Vapor-induced Phase Separation Method Research Articles

Preparation of thermoplastic polyurethane blend foams with controlled hydrophobicity via vapor induced phase separation

AbstractOil–water separation has attained great attention due to recent concern in environmental safety. Porous material from tailored engineering is the best candidate to selectively adsorb oil from water. Among the various porous materials, polymer based adsorbent has several advantages over others, in terms of controllable porosity and functionality. Here, we propose thermoplastic polyurethane (TPU) based blend foam through vapor induced phase separation method as a potential candidate for oil–water separation. In order to adjust hydrophobicity and compatibility of TPU blend, PDMS‐based TPU (Si‐TPU) is designed and synthesized to be blended with commercialized TPU. Si‐TPU with tailored weight ratio (PDMS/PTHF = 4/6) in synthetic level make it possible to achieve both of demanded hydrophobicity (the water contact angle increased from 85.19 ± 1.83° to 121.15 ± 3.79° after adding Si‐TPU) and controlling compatibility with CTPU during VIPS foaming. Thus, these well‐designed Si‐TPU can be utilized in various fields such as improving compatibility of polymer blend, adsorption efficiency of oil, and smart filtration, and so forth.

A facile fabrication of acid-proof membranes with superhydrophobic high adhesion in air

superhydrophobic surfaces with superhigh adhesion is significant in special engineering applications, but an elaborate superhydrophobic structure is difficult at artificial fabrication. In this study, a poly[2,2′-(4,4′-oxybis(1,4-phenylene)− 5,5′-bibenzimidazoles]-polydimethylsiloxane (OPBI-PDMS) membrane is prepared via a facile vapor-induced phase separation method, which exhibits high contact angle of 154.1°, high water adhesion and high acidic resistance for 200 h. The results indicate that the sponge-like hierarchical structure formed on the sticky surface of OPBI-PDMS membrane, which offers high hydrophobic property and high adhesion in air, based on the capillary action and pinning effect. Coupled with the high acid-proof performance, the OPBI-PDMS blending membrane is successfully applied in the controllable transferring of acid droplets.

Low-energy-consumption fabrication of porous TPU/graphene composites for high-performance microwave absorption and the influence of Fe3O4 incorporation

Fabrication of lightweight, thin thickness, broad bandwidth, strong absorption, and lower filler loading materials are of great interest for microwave absorption. Herein, porous thermoplastic polyurethane (TPU) /graphene composites were successfully prepared via a facile vapor induced phase separation (VIPS) technique. Compared with TPU foam, the introduction of graphene endows the composites favorable microwave absorption ability. The optimized composite foam with 3 wt% graphene (TPU/G-3) exhibits extraordinary wave attenuation capacity with a minimum reflection loss (RL min ) value of − 51.86 dB and effective absorption bandwidth (EAB) of 4.28 dB (12.6–17.0 GHz) at the thickness of 3.1 mm. Microwave attenuation mechanism indicates that the remarkable microwave absorption ability derives from conduction loss, dipole polarization loss, interfacial polarization loss as well as multiple scattering. Incorporating the same amount of Fe 3 O 4 as graphene to TPU/G-3 endows the composites with the RL min of − 58.96 dB, which is slightly better than TPU/G-3 due to more favorable impedance matching. However, the matching thickness becomes much higher to about 8.0 mm, which is mainly attributed to bigger pores caused by Fe 3 O 4 . Moreover, the VIPS strategy provides insight into the fabrication of facile and lightweight polymer-based porous electromagnetic absorption materials. • Vapor induced phase separation method for preparation of TPU-based porous composites. • Graphene facilitates heterogeneous nucleation for smaller pores than TPU foam. • Graphene content of 3 wt% endows composite favorable microwave absorbing performance. • Fe 3 O 4 influences the process of vapor induced phase separation with bigger pores. • Fe 3 O 4 improves the reflection loss but increases matching thickness due to big pores.

Tailoring Morphology of PVDF-HFP Membrane via One-step Reactive Vapor Induced Phase Separation for Efficient Oil-Water Separation

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) receives increasing attention in membrane separation field based on its advantages such as high mechanical strength, thermal and chemical stability. However, controlling the microporous structure is still challenging. In this work, we attempted to tailor the morphology of PVDF-HFP membrane via a one-step reactive vapor induced phase separation method. Namely, PVDF-HFP was dissolved in a volatile solvent and then was cast in an ammonia water vapor atmosphere. After complete evaporation of solvent, membranes with adjustable porous structure were prepared, and the microstructures of the membranes were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction characterizations. Based on the results, a mechanism of dehydrofluorination induced cross-linking of PVDF-HFP has been suggested to understand the morphology tailoring. To our knowledge, this is the first report of one-step reactive vapor induced phase separation strategy to tailor morphology of PVDF-HFP membrane. In addition, the membranes prepared in the ammonia water vapor exhibited enhanced mechanical strength and achieved satisfactory separation efficiency for water-in-oil emulsions, suggesting promising potential.

Tuning the Pore Structure of Poly(vinylidene fluoride) Membrane for Efficient Oil/Water Separation: A Novel Vapor-Induced Phase Separation Method Based on a Lower Critical Solution Temperature System

The conventional vapor-induced phase separation (VIPS) method for membrane fabrication faces practical challenges related to the long contact time to gaseous nonsolvent and complexity in pore struc...

Holey, anti-impact and resilient thermoplastic urethane/carbon nanotubes fabricated by a low-cost “vapor induced phase separation” strategy for the detection of human motions

It is a great challenge to develop a scalable and cost-effective strategy for fabricating porous polymer-based piezoresistive devices. Here we presented a sort of conductive porous thermoplastic urethane (TPU) composites incorporated with carbon nanotubes by a vapor-induced phase separation method. By the introduction of carbon nanotubes (CNTs), the TPU composite exhibits moderate electric conductivity and improved compressive property. TPU composites are demonstrated to be highly sensitive sensors for monitoring both compression and bending strain. The value of ΔR/R0 changed from 90.0 to 98.7% while the gauge factor varied from 1.98 to 9. Further study on the dynamic mechanical performances indicates the produced TPU composites are strain-rate sensitive and the addition of CNTs can improve the anti-impact performances of TPU foam. The strategy adopted to fabricate TPU/CNT composite will pave the way for the development of low-cost and wearable sensors in practical applications of health monitor and sports.

Studies on thermal degradation kinetics and dielectric properties of polyether imide foam/nanosilica-based nanocomposites

ABSTRACTIn this paper, polyether imide (PEI) having properties such as a high glass transition temperature of 216°C, high heat resistance, high flame resistance, low smoke generation and a high melting point within the range of 400°C, having low thermal conductivity and low dielectric constant was chosen to be a polymeric foam. Water vapor-induced phase separation method was used to prepare PEI foams. PEI foams were reinforced with nano-silica (weight 1, 3 and 5%) in order to alter the dielectric properties, thermal conductivity and degradation kinetics of foamed polymer. The tested samples showed a reduction in dielectric constant than that of solid PEI but at a higher loading, it showed a higher value due to threshold percolation and a reduction in thermal conductivity was observed for foamed PEI. From thermogravimetric analysis, we can conclude that PEI with 3% filler loading showed better thermal stability compared to other PEI foam compositions.

Biophotonic Films: Biomimetic Polymer Film with Brilliant Brightness Using a One‐Step Water Vapor–Induced Phase Separation Method (Adv. Funct. Mater. 23/2019)

Biophotonic Films: Biomimetic Polymer Film with Brilliant Brightness Using a One‐Step Water Vapor–Induced Phase Separation Method (Adv. Funct. Mater. 23/2019)

Biomimetic Polymer Film with Brilliant Brightness Using a One‐Step Water Vapor–Induced Phase Separation Method

AbstractThe scales of the white Cyphochilus beetles are endowed with unusual whiteness arising from the exceptional scattering efficiency of their disordered ultrastructure optimized through millions of years of evolution. Here, a simple, one‐step method based on water vapor–induced phase separation is developed to prepare thin polystyrene films with similar microstructure and comparable optical performance. A typical biomimetic 3.5 µm PS film exhibits a diffuse reflectance of 61% at 500 nm wavelength, which translates into a transport mean free path below 1 µm. A complete optical characterization through Monte Carlo simulations reveals how such a scattering performance arises from the scattering coefficient and scattering anisotropy, whose interplay provides insight into the morphological properties of the material. The potential of bright‐white coatings as smart sensors or wearable devices is highlighted using a treated 3.5 µm film as a real‐time sensor for human exhalation.

Octadecylsilyl-bonded silica based novel solid phase extraction membranes

Octadecylsilyl-bonded silica based novel solid phase extraction membranes were fabricated by non-solvent vapor induced phase separation method for the first time, and employed for extraction trace phenol as a model. The effects of membrane fabrication conditions and extraction parameters on the recoveries were explored. Under the optimized fabrication conditions, the extraction recovery of phenol (0.02 mg/L, 100 mL) attains 100% with enrichment factor of 10. The spike recovery of real water samples reaches 97.67%–99.40% with standard deviation of 1.16%–1.42%, demonstrating great potential in solid phase extraction.

Few-layer graphene sheets/poly(vinylidene fluoride) composites prepared by a water vapor induced phase separation method

Few-layer graphene sheets/poly(vinylidene fluoride) (FGS/PVDF) composites were prepared by a water vapor induced phase separation (WVIPS) method. The composites were investigated by SEM, TEM, FTIR, Raman, XRD, TG, analysis. The analytical results showed that the FGS were uniformly distributed in the PVDF forming continuous network structure in the PVDF matrix, as a direct result of the WVIPS method. The introduction of FGS was found to endow the PVDF with satisfactory electrical conductivity and good electromagnetic interference shielding effectiveness (EMI SE). The composites with 15 wt% FGS content exhibited an electrical conductivity of 1.68 S cm−1. In addition, the same composites showed the excellent EMI SE in the X-band frequency region (high as 45.6 dB at 10 GHz). The proposed preparation process was found to be an easy, convenient and efficient synthetic route to prepare FGS/PVDF composites, that prove useful in the preparation of similar FGS/polymer composites.

The effects of processing conditions on the surface morphology and hydrophobicity of polyvinylidene fluoride membranes prepared via vapor-induced phase separation

The present investigation reveals how the surface morphology and the hydrophobicity of polyvinylidene fluoride (PVDF) membranes, which were prepared via a vapor-induced phase separation method, were affected by the initial PVDF content in the casting solution and the air temperature. The surface morphology was characterized with scanning electron microscopy. A ternary phase diagram of PVDF/N, N-dimethylacetamide/water was constructed to explain the formation mechanism of the different morphologies. The results show that different membrane morphologies and hydrophobicities can be obtained by changing the processing conditions. Low air temperature and high PVDF contents facilitate the crystallization process, resulting in the formation of a porous skin and particle morphology, which increases the hydrophobicity of the surface. High air temperature and low PVDF contents are favorable for the formation of a net-like surface morphology via spinodal decomposition and lead to a superhydrophobic surface. Theoretical calculations were performed to testify that the net-like surface was more favorable for superhydrophobicity than the particle-based surface.

Biopolymers-based nanocomposites: Membranes from propionated lignin and cellulose for water purification

Nanocomposite membranes for water treatment were prepared by vapor-induced phase separation method from propionated lignin and cellulose triacetate (CTA). Three kinds of lignin were used: Kraft, Organosolv and Hydrolytic, which were propionated for improving their compatibility with CTA. Such chemical lignin modification was analyzed by FTIR, UV spectrophotometry and GPC. Morphology (through FE-SEM and AFM), mechanical properties (DMA), and surface potential (SPKM) were investigated for all membranes obtained. For determining membrane performance, groundwater from Chihuahua (Mexico) containing high concentrations of fluoride, arsenic, calcium, sodium and magnesium, was filtrated. Membrane rejection was 15–35% for anions present, and 12–42% and 27–54% for monovalent and divalent cations, respectively. Arsenic and fluoride removal by membranes was found to be affected by ionic and organic matter present in groundwater.