PU Composites Research Articles

Effect of Tris(1,3-Dichloroisopropyl) Phosphate as Flame Retardant on Mechanical Properties and Fire Resistivity of PU Composites

Palm oil based polyurethane composites that are reinforced with Tris(1,3- dichloroisopropyl) phosphate TDCPP which function as flame retardants (FR) at different proportions of 3, 6 and 9% were synthesized. The polyurethane composite’s influence on the mechanical (tensile strength, impact and flexural limits and modulus) and thermal characteristics (fire test) of the polyurethane composites were examined. Increased loading of TCPP resulted in increased hardness (up to 39%) which translates to a marginal increase in Shore D hardness as the TDCPP content increases. With higher TDCPP loading, the impact and flexural capabilities decreased because of the fragile interfacial bonding between the TDCPP and PU matrix. Loading of 3%, 6% and 9% of TDCPP resulted in the decrease of impact strength by 25%, 24% and 23% respectively. Lowest flexural ability (at a reduction of 21%) was exhibited with the highest amount of TDCPP loading (9%) and the modulus had decreased by 23%. When the percentage of TDCPP loading increased, this resulted in a lower heat of combustion of the composites which manifested in the form of lower burning rate from 5.4 mm/s to 2.7 mm/s in the fire test operated.

Effect of polyhydric alcohols on the mechanical and thermal properties, porosities, and air permeabilities of polyurethane‐blended films

ABSTRACTPolyurethane (PU) and polyhydric alcohols composites were successfully prepared to be used as coating materials for fabrics. The effects of various polyhydric alcohols on the PU composites properties have been investigated. The tensile strengths, glass‐transition temperatures, thermal‐mechanical properties, and swelling capacities of the PU/polyhydric‐alcohol‐blended films are described in detail, along with their surface and cross‐sectional morphologies. The tensile strengths and glass‐transition temperatures of the PU/polyhydric‐alcohol‐blended films were found to decrease remarkably with increasing polyhydric‐alcohol concentration. The swelling capacities and porosities of the PU/poly(propylene glycol) (PPG)‐blended and PU/glycerol‐blended films were observed to increase with increasing PPG or glycerol concentration. However, the poly(ethylene glycol) (PEG) concentration in the PU/PEG‐blended film did not significantly affect its properties. The air and water‐vapor permeability of nonwoven nylon fabrics coated with PU/PPG and PU/glycerol increased with increasing PPG or glycerol contents, while those coated with PU/PEG were unaffected by PEG content. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47429.

Effect of NiTi content and test temperature on mechanical behaviors of NiTi–PU composites

For purpose of developing damping materials with increased damping capacity over a wide band, NiTi–PU composites were fabricated by vacuum molding polyether polyurethane melt with NiTi alloy chips additive. The composites were tested using three-point bending at various testing temperatures. Appreciable improvements were observed in bending modulus and load-deflection hysteresis loops of PU matrix. The bending modulus and hysteresis loop area of a composite with 70% NiTi volume content reach a maximum, which are 5.4 times and 5.6 times higher than those of PU matrix, respectively. The mechanism of bending modulus enhancement of NiTi additive was discussed.

Thermal degradation study of rigid polyurethane foams containing tris(1-chloro-2-propyl)phosphate and modified aramid fiber

The rigid polyurethane foams (RPUF) were prepared using tris(1-chloro-2-propyl)phosphate(TCPP) and modified aramid fiber(MAF) as flame retardants. The thermal degradation behaviors of RPUF and flame retardant RPUF were investigated by thermogravimetric analysis/infrared spectrometry (TG–IR), gas chromatography-mass spectrometry (GC–MS). Char residue for PU composites at different temperatures was analyzed by fourier transform infrared spectra (FTIR). The TGA curves suggested that aramid fiber(AF) has good ability of char formation. In TG–IR measurement, simultaneously use of TCPP and MAF in the RPUF exhibited lower smoke and toxicant production and increased char residue compared to RPUF containing TCPP. Production of toxic gases such as hydrogen cyanide (HCN) was significantly decreased, nonflammable gases carbon dioxide (CO2) and water were increased. GC–MS illustrated that TCPP and MAF exerted barrier effect in the condensed phase and the quench effect in the gaseous phase. Based on these facts, a potential thermal degradation mechanism was primarily proposed.

Thermal conductivities of PU composites with graphene aerogels reduced by different methods

Thermal management has become a serious problem with development of miniaturized, high integration and high performance electronics devices, where the improvement of thermal conductivity on polymer composites is crucial for the internal heat transfer and dissipation. In this work, graphene aerogels (GA) with three-dimensional (3D) structure were prepared by a simple method and reduced by different ways. Then, GA were used as fillers to prepare high thermal conductivity polymer composites. A thermal conductivity of 3.36Wm−1K−1 at room temperature was obtained when use polyurethane filling the hydroiodic acid reduced GA composite (HI-RGA/PU), and the graphene loading was as low as 2.5wt.%. This result is better than most researches of polymer-based thermal conductive composites. Furthermore, the heat transfer test and thermal cycling test show that HI-RGA/PU has a good and stable performance in the practical application as thermal interface material (TIM), which proves that GA is a promising filler for thermal conductive material.

Large area and flexible micro-porous piezoelectric materials for soft robotic skin

The need for flexible, highly sensitive tactile sensors that can fit onto curved surfaces is driving the conformable sensor materials research in the field of human–machine interactions. Here we report a new type of compliant piezoelectric active composite, a micro-porous polyurethane-PZT material, capable of generating a voltage output upon touch. The composites are synthesized with the aim of maximizing the piezoelectric sensitivity of particulate composite sensor materials. The goal is to reduce the dielectric constant of the polymer matrix and improve flexibility of conventional bulk piezo-composites, consisting of ceramic particles in a dense polymeric matrix, by adding a third (gaseous) phase to the system in the form of uniformly sized pores. The presence of the gaseous component in the polymer matrix in the form of well-distributed spherical inclusions effectively decreases the polymer dielectric permittivity, which increases the piezoelectric voltage sensitivity (g33) of the composite sensors significantly. The unique combination of dielectrophoretic structuring of PZT particles and the addition of a gaseous phase to the polymer resin results in the highest performance of the particulate composite sensors reported in the literature so far. The newly developed micro-porous composites show g33 value of 165mVm/N that is twice that of the structured PZT-bulk PU composites (80mVm/N) and more than five times the g33 value of bulk PZT ceramics (24–28mVm/N). The capability of the flexible freestanding sensors for application in touch sensing devices for soft robotics is demonstrated.

Biodegradable poly(ester-urethane) incorporated with catechin with shape memory and antioxidant activity for food packaging

Biodegradable poly(ester-urethane) (PU) based on a tri-block copolymer of poly(l-lactic acid) and poly(ɛ-caprolactone), with shape-memory behaviour, and further loaded with catechin (Cat), as antioxidant agent, were developed with the dual objective to obtain a smart as well as an active material for food packaging purpose. Well dispersed catechin produced somewhat UV blocking effect, but slightly amber and red tonality. Catechin demonstrated positive interaction with PU matrix enhancing the interfacial adhesion and leading to a reduction in the surface wettability. The active PU composites, with thermally-activated shape memory ability at temperatures close to those required to pack thermally proceeded food (i.e. 40°C), showed increased ability to recover the initial shape of the neat PU matrix. The antioxidant effectiveness of catechin released after the exposition to a fatty food simulant was proven after 10days which represents the worst foreseeable conditions of the intended use. The disintegration process in composting conditions of the active PU-based materials was speeded up due to the catechin incorporation. The PU formulation loaded with low amount of catechin (1wt% or 3wt%) showed enough transparency, enhanced shape memory behaviour, improved water resistance, reduced UV-light transmission, right catechin release and effective antioxidant activity as well as appropriate disintegration in compost. Thus, active PU-Cat composites result very interesting as smart and active materials for biodegradable food packaging applications.

One-pot two-step perfluoroalkylsilane functionalization of multi-walled carbon nanotubes for polyurethane-based composites

A facile approach has been developed to prepare perfluoroalkylsilane functionalized multi-walled carbon nanotubes (MWCNTs) with high grafting content through one-pot two-step reactions. In this process, hydroxyl derivatized MWCNTs (hydroxylized MWCNTs) were covalently functionalized with 3-aminopropyl triethoxysilane by silanisation reaction, and subsequently reacted with hexafluorobutyl acrylate or dodecafluoroheptyl acrylate by Micheal-addition reaction. SEM, FT-IR and TGA characterizations demonstrated that the perfluoroalkylsilane were covalently attached onto the surface of MWCNTs and the higher molecular weight of perfluoroalky acrylate yielded higher grafting content. The perfluoroalkylsilane functionalized MWCNTs showed improved dispersibility and strong interfacial adhesion in/with polyurethane matrix. An increase in the grafting content led to a decrease the crystallinity and hydrogen bonding in the PU composites. As a result, the composites showed increased elongation and unimproved tensile strength, but reduced storage modulus and loss factor. Meanwhile, the higher grafting content offered their composite with higher hydrophobicity, lower percolation threshold and more enhanced electronic conductivity.

Highly foldable PANi@CNTs/PU dielectric composites toward thin-film capacitor application

In this work, we synthesized a core-shell conductive filler of carbon nanotubes covered with polyaniline (PANi@CNTs), which showed good dispersibility to prepare highly flexible and foldable dielectric PMCs (PANi@CNTs/PU). The dielectric, mechanical, and thermal properties of the PANi@CNTs/PU composites were investigated. The mechanical flexible and foldable PANi@CNTs/PU composites could be promising dielectric material for preparing thin film capacitors.

The Influence of Trisilanolisobutyl POSS on Domain Microstructure of a Polyurethane Hybrid Composite: A Molecular Simulation Approach

A molecular dynamics simulation approach was adopted to investigate the domain microstructure of polyurethane (abbreviation PU) hybrid compositeswith trisilanolisobutyl polyhedral oligomeric silsesquioxane (abbreviation TSI-POSS) covalently bonded to polymer chains. The accuracy of models and force field has been verified by wide-angle X-ray scattering and volume-temperature behavior analysis. TheWAXS results indicate that with TSIPOSS concentration increasing in PU hybrid composites, distinct crystallite clusters are formed which increase the volume of hard segments and lead to the microphase separation. Furthermore, details of chain packing have been evaluated by radial distribution function, which shows that below 13wt% TSI-POSS concentration, the number of contacts between neighboring chains is decreased due to the prominent cage of TSI-POSS. However, when TSI-POSS concentration is up to 22wt%, the number of contacts is increased because the formation of crystallite cluster pulls neighboring chains closer to each other and significantly shortens their distance. The mobility of the TSI-POSS cores and PU composite backbones has been determined by the mean square displacement. The result reveals that the incorporation of TSI-POSS as the rigid core in the polymer backbone apparently restricts motions of the surrounding chains, which is also supported by volume-temperature behavior analysis as the glass transition temperature of PU composites increases with rising TSI-POSS concentration.

Surface modification of aluminum hypophosphite and its application for polyurethane foam composites

Aluminum hypophosphite (AHP) is surface modified by melamine derivative to fabricate reactive solid flame retardant (MCAHP) for polyurethane foam. MCAHP is successfully prepared and characterized by FTIR and SEM. The flame-retarded efficiency of MCAHP in PU is higher than that of AHP. It demonstrated that MCAHP has better compatibility in PU matrix compared with AHP based on the SEM observation. After surface modification, due to the reaction between MCAHP and PU matrix, crosslinking might be formed between MCAHP and PU matrix, which contributes to the excellent compatibility of MCAHP in PU matrix, and as a result, the glass transition temperature of PU/MCAHP is 4 °C higher than that of PU/AHP. The thermal behavior of PU composites is characterized by TG and TG-FTIR, and results suggest the sublimation of melamine at about 320 °C because of the decomposition of the melamine derivative. The sublimation of melamine can consume abundant heat and dilute the oxygen concentration, which is benefit for the improvement of flame retardancy.

Preparation and characterization of polyurethane/silica aerogel nanocomposite materials

ABSTRACTIn this investigation, silica aerogel (SA)/Rigid Polyurethane (PUR) foam composites and silica aerogel/Polyurethane (PU) composites were prepared by dry mixing of granular and grinded silica aerogels with polyol part. They were then combined with diisocyanate part. Three different types of PUR foams and an elastomeric coating grade of PU were studied as well. Results show that thermal conductivity of foams did not decrease by adding silica aerogel. It even increased for some grades which is assumed to be due to the change in cell configuration of these foams. It was also found that sound insulation performance of these cellular composites did not improve significantly. Unlike foam composites, addition of silica aerogel into elastomeric PU improved its thermal and acoustic insulation properties. Because of the more promising properties of elastomeric PU composites, further examinations including measurements of compression strength and water contact angle of silica aerogel/PU composites were also taken. Final results showed a significant improvement in general properties of PU coatings by adding little amounts of silica aerogel (1–4 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44521.

Enhancement of the gas separation properties of polyurethane membrane by epoxy nanoparticles

In this study, we report highly selective CO2 polyurethane incorporated with cured epoxy nanoparticles. PU–epoxy composite membranes were prepared via solution casting method. The obtained SEM micrographs confirmed the nano-scale distribution of epoxy particles in the polymer matrix. DSC and FTIR spectra showed different phase separation for the PU composites compared to the pure PU. The effect of epoxy nanoparticles on the gas permeability of CO2, CH4, O2 and N2 was studied at 25°C and 10bar. The selectivity of CO2/N2 increased from 25 for the pure PU membrane to 55.5 for the PU–EP10, while the CO2 permeability was unchanged.

Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

High performance of reduced sulfonated graphite oxide nanoplatelets/polyurethane composites

In the study reported in this paper, sulfonated graphite oxide (SGO) was chemically reduced and then incorporated into a polyurethane matrix to produce reduced sulfonated graphite oxide/polyurethane (RSGO/PU) composites. Following reduction, the oxygen-containing functional groups attached to SGO had been effectively removed. The thermally conductive and electrical properties of RSGO/PU composites were thereby enhanced. Percolation thresholds of PU composites filled with RSGO were obtained at loadings below 1wt%. The RSGO/PU composites exhibited improved gas barrier properties as the loading of RSGO was increased. Based on the fracture morphology investigation, the RSGO was evenly distributed throughout the PU composites and strong filler–matrix interactions were observed.

A novel intumescent flame retardant with nanocellulose as charring agent and its flame retardancy in polyurethane foam

Ammonium polyphosphate (APP) is microencapsulated with nanocellulose and dicyandiamide‐formaldehyde using in situ polymerization and flocculation method. The presence of nanocellulose and dicyandiamide‐formaldehyde significantly affects the thermal behavior and flame retardancy of microencapsulated ammonium polyphosphate (DFNAPP). DFNAPP is much more stable from 524 to 637°C than that of APP because of the charred formation. Rigid polyurethane foam (PU) composites added DFNAPP obtain higher limiting oxygen index (LOI) values than that with the same loading of APP. Due to the presence of shell, experimental results indicate that DFNAPP obtains better compatibility and water resistance in PU matrix, resulting in the improved mechanical properties of the PU composites and the water durability. LOI value of PU/APP composite added 16.7 wt% additives has a decrement of 3.0% after water treatment. By comparison, that of PU/DFNAPP composite with the same loading of DFNAPP is only 0.3%. Compression strength of PU composite is increased from 195 kPa to 213 kPa when the DFNAPP (16.7 wt%) additive substitutes for APP (16.7 wt%). POLYM. COMPOS., 38:2762–2770, 2017. © 2015 Society of Plastics Engineers

Preparation and characterization of silver nanoparticle-reduced graphene oxide decorated electrospun polyurethane fiber composites with an improved electrical property

Abstract An approach for the preparation of silver nanoparticle-reduced graphene oxide/polyurethane composites (AgNP@RGO/PU) was proposed. An electrospinning process was utilized to fabricate a lightweight and flexible PU fiber mat. Graphene oxide (GO)/PU composites were prepared using a dip-coating method. Thus there happens a hydrogen bonding interactions between the GO sheets and PU fibers. A powerful reducing agent, hydriodic acid, was used to reduce GO/PU composites which transforms into RGO/PU composites. The composite exhibited low electrical resistance (3.5 × 10 2 Ω/sq) because of reduction reaction. Furthermore, AgNPs, which were modified with thiophenol, were deposited on the RGO/PU composite through π–π interactions between the aromatic functional groups on the AgNPs and the RGO by a dip-coating method. The obtained AgNP@RGO/PU composite exhibited a remarkably enhanced electrical property (

Cyclic compression behavior and energy dissipation of aluminum foam–polyurethane interpenetrating phase composites

This paper presents a study of the mechanical behavior of aluminum foam–polyurethane interpenetrating phase composites (AF–PU composites) with different corresponding porosity and pore size under cyclic compressions. The dissipated energy of AF–PU composite is described by the area of the compression cycle. Cyclic frequency, strain amplitude, temperature aging and cycle numbers were taken as reacting influence parameters to evaluate the damping capacity of AF–PU composites with different corresponding porosity and pore size. These cyclic tests demonstrate that AF–PU composites can make up the disadvantage of pure aluminum foams (AF) that are not suffered by the recoverable deformation in the stage of plastic plateau, and AF–PU composites with high porosity and large pore size have a good potential applied in hysteretic damping devices for seismic resistant structures under the condition of large strain level and preloading several cycles.

The Effect of Humping Semi-Enclosed Cage Structure on Polymer Chains Characteristics of TSI-POSS/PU Hybrid Composites

Trisilanolisobutyl polyhedral oligomeric silsesquioxane (TSI-POSS) with the humping semi-enclosed cage structure, was incorporated in concentrations of 7, 13 and 22 wt% into 4,4’-methylenebis (phenyl isocyanate) (MDI) and glycerol propoxylate to prepare TSI-POSS/PU hybrid composites, respectively. The polymer chain characteristics of these composites were investigated by wide angle X-ray scattering (WAXS) and molecular dynamics simulation approach. The results indicate that with TSI-POSS concentration increasing up to 22 wt% in hybrid composites, due to the humping semi-enclosed cage structure, distinct crystallite clusters are formed which lead to the micro-phase separation in composites. Meanwhile, the mobility of TSI-POSS cores and backbones in PU composites has been evaluated by the mean square displacement, which confirms that as the concentration of TSI-POSS increasing, the mobility of polymer chains are restricted apparently. Furthermore, it also indicates that the incorporation of TSI-POSS is as the rigid core in hybrid composites.

Thermal degradation and flame retardancy of microencapsulated ammonium polyphosphate in rigid polyurethane foam

Microencapsulated ammonium polyphosphate MFAPP or VMFAPP with shell of melamine–formaldehyde or poly (vinyl alcohol)–melamine–formaldehyde resin was prepared by in situ polymerization, respectively. The flame-retardant performance of rigid polyurethane foam (PU) containing MFAPP or VMFAPP was analyzed by limiting oxygen index and UL-94 test. Thermal degradation behaviors of PUAPP, PUMFAPP and PUVMFAPP were studied using TG and TG–FTIR. Above results indicated that VMFAPP and MFAPP have better water resistance and flame retardancy compared with ammonium polyphosphate (APP) in PU composites. Flame-retardant properties of PUMFAPP and PUVMFAPP composites were rarely changed after hot water treatment. Due to better compatibility and the presence of active groups on the surface of APP, microencapsulation demonstrated a positive effect on the mechanical property of PU composites.