A study to determine electromagnetic interference-shielding effectiveness on bio-based polyurethane foam reinforced with PVDF/MgO/Ni for emerging applications

The main objective of this study is to prepare nanoparticles-induced bio-based polyurethane foam to shield electromagnetic interference (EMI) radiation in the 8–12 GHz frequency range and compare the experimental result with optimization and simulation. Polyvinylidene fluoride (PVDF), magnesium oxide (MgO), and Nickel (Ni) nanoparticles were induced into bio-based PU (polyurethane) foam through absorption and hydrothermal reduction technique, which includes mechanical stirring, compressing, heating and evaporating. The design of experiment (DOE) methodology was used to find nanoparticle weight percentage (wt%). EMI shielding effectiveness of the bio-based PU foam composite was measured using Vector Network Analyzer (N5230A PNA-L). The weight percentages of the optimized sample were predicted using the response surface methodology (RSM), in which the central composite design (CCD) employed the weight percentages of the three nanoparticles as input and the results of the electromagnetic interference shielding effectiveness (EMI SE) experiment as the response output. The result from CCD showed that 3 wt% of PVDF, 10 wt% of MgO, and 1 wt% of Ni gave a maximum EMI SE of 27.78 dB. Then a confirmation sample was created for the same, and EMI SE was estimated empirically. The results obtained for the confirmation sample are 27.56 dB. Then, a scanning electron microscope image was taken for the confirmation sample to analyze nanoparticle-induced bio-based PU foam's structural properties. The SEM image with dxf format is imported into the radio frequency (RF) module to calculate the EMI SE through COMSOL Multiphysics. The simulated EMI SE for the confirmation sample was 25.1 dB.     

Acoustic characterization of natural areca catechu fiber-reinforced flexible polyurethane foam composites

The development of acoustic absorbers from natural resources is a novel approach in acoustics. In the current study, the effect of unprocessed raw areca fiber (AF) particle reinforcement on the sound absorption (SA) behavior of polyurethane (PU) foam composites is investigated. Influences of fiber weight percentage and graded distribution of fiber with varying fiber weight percentage on the SA coefficient (SAC) of the composite foams are examined through the impedance tube approach. Morphological studies are carried out with the help of FESEM images to investigate the acoustic energy dissipation mechanism of PU foam and its composites. It is found that the SA capability of the composite foam is enhanced by increased fiber weight percentage, graded distribution of fiber wt%, varying sample thickness, and air cavity length. In general, PU-AF composite specimens show a peak SA value of 0.95 around 450 Hz, which is not the case for other natural fiber results available in the literature. Theoretical results predicted using the JCA (Johnson-Champoux Allard) model agree with the experimental results.     

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.     

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。     

Synergistic effect between CuCr2O4 nanoparticles and plasticizer on mechanical properties of EP/PU/CuCr2O4 nanocomposites: Experimental approach and molecular dynamics simulation

In this research, copper chromite (CuCr₂O₄) nanoparticles (NPs) were synthesized by the sol–gel auto-combustion method. The effects of CuCr₂O₄ NPs and polyurethane (PU) on the tensile strength of the epoxy (EP) resin were studied by considering different weight percentages (wt%). The response surface methodology (RSM) coupled with central composite design (CCD) (RSM/CCD) methods were also used to optimize the Young's modulus, yield strength, and ultimate tensile strength of the EP/PU/CuCr₂O₄ nanocomposites. The composition structure and morphology of the EP/PU/CuCr₂O₄ nanocomposites were determined using the Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction, UV–vis diffuse reflection, Scanning Electron Microscopy, X-ray energy dispersive spectroscopy, and thermogravimetric analysis. It was also shown that the RSM/CCD methods could be utilized effectively to find the optimum process variables in the tensile test of the EP/PU/CuCr₂O₄ nanocomposites. Moreover, the tensile test revealed that the presence of the CuCr₂O₄ NPs in the EP/PU matrix improved the mechanical properties. Best results were obtained with the 0.76 wt% of the CuCr₂O₄ NPs and the 2.6 wt% PU in the epoxy resin. The molecular dynamic simulation was used to illustrate the effect of the NPs on the interaction energy and mechanical properties of this nanocomposite. The calculated interaction energy for the EP/PU/CuCr₂O₄ nanocomposites was −437.96 Kcal/mol. The results showed that Young's modulus had relative agreement with the experimental results.     

Electrospun PVDF/MWCNT/OMMT hybrid nanocomposites: preparation and characterization

Electrospinning technique was employed to prepare neat PVDF, nanoclay-PVDF and carbon nanotube (MWCNT)-PVDF nanocomposites, and nanoclay-carbon nanotube-PVDF hybrid nanocomposites. A mixture of dimethyl formamide/acetone (60/40) was used to fluidize the polymer and nanofillers. Electrospinning process was conducted under optimized conditions. Maximum modification was achieved at 0.15 wt% nanofiller. Rheological measurements on the prepared solutions revealed decreased material functions in the presence of nanoclay, whereas the rheological properties of MWCNT-PVDF solution did not show any significant reduction compared with those of neat PVDF solution. The behaviors of the hybrid nanocomposite solutions, though dependent on their composition and their material functions, increased with MWCNT concentration. These differences, together with variations in electrical properties of nanoclay and MWCNT, led to changes in morphology of the fiber during electrospinning process. Under electrospinning conditions designed for neat PVDF solution, mats with beads and with the highest fiber diameter were produced. Meanwhile, incorporation of both nanoclay and MWCNT into the solutions resulted in bead-free fibers with thinner diameter. Fourier transformed infrared spectrophotometry (FTIR) and X-ray diffractometry (XRD) were used to measure the β-phase crystalline content in electrospun mats. Complete agreement was found between the FTIR and XRD results. The lowest and highest β-phase contents were obtained for neat PVDF mat and hybrid nanocomposite mat containing 0.1 wt% clay, respectively. The mixing procedure of nanofillers and the PVDF solution was also found to be important. In case of hybrid nanocomposites, more β-crystals were formed when the nanoclay was first mixed in the absence of MWCNT.     

Synthesis and characterization of bio-based intumescent flame retardant and its application in polyurethane

A novel bio-based P-N containing intumescent flame retardant melamine starch phytate (PSTM) was prepared via the reaction of phytic acid starch ester with melamine and characterized by Fourier transform infrared, scanning electron microscopy and thermogravimetric analysis (TGA). The effects of PSTM on thermal properties and flammability of rigid polyurethane (PU) foams were analyzed by TGA, limit oxygen index (LOI), vertical burning tests (UL-94) and cone calorimeter measurement. The TGA results demonstrated that the thermal stabilities of PU/PSTM foam at high temperature was enhanced with the increasing additive amount of PSTM. The results showed that PU foam with 30 php PSTM (PU/PSTM-30%) observed an LOI value of 25.9 and a UL-94 rating of V-0. Cone calorimetry data showed that peak heat release rate, total heat release and smoke production rate of PU/PSTM-30% were distinctly lower than that of pure PU. Further experimental results demonstrated that PSTM promotes well charring of PU which could protect the foam from combustion. This work developed a novel bio-based intumescent flame retardant by suing phytic acid and starch as the acid source and carbon source, respectively, which is of great significance to the preparation of environmental-friendly flame retardants.     

Glass bubble reinforced polyurethane foams with high mechanical strength for cryogenic temperature insulation

In this study, glass bubble (GB) is added to polyurethane (PU) foams at different weight ratios—0, 0.25, 0.5, 0.75, and 1 wt% —to investigate the changes in the mechanical and thermal properties of the foam. By conducting several tests and measurements, the density, cell morphology, compressive strength, and thermal conductivity of the foam are studied. In particular, the effect of GB additives is examined by conducting compression tests at various temperatures (−163, −100, −40, and 20°C). Scanning electron microscopy and X-ray microscope reveal that the foams exhibit higher stability below 0.5 wt%, which improves the thermal performance. On the other hand, the compressive strength of the foams increases for all weight ratios of GB, and it increases sharply at 0.75 wt%. In addition, the chemical interactions and the dispersion of additives in the PU matrix are investigated through Fourier transform infrared and X-ray diffractions analysis. It is found that the synthesis of PU foams with GB nanoparticles is an efficient method for improving the mechanical properties and insulation performance of the foam for LNG insulation technology.     

Nanofibers (PU and PAN) and nanoparticles (Nanoclay and MWNTs) simultaneous effects on polyurethane foam sound absorption

In this research, simultaneous effects of polyacrylonitrile (PAN) and polyurethane (PU) nanofibers, multi wall carbon nanotubes (MWNTs) and nanoclay incorporation on sound absorption behavior of polyurethane foam were studied. The most important parameters such as nanoparticles content, number and mass per unit area of nanofiber layers and foam thickness were chosen and their influences on sound absorption in a wide band of frequencies were investigated. Applying of both nanoparticles gave rise to considerable improvement in PU foam sound absorption, however in case of MWNTs more satisfied results were observed. Sound absorption tests of simultaneous incorporation of MWNTs and nanoclay showed that the optimized result can be obtained at moderate to high MWNTs percents (0.1–0.15 wt.%) and low percents of nanoclay (0.5 wt.%). On the other hand, by adding PAN or PU nanofiber layers within the PU foam structure, superior sound absorption was achieved. Upper sound absorption by increasing the numbers of nanofiber layers was obtained. Incorporation of PAN nanofiber layers showed a better effect at high mass per unit area (5 g/m²), however the higher sound absorption in case of PU nanofiber layers was observed at low mass per unit area (1 g/m²).     

Thin polymer films based on poly(vinyl alcohol) containing graphene oxide and reduced graphene oxide with functional properties

In this article, the effect of the addition of graphene oxide (GO) and reduced graphene oxide (rGO) on the mechanical properties, thermal stability, and electrical conductivity of polyvinyl alcohol (PVA) has been investigated. Different weight percentages of nanofillers ranging from 0.5 to 5 wt% have been combined with PVA. The ultrasonic technique has been applied to disperse nanofillers in the PVA solution. The nanocomposite films have been prepared via solution casting technique and the dispersion of nanofillers into the PVA has been studied through optical microscopy. The microstructure, crystallization behavior, and interfacial interaction were characterized through X-ray diffraction and Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis have been applied to study the thermal properties of the prepared nanocomposites. The DSC results revealed that the crystallization temperature and melting temperature were enhanced in the presence of GO nanofiller. Besides, the tensile strength at break was improved along with the addition of GO; however, elongation at break for PVA/GO and PVA/rGO was diminished. Moreover, all specimens showed insulating behavior and the only sample was electrically conducting, which contain a high amount of rGO (5 wt%).     

Structure–properties relations in flexible polyurethane foams containing a novel bio-based crosslinker

The structure, morphology and properties of PU foams containing the novel bio-based crosslinker 3-hydroxy-N,N-bis(2-hydroxyethyl)butanamide (HBHBA) were investigated in comparison with PU foams containing the conventional crosslinker diethanolamine (DEOA). FTIR results indicate that HBHBA increases the degree of microphase separation in the foam and hydrogen bond concentration in the hard domains, suggesting that the incorporation of HBHBA produces better ordering of hard domains as compared with DEOA-crosslinked foam. Uniquely, the tri-functional crosslinker, HBHBA, can act as a chain extender due to the presence of a low reactivity secondary hydroxyl, reducing the crosslink density of the HBHBA foam vs. that of DEOA foam. Concerning foam morphology, the lower reactivity of HBHBA tends to favor larger cell sizes and more complete cell opening as compared to the more reactive DEOA. This behavior may in turn be related to the onset of phase separation and the rate of viscosity build-up. Mechanical properties measurements indicate that the elongation at break and the tensile strength of the HBHBA foam are ∼33% and 41% higher than the DEOA foam, respectively. The HBHBA foam also exhibits 40% greater tear strength and 10% greater compression strength without any loss in resilience. These results indicate that this bio-based crosslinker enhances properties and has clear potential in molded foam applications.     

Morphology and properties of stearate‐intercalated layered double hydroxide nanoplatelet‐reinforced thermoplastic polyurethane

In the past few years, layered double hydroxides (LDHs) with monolayer structure have been much studied for the development of polymer nanocomposites. LDHs with intercalated stearate anions form a bilayer structure with increased interlayer spacing and are expected to be better nanofillers in polymers. In the work reported, thermoplastic polyurethane (PU)/stearate‐intercalated LDH nanocomposites were prepared by solution intercalation and characterized. X‐ray diffraction and transmission electron microscopy confirmed the exfoliation at lower filler loading followed by intercalation at higher filler loading in PU matrix. As regards mechanical properties, these nanocomposites showed maximum improvements in tensile strength (45%) and elongation at break (53%) at 1 and 3 wt% loadings. Maximum improvements in storage and loss moduli (20%) with a shift of glass transition temperature (15 °C) and an increase in thermal stability (32 °C) at 50% weight loss were observed at 8 wt% loading in PU. Differential scanning calorimetry showed a shift of melting temperature of the soft segment in the nanocomposites compared to neat PU, possibly due to the nucleating effect of stearate‐intercalated LDH on the crystal structure of PU. All these findings are promising for the development of mechanically improved, thermally stable novel PU nanocomposites. Copyright © 2011 Society of Chemical Industry     

Reprocessing polyurethane foam using dynamic covalent chemistry in extrusion

Thermoset polyurethanes (PUs) pose recycling challenges due to their crosslinked structure. This study investigates the possibility to directly reprocess PU foams through (dynamic) carbamate exchange using reactive extrusion. By varying compounding temperature and catalyst (dibutyltin dilaurate, DBTDL) concentration, the extrusion process is examined using torque measurements. We clearly show that it is possible to reprocess the PU foam at temperatures well below 200°C and that DBTDL catalyst greatly enhances bond exchange rates during compounding. Reproducible extrusions at 160°C with 0.3 wt% DBTDL result in a material with a gel fraction of 0.90 displaying typical dynamic covalent network behavior, as confirmed by stress relaxation measurements. The measured characteristic relaxation times display an Arrhenius-type temperature dependence with an activation energy of 41 kJ/mol. Successful extrusion of fully crosslinked PU foam at milder temperatures with DBTDL catalyst demonstrates potential for PU foam recycling using reactive extrusion, and generally highlights the feasibility of dynamic crosslink reconfiguration for waste reduction and improved sustainability.     

磁场取向镀镍碳纳米管/聚氨酯复合泡沫材料的制备及性能

在磁场作用下通过一步法原位聚合制备了磁场取向镀镍多壁碳纳米管/聚氨酯复合泡沫材料.通过透射电镜、扫描电镜等表征了泡沫材料的结构,并测试了材料的压缩性能和吸声性能.结果表明:镀镍碳纳米管可使聚氨酯泡沫材料的泡孔更均匀.在磁场作用下,镀镍碳纳米管取向能显著提高材料的压缩强度,当碳纳米管的质量分数为1.0%时,其压缩强度为纯PU泡沫材料的3倍.同时,取向镀镍碳纳米管/PU复合泡沫材料的吸声性能也得到了进一步提高.     

Cage-like structured flexible hybrid fiber/SiO2 aerogel composite for noise reduction

The fiber/aerogel material prepared by the traditional method of sol-gel has a serious powder shedding phenomenon, and has serious environmental pollution and health hazards. In this study, an environmentally friendly porous sound absorption material with a cage-like structure, which used flexible ultrafine glass/quartz hybrid fibers (HFs) as the carrier and SiO₂ aerogel as the pore filler, was produced using the wet manufacturing process. The addition of aerogel enhanced the internal reflection of sound waves, reduced the propagation speed, increased the acoustic energy loss and improved the sound absorption coefficient (SAC). The noise reduction coefficient (NRC) reaches 0.49 in the range of 250–6300 Hz. The obtained composite presented a low density (73.5 mg/cm³) and heat resistance up to 500 °C.     

端羟基PU半预聚体改性酚醛发泡材料的研究

采用端羟基聚氨酯(PU)半预聚体改性酚醛发泡材料,研究了端羟基PU半预聚体的结构、用量等因素对增韧效果的影响。结果表明,采用端羟基PU半预聚体法能够有效增加发泡材料的回弹性,在设计n(OH)/n(NCO)为4/1、端羟基PU半预聚体用量占总量2%～8%(质量分数)下,增韧效果良好。     

Mechanical properties and fire retardant behavior of polyurethane foam reinforced with oil palm empty fruit bunch

The objective of this study was to investigate the effects of isocyanate/hydroxyl ratio and ammonium polyphosphate (APP) content on the properties of polyurethane foam. Polyurethane (PU) foam was prepared from polymeric diphenylmethane diisocyanate and polyethylene glycol with molecular weight of 200, reinforced with oil palm empty fruit bunch (EFB) using one shot process. The effect of EFB content on the properties of PU foam was also studied. It was noticed that EFB enhanced the properties of the PU foam. This was due to EFB acting as hard segment in PU foam system. The NCO/OH ratio played an important role in determining the properties of the PU foam produced. However, since EFB is a highly flammable material, APP was introduced to the PU foam system. From the results, APP improved the fire retardant behavior of the PU foam. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Development,characterization, and modeling of environmentally friendly open‐cell acoustic foams

This study shows the development of new polymeric open‐cell foams from polypropylene (PP) and polylactide (PLA) resins with a focus on sound absorption properties and modeling of these foams. The objective is to develop new environmentally friendly foams to replace the existing non‐recyclable Polyurethane foams are currently used for sound insulation in industry. Through this research, open‐cell foams of about 90% porosity were fabricated from PP and PLA. These resins were selected since PP is a recyclable thermoplastic polymer, and PLA is a bio‐based thermoplastic polymer made from renewable resources. Polyurethane (PU) foam which is currently used for sound absorption and noise control in industry was compared to the fabricated PP and PLA foams. As the first attempt to fabricate environmentally friendly acoustic foams, the resulting foam structures show improved properties as compared to the existing materials. The average absorption of PP and PLA foams fabricated is in the range of 0.42–0.55 which is comparable or even higher than the average absorption of PU foam. To better understand the effect of structural and material properties on sound absorption and further improve the acoustic performance of bio‐based foams, an analytical model based on Johnson–Champoux–Allard model was used to numerically simulate the acoustic performance of foams under study. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Noise control and experimental study of a highpressure oil pump enclosure

ABSTRACT

The present experimental study has been conducted to evaluate the impact of an acoustic enclosure of high-pressure oil pump, which is used to reduce the noise emission of an automobile engine. The enclosure is double-layered and made of nylon 66 (PA66) as an outer structure and polyurethane foam as the inner material. The sound signals of the engine were measured separately without an acoustic enclosure and covered by the enclosure. The signals were measured with 5 microphones around the engine under two electric loading conditions (0% and 100% load). The results revealed that the sound pressure level (SPL) of the engine increased significantly with the high-pressure oil pump installed, and the gap between SPL was larger for 100% load than 0% load. Furthermore, the enclosure of high-pressure oil pump was effective to attenuate the engine noise at almost the entire audio frequency range. The SPL reduced approximately 2?dB within nearly the entire test frequency range, supporting the remarkable noise reduction effect of the high-pressure oil pump enclosure.