Highly Durable Superhydrophobic Polymer Foams Fabricated by Extrusion and Supercritical CO2 Foaming for Selective Oil Absorption

Supercritical CO2 extrusion foaming of highly open-cell poly(lactic acid) foam with superior oil adsorption performance

Addressing marine oil spills and industrial water pollution necessitates the development of eco-efficient oil-absorbing materials. With increasing concern for the environment, there is a consensus to decrease the use of petroleum-based polymers. Herein, lightweight poly(lactic acid) (PLA) blend foams with varying thermoplastic polyurethane (TPU) content were fabricated via a solvent-free, eco-friendly supercritical carbon dioxide (scCO2) extrusion foaming technology. The incorporation of TPU significantly enhanced the crystallization rate of PLA, with the semi-crystallization time of PT30 and PT50 blends at 105 °C exhibiting a reduction of 77.2 % and 47.9 %, respectively, compared to neat PLA. The resulting foams exhibited an open-cell structure with excellent selective oil adsorption capabilities. Notably, the PT30 foam achieved a remarkable maximum expansion ratio of 36.0, while the PT50 foam attained the highest open-cell content of 96.2 %. The PT50 foam demonstrated an outstanding adsorption capacity, spanning from 4.7 to 18.8 g/g for diverse oils and solvents, with rapid adsorption kinetics, reaching 94.9 % of the equilibrium adsorption capacity for CCl4 within just 1 min. Furthermore, the PT50 foam retained 95.2 % of its adsorption capacity for CCl4 over 10 adsorption-desorption cycles. This study presents a scalable and sustainable approach for large-scale production of high-performance, bio-based foams, facilitating efficient oil-water separation.

Preparation of Open-Cell Long-Chain Branched Polypropylene Foams for Oil Absorption

This study aimed to prepare open-cell foams using a blend of long-chain branched polypropylene and polyolefin elastomer (LCBPP/POE) for the production of reusable oil absorbents. The supercritical CO2 foaming process was conducted using a two-step batch rapid depressurization method. This unique two-step foaming approach significantly expanded the temperature and pressure windows, resulting in more uniform cells with smaller sizes, ultimately leading to higher expansion ratios and an increased open cell content. The foaming process was optimized by adjusting parameters, such as the LCBPP/POE ratio, foaming temperature, and foaming pressure, reaching a maximum open cell content of 97.6% and a maximum expansion ratio of 48. The influence of polypropylene (PP) crystallization was investigated with the aid of scanning electron microscopy and differential scanning calorimetry. Furthermore, the hydrophobic and lipophilic characteristics of the LCBPP/POE open-cell foam were determined via contact angle measurements and oil/water separation tests. Oil absorption tests revealed that the blended LCBPP/POE foam has a higher oil absorption capacity than that of the pure LCBPP foam. The cyclic oil absorption tests demonstrated the outstanding ductility and recoverability of the LCBPP/POE open-cell foam in comparison to those of the pure LCBPP foam. Over 10 cycles, the LCBPP/POE foam maintained a substantial adsorption capacity, retaining 99.3% of its initial oil absorption capacity. With its notable features, including a high open cell content, excellent hydrophobic and lipophilic characteristics, superior oil absorption capacity, impressive cyclic oil absorption performance, and robust reusability, LCBPP/POE open-cell foams exhibit significant promise as potential oil adsorbents for use in oil spill cleanup applications.

Nanostructured Bioaerogels as a Potential Solution for Particulate Matter Pollution

Particulate matter (PM) pollution is a significant environmental and public health issue globally. Exposure to high levels of PM, especially fine particles, can have severe health consequences. These particles can come from a variety of sources, including natural events like dust storms and wildfires, as well as human activities such as industrial processes and transportation. Although an extensive development in air filtration techniques has been made in the past few years, fine particulate matter still poses a serios and dangerous threat to human health and to our environment. Conventional air filters are fabricated from non-biodegradable and non-ecofriendly materials which can cause further environmental pollution as a result of their excessive use. Nanostructured biopolymer aerogels have shown great promise in the field of particulate matter removal. Their unique properties, renewable nature, and potential for customization make them attractive materials for air pollution control. In the present review, we discuss the meaning, properties, and advantages of nanostructured aerogels and their potential in particulate matter removal. Particulate matter pollution, types and sources of particulate matter, health effect, environmental effect, and the challenges facing scientists in particulate matter removal are also discussed in the present review. Finally, we present the most recent advances in using nanostructured bioaerogels in the removal of different types of particulate matter and discuss the challenges that we face in these applications.

C-shaped porous polypropylene fibers for rapid oil absorption and effective on-line oil spillage monitoring

Development of efficient absorbent materials for detection and treatment of offshore oil spillages remained a challenge. In this work, C-shaped polypropylene oil-absorbent fibers with sub-micron internal pores were prepared by combining spun-bonding technique and thermally induced phase separation (TIPS). The effect of drawing speed on the phase separation and the porous morphology of the shaped fiber non-woven fabric (NWF) was investigated. C-shaped NWF with porous morphology had large water contact angle, higher porosity, larger specific surface area, and increased oil absorption speed and capacity. An online oil spillage detection system was developed using porous C-shaped NWF and an oxygen sensing probe, showing shorter response time and higher signal-to-noise (STN) ratio. The response time for detecting the spillage of soybean oil and diluted crude oil (0.5 mL/0.8 L) in water were only 24 s and 10 s, respectively. The reliable oil detection low detection limit (RLDL) of the oxygen sensing probe was reduced 173 times (from 36.5 g/L to 0.21 g/L) when combined with C-shaped porous fiber NWF.

Green fabrication of durable foam composites with asymmetric wettability by an emulsion spray-coating method for photothermally induced crude oil cleanup

Chemical spills, especially oil spills, are becoming an increasingly serious environmental issue. It remains a challenge to develop green techniques to prepare mechanically robust oil-water separation materials, especially those capable of separating high-viscosity crude oils. Herein, we propose an environmentally friendly emulsion spray-coating method to fabricate durable foam composites with asymmetric wettability for oil-water separation. After the emulsion, composed of acidified carbon nanotubes (ACNTs), polydimethylsiloxane (PDMS) and its curing agent, is sprayed onto melamine foam (MF), water in the emulsion is first evaporated, while PDMS and ACNTs are finally deposited on the foam skeleton. The foam composite exhibits gradient wettability and turns from superhydrophobicity of the top surface (the water contact angle reaches as high as 155.2°) to hydrophilicity of the interior region. The foam composite can be used for the separation of oils with different densities and has a 97% separation efficiency for chloroform. In particular, the photothermal conversion-induced temperature rise can reduce the oil viscosity and complete the high-efficiency cleanup of crude oil. This emulsion spray-coating technique and asymmetric wettability show promise for the green and low-cost fabrication of high-performance oil/water separation materials.

Versatility of the Preparation Method for Macroporous Cryogel Particles Utilizing the Inverse Leidenfrost Effect

We have investigated the versatility of a two-step preparation method, without a detergent, that combines both the inverse Leidenfrost effect and the cryogelation technique by using the macroporous particles of different kinds of monomers (four vinyl monomers) or a natural polymer (agarose). First, the precursor of polymers was dropped into liquid nitrogen to prepare the spherical frozen droplet by the inverse Leidenfrost effect. Second, the frozen droplets were cryo-polymerized at the frozen temperature; then, cryogel particles were prepared after thawing. Subsequently, the basic characteristics of the macroporous polymer particles obtained above were compared, focusing on the appearances, porous morphologies, and mechanical properties. It was found that the similar polymer particles could be obtained by the two-step preparation method, while there was a slight difference in their characteristics, depending on the type of monomers. Especially for the mechanical properties, the cryogel particles of the hydrophilic polymer exhibited a shape memory function with sponge-like elasticity, whereas the hydrophobic polymer particles were observed to be cracked after compression (i.e., no shape memory function). This work provides a versatile method of adopting various kinds of monomers and natural polymers for the preparation of macroporous particles. Hence, the method possibly has a potential to prepare and design "tailor-made" macroporous polymer particles for the application purpose.

Production and Application of Polymer Foams Employing Supercritical Carbon Dioxide

Polymeric foams have characteristics that make them attractive for different applications. However, some foaming methods rely on chemicals that are not environmentally friendly. One of the possibilities to tackle the environmental issue is to utilize supercritical carbon dioxide ScCO2 since it is a “green” solvent, thus facilitating a sustainable method of producing foams. ScCO2 is nontoxic, chemically inert, and soluble in molten plastic. It can act as a plasticizer, decreasing the viscosity of polymers according to temperature and pressure. Most foam processes can benefit from ScCO2 since the methods rely on nucleation, growth, and expansion mechanisms. Process considerations such as pretreatment, temperature, pressure, pressure drop, and diffusion time are relevant parameters for foaming. Other variables such as additives, fillers, and chain extenders also play a role in the foaming process. This review highlights the morphology, performance, and features of the foam produced with ScCO2, considering relevant aspects of replacing or introducing a novel foam. Recent findings related to foaming assisted by ScCO2 and how processing parameters influence the foam product are addressed. In addition, we discuss possible applications where foams have significant benefits. This review shows the recent progress and possibilities of ScCO2 in processing polymer foams.

Open-Celled Foams from Polyethersulfone/Poly(Ethylene Glycol) Blends Using Foam Extrusion

Polyethersulfone (PESU), as both a pristine polymer and a component of a blend, can be used to obtain highly porous foams through batch foaming. However, batch foaming is limited to a small scale and is a slow process. In our study, we used foam extrusion due to its capacity for large-scale continuous production and deployed carbon dioxide (CO₂) and water as physical foaming agents. PESU is a high-temperature thermoplastic polymer that requires processing temperatures of at least 320 °C. To lower the processing temperature and obtain foams with higher porosity, we produced PESU/poly(ethylene glycol) (PEG) blends using material penetration. In this way, without the use of organic solvents or a compounding extruder, a partially miscible PESU/PEG blend was prepared. The thermal and rheological properties of homopolymers and blends were characterized and the CO₂ sorption performance of selected blends was evaluated. By using these blends, we were able to significantly reduce the processing temperature required for the extrusion foaming process by approximately 100 °C without changing the duration of processing. This is a significant advancement that makes this process more energy-efficient and sustainable. Additionally, the effects of blend composition, nozzle temperature and foaming agent type were investigated, and we found that higher concentrations of PEG, lower nozzle temperatures, and a combination of CO₂ and water as the foaming agent delivered high porosity. The optimum blend process settings provided foams with a porosity of approximately 51% and an average foam cell diameter of 5 µm, which is the lowest yet reported for extruded polymer foams according to the literature.

A Hybrid Syntactic Foam-Based Open-Cell Foam with Reversible Actuation

Herein, we report the first hybrid open-cell foam with revisable actuation. Open-cell foams with revisable actuation are favoable for many applications. However, it is challenging to fabricate such open-cell foams with very low density. This study presents a novel concept of creating hybrid two-way (2W) shape memory open-cell foams using two-way shape-memory-polymer-based syntactic foams as the matrix. Previously, a syntactic foam prepared by incorporating hollow glass microbubbles in the cross-linked semicrystalline cis-poly(1,4-butadiene) (cPBD) was proved to have enhanced strength and specific energy output compared to the neat cPBD. Here, the same syntactic foam was used as the matrix, and the open-cell structure was produced by the salt-leaching method. The hybrid foam exhibits very attractive properties, including reversible actuation strain up to 50%, density as low as 0.07 g/cm³, energy output up to 0.23 J/g, tensile strength up to 0.84 MPa, elongation at break as high as 339%, high thermal stability with peak decomposition temperature at 450 °C, and Joule heating and strain sensing capabilities. The tensile strength and stiffness are shown to follow the well-known Gibson-Ashby model for porous materials. Combining the open-cell structure with the reversible actuation and other functionalities enables numerous potential applications for the prepared hybrid foam, including adjustable filters, insulators, sealers, and smart scaffolds.

Rigid, eco-friendly and superhydrophobic SiO2-Polyvinyl alcohol composite sponge for durable oil remediation

Development of durable and eco-friendly adsorbents for oil remediation is in great demands. However, most of adsorbents were designed to pursue large capabilities while ignored their strength after adsorbing oil, which might cause secondary oil spilling during complex salvage process. Herein, an eco-friendly and superhydrophobic SiO₂-modified polyvinyl alcohol composite (H-SiO₂-G-PVA) sponge with extraordinary rigid structure after oil adsorption is designed for durable oil remediation. Through a two-step hydrolysis-condensation process including deposition of silica microparticles and introduction of hexadecyltrimethoxysilane (HDTMS), a superhydrophobic H-SiO₂-G-PVA sponge has been successfully constructed. The sponge presents stable superhydrophobicity in various complex environments，therefore it efficiently adsorbs oil from water (up to 6 g g^-1) and separate surfactant-stabilized water/oil emulsion with high efficiency (>99%). Noticeably, the H-SiO₂-G-PVA sponge maintains tough strength (3.5 MPa) after oil adsorption, which ideally overcomes secondary oil spilling problem and endows the sponge with excellent recycling performances (>20 cycles). Meanwhile, the excellent biocompatibility of the sponge (high cell viability of 91.85%) ensures the potential for practical applications. This rigid, eco-friendly oil-adsorbing sponge that achieves stable superhydrophobicity and recyclability, fulfills the application needs for durable oil remediation.

Estimating the Dissolution of Anticancer Drugs in Supercritical Carbon Dioxide with a Stacked Machine Learning Model

Synthesizing micro-/nano-sized pharmaceutical compounds with an appropriate size distribution is a method often followed to enhance drug delivery and reduce side effects. Supercritical CO2 (carbon dioxide) is a well-known solvent utilized in the pharmaceutical synthesis process. Reliable knowledge of a drug's solubility in supercritical CO2 is necessary for feasible study, modeling, design, optimization, and control of such a process. Therefore, the current study constructs a stacked/ensemble model by combining three up-to-date machine learning tools (i.e., extra tree, gradient boosting, and random forest) to predict the solubility of twelve anticancer drugs in supercritical CO2. An experimental databank comprising 311 phase equilibrium samples was gathered from the literature and applied to design the proposed stacked model. This model estimates the solubility of anticancer drugs in supercritical CO2 as a function of solute and solvent properties and operating conditions. Several statistical indices, including average absolute relative deviation (AARD = 8.62%), mean absolute error (MAE = 2.86 × 10-6), relative absolute error (RAE = 2.42%), mean squared error (MSE = 1.26 × 10-10), and regression coefficient (R2 = 0.99809) were used to validate the performance of the constructed model. The statistical, sensitivity, and trend analyses confirmed that the suggested stacked model demonstrates excellent performance for correlating and predicting the solubility of anticancer drugs in supercritical CO2.

Emerging Separation Applications of Surface Superwettability

Human beings are facing severe global environmental problems and sustainable development problems. Effective separation technology plays an essential role in solving these challenges. In the past decades, superwettability (e.g., superhydrophobicity and underwater superoleophobicity) has succeeded in achieving oil/water separation. The mixture of oil and water is just the tip of the iceberg of the mixtures that need to be separated, so the wettability-based separation strategy should be extended to treat other kinds of liquid/liquid or liquid/gas mixtures. This review aims at generalizing the approach of the well-developed oil/water separation to separate various multiphase mixtures based on the surface superwettability. Superhydrophobic and even superoleophobic surface microstructures have liquid-repellent properties, making different liquids keep away from them. Inspired by the process of oil/water separation, liquid polymers can be separated from water by using underwater superpolymphobic materials. Meanwhile, the underwater superaerophobic and superaerophilic porous materials are successfully used to collect or remove gas bubbles in a liquid, thus achieving liquid/gas separation. We believe that the diversified wettability-based separation methods can be potentially applied in industrial manufacture, energy use, environmental protection, agricultural production, and so on.

Review on the recent development of durable superhydrophobic materials for practical applications

Biomimetic superhydrophobic surfaces show great potential in oil-water separation, anti-icing and self-cleaning. However, due to the instability caused by its fragile structure and non-durable superhydrophobicity, it is difficult to apply them in the actual field. Here, by introducing surface wettability and analysing the mechanism of superhydrophobic failure, it is concluded that the reason for the failure of the superhydrophobic surface comes from the transition of the surface energy and the hysteresis of the contact angle (CA). On the basis of this analysis, it is concluded that the principle of designing a durable superhydrophobic surface is to satisfy one of the following three points: improving the binding force between molecules, introducing durable materials and improving chemical durability. On this basis, a variety of preparation methods are proposed, such as assembly method and spray/dip coating method, and the design and preparation of a self-healing surface inspired by nature will also be included in the introduction. Last but not least, the preparation and application of a durable super-hydrophobic surface in oil-water separation, anti-icing and self-cleaning are also introduced in detail. This review reveals the conclusions and prospects of durable superhydrophobic surfaces, and aims to inspire more researchers to invest in this research.

Shape Memory Poly(β-hydroxythioether) Foams for Oil Remediation in Aquatic Environments

Shape memory poly(β-hydroxythioether) foams were produced using organobase catalyzed reactions between epoxide and thiol monomers, allowing for the rapid formation of porous media within approximately 5 min, confirmed using both rheology and physical foam blowing. The porous materials possess ultralow densities (0.022 g × cm^-3) and gel fractions of approximately 93%. Thermomechanical characterizations of the materials revealed glass transition temperatures tunable from approximately 50 to 100 °C, elastic moduli of approximately 2 kPa, and complete strain recovery upon heating of the sample above its glass transition temperature. The foams were characterized for their ability to take up oil from an aqueous multilayered ideal environment, revealing more than 2000% mass of oil (relative to the foam mass) could be collected. Importantly, while post-fabrication functionalization was possible with isocyanate chemistry followed by addition of hexadecanethiol or 3,3-bis(hexadecylthio)propan-1-ol, the oil collection efficiency of the system was not significantly enhanced, indicating that these materials, as porous media, possess unique attributes that make them appealing for environmental remediation without the need for costly modifications or manipulations.

Shish-Kebab-Structured UHMWPE Coating for Efficient and Cost-Effective Oil-Water Separation

High-performance low-cost superhydrophobic sponges are desired for selective recycling of leaking oils from open water. Herein, an ingenious method is proposed to fabricate an ultrathin superhydrophobic coating layer on a commercial sponge. The coating layer is composed of a shish-kebab-structured porous ultrahigh molecular weight polyethylene (UHMWPE) film that is fabricated from a UHMWPE/xylene solution by shear flow-induced crystallization. A strong relationship between the shish-kebab crystallite morphology and the superwetting performance is confirmed. The UHMWPE coating layer fabricated at a 900 rpm rotation rate possesses a lamellae size of 95.1 nm and a lamellae distance of 27.4 nm, which lead to a high water contact angle of 157° and a low contact angle hysteresis of 4.5°. The UHMWPE layer prepared in 4 min of treatment is thick enough to prevent the intrusion of water even under vacuum and remain superoleophilic. The developed UHMWPE-coated sponge (UCS) exhibited a high absorption capability of 70-191 g/g toward various oils and solvents, which is comparable with the neat melamine sponge. Its excellent compressibility and durability enabled fast recovery of absorbed oil with a high recovery rate (over 85%) by mechanical squeezing. The UCS could be assembled into small devices to selectively collect oil from open water and a water/oil mixture using a pump, which manifests its promising practical applicability. Apart from these extraordinary properties, the approach developed has the lowest material cost and the shortest processing time hitherto.

Asymmetric Sc-PLA Membrane with Multi-scale Microstructures: Wettability, Antifouling, and Oil-Water Separation

In this work, an eco-friendly superhydrophobic stereo-complex polylactic acid (Sc-PLA) membrane was fabricated by a facile non-solvent-induced phase separation (NIPS) method, followed by peeling off its skin layer. By adjusting the thickness and roughness, membranes with various multi-scale microstructures could be obtained due to the formation of stereo-complex crystals during the process of phase separation. The Sc-PLA membranes display a hydrophobic wetting property. Interestingly, when the skin layer of the membrane with a 600 μm thickness was peeled off, the water contact angle on the surface of the membrane significantly improved from 142 to 152°, and the membrane displayed superhydrophobic wetting properties, which may be owing to the improvement of roughness for the surface by enlarging the exposure opportunity of finger holes and microstructures. In addition, the Sc-PLA membrane with superhydrophobicity shows excellent antifouling performance and large oil absorption capacity. Predictably, the Sc-PLA membranes may have potential applications in antifouling and oil-water separation.

A Review on Revolutionary Natural Biopolymer-Based Aerogels for Antibacterial Delivery

A biopolymer-based aerogel has been developed to become one of the most potentially utilized materials in different biomedical applications. The biopolymer-based aerogel has unique physical, chemical, and mechanical properties and these properties are used in tissue engineering, biosensing, diagnostic, medical implant and drug delivery applications. Biocompatible and non-toxic biopolymers such as chitosan, cellulose and alginates have been used to deliver antibiotics, plants extract, essential oils and metallic nanoparticles. Antibacterial aerogels have been used in superficial and chronic wound healing as dressing sheets. This review critically analyses the utilization of biopolymer-based aerogels in antibacterial delivery. The analysis shows the relationship between their properties and their applications in the wound healing process. Furthermore, highlights of the potentials, challenges and proposition of the application of biopolymer-based aerogels is explored.

Reactive amphiphilic hollow SiO2 Janus nanoparticles for durable superhydrophobic coating

Durable superhydrophobic coating is attractive due to its long-term superhydrophobicity, anti-fouling and self-cleaning properties. However, the fabrication of durable superhydrophobic coatings on a fragile surface, including leather and paper, is still a challenge due to its bad resistance to harsh environments such as high temperature, high pressure and strong acid or strong base. Herein, we developed a universal way to fabricate long-lasting superhydrophobic coating on leather via amphiphilic Janus particles, which have one of the semispheres functionalized with hydrophobic 1-dodecanethiol and the other semisphere functionalized with hydrophilic β-mercaptoethylamine. Polyurethane with isocyanate end groups was sprayed on the leather surface as an intermediate layer to strongly link Janus particles with leather via cross-linking. Moreover, amphiphilic Janus particles were fabricated from hollow SiO₂ particles via a thiol-ene click reaction due to its low density. The superhydrophobic coating on leather possessed a high water contact angle of 162.2°. Furthermore, it still retained excellent hydrophobicity with a water contact angle of 154° after 140 cycles of abrasion using sandpaper. This study not only provides a novel method for the fabrication of amphiphilic hollow SiO₂ Janus nanoparticles, but also resolves the difficulties in constructing long-lived superhydrophobic coatings on fragile surfaces by existing methods. Meanwhile, the present study also suggests a potential way to translocate functional Janus microcapsules, which may give some significant suggestions on the future nanoparticle design for drug delivery and energy storage.

Rapid UV-radiation synthesis of polyacrylate cryogel oil-sorbents with adaptable structure and performance

Macro-porous poly(lauryl acrylate) cryogel sheets as oil-sorbents were prepared through UV-radiation cryo-polymerizations in 1, 4-dioxane at low temperatures (-5, -2 and 0 °C) within 30 min. The influences of total monomer concentration, crosslinking monomer amount and polymerization temperature on the formation of cryogels were studied. The chemical structure and porous morphology were characterized through the techniques of Fourier transform infrared spectroscopy, thermal gravimetric analysis, contact angle measurement and scanning electron microscopy, confirming the features of high hydrophobicity, macro-porosity and good thermal stability. As well, the comparison between conventional gels prepared at room temperature and cryogels at lower temperatures was made, showing the higher rate of cryo-polymerization than conventional polymerization under the same UV-radiation condition. The swelling investigation was carried out with several organic solvents and oils. Enhanced performance of oil absorption was observed for those cryogels considering the absorption capacity and absorption rate. Variation of initiator amount and acrylate monomers could also modulate the absorption capacity. Those cryogel oil-sorbents exhibited wide adaptability, good reusability and high-temperature tolerance. Thus, this rapid and low-cost fabrication opens out a novel pathway to prepare efficient oil-sorbents used in waste water treatment.

Fabrication of hierarchically porous superhydrophilic polycaprolactone monolith based on nonsolvent-thermally induced phase separation

Monoliths with a continuous porous structure are of great interest due to high transfer efficiency and large surface area in environmental and tissue engineering fields. This study demonstrated a facile method to prepare PCL monoliths with hierarchically porous structure by nonsolvent-thermally induced phase separation. A suitable mixed solvent mixture using ethanol as nonsolvent reduced the amount of dioxane and provided PCL monoliths with three levels of structures. The monolith structure was easily controlled by changing the fabrication parameters, such as the nonsolvent, the temperature of phase separation, the concentration of the PCL. Finally, the superhydrophilic monolith was easily obtained by polydopamine surface modification. The easy way of fabrication of a hierarchically porous PCL monolith with superhydrophilicity will find applications such as in tissue engineering and purification.

Improving the Continuous Microcellular Extrusion Foaming Ability with Supercritical CO2 of Thermoplastic Polyether Ester Elastomer through In-Situ Fibrillation of Polytetrafluoroethylene

In-situ fibrillated polytetrafluoroethylene (PTFE) enhanced nanocomposites were successfully prepared by mixing thermoplastic polyether ester elastomer (TPEE) and PTFE using a twin-screw extruder. Well-dispersed, long aspect ratio PTFE nanofibrils with a diameter of less than 200 nm were generated and interwoven into networks. Differential scanning calorimetry and in-situ polarized optical microscopy showed that the PTFE nanofibrils can greatly accelerate and promote crystallization of the TPEE matrix and the crystallization temperature can be increased by 6 °C. Both shearing and elongational rheometry results confirmed that the introduction of PTFE nanofibrils can significantly improve the rheological properties. The remarkable changes in the strain-hardening effect and the melt viscoelastic response, as well as the promoted crystallization, led to substantially improved foaming behavior in the continuous extrusion process using supercritical CO2 as the blowing agent. The existing PTFE nanofibrils dramatically decreased the cell diameter and increased cell density, together with a higher expansion ratio and more uniform cell structure. The sample with 5% PTFE fibrils showed the best foaming ability, with an average diameter of 10.4-14.7 μm, an expansion ratio of 9.5-12.3 and a cell density of 6.6 × 107-8.6 × 107 cells/cm3.

Macroporous Oil-Sorbents with a High Absorption Capacity and High-Temperature Tolerance Prepared through Cryo-Polymerization

The facile preparation and admirable performance of macro-porous poly(lauryl acrylate)-based oil-sorbents for organic solvents and oils are reported in this manuscript. Cryo-polymerizations of lauryl acrylate (LA) with ethylene glycol dimethacrylate (EGDMA) as the cross-linker were carried out at temperatures below the freezing point of the polymerization mixture. The polymerization medium and pore-forming agent was 1,4-dioxane. The influences of the total monomer concentration, EGDMA content and cryo-polymerization temperature on the structure of the obtained P(LA-co-EGDMA) cryogels were investigated with the techniques of Fourier transform infrared spectroscopy, scanning electron microscopy, contact angle measurement and thermo-gravimetric analysis. Through the modulation of the crosslinking density and porosity of these cryogels, the P(LA-co-EGDMA) oil-sorbents demonstrated a high absorption capacity for organic solvents and oils, recyclability and high-temperature tolerance. The absorption capacity reached 20-21 and 16-17 g/g for toluene and gasoline oil, respectively. Those fabricated sorbents survived high temperatures up to 150 °C without any change in absorption capacity as well as porosity. Considering the convenient synthesis process and absorption performance, the present work offers a remarkable opportunity to bring polymer cryogels to practical application in waste oil clean-up.

Preparation of compressible polymer monoliths that contain mesopores capable of rapid oil–water separation

A bottom-up design enables the preparation of a mesoporous, compressible, polymer monolith that shows rapid separation of oil–water mixture.