Mechanical,acoustic, and thermal performances of shear thickening fluid–filled rigid polyurethane foam composites: Effects of content of shear thickening fluid and particle size of silica

Shear thickening fluid (STF) features a rheological property, and rigid polyurethane (PU) foams feature low thermal conductivity and excellent acoustic insulation. In this study, an STF/PU rigid foam composite sandwich structure was designed using different contents (0, 0.5, 1, or 1.5 wt %) of STF that contained 14 nm, 40 nm, or 75 nm silicon dioxide (SiO₂). The effects of STF content and silica size on the cell structure, mechanical performance, acoustic absorption, and thermal performance of the STF/PU foam were explored. The test results show that STF/PU foam exhibited three characteristic acoustic absorption peaks, and the maximum acoustic absorption coefficient reached 0.841. STF addition increased compression, bending strength, and maximum acoustic coefficient, as well as initial mass loss temperature. STF-filled PU foam composites containing 14 nm and 40 nm SiO₂ had a mild rise in thermal insulation. The rigid STF/PU foam composites with a cell structure had the maximum thermal conductivity of 0.22 W m⁻¹ K⁻¹ and sound absorption coefficient of 0.841, which confirm that they are a good candidate for sound-absorbing energy conservation materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47359.     

Polyurethane/poly(vinylidene fluoride)/MWCNT composite foam for broadband airborne sound absorption

A polyurethane/poly(vinylidene fluoride)/multi-walled carbon nanotubes (PU/PVDF/MWCNT) (83/15/2) composite foam was designed and fabricated. The foam exhibited high airborne sound absorption performance in a wide-frequency range. The sound absorption coefficient reached the value of 0.85 at 1 kHz, which is a significant improvement over PU foam. It was found that PVDF formed a separate immiscible phase and part of it was crystallized in a polar phase in the PU scaffold in the PU/PVDF/MWCNT composite, which could benefit the sound absorption performance by introducing interfacial damping and local piezoelectric damping effects. The introduction of the conductive MWCNT filament in the composite foam further improved sound absorption, possibly by facilitating the dissipation of the electrical charges generated from local piezoelectric effect and enhancing both the interfacial damping effect and local piezoelectric damping effect. With PU as the main ingredient, the fabrication scalability of the foam can be improved with significantly reduced material and production cost in comparison with PVDF foam. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47868.     

Nanoclay filled soy‐based polyurethane foam

Polyurethane foam was fabricated from polymeric diphenylmethane diisocyanate (pMDI) and soy‐based polyol. Nanoclay Cloisite 30B was incorporated into the foam systems to improve their thermal stabilities and mechanical properties. Neat polyurethane was used as a control. Soy‐based polyurethane foams with 0.5–3 parts per hundred of polyols by weight (php) of nanoclay were prepared. The distribution of nanoclay in the composites was analyzed by X‐ray diffraction (XRD), and the morphology of the composites was analyzed through scanning electron microscopy (SEM). The thermal properties were evaluated through dynamic mechanical thermal analysis (DMTA). Compression and three‐point bending tests were conducted on the composites. The densities of nanoclay soy‐based polyurethane foams were higher than that of the neat soy‐based polyurethane foam. At a loading of 0.5 php nanoclay, the compressive, flexural strength, and modulus of the soy‐based polyurethane foam were increased by 98%, 26%, 22%, and 65%, respectively, as compared to those of the neat soy‐based polyurethane foam. The storage modulus of the soy‐based polyurethane foam was improved by the incorporation of nanoclay. The glass transition temperature of the foam was increased as the nanoclay loading was increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

In situ preparation,electrospinning, and characterization of polyacrylonitrile nanofibers containing silver nanoparticles

Silver nanoparticles were prepared from a polyacrylonitrile (PAN)/N,N‐dimethylformamide solution of silver nitrate (0.05–0.5 wt %) with light treatment (xenon arc) to reduce Ag⁺ ions into Ag⁰. The formation of silver nanoparticles in the PAN solution and the effect of treatment time on the numbers of silver nanoparticles, their average diameter and size distribution were investigated by UV–visible spectroscopy. In addition, the average size of silver nanoparticles and their shapes in colloidal solution were determined by transmission electron microscopy images and found to be on the order of 10 nm. The resulting solution was electrospun into PAN nanofibers. An increase in the salt concentration led to decreases in the nanofiber diameter and bead numbers (determined by scanning electron microscopy images) and an increase in the crystallinity (confirmed by X‐ray diffraction patterns). A continuous rate of silver release from the nanofiber web was monitored by the atomic absorption technique. These nanofibers showed strong antibacterial activity against Pseudomonas aeruginosa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of water‐absorbing polyurethane foam composites with microsized sodium polyacrylate particles

This article introduces the preparation of rigid polyurethane foam (PUF) and studies the effect of various mass percentages of sodium polyacrylate (PAAS, microsized) on PUF hydrophilicity. The characterization of PUF (with 0–5.5 wt % PAAS) was conducted via scanning electron microscopy, contact angle analysis, differential scanning calorimetry, and pore size distribution. All modified foams showed an improvement in their water sorption and water maintenance capacities, and the PU foam content of 5.5 wt % PAAS showed a water absorption of 891%, and the water retention performance was 408% (96 h) compared to the pure PU foam. Through contact angle measurements, the relationship between the hydrophilicity of the modified foams and PAAS content was investigated. The compression strength of the samples was also tested. When the PAAS is 2.6 wt %, the compression strength of the composites decreased about 50% compared with the pure PU foam. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46702.     

聚酰亚胺泡沫材料吸声性能对比研究

通过阻抗管法研究了聚酰亚胺(PI)、三聚氰胺(MFF)和聚氨酯(PU)3种泡沫材料对声音的吸收特性。结果表明:与MFF和PU泡沫材料相比,PI泡沫材料具有优异的吸声降噪性能;随着材料密度的增大,3种泡沫的吸声降噪性能都有相应提高。     

Electrical conductivity and major mechanical and thermal properties of carbon nanotube‐filled polyurethane foams

The carbon nanotubes (CNTs)/rigid polyurethane (PU) foam composites with a low percolation threshold of ～ 1.2 wt % were prepared by constructing effective conductive paths with homogeneous dispersion of the CNTs in both the cell walls and struts of the PU foam. The conductive foam presented excellent electrical stability under various temperature fields, highlighting the potential applications for a long‐term use over a wide temperature range from 20 to 180°C. Compression measurements and dynamical mechanical analysis indicated 31% improvement in compression properties and 50% increase in storage modulus at room temperature in the presence of CNTs (2.0 wt %). Additionally, the incorporation of only 0.5 wt % CNTs induced remarkable thermal stabilization of the matrix, with the degradation temperature increasing from 450 to 499°C at the 50% weight loss. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication and characterization of hollow nanofibrous PA6 yarn reinforced with CNTs

Core-sheath nanofibrous yarns were obtained through electrospinning of polyamide 6 (PA6) solution containing different concentrations of multi-wall carbon nanotubes (MWNTs) as sheath and PVA multifilament as the yarn core. By dissolving PVA, for obtaining conductive hollow nanofibrous PA6/MWNTs yarn, two types of porosity could be obtained including hollow central tube due to the structure of hollow yarn and nano-porous areas embedded in electrospun nanofibers. SEM results showed that the diameters of nanofibers were varying in the range of 103–145 nm obeying MWNTs concentrations and TEM results revealed that the MWNTs were embedded in nanofiber matrix as straight and aligned form. DSC analysis showed that electrospinning process caused the formation of less-ordered γ phase in nanofibers. The electrical conductivity of yarns increased from 10^?13 S m^?1 to 2.4?×?10^?6 S m^?1 with increasing the concentration of nanotubes from 0 wt.% to 7 wt.%.     

Synthesis and characterization of elastomeric polyurethane and PU/clay nanocomposites based on an aliphatic diisocyanate

This investigation reports preparation of polyurethane and polyurethane/clay nanocomposites based on polyethylene glycol, isophorone diisocyanate (IPDI), an aliphatic diisocyanate and 1,4‐ Butanediol as chain extender by solution polymerization. In this case PU/clay nanocomposites were prepared via ex‐situ method using 1, 3, and 5 wt % of Cloisite 30B. Thermogravimetric analysis showed that the maximum decomposition temperature (T_max) of the PU/clay nanocomposite is much higher than the pristine PU. The tensile properties improved upon increasing the organoclay (Cloisite 30B) content upto 3 wt %, and then decreased to some extent upon further increasing the nanoparticle loading to 5 wt %. Optical properties of the nanocomposites were studied by UV‐vis spectrophotometer. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the morphology of the nanocomposites. It was observed that with the incorporation of 3 wt % nanoclay the crystallinity in PU nanocomposite increases, then diminishes with further loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3328–3334, 2013     

Preparation and characterization of multiwalled carbon nanotubes/polyacrylonitrile nanofibers

Multiwalled carbon nanotube/Polyacrylonitrile (MWNT/PAN) composite nanofibers were prepared by electrospinning technique, whereby functionalized MWNTs (F-MWNTs) and pristine MWNTs (P-MWNTs) were used as reinforcing materials. The F-MWNTs were functionalized by Friedel-Crafts acylation, which introduced aromatic amine (COC₆H₄-NH₂) groups onto the sidewall. The diameter range of the PAN nanofibers was 400-100 ± 50 nm. The beads formation was also observed when the amounts of MWNTs were increased in the PAN solution. The bead formation in F-MWNT/PAN composite nanofibers was less as compared to P-MWNT/PAN. The MWNTs were embedded within nanofibers and were well oriented along the nanofiber axis, as confirmed by transmission electron microscopy. The mechanical and thermal properties of the PAN nanofibers were improved by the incorporation of MWNTs.     

Influences of rice hull in polyurethane foam on its sound absorption characteristics

In this article, rice hull (RH) was used in the moulding of polyurethane (PU) foam system. The article analyzed the participation of RH in the chemical reaction of PU synthesis with Attenuated Total Reflection‐Fourier Transform Infrared spectroscopy method. Besides, the influence of RH on the formation of pore structure along with the acoustic performance such as sound impedance rate, acoustic reflection factor, sound absorption coefficient, and transmission loss of the products were studied with the Transfer Function Method. The results indicated that RH significantly influenced the uniformity of pore diameter in PU foam. As the content of RH increased, the sound absorption peak shifted toward lower frequency region. And the sound absorption coefficients increased till a threshold value of RH content. POLYM. COMPOS., 34:1847–1855, 2013. © 2013 Society of Plastics Engineers     

Bio-based engineered nanocomposite foam with enhanced mechanical and thermal barrier properties

Bio-based polyurethane (PU) foams were developed from bio-polyol (castor oil-based) in the presence of selective catalyst, surfactant, and blowing agent. Bentonite nanoclay (NC) was incorporated into the bio-polyol mixture as nano-reinforcement, while, triethyl phosphate was used as flame-retardant agent. After fabrication, these bioengineered foam nano-composites were studied for microstructural, mechanical and thermal characterizations. Fourier transform infrared spectroscopy analysis indicated the presence of characteristic functionalities within biopolyol segments, which was influenced by reactant activity within the polyurethane (PU) foams. Scanning electron microscopy revealed the cellular morphology of the foam. Thermogravimetric analysis enabled the study of foam decomposition behavior for different sample compositions. Incorporation of NC into pristine foam was found to delay the onset degradation temperature. Flammability studies depicted significant enhancement of flame retardancy with incorporation of NC up to a certain loading level. Compression tests demonstrated that significant improvement of compressive strength properties of foams could be achieved by incorporating bentonite nanoclay, owing to nucleation effect of nanoclay and corresponding enhanced structural integrity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47063.     

Magnetically-separable hierarchically porous carbon monoliths with partially graphitized structures as excellent adsorbents for dyes

Magnetically-separable hierarchically porous carbon monoliths with partially graphitized structures were synthesized through confinement self-assembly in polyurethane (PU) foam associated with a direct carbonization process from triblock copolymer F127, phenolic resol and ferric nitrate. It was observed that the magnetic Fe nanoparticles were embedded in the walls of graphitic porous carbon matrix, and the resulting materials exhibited hierarchically porous structure with macropores of 100–450 μm, mesopore size of 4.8 nm, BET surface area of 723 m²/g, pore volume of 0.46 cm³/g, and saturation magnetization of 3.1 emu/g. Using methylene blue as model dye pollutant in water, the carbon monolith materials showed high adsorption capacity of 190 mg/g, exhibiting excellent adsorption characteristics desirable for the application in adsorption of dyes and easy separation under an external magnetic field.     

Lung tissue substitute: synthesis,characterization and attenuation studies for low energy photons

Towards development of lung tissue substitute used in the calibration of lung counters, seven sets of polyurethane (PU) foam were synthesized exhibiting a density range of 0.14–0.42 g/cm³ by varying the quantity of foaming agent (water) in the formulation. Foam sets were characterized by Fourier transform infrared spectroscopy, elemental analysis and thermo gravimetric analysis. Effect of density on the properties of PU foam is investigated. In addition, attenuation behavior of synthesized material for low energy (<100 keV) gamma rays was checked by using ²⁴¹Am & ¹³³Ba sources and planar high purity germanium detector. Moreover, the linear and mass attenuation coefficients of all sets were calculated and were found to be in agreement to the reported values.     

Studying the effect of organo-modified nanoclay loading on the thermal stability,flame retardant,anti-corrosive and mechanical properties of polyurethane nanocomposite for surface coating

Clay polyurethane nanocomposite (CPN) coating films were fabricated by uniformly dispersing nanoclay, organically modified with 25–30 wt.% octadecylamine in varying concentrations up to 5 wt.%, in a commercial two component, glossy, acrylic aliphatic polyurethane using ultrasonication. Organo-modified nanoclay was characterized by X-ray diffraction (XRD). The dispersion of the nanoclay into the matrix was investigated by scanning electron microscopy (SEM). CPN coating films were characterized by thermogravimetric analysis (TGA), and flame retardant, corrosion resistance and mechanical properties were also investigated. The XRD measurement indicated that, the organo-modified nanoclay particles were mainly constituted of montmorillonite with traces of quartz and calcite also found to be present. The SEM analysis showed that the nanoclay layers were dispersed and intercalated into the polyurethane coating. Thermogravimetric analysis showed that incorporating 5 wt.% organo-nanoclay into polyurethane considerably enhanced the thermal stability and increased the char residue to 14.11 wt.% relative to 4.58 for the sample without organo-nanoclay (blank polyurethane). The limiting oxygen index (LOI) test revealed that incorporation of organo-nanoclay led to a further increase in LOI values, which indicate an improvement in flame retardancy properties. The corrosion resistance also improved and this improvement increases with increase nanoclay wt.%. The mechanical resistance measurements demonstrated that the gloss of the CPN coating films slightly decreased, although hardness, adhesion and impact resistance of the CPN coating films improved with the incorporation of the organo-nanoclay.     

A high flux graphene oxide nanoparticles embedded in PAN nanofiber microfiltration membrane for water treatment applications with improved anti-fouling performance

A high flux and anti-fouling graphene oxide (GO) nanoparticles embedded in polyacrylonitrile (PAN) nanofiber microfiltration membranes (PANGMs) were fabricated through the facile electrospinning method and were characterized by water treatment applications. The synthesized GO nanoparticles and GO nanoparticles embedded in PAN nanofiber membranes were characterized by FESEM, FTIR, and EDS. SEM images showed that the PANGMs possessed randomly overlaid fibers with a network-like highly porous structure similar to the pristine PAN nanofiber membrane, while agglomeration of GO nanoparticles was observed at high GO concentration. The introduction of GO nanoparticles into the PAN polymeric matrix significantly increased the permeation flux of the resulting membrane in both dead-end and cross-flow filtration systems. A high flux recovery ratio of 96.6% and a low irreversible fouling ratio of 3.4% were obtained at 2% (wt.) GO nanoparticles. More importantly, a high flux recovery ratio of GO nanoparticles embedded in PAN nanofiber membrane was retained after 20 repeated cycles of activated sludge suspension filtration. Therefore, it can speculate that the incorporation of GO nanoparticles into the PAN nanofibers could efficiently improve the anti-fouling ability of membranes which had opened up an alternative for the preparation of high flux and anti-fouling microfiltration membranes in practical water treatment applications such as membrane bioreactors.

     

Mechanical and thermal properties of functionalized multiwalled carbon nanotubes and multiwalled carbon nanotube–polyurethane composites

Multiwalled carbon nanotube (MWNT)–polyurethane (PU) composites were obtained by an in situ polycondensation approach. The effects of the number of functional groups on the dispersion and mechanical properties were investigated. The results showed that the functionalized MWNTs had more advantages for improving the dispersion and stability in water and N,N′‐dimethylformamide. The tensile strength and elongation at break of the composites exhibited obvious increases with the addition of MWNT contents below 1 wt % and then decreases with additions above 1 wt %. The maximum values of the tensile strength and elongation at break increased by 900 and 741%, respectively, at a 1 wt % loading of MWNTs. Differential scanning calorimetry measurements indicated that the addition of MWNTs resulted in an alteration of the glass‐transition temperature of the soft‐segment phase of MWNT–PU. Additionally, new peaks near 54°C were observed with differential scanning calorimetry because of the microphase‐separation structures and alteration of the segment molecular weights of the hard segment and soft segment of PU with the addition of MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of PAN@PU coaxial electrostatic spun nanofibers for oil/water separation

Coaxial electrostatic spinning (co-electrostatic spinning) technology has greatly expanded the versatility of the preparation of core–shell polymer nanofibers and has found a wide range of applications in the environmental and biological fields. Here we present a method for the preparation of coaxial nanofibers using polyacrylonitrile (PAN) and polyurethane (PU) as raw materials. It was found that the tensile strength ranges from 2.14 to 4.07 MPa with the increasing spinning speed of the nucleated PU layer, and the elongation at break was up to 95.09% for M_6:4, which was three times higher than that of the original M_PAN (30.54%), and the toughness of the nanofiber film was also significantly improved. Finally, the oil/water separation capacity of the coaxial nanofiber membrane was investigated, and the results showed that the separation fluxes for various oil compounds ranged from 2380.18 to 3130.17 L·m⁻²·h⁻¹, with separation efficiencies above 99%. This study not only investigates the effect of different flow rates of core (PU)/shell (PAN) on the performance of coaxial electrostatic spun nanofiber membranes, but also provides a new insight into the coaxial electrostatic spinning process.     

Effect of nanoparticles on mode‐I fracture toughness of polyurethane foams

Mode‐I fracture toughness of rigid polyurethane (PUR) foam modified with nanosize particles of different shapes and sizes have been examined using a single edge notched bend (SENB) specimen under three‐point bending configuration. The PUR foams with density of 260 kg/m³ and four different types of nanoparticles, namely, nano TiO₂ (5, 10, and 35 nm), nanoclay, carbon nanofibers (CNFs), and multiwall carbon nanotubes (MWNTs) are considered. Nanophased PUR foams are prepared through the infusion of nanoparticles into liquid PUR foam precursor in the range of 0.5–2 wt% with 0.5‐wt% increment using a sonochemical method. The linear elastic fracture mechanics (LEFM) model has been used to determine the mode‐I fracture toughness. The fracture toughness data have been validated with the plain strain fracture criteria and found to be appropriate. It is observed that the infusion of CNF at 0.5‐wt% loading shows the highest enhancement in fracture toughness (about 28%) over neat counter part. Among different sized nano TiO₂, 5 nm nanoparticles show the highest improvement (about 16%) at a doping of 1.0 wt%. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Structure Stability,Flame Retardancy,and Antimicrobial Properties of Polyurethane Composite Nanofibers Containing Tannic Acid and Boron-Doped Carbon Nanotubes

A polyurethane (PU) composite nanofiber with superior flame retardancy and antimicrobial property is developed through the simultaneous incorporation of boron-doped carbon nanotubes (CNTs) and tannic acid (TA), resulting in excellent thermal, mechanical, and eco-friendly flame-retardant properties. The tensile strength and peak heat-release rate of the composite nanofiber increase with increasing filler content, with the optimal performance (7.38 ± 1.04 MPa and 254 W g⁻¹) being achieved at 3 wt% filler. Using a series of analytical techniques, it is demonstrated that the nanostructure of the neat PU completely collapses upon heating, transforming into a film-like structure; in contrast, a higher loading of nanofiller leads to a higher heat-shielding capability, thereby facilitating preservation of the composite nanofiber structure. Finally, the antibacterial activity is shown to increase as a result of the synergic effect of the boron-doped CNTs and TA.