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A series of polyimide foam materials were prepared via one-step process, and the effect of polyethylene glycol on the morphology and properties of the foams was investigated. The results showed that the mean cellular diameter increased from 0.49 to 0.57 mm with the increase of polyethylene glycol content. Meanwhile, with the addition of polyethylene glycol, the tensile strength of polyimide foams increased from 18 to 23 kPa. It was proved that the foaming behavior and flexibility of polyimide foams were greatly improved due to the introduction of polyethylene glycol. As a kind of chain extender, polyethylene glycol reacted with isocyanate to form the flexible urethane segment, which improved the flexibility of polyimide molecular chain and promoted foaming behavior. In addition, all the foams exhibited fine thermal stability with temperature at 5% weight loss of about 350°C. The limiting oxygen index values of the prepared polyimide foams decreased with the increase of polyethylene glycol content, while the heat release rate increased, indicating certain decrease of the flame retardant properties. However, the fine cell structure can still be observed under the residual carbon structure after the burning, indicating fine flame retardancy. [ABSTRACT FROM AUTHOR]

As one kind of novel nanomaterial, polyhedral oligomeric silsesquioxane (POSS) can improve the thermal stability, water resistance, and mechanical properties of the composites when introduced into a polymer matrix. In this work, we carried a novel method to fabricate polymeric nanocomposite films from poly(vinyl alcohol) (PVA) by grafting octa(−chloropropyl) POSS using sodium hydroxide (NaOH) as a catalyst. Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (1H NMR) spectral analysis confirmed the structure of POSS‐graft‐PVA (POSS‐g‐PVA) nanoparticles. For the cast nanocomposite films, transmission electron microscopy (TEM) micrographs revealed that good POSS dispersion/distribution into PVA matrix was achieved, leading to substantial improvement of mechanical properties, reduced water absorption, and enhanced thermal stability. The chemical grafting of PVA on the nanoparticles plays an important role in improving these properties compared with conventional filled composites. POLYM. COMPOS., 40:2768–2776, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

With the aim of improving the mechanical strength of polypropylene (PP) materials, carbon fibers (CFs) were incorporated into it to prepare composites with PP‐graft‐maleic anhydride (PP‐g‐MAH) as the compatibilizer. In order to improve the interfacial bonding between filler and matrix, the CFs were oxidized with concentrated nitric acid for different times. The results showed that with the increase of oxidation time, the surface roughness and specific areas of CF increased. Nitric acid oxidation can effectively introduce polar groups on the surface of CFs, leading to the increased wetting ability. The tensile and impact strength of PP/CF composites were highly improved with the increase of oxidation time. Both the increased surface areas and roughness were beneficial for mechanical interlocking. In addition, the chemical bonding between activated CF and PP‐g‐MAH contributed to the enhanced mechanical properties of the resulting composites. The ‐OH groups on CF produced by surface oxidation could react with anhydride groups, while the PP chains of PP‐g‐MAH diffused into the PP matrix, resulting in good adhesion or entanglement. These PP/CF composites with high performance can find wide applications as light weight structural materials. POLYM. COMPOS., 40:E654–E662, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In order to improve the mechanical, thermal and flame-resistant properties of polyimide foams (PIFs), in the present study, flexible polyimide (PI)/graphite composite foams were prepared with dianhydride and isocyanate as the starting materials and graphite as the filler. The experimental results showed that most cells of PIFs possessed an open cell structure, and the open cell content decreased by graphite incorporation. While with the increase in graphite, the distribution of cellular size became uneven and the size distribution became broad. The compressive strength increased initially and then decreased and reached the maximum value of 26.4 kPa when the graphite content was 1.98 wt%, but all the composite foams exhibited higher strength than the neat PIF. In addition, the limiting oxygen index increased from 31% to 34.8% with the increase in graphite from 0 wt% to 3.25 wt%. The peak heat release rate of composite foams was 2.3% to 24.7% lower than the neat PIF and reached a minimum value of 42.36 kW m−2 with the graphite content of 1.98 wt%. Considering the above analysis, it is feasible to improve mechanical properties, thermal stability and flame-resistant properties of PIFs by graphite addition. [ABSTRACT FROM AUTHOR]

Polyurethane‐imide (PUI) foams containing both polyimide and polyurethane segments combined the advantage of fine mechanical properties as well as high thermal stability of the two polymers. To further improve the thermal stability and flame resistance of PUI foams, a series of PUI composite foams with different content of SiC (silicon carbide) as fillers were prepared. The cell structure, mechanical properties, flame resistance, and thermal properties of resulting PUI/SiC composite foams were characterized in detail. The experimental results showed that the cell size distribution became uneven, the apparent density was increased, and the compressive strength decreased with the increase in silicon carbide content. Meanwhile, the limiting oxygen index (LOI) showed an increase from 24.7% to 28.1% with increasing of SiC content from 0% to 9.6%. The thermogravimetric analysis showed that the addition of SiC could significantly enhance the thermal stability and flame retardancy of PUI foams. [ABSTRACT FROM AUTHOR]

In this work, the surface coated silicon carbide (SiC) obtained by dispersing it in silane coupling agent/ethanol solutions of different concentrations was used as a filler in poly (vinyl alcohol)(PVA) and the composites of (PVA)/SiC were prepared by melt process. The structure and properties of PVA/SiC composites were studied by Fourier‐transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), mechanical and wear resistance tests in detail. The silane coupling agent was hydrolyzed under acidic conditions, and as a result, large number of hydroxyl and amino groups were generated, which could form hydrogen bonds with hydroxyl groups of the PVA molecular chains, this effect subsequently improved the interactions between the filler and matrix. The surface modified SiC particles dispersed well in PVA matrix resulting a good compatibility with the matrix. For the PVA/SiC composites with the same content of SiC filler, both tensile strength and elongation at break improved with the increase of silane coupling agent concentration. In addition, a good improvement in the wear resistance of the PVA/SiC composites was also achieved compared with the neat PVA/SiC composite. POLYM. COMPOS., 39:3849–3857, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A series of poly (vinyl alcohol) (PVA) films with urea/formamide complex plasticizers were prepared by a melt processing method, and their structure and properties were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and mechanical measurement. The results indicated that the urea/formamide complex plasticizer affected the ordered structure of PVA molecular chains by destroying their inter/intra hydrogen bonds, thus improving the melt processing performance of PVA and decreasing its crystallinity degree. Furthermore, the toughness of the films was enhanced effectively. [ABSTRACT FROM AUTHOR]

Abstract In this work, high-alcoholysis polyvinyl alcohol (PVA) films with sorbitol as plasticizer are obtained through the melt processing and characterized with low field nuclear magnetic resonance (LF-NMR), differential scanning calorimetry (DSC) etc. to investigate the water mobility, state and distribution as well as its effect on the performance of the films. The results show that two state of water, e.g. bound water and free water, exist and sorbitol can effectively bind w'ater in PVA films. The sorbitol molecules can effectively promote the formation of bound water. Therefore, with the increase of sorbitol plasticizer, the bound water content increases. The water migration study indicates that sorbitol can form strong hydrogen bonds with water and make the bound water more stable. The tensile strength and the haze of the films increase with increased bound water content. Graphical abstract Brief schematic of paper. Image 1 Highlights • LF-NMR investigates water state. • Change state of water. • Retain the bound water in PVA. • Bound water increases haze. • The bound water increases. [ABSTRACT FROM AUTHOR]

Bagasse fibers reinforced poly(vinyl alcohol) (PVA) composite films were successfully prepared by solution casting method. To enhance the dispersing effect of the fillers, alkali treatment of the plant fibers was adopted before the fabrication of composites. The structure and properties of the resulting composites were characterized by scanning electron microscopy (SEM), X-ray diffraction, differential scanning calorimetry, mechanical tests, water uptake and thermal stability in detail. The results showed that bagasse fibers after surface modification exhibited good compatibility with PVA matrix. The increased polarity as well as the roughness would be beneficial to the interaction and mechanical interlocking between the fiber and matrix. Acting as the heterogeneous nucleation agents, the fibers could enhance the degree of crystallization and decrease the supercooling degrees of PVA matrix. The fibers exhibited dramatically reinforcing effect in the matrix, and with the increase of fiber, the Young’s modulus and tensile yield stress increased. The Young’s modulus and tensile yield stress of composites with 8% filler would be 3 and 2 times compared with neat PVA films. The thermal stability decreased a little and the water uptake increased with the increase of filler content. These composite films would find wide applications in green packaging areas for their fine mechanical and thermal properties. [ABSTRACT FROM AUTHOR]

Development of “green” multi-functional air filters with features such as excellent filtration efficiency, eco-friendliness, and environmental stability are critically required to address the increasing concerns of polluted air. Natural proteins, such as soy protein and gelatin, are attractive candidates as multi-functional air-filtration materials owing to the rich functional groups; however, these bio-materials are vulnerable to moisture, which limits their broad application in practice. In this work, a hydrophobic protein of zein derived from abundant corn is modified for the first time to produce high-performance nanofilters via electrospinning. The zein nanofabrics are fabricated with the aid of a non-toxic solvent and co-electrospinning agent, poly(ethylene oxide). The results reveal that the zein-based nanofabrics show high efficiency for the simultaneous removal of particulate matters of different sizes ranging from 0.1 to 10 μm (>99.5%) and certain gaseous toxic chemicals (>70%). In addition, the zein nanofabrics show excellent moisture-resistance and good adhesion to the cellulose paper towel used as the air-filter substrate. This study demonstrates that nanofabrics based on hydrophobic natural proteins such as zein are promising materials for developing multi-functional “green” air filters. [ABSTRACT FROM AUTHOR]

Glycerol plasticized soy protein is an important kind of biodegradable materials among the possible soy protein systems. Fully realized performance relies on the investigation and understanding of the molecular structure of the plasticized soy protein. However, the relevant research is primarily limited in the microstructure and physical properties of the mixtures with a lack of knowledge on the intermolecular interactions at molecular and nano-scale levels. In this work, intermolecular interaction and molecular motion of soy protein in glycerol plasticized systems were investigated at molecular and nanometer levels. Several techniques including atomic force microscope (AFM), transmission electron microscope (TEM) and 13 C solid-state nuclear magnetic resonance ( 13 C NMR), have been effectively employed. Observations from AFM and TEM indicated that the glycerol plasticized soy protein materials were heterogeneous at nanometer scale and there were two important phases existing in the materials, i.e. protein-rich domain and glycerol-rich domain. The protein-rich domain was composed of compact aggregations of pan-like protein while the glycerol-rich domain possessed a loose chain-like structure. Further studies on the interactions between soy protein and glycerol at molecular level using NMR indicated that the strong hydrogen bonds between glycerol and protein molecules was greatly affected by amino acid residues on protein chains. The protein-rich micro-domains were mainly composed of amino acids with long alkane lateral chains or aromatic ring lateral groups, while amino acids with polar groups or short nonpolar lateral groups formed glycerol-rich micro-domains. These results would be beneficial for the development and realization of plasticized soy protein based nanocomposites and blend materials with high performance. [ABSTRACT FROM AUTHOR]

Cellulose nanocomposite membranes with predesigned functions were prepared and evaluated as adsorbents for protein adsorption. Maghemite nanoparticles (MNP) with amino groups and carboxyl groups were obtained by modifying maghemite nanoparticles with glycine and sodium citrate, respectively. The functional maghemite nanoparticles were then dispersed into NaOH/urea aqueous solution for dissolving cellulose, and the magnetic membranes were constructed using a tape casting method. The modified MNP were evaluated by zeta potential and FTIR measurements. The developed cellulose nanocomposite membranes possess microporous structure with porosity higher than 88.3%. The introduction of MNP with carboxyl groups into the cellulose nanocomposite membranes could absorb the highest amount of protein at a pH of 4, and gradually decreased with the increase of pH from 4 to 6. However, cellulose nanocomposite membranes with introduced MNP with amino groups absorb the highest and lowest amount of protein at pH of 5 and 4, respectively. This study provides a green and simple method for the design of multifunctional cellulose nanocomposite membranes for controllable protein adsorption, and is expected to open new venues for biomolecule binding by choice of various nanofillers and pH of the medium. [ABSTRACT FROM AUTHOR]

In this work, soy protein/polyurethane (PU) composite foams were synthesized with polyether polyol and polyaryl polymethylene isocyanate as the starting materials, soy protein isolate as the reactive fillers, and water as the blowing agent. The structure and properties of the resulting composite foams were characterized by Fourier transform infrared spectra, scanning electron microscope, close cell ratio, density, mechanical properties, and so on. Strong hydrogen bonding interactions as well as chemical crosslinking occurred between the soy protein filler and PU matrix. The composite foams have more cell density, in the meantime, the average cell size decreased. The close cell ratio and foam density increased with the increase of soy protein. In addition, the compressive strength and thermal stability were enhanced, mainly ascribing to the reinforcing effect as well as the crosslinking effect of reactive soy protein fillers. Therefore, the resulting composite foams would possess improved properties compared with neat PU foam and their applications could be highly enlarged. J. VINYL ADDIT. TECHNOL., 24:E105–E111, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

To decrease the usage of petroleum based materials, a kind of bio-resource based composite foams were developed with soy protein isolate (SPI) as reactive reinforcing filler in castor oil based polyurethane foams (PUF) prepared by self-rising method using water as a blowing agent. The resulting composite foams were evaluated for their morphology, density, mechanical and biodegradation properties, etc. Fourier transform infrared spectroscopy study exhibited characteristic peaks for SPI and PUF and indicated that the amino groups and hydroxyl groups on SPI reacted with polyphenyl polymethylene polyisocyanates (PAPI) to increase the crosslinking degrees of the composite foams. Densities of the resultant composites were found to increase with increasing SPI content. Mechanical properties of the samples were improved with the increase of SPI content. The compost tests further proved that the composite PUF had better biodegradability than neat PUF. Therefore, this research has provided a simple method of preparing the bio-resource based polyurethane foams, while exploring the potential of using SPI in polyurethane foam applications. [ABSTRACT FROM AUTHOR]

Acid treated multiwalled carbon nanotubes (MWNTs) were incorporated into glycerol plasticized soy protein to form MWNTs/soy protein nanocomposite plastics. The influence of the polar groups grafted on carbon nanotubes by acid treatment on the compatibility would be studied. The results showed that aggregation of carbon nanotubes was reduced by acid treatment and some polar groups were grafted on the nanotubes. The modified MWNTs were dispersed in soy protein matrix homogeneously and exhibited good compatibility with soy protein matrix. The crystalline structure of soy protein was not changed by MWNTs. The mechanical properties were dramatically enhanced through MWNTs incorporation due to the strong hydrogen bonding between them and the homogeneously dispersion of MWNTs in protein matrix, indicating the reinforcing effect of MWNTs in soy protein matrix. The water uptake was reduced and the thermal stability was enhanced by MWNTs incorporation. [ABSTRACT FROM AUTHOR]

In this work, carbon fiber (CF)-reinforced polypropylene (PP) composites were prepared by melt processing with maleic anhydride-grafted polypropylene as compatibilizer. The mechanical properties and crystallization behaviors of the resulting composites were investigated detailedly. The interfacial compatibility of CRP composites was fine and CF dispersed in PP matrix homogeneously. CF played a nucleation agent for the crystallization of PP. The crystallization temperature increased with increasing CF content. Carbon fibers could act as the heterogeneous nucleation agent for PP, which would decrease the activation energy of crystallization, shorten the crystallization time and raise the crystallization rate dramatically. The original spherulite morphology of neat PP was also destroyed by CF. CF exhibited obvious reinforcing effects on PP matrix and improved the mechanical properties of PP materials. The tensile strength and flexural strength were increased over 100% with 20 mass% CF. [ABSTRACT FROM AUTHOR]