 75.4 MPa, respectively. Additionally, all epoxy resins are able to hydrolyze quickly in both acid and alkaline solutions. It is worth to mention that these epoxy resins are transparent, with a transmittance of around 85%.utf-8

A High-efficiency Cathode Using Co₃O₄ and Carbon Paper by Electrodeposition for Rechargeable Lithium-oxygen Batteries

The conductivity, microstructure, low cost, eco-friendliness, simple and controllable preparation are key points of the preparation and application of cathode materials for lithium-oxygen batteries. Considering the above-mentioned important factors comprehensively, the Co₃O₄@CP electrode with a three-dimensional structure was prepared by directly growing Co₃O₄ on the surface of carbon paper (CP) using a simple and controllable electrodeposition method. The obtained Co₃O₄ depositing layer has a nanosheet microstructure and can provide abundant catalytic active sites for the oxygen evolution and reduction reactions. The network architecture of electronic transmission is constructed by CP in the cathode, promoting the efficiency of the electrode reaction. It’s worth noting that the binder-free and conductive additive-free cathode is beneficial to reduce side reactions. The lithium-oxygen battery assembled with the obtained Co₃O₄@CP electrode showed satisfactory electrochemical performance. The cell assembled with the obtained Co₃O₄@CP electrode provided a discharge specific capacity of 10954.7 mA·h·g⁻¹ at a current density of 200 mA·g⁻¹, and the voltage profiles of the cell were good under 100 mA·g⁻¹ at a limited capacity of 500 mA·h g⁻¹ based on the mass of Co₃O₄. Therefore, the Co₃O₄@CP composite material is a promising candidate with good application prospects as a cathode material for lithium-oxygen batteries.utf-8

Creating Shape Memory Polymers from Biobased Resources

Developing polymer materials from biomass is a promising pathway to address serious environmental and resource issues. To date, a series of biobased general polymer materials have been successfully industrialized. However, exploring highly valuable functional polymers and intelligent polymer materials from biomass, such as shape memory polymers (SMPs) and self-healing materials, is still a great challenge. The present review intends to bridge a sustainable pathway for the creation of SMPs from biobased resources. Thus, we first recall some backgrounds of the design principle of SMPs and highlight the biobased monomers or building blocks for SMPs, and then we focus on the main varieties of biobased SMPs to clarify their fabricating approaches, functionalizing strategies, new manufacturing methods and the application potential.utf-8