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The pseudo 3D hierarchical structure mimicking in vivo microenvironment was prepared by phase separation on tissue culture plastic. For surface treatment, time-sequenced dosing of the solvent mixture with various concentrations of polymer component was used. The experiments showed that hierarchically structured surfaces with macro, meso and micro pores can be prepared with multi-step phase separation processes. Changes in polystyrene surface topography were characterized by atomic force microscopy, scanning electron microscopy and contact profilometry. The cell proliferation and changes in cell morphology were tested on the prepared structured surfaces. Four types of cell lines were used for the determination of impact of the 3D architecture on the cell behavior, namely the mouse embryonic fibroblast, human lung carcinoma, primary human keratinocyte and mouse embryonic stem cells. The increase of proliferation of embryonic stem cells and mouse fibroblasts was the most remarkable. Moreover, the embryonic stem cells express different morphology when cultured on the structured surface. The acquired findings expand the current state of knowledge in the field of cell behavior on structured surfaces and bring new technological procedures leading to their preparation without the use of problematic temporary templates or additives.

Emulsion-templated highly porous polymers (polyHIPEs), containing distinct regions differing in composition, morphology, and/or properties, are prepared by the simultaneous polymerization of two high internal phase emulsions (HIPEs) contained within the same mould. The HIPEs are placed together in the mould and subjected to thiol-acrylate photopolymerization. The resulting polyHIPE material is found to contain two distinct semicircular regions, reflecting the composition of each HIPE. The original interface between the two emulsions becomes a copolymerized band between 100 and 300 μm wide, which is found to be mechanically robust. The separate polyHIPE layers are distinguished from one another by their differing average void diameter, chemical composition, and extent of contraction upon drying., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mesostructured cellular foam (MCF) silica spheres with different textual parameters were synthesized using a triblock copolymer as a template. The effects of acid concentration and aging time on the window size and morphology were discussed. Besides, the adsorption performances of lysozyme and bovine serum albumin on the blank MCF with different window size and aminopropyl-modified MCFs were studied. The adsorption capacity and rates were shown to be dependent on the window size and surface chemical properties of the adsorbents. In particular, the MCF with window size of 15.2 nm showed fast adsorption for lysozyme with an adsorption capacity of 500 mg/g in 10 min. Furthermore, it has been shown that MCF spheres are potential materials in the separation of biomolecules because of their chemical tunable surface and molecular sieve properties., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In line with the ongoing advancement of high-performance materials that are multifunctional and environmentally friendly, this paper provides an overview of recent developments in lightweight and ultra-lightweight multifunctional materials. We primarily examine the various types of low-density multifunctional materials, their production techniques, and their applications within the context of a sustainable future. From a structural point of view, ultra-light materials are classified into three main groups: aerogels, foam, and micro/ nanolattice. In terms of composition, they can be derived from ceramic, metallic, or polymeric materials. This overview pays particular attention to silica, carbon and composite aerogels, as well as metal, ceramic (carbon), and polymer foams. [ABSTRACT FROM AUTHOR]

The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials. [ABSTRACT FROM AUTHOR]

To further the computational design of polymer foaming, this work investigated the interactions between polymer and nucleating agents by evaluating the removal forces needed to remove the polymer from the nucleating agent using molecular dynamics simulations. Silica nanoparticles modified with different organic groups and different surface modification ratios represented model nucleating agents and poly methyl methacrylate (PMMA), a model polymer. Modified organic groups with a certain length and flexibility grafted sparsely on the silica surface, creating a "savanna‐like" structure, increased the interaction between PMMA and the silica nanoparticle. The simulation results predicted the effects of the modified organic group and surface modification ratio R of the silica nanoparticle seen in actual batch foaming experiments using CO2 and PMMA with modified silica nanoparticles. Cell size shows a minimum and cell nucleation density a maximum in the foamed polymer under certain conditions, which correlate with the simulation results for the interactions between the polymer and nucleating agent. Based on the correspondence between the simulation and the experimental results, the effectiveness of such simulations for the design of nucleation agents appeared promising. Highlights: Computational design of nucleating agents for microcellular foams.Evaluation of the interaction of polymers with various nucleating agents.Large interactions due to the "savanna‐like" structure of nucleating agents.Demonstration of polymer foaming with designed nucleating agents. [ABSTRACT FROM AUTHOR]

Polymeric foam applications have rapidly increased over the years and most of them are submitted to cyclic loading conditions. Therefore, their fatigue behavior is highly important to ensure safe operation for which limited information is available compared to compact materials like asphalt, concrete, and metals. Starting with an understanding of the main parameters controlling the mechanical properties of polymer foams, this literature review further presents a broad overview of the information available to understand the relations between loading conditions and fatigue lifetime, including damage level development. The review is composed into three main classes of polymers: thermoplastics, thermosets, and elastomers. The effect of loading conditions, including stress/strain amplitude, loading ratio (R, r), frequency (f), moisture content, type of deformation and temperature (T) is presented and discussed. Finally, the effect of foam morphology in terms of cell size (d) and density (ρ) on the fatigue performance is included to make a link between Paris' law and crack propagation. A conclusion is also provided with openings for future development. [ABSTRACT FROM AUTHOR]

This article reviews the main developments associated with density graded polymer composite foams. After a short introduction, a discussion is made on both density graded polymer-based composites and foams separately to better understand the challenges when both structures are combined together to produce composite foams. In all cases, the basic concepts, fabrication methods, main properties and general applications are presented. Opening for future works are also presented to conclude. [ABSTRACT FROM AUTHOR]

In the presented work, the influence of two flame retardants—ammonium polyphosphates and 2,4,6-triamino-1,3,5-triazine on the polyurethane foam (PUR) systems were studied. In this paper, these interactive properties are studied by using the thermal analytical techniques, TGA and DTA, which enable the various thermal transitions and associated volatilization to be studied and enable the connection of the results with thermal and mechanical analysis, as are thermal conductivities, compression and bending behavior, hardness, flammability, and surface morphology. In this way, a greater understanding of what the addition of fire retardants to polyurethane foams means for system flammability itself and, on the other hand, how this addition affects the mechanical properties of PUR may be investigated. It was obtained that retardants significantly increase the fire resistance of the PURs systems while they do not affect the thermal conductivity and only slightly decrease the mechanical properties of the systems. Therefore, the presented systems seem to be applicable as thermal insulation where low heat conductivity coupled with high flame resistance is required. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvesters (PEHs) have the potential to power low‐power electronic devices and can advance, self‐powered, autonomous electronics to the next level. Conventional ceramic‐based piezoelectrics have various properties such as fragility, rigidity, toxicity, high density, and lack of design flexibility which limit their use in more flexible environments. A ton of research has been carried out and published on novel piezomaterials, their transduction mechanisms, analytical models, and electrical circuits to improve various aspects of PEHs. Among these materials, studies on polymeric cellular (or foamed) ferroelectrets or piezoelectrets as PEHs have grown significantly since their discovery. Also, very limited or short reviews are available covering only few aspects. There is a necessity of recognizing their past and present advances in their various generation technology and polymer systems. Herein, a broader review of almost all conventional and recent polymeric foam‐based piezoelectrics for PEH applications is summarized. These cellular polymer piezoelectric systems either in bulk, composite, layered, or film form can be fabricated, and depending on the application and conditions, different polymers groups, mainly, polyolefins, polyester, fluoropolymer, and others, are considered. Their applications and future perspectives are also presented and discussed.

Background/Aim. Vinegar is one of the main international traditional nutraceuticals, and it has been used as a vaginal health protectant due to vagina pH balance maintenance and antimicrobial properties. Since the main form of vinegar is liquid, it is difficult to apply vaginally due to its short retention. The aim of this study was to design a vaginal mucoadhesive gel made of vinegar. Methods. Xanthan gum and tragacanth were utilized as natural gel-forming polymers. The effects of xanthan gum and tragacanth on mucoadhesion strength and drug release of the gel formulations were optimized using a 3 level (32) factorial design. Several physicochemical properties of the gel formulations, including gel viscosity, lubricity, scanning electron microscopy (SEM) images of hydrogel chains, and chain release kinetic, were also investigated. Results. It was found that tragacanth possessed a statistically significant effect on release rate control (p-value = 0.0027), while both tragacanth and xanthan gum had a significant effect (p-value = 0.0001 and 0.0017, respectively) on mucoadhesion property. Formulation F7 with 5% xanthan gum and 1% tragacanth (mucoadhesion = 0.4632 N and release rate = 88.8% in 6 hours) considered as the optimum formulation with some modifications. Conclusion. Xanthan gum and tragacanth can be considered as appropriate natural polymers for vaginal drug delivery. [ABSTRACT FROM AUTHOR]

Open‐cell foams are foams with porous, interconnected cellular structure. This unique structure has given open‐cell foams the versatility to be used in different types of applications including acoustics, filtration, membranes, and bioscaffolds. Conventional open‐cell polymer foams comprise mainly thermosetting and/or crosslinked materials; such materials are difficult to process and have limited end‐product recyclability. This article presents a commercially viable molding process to fabricate open‐cell foams using noncrosslinked thermoplastic polypropylene (PP). Highly open‐cell and/or reticulated structures at an open‐cell content of 84% are attained. The strategies employed in molding of PP foam with high open‐cell degree include: 1) use of mold‐opening method to achieve high void fractions; 2) reduction of cell‐wall thickness through increasing the cell densities via controlled crystallization; and 3) use of low viscosity or low melt‐strength polymer resins to promote cell‐wall opening. The molding process proposed may be extended to other semicrystalline thermoplastic materials for fabricating recyclable open‐cell foams. [ABSTRACT FROM AUTHOR]

Foamed plastics are increasingly employed due to the high demand in functional materials with reduced weight. Bead foams in general offer low weight and excellent thermal insulation properties combined with extremely high freedom in design. Though foams show increased risk of ignition and heightened heat release, literature on burning behavior is rather limited. Therefore, this study investigates density‐dependent burning behavior of commercial bead foams like expanded polypropylene (EPP) and expanded modified polyphenyleneether (E‐mPPE) by cone calorimetry. The results are compared to existing studies on the density‐dependent burning behavior of different foams, mainly expanded polystyrene and foamed polyurethane. The importance of density as a characteristic is highlighted by the linear dependence of total heat emission on density for all investigated polymers, making a prediction of thermal loads possible. The peak heat release rate of flame‐retarded EPP and E‐mPPE was found not to be dependent on density, indicating an increased homogeneity by addition of flame retardant. [ABSTRACT FROM AUTHOR]

Solid particles have been well known to stabilize foams/bubbles by adsorption at gas–liquid interfaces. Synthetic polymer particles are a particularly attractive stabilizer for the foams/bubbles, because their sizes, shapes, surface/bulk chemistries, hydrophilicity-hydrophobicity balance and softness can be tailored and modified by heterogeneous polymerization techniques, (co)polymerizations of functional monomers, polymer reactions and polymer processing. Additionally, a wide range of stimulus-responsive characteristics and film-forming nature of the polymer particles could inspire the design of functional and well-defined particle-stabilized foams/bubbles and materials based on them. This short review overviews aqueous foams/bubbles stabilized solely with synthetic polymer particles and material chemistry based on them, followed by discussions on research directions for the future. [Display omitted] • Polymer particles as a particulate stabilizer for foams/bubbles. • Effects of particle characteristics on formability, stability and structure of foams/bubbles: • Stimulus-responsive polymer particles as a foam/bubble stabilizer. • Material chemistry based on foams/bubbles stabilized with polymer particles. • Future research directions of foams/bubbles stabilized with polymer particles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon-polymer synergy: Key for diverse applications. • Enhanced properties: Mechanical, thermal, electrical. • Industry applications: Biomed, aerospace, autos, energy. • Future prospects: Breakthroughs, research directions. • Overcoming obstacles: Advancing carbon composites. Carbon-integrated polymer composites and foams have garnered significant attention in recent years due to their unique properties and wide-ranging applications. This review paper aims to comprehensively analyse the synthesis methods, characteristics, and utilization of these materials. It examines diverse strategies for incorporating carbon-based additives into polymer matrices, elucidating the resultant enhancements in mechanical, thermal, electrical, and barrier properties. Moreover, the review investigates the myriad applications of carbon-integrated polymer composites and foams in industries such as biomedical engineering, aerospace, automotive, and energy storage. Additionally, it offers insights into prospective breakthroughs and research directions, shedding light on future opportunities and challenges within this field. By synthesizing existing knowledge and identifying avenues for further exploration, this review contributes to advancing the understanding and development of carbon-integrated polymer composites and foams, addressing critical needs in contemporary industrial and technological contexts. [ABSTRACT FROM AUTHOR]

MXene/polymer composites are attractive materials and find extensive use in many applications, such as energy storage, electromagnetic interference (EMI) shielding, membranes, catalysis, sensors, and biomedicine. The major challenge to fabricate MXene/polymer composites are the processing conditions and poor control over the distribution of the MXene nanosheets within the polymer matrix. Traditional ways involve the direct mix of fillers and polymers to form a random homogeneous composite, which leads to inefficient use of fillers. To address these challenges, researchers have focused on the development of ordered MXene/polymer composite structures using various fabrication strategies. In this review, we summarize recent advances of structured MXene/polymer composites and their processing-structure-property relationships. Two main forms of MXene/polymer composites (films and foams) are separately discussed with a focus on the detailed fabrication means and corresponding structures. These architected composites complement those in which MXenes nanosheets are isotropically dispersed throughout, such as those formed by aqueous solution mixing approaches. This review culminates in a perspective on the future opportunities for architected MXene/polymer composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymer foams are used in everyday life for industrial and household applications. However, the time‐releasing ammonia is environmentally harmful that becomes attractive. Here, we introduce a technically advanced synthetic process for the polyvinyl chloride (PVC) foam, in which the emission of ammonia gas is significantly reduced by using the polymeric acids. The PVC foam has processed with azodicarbonamide (ADCA) as a chemical blowing agent after the solid type polymeric acid is mixed as supporting agent. While the characteristic properties such as specific gravity (density) and chromaticity of PVC foams are not critically changed, the reduction of time‐releasing ammonia is up to 85% compared to the PVC foam without polymeric acid. This is attributed to the cell structure with small sub‐cells and lots of connecting channels and the chemically capturing ammonia of polymeric acids. [ABSTRACT FROM AUTHOR]

Introducing electrical conductive function to discharge local piezoelectric effect is found effective for improving airborne sound absorption performance. In this work, instead of conductive fillers, a composite with two piezoelectric materials with opposite piezoelectric responses was explored aiming at enhanced sound absorption effect. Open‐cell poly(vinylidene fluoride)/(K0.5Na0.5)NbO3 (PVDF/KNN)‐nanofiber composite foams were proposed and investigated for airborne sound absorption purpose. Structural and thermal analyses showed that the KNN nanofibers were well dispersed in the PVDF matrix and enhanced the degree of crystallinity of polar phase of PVDF. Significantly enhanced airborne sound absorption over a broad frequency range was observed in the PVDF/KNN‐nanofiber composite foams, with increasing KNN nanofibers. One possible mechanism for the improved sound absorption with the piezoelectric KNN nanofibers with positive piezoelectric coefficient added in the PVDF matrix with negative piezoelectric coefficient is that electrical discharge could be facilitated for energy dissipation with the opposite charges generated through the piezoelectric effects in the two phases with opposite polarity. The experimental results show that the open‐cell PVDF/KNN‐nanofiber composite foams are promising for broadband airborne sound absorption application, and our analysis shed a light on the strategy in designing piezoelectric composite foam with high sound absorption performance. [ABSTRACT FROM AUTHOR]

Highly porous polymer-derived SiCN(O) and SiOC ceramics with low thermal conductivity were developed by replicating polyurethane (PU) foams. The PU templates were impregnated with polysilazane or polysiloxane precursor, followed by pyrolysis at different temperatures (1200 °C - 1500 °C) yielding SiCN(O) or SiOC ceramic foams, respectively. The swelling and cross-linking behavior of the used precursors had a significant impact on the morphology of the prepared foams. The samples had bulk densities ranging from 0.03 g.cm-3 to 0.56 g.cm-3 and a total porosity in the range from 75 to 98 vol%. Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) were employed to follow the structural evolution together with morphological characterization by scanning electron microscopy (SEM). The obtained ceramics were thermally stable up to 1400 °C, and the linear thermal expansion coefficient values of the porous SiCN(O) and SiOC components in the temperature range from 30 to 850 °C were found to be ~1.72 x 10-6.K-1 and ~1.93 x 10-6.K-1, respectively. Thermal conductivity (λ) as low as 0.03 W.m-1 K-1 was measured for the SiCN(O) and SiOC foams at room temperature (RT). The λ of the ceramic struts were also assessed by using the Gibson-Ashby model and estimated to be 2.1 W.m-1 K-1 for SiCN(O), and 1.8 W.m-1 K-1 for SiOC. [ABSTRACT FROM AUTHOR]

Introduction: Percutaneous pedicle screw (PPS) can provide internal fixation of the thoracolumbar spine through a minimally invasive surgical procedure. PPS fixation has been widely used to treat various spinal diseases. Rigid fixation of PPS is essential for managing osteoporotic spine in order to prevent the risks of screw loosening and implant failure. We recently developed a novel augmentation method using hydroxyapatite (HA) granules for PPS fixation. The aim of this study was to evaluate the strength and stiffness of PPS fixation augmented with HA granules using an osteoporotic bone model. Methods: Screws were inserted into uniform synthetic bone (sawbones) with and without augmentation. The uniaxial pullout strength and insertion torque of the screws were evaluated. In addition, each screw underwent cyclic toggling under incrementally increasing physiological loads until 2 mm of screwhead displacement occurred. The maximal pullout strength (N), maximal insertion torque (N·cm), number of toggle cycles and maximal load (N) required to achieve 2-mm screwhead displacement were compared between the screws with and without augmentation. Results: The maximal pullout strength was significantly stronger for screws with augmentation than for those without augmentation (302 ± 19 N vs. 254 ± 17 N, p < 0.05). In addition, the maximal insertion torque was significantly increased in screws with augmentation compared to those without augmentation (48 ± 4 N·cm vs. 26 ± 5 N·cm, p < 0.05). Furthermore, the number of toggle cycles and the maximal load required to reach 2 mm of displacement were significantly greater in screws with augmentation than in those without augmentation (106 ± 9 vs. 52 ± 10 cycles; 152 ± 4 N vs. 124 ± 5 N, p < 0.05). Conclusions: Augmentation using HA granules significantly enhanced the rigidity of PPS fixation in the osteoporotic bone model. The present study suggested that novel augmentation with HA granules may be a useful technique for PPS fixation in patients with osteoporotic spine. [ABSTRACT FROM AUTHOR]

Developing a robust biofilm is a prerequisite for a biotrickling filter to obtain the good performance in removing volatile organic compounds (VOCs). But the biofilm formation can be seriously disturbed under intermittent loading condition due to carbon starvation stress in idle time. In this study, a biotrickling filter, with its packing materials being modified by 3% sodium alginate and 5% polyvinyl alcohol (v/v = 1:3), was employed to treat intermittent VOCs. Results showed that the removal efficiencies of toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene was significantly enhanced in the BTF compared to the control one. Under relatively lower inlet loading, nearly complete removal of the five pollutants was achieved. A quantitative analysis showed that the concentration of total organic compound (TOC) in the leachate maintained at a high level, and had a strongly positive correlation with the divergence of microbial communities. The capacity of biofilm formation in the BTF was approximately four-fold higher than the control BTF, while the quantity of EPS secreted was more than ten-fold. EPS comprised largely of protein, and to less extent, polysaccharide. The biofilm formed on the modified packing materials maintained higher levels of microbial diversity and stability, even when modifiers were complete depleted or the VOCs inlet loading was increased. This study highlights the importance of packing materials for reducing the gap in performance between laboratory and industrial applications of BTFs. [ABSTRACT FROM AUTHOR]

A simple method was used to prepare microcellular foams of poly(lactic acid) (PLA) and its nanocomposites to improve its shortcomings such as low impact resistance and high cost. The batch foaming process of pure PLA and PLA filled with Nano calcium carbonate (NCC) was conducted using supercritical nitrogen (N2) as a blowing agent. The effect of NCC on crystallization of PLA is discussed as a remarkable parameter in foaming of semicrystalline polymers. Differential scanning calorimetry (DSC) was used to optimize the process temperature. The effect of foaming conditions (temperature, pressure, and cooling rate) and nanoparticle content on the foam microstructure of PLA and its nanocomposites were investigated using scanning electron microscopy (SEM). Foams were obtained in the range of macro‐ and microscale (different cell sizes) using different foaming conditions. The results revealed that nanoparticles show excellent nucleation performance on PLA foaming. Results of dynamic mechanical thermal analysis (DMTA) also showed significant influences of NCC on foamed and prefoamed samples to different foaming structures. [ABSTRACT FROM AUTHOR]

Poly(ethylene oxide)‐grafted multiwall carbon nanotubes (PEO‐graft‐MWCNT) were successfully prepared by a ring‐opening polymerization of ethylene oxide. Thermogravimetric analysis results indicated that the amount of the grafted PEO polymer was about 40.0 wt%. Rigid polyurethane foams (PUFs) filled with MWCNTs and PEO‐graft‐MWCNT were also fabricated to investigate the influence of grafted PEO interfacial layer on the foaming process, morphology and mechanical properties of PUF. The results indicated that PEO‐graft‐MWCNT had a limited impact on the viscosity and viscoelastic properties of polyol. Meanwhile, the addition of PEO‐graft‐MWCNT was beneficial for decreasing the pore size of PUF. The glass transition temperature and mechanical properties of PEO‐graft‐MWCNT/PUF composites increase gradually with filler content, which can be attributed to the good compatibility and strong interaction between PEO‐graft‐MWCNT and PUF. © 2018 Society of Chemical Industry Poly(ethylene oxide)‐grafted multiwall carbon nanotubes (PEO‐graft‐MWCNT) were successfully prepared. The grafted PEO layer can enhance the interfacial compatibility and interaction between PEO‐graft‐MWCNT and rigid polyurethane foams. [ABSTRACT FROM AUTHOR]

ABSTRACT: Morphology evolution of immiscible polymer blends during processing is a common phenomenon, but how it affects the foaming behavior is still unknown. The present work aims to study the effect of morphology evolution of polystyrene/poly(methyl methacrylate) (PS/PMMA) blends driven by phase separation on foaming behavior via a batch foaming process. Morphology evolution of PS/PMMA blends were conducted via thermal annealing using a compression molding machine. Phase contrast optical microscope and scanning electron microscope were used to investigate the morphology evolution and cell structures. The diffusion coefficients were calculated to study the effect of morphology evolution on gas diffusion behavior. It was found that phase domain was increased in size with the annealing and that cell structure was significantly dependent on morphology evolution. The thermal annealing with a long time could dramatically impact cell structures, especially for the blends with a bi‐continuous phase structure or a sea‐island structure with very large phase domains. The diffusion coefficient for the interface was increased with the annealing, which resulted in the generally decreased expansion ratio. Therefore, annealing for a long time at melt states during processing should be avoided for obtaining well‐defined cell structures for immiscible polymer blends. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46704. [ABSTRACT FROM AUTHOR]

Copolymerisation of a sorbitol‐derived bis‐carbonate with simple diamines, including cadaverine that was sustainably produced from lysine, under solvent‐free conditions was shown to produce rigid foams. Thermogravimetric analysis carried out in tandem with infrared spectroscopy of the released gases confirmed that the foaming agent was carbon dioxide produced during the polymerisation process itself. Such a bio‐based foam, being made under mild conditions from stable, benign precursors, with no toxic isocyanates, has great potential application for both thermal insulation and packaging. [ABSTRACT FROM AUTHOR]

In hydraulic fracturing, water is injected at high pressure to crack shale formations. More sustainable techniques use aqueous foams as injection fluids to reduce the water use and wastewater treatment of conventional hydrofractures. However, the physical mechanism of foam fracturing remains poorly understood, and this lack of understanding extends to other applications of compressible foams such as fire-fighting, energy storage, and enhanced oil recovery. Here we show that the injection of foam is much different from the injection of incompressible fluids and results in striking dynamics of fracture propagation that are tied to the compressibility of the foam. An understanding of bubble-scale dynamics is used to develop a model for macroscopic, compressible flow of the foam, from which a scaling law for the fracture length as a function of time is identified and exhibits excellent agreement with our experimental results. [ABSTRACT FROM AUTHOR]

ABSTRACT: Superheated water (shH2O) is investigated as a process aid in conventional aliphatic polyamide (PA) systems. The polymers investigated include PA 6 (PA6), PA 6,6 (PA66), PA 6,12 (PA612), and PA 12 (PA12). It is shown that the PA melting and crystallization temperatures are significantly reduced when exposed to shH2O. For example, the melting temperature of PA6 is depressed from 206 to 153 °C in the presence of shH2O. A relationship between amide group density and thermal transition temperature reduction is observed. Processing these materials in shH2O has led to a variety of materials ranging from low‐density foams to higher density locally anisotropic foamed morphologies. In situ observations of PAs melting in the presence of shH2O are performed using a specially designed reactor. Results from these experiments are used to estimate the diffusion coefficient of shH2O in PA6. Finally, low‐temperature extrusion is performed with PA6 and shH2O at temperatures as low as 180 °C and mixture viscosity is estimated. A 20‐fold depression in the melt viscosity of PA6 is observed at 240 °C with shH2O. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 803–813 [ABSTRACT FROM AUTHOR]

In this paper, we examine the state of the art of the physical foaming of polymers with supercritical fluids with a primary focus on carbon dioxide. We provide a critical analysis of the current research pathways and the main scientific open questions. We discuss the knowledge gaps along with technological challenges for further advances. Perspectives on the foaming of amorphous and semi-crystalline polymers, polymer blends, copolymers, and thermosetting polymers are presented. Challenges pertaining to the improved understanding of the nucleation phenomena and the limitations on the modeling and processing methodologies are discussed. [ABSTRACT FROM AUTHOR]

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Hypothesis Previous efforts to formulate smart foams composed of mixtures of PNIPAAm, a thermoresponsive uncharged polymer, and surfactants have failed because the surfactant displaces the PNIPAAm from the liquid-air interface, removing the thermal responsiveness. We hypothesized that thermoresponsive foams could be formulated with such a mixture if a charged surfactant were used in order to anchor an oppositely charged brush-type polyelectrolyte, for which PNIPAAm could be incorporated as side chains, to the interface. Experiments A brush-type negatively charged co-polyelectrolyte (Cop-L) with PNIPAAm as side chains was synthetized. Its mixtures with DTAB, a cationic surfactant, in aqueous solution were characterized by dynamic light scattering, surface tension and surface compression viscoelasticity measurements, as a function of both surfactant concentration and temperature. The foam stability and its responsiveness to temperature changes were studied with a homemade apparatus. Findings The Cop-L/DTAB mixtures were capable of producing thermoresponsive foams but only in a very narrow surfactant concentration (c s ) range, 0.3 < c s < 1.6 mM. The responsiveness is due to a modification of the interfacial compression elasticity induced by conformational changes of the Polyeletrolyte/surfactant aggregates at the interface. This is possible only for c s  < 1.6 because higher surfactant concentrations induce the polymer collapse at all temperatures, eliminating the thermal responsiveness. [ABSTRACT FROM AUTHOR]

ABSTRACT Microcellular polymers have been produced by ScCO2 foaming, based on 1-vinyl-2-pyrrolidone (VP) and butyl-acrylate (BA). Three different copolymers were prepared, varying the compositions of VP and BA, following a simple radical polymerization process using an UV initiator. The samples a good foaming behavior and also excellent flexibility and handle ability, with expansion ratios between 1.53 and 1.72, and cell sizes in the microcellular range (below 5 µm). However, it was observed that the gas distribution and, consequently, the cellular structure inside the polymer foams was highly dependent on the VP and BA proportions, leading to very different thermal conductivity values, even for similar volume gas fraction values. These results were related to the copolymer nanostructuration, which seems to have an influence in the final pore structure, thus opening the possibility of designing microcellular foams with similar macroscopic characteristics but different thermal conductivity values. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45872. [ABSTRACT FROM AUTHOR]