Urethane Composites Research Articles

Synthesis and Property Evaluations of a Bio‐Based Anticorrosive Urethane Composites Containing Bisphenol a as Extender

AbstractThis article reports the synthesis of an eco‐friendly polyurethane composite system, which was successfully prepared in a one‐pot synthetic pathway by combining castor seed oil (CSO), bisphenol A (BPA), isophorone diisocyanate (IPDI), and functional hybrid nanoparticles (prepared by modifying the peripheral surface of silica with 3‐aminopropyltrimethoxysilane (APTMS). The urethane composites were cast as thin films on tin foils and mild steel and cured under atmospheric moisture. Attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy was used to characterise the cured composite films, scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), corrosion resistance, antimicrobial analysis, salt spray test, and water contact angle measurements. Our evaluations showed improved thermal and hydrophobic properties of the composite coatings. Also, the electrochemical and antimicrobial analyses clearly show resistance to corrosion and test organisms as the percentage composition of APTMS‐SiO2 increases in the urethane system.

Significantly enhanced thermal conductivity of polymer composites via establishing double-percolated expanded graphite/multi-layer graphene hybrid filler network

Utilization of hybrid fillers with high thermal conductivity enhancement (TCE) efficiency is an effective method for the large-scale fabrication of polymeric thermal interface materials (TIMs) with exceptional thermal conductivity. Herein, we report the thermally conductive properties of thermoplastic urethane (TPU) composites incorporated with expanded graphite (EG) and multi-layer graphene (MLG). The effect of percolation behavior of EG/MLG hybrid fillers on the thermal conductivity is systematically revealed. It is found that the high-loading TPU composite with 20 wt% EG and 10 wt% MLG reveals an exceptional thermal conductivity of 8.52 Wm−1K−1, which corresponds to a TCE of 3450% compared to that (0.24 Wm−1K−1) of pure TPU matrix. Notably, the TCE per 1 wt% filler reaches a substantial value of 115%. The thermally conductive mechanism is proposed based on morphology and thermal contact resistance analyses. Moreover, the application of such TPU composites in thermal management of light-emitting diode lamps is exhibited, and the effectiveness is further verified through finite element simulation. Our results shed light on the significant thermal synergy between EG and MLG and demonstrate their application potential in high-performance TIMs.

Improvement of interfacial adhesion of unidirectional textile grade carbon fiber (TCF) with unsized, epoxy and urethane sizing reinforced in thermoset urethane composites

This work considers a unique wide tow (450k filaments) form of low-cost carbon fiber intended for non-aerospace applications. TCF is currently produced in epoxy and urethane sizing, and there is a need to understand its resulting composite properties. In this study, the interfacial adhesion of sized TCF reinforced in thermoset urethane (TSU) composites are examined through the surface, thermal and mechanical characterization techniques. Atomic force microscopy (AFM) results showed an increase in surface roughness for urethane (276%) and epoxy sized (78%) versus unsized TCF. XPS results showed 531% increase in O in epoxy sized TCF and 250% N content in urethane sized TCF compared to unsized TCF. The surface energy of epoxy and urethane sized TCF is enhanced by 78% and 96%, respectively compared to unsized TCF. The storage modulus showed improvement for urethane (23%) and epoxy (21%) sized than unsized TCF-TSU composites. The flexural, interlaminar shear strength (ILSS), and impact properties of urethane sized TCF increase by 24%, 50%, and 273%, respectively, than unsized TCF. The results demonstrate that the surface and thermal properties correlate with the mechanical properties of TCF-TSU composites and sizing enhances the wettability of the composites.

Cyclic carbonates of rapeseed methyl esters as monomers for urethane composites

The two-stage synthesis of cyclic carbonates based on methyl esters of fatty acids from rapeseed oil is characterized. The first stage involves the synthesis of epoxides by the reaction of unsaturated methyl esters of rapeseed fatty acids with hydrogen peroxide, orthophosphoric and acetic acids. The second step is a carbonization reaction, which was carried out by passing carbon dioxide through the reactive mixture in the presence of tetrabutylammonium bromide as a catalyst. A reactive oligourethane based on cyclocarbonates cyclic carbonates of rapeseed fatty acids and piperazine was synthesized by the non-isocyanate method via the interaction of cyclocarbonate group with the amino group of piperazine. Polymer composites based on synthesized cyclocarbonates, epoxides and amines of different chemical nature were prepared and studied. Thus, there is a possibility of regulating the physical and mechanical properties of epoxyurethane composites.

THERMOPHYSICAL AND PHYSICO-MECHANICAL CHARACTERISTICS OF EPOXYURETHANE COMPOSITES

Epoxy urethane composites (EU) have been developed based on polyisocyanate (PIC), epoxy resin (ED-20), and sodium silicate (SS). The results of the study of the influence of the ratio of the components of the EU on their thermophysical and physicomechanical characteristics are presented. The method ofdifferential scanning calorimetry revealed thatthese systems do not have clear temperature transitions, which indicates a fairly homogeneous and rigid structure. Studies of thermal properties by the method of dynamic thermogravimetry have shown that as the amount of sodium silicate increases, the temperature of the onset of decomposition of the EU is shifted by 20 ° C towards lower temperatures. At the same time, there is a slowdown in the decomposition of epoxy urethanes (weight loss is 12-14%), due to the presence of heterocyclic isocyanurate fragments, which is inherent in its own high thermal stability. The mechanical properties of the EU, such as compressive strength, modulus of elasticity, relative compression deformation, flexural strength, and water absorption, are determined depending on the ratio of components. High mechanical properties are shown regardless of the inorganic component amount. The modulus of elasticity, strength, and relative deformation in compression is in the range of 1916.4 - 4187.6 MPa, 117.4 - 133.1 MPa, and 24.7-30.4%, respectively. The highest flexural strengths are characterized by the EC composition of the PIC / SS / ED-20 = 80/20/20, and the lowest - the EC composition of the PIC / SS / ED-20 = 70/30/20. The results of the studies show that, by changing the ratio of organic and inorganic constituents in the EC, it is possible to regulate the thermal stability and physicomechanical properties of epoxy urethane composites depending on their purpose.

Damage Detection in Fiber-Reinforced Foamed Urethane Composite Railway Bearers Using Acoustic Emissions

To a certain degree, composite railway sleepers and bearers have been recently employed as a replacement for conventional timber sleepers. Importantly, attributed to the rise in traffic demand, structural health monitoring of track structural members is essential to improve the maintenance regime and reduce risks imposed by any structural damage. A potential modern technique for detecting damage in railway components by using energy waves is called acoustic emission (AE). This technique has been widely used for concrete structures in other engineering applications, but the application for composites is relatively limited. Recently, fiber-reinforced foamed urethane (FFU) composites have been utilized as railway sleepers and bearers for applications in the railway industry. Neither does a design standard exist, nor have the inspection and monitoring criteria been properly established. In this study, three-point bending tests were performed together with using the AE method to detect crack growth in FFU composite beams. The ultimate state behaviors are considered to obtain the failure modes. This paper is thus the world’s first to focus on damage detection approaches for FFU composite beams using AE technology, additionally identifying the load-deflection curves of the beams. According to the experimental results, it is apparent that the failure modes of FFU composite beams are likely to be in brittle modes. Through finite element method, the results were in good agreement with less than 0.14% discrepancy between the experimental and numerical data. The attractive insights into an alternative technique for damage assessment of the composite components will help railway engineers to establish structural monitoring guidelines for railway composite sleepers and bearers.

Holey, anti-impact and resilient thermoplastic urethane/carbon nanotubes fabricated by a low-cost “vapor induced phase separation” strategy for the detection of human motions

It is a great challenge to develop a scalable and cost-effective strategy for fabricating porous polymer-based piezoresistive devices. Here we presented a sort of conductive porous thermoplastic urethane (TPU) composites incorporated with carbon nanotubes by a vapor-induced phase separation method. By the introduction of carbon nanotubes (CNTs), the TPU composite exhibits moderate electric conductivity and improved compressive property. TPU composites are demonstrated to be highly sensitive sensors for monitoring both compression and bending strain. The value of ΔR/R0 changed from 90.0 to 98.7% while the gauge factor varied from 1.98 to 9. Further study on the dynamic mechanical performances indicates the produced TPU composites are strain-rate sensitive and the addition of CNTs can improve the anti-impact performances of TPU foam. The strategy adopted to fabricate TPU/CNT composite will pave the way for the development of low-cost and wearable sensors in practical applications of health monitor and sports.

Dynamic properties of fibre reinforced foamed urethane composites in wet and dry conditions

Advanced materials such as plastics and composites have been invented and adopted for bespoke products in railway industry. For instance, they have been employed as railway track sleepers, switches and crossings’ bearers, bridge transom girders, and so on. Railway track sleepers and bearers are essential for operations that enhance safety and reliability of railway turnouts. The degradation mechanism of railway sleepers/bearers is attributable largely to the type of materials used. The utilisation of composite material as turnout bearers, located in railway switches and crossings, has resulted in many questions whether they can experience aggressive environments. In reality, the dynamic properties of bearers play a key role in the serviceability performance of the switches and crossings. Exposed to high-intensity impact loading condition, switches and crossings withstand excessive vibrations, which can disable crawlock or signalling gear systems. Even though such effects are well-known, the influence of environmental variance on the dynamic properties of the bearers has yet been determined thoroughly. The goal of this investigation is to identify the influence of wet and dry conditions for the practical guideline and design solutions using composite materials for railway turnout systems. In this investigation, ‘fibre-reinforced foamed urethane (FFU)’, is emphasized since FFU has been installed in several railway switches and crossings globally. The dynamic properties of the FFU materials will be identified using the instrumented impact hammer testing method. The dynamic damping property of FFU can be calculated by exponential curve fittings, and logarithmic decrements. The results show that FFU on average absorbs less than 5% of water. Interestingly, the water absorption has led to the increment in dynamic moduli in both fibre-grain directions up to 16%.

Preparation and Thermal Analysis of Blended Nanoaluminum/Fluorinated Polyether-Segmented Urethane Composites

The thermally induced reaction of aluminum fuel and a fluoropolymer oxidizer such as polytetrafluoroethylene (via C-F activation) has been a well-studied thermite event for slow-burning pyrolants among a multitude of energetic applications. Generally, most metallized thermoplastic fluoropolymers suffer from manufacturing limitations using common melt or solvent processing techniques due to the inherent low surface energy and high crystallinity of fluoropolymers. In this report, we prepared an energetic composite utilizing the versatility of urethane-based polymers and provide a comparative thermal characterization study. Specifically, a thermite formulation comprising of nanometer-sized aluminum (nAl) fuel coated with perfluoropolyether (PFPE) oxidizer was solvent-blended with either a polyethylene glycol (PEG) or PFPE-segmented urethane copolymer. Thermal data were collected with calorimetric and thermogravimetric techniques to determine glass transition temperature and decomposition temperature, which showed modest effects upon various loadings of PFPE-coated nAl in the urethane matrix. While our application focus was for energetics, this study also demonstrates the potential to expand the ability to broadly manufacture structural metallized composites to their consideration as coatings, foams, or fibers.

The effects of carbonized Eucalyptus globulus leaves on castor seed oil based urethane coating system

The usability of nanomaterials in various research endeavour has been on the front. burner in the past few decades. This is due to its high aspect ratio and steep electrical, molecular defined structure, mechanical and physical properties. This present study reports the synthesis of carbon nanomaterials (CNM) from Eucalyptus globulus leaves. Fresh green leaves of Eucalyptus globulus were collected and dried under the sun. The dried brown leaves were later incinerated completely under atmospheric oxygen. Obtained ashes were treated with acid piranha solution in other to modify the peripheral of the ashes with carboxyl groups (CNM-COOH). Scanning electron microscopy image divulges the presence of carbon nanorods in the ash. CNM-COOH materials in percentages were then incorporated within the polyurethane polymer matrix of which Castor seed oil (Ricinus communis) and trimethylopropane (TMP) provided the hydroxyl base for urethanation. Infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis was used to confirm material modification. Synthesized urethane composites of CNM-COOH material shows improved thermal, mechanical, hydrophobicity and anticorrosion properties when compared with that of pristine polyurethane (PU).

Poly(lactic acid)–thermoplastic poly(ether)urethane composites synergistically reinforced and toughened with short carbon fibers for three‐dimensional printing

ABSTRACTIn this study, we prepared short‐carbon‐fiber (CF)‐reinforced poly(lactic acid) (PLA)–thermoplastic polyurethane (TPU) blends by melt blending. The effects of the initial fiber length and content on the morphologies and thermal, rheological, and mechanical properties of the composites were systematically investigated. We found that the mechanical properties of the composites were almost unaffected by the fiber initial length. However, with increasing fiber content, the stiffness and toughness values of the blends were both enhanced because of the formation of a TPU‐mediated CF network. With the incorporation of 20 wt % CFs into the PLA–TPU blends, the tensile strength was increased by 70.7%, the flexural modulus was increased by 184%, and the impact strength was increased by 50.4%. Compared with that of the neat PLA, the impact strength of the CF‐reinforced composites increased up to 1.92 times. For the performance in three‐dimensional printing, excellent mechanical properties and a good‐quality appearance were simultaneously obtained when we printed the composites with a thin layer thickness. Our results provide insight into the relationship among the CFs, phase structure, and performance, as we achieved a good stiffness–toughness balance in the PLA–TPU–CF ternary composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46483.

Enhanced shape memory property of polylactide/thermoplastic poly(ether)urethane composites via carbon black self-networking induced co-continuous structure

The preparation of elastomer/plastic blends with co-continuous structure is beneficial to achieve good shape recovery and fixing performances. In this work, carbon black (CB) nanoparticles with self-networking capability were introduced to tailor the phase morphology and shape memory properties of polylactide (PLA)/thermoplastic poly(ether) urethane (TPU) blend (70/30 by weight). A morphological change from sea-island structure to co-continuous structure was observed with increasing CB content. The strong affinities between CB nanoparticles and TPU as well as the self-networking capability of CB nanoparticles led to the formation of this co-continuous structure. With such novel structure, the PLA70/TPU30/CB ternary composites owned an outstanding shape memory property because the continuous TPU phase provided stronger recovery driving force. Moreover, the selective localization of CB nanoparticles in the continuous TPU phase imparted the composites with enhanced mechanical properties and excellent electrical conductivities with low filler content. The composites then showed a good electroactive shape memory behavior, which could recover to their original shape within 80 s at 30 V. Our work provides a universal strategy via CB self-networking to prepare double percolated conductive polymer composites with optimal shape memory properties and excellent electrical conductivities, which may promote specific applications in intelligent devices.

The Use of Infrared Thermography in Detecting the Defects in Kenaf-Poly Urethane Composites

This paper explores the use of active thermography technique for Kenaf-Polyurethane (PU) composites. Presently the industry is going toward environmental friendly materials, so investigating more methods in quality control of products is an essential issue. Thermography has potential to detect the defects in-depth. The samples were manufactured by a hand lay-out method and use of a hot press to produce the composites. This method proves that the defects of Kenaf-PU boards are dependent on the amount of fiber and the thickness of the boards. Non-destructive infrared thermography technique has the capability of detecting the defects in Kenaf-PU boards. This study demonstrates evidence that this method can investigate some defects such as voids and kenaf fiber pulled out from its original place with an accuracy of 90%.

Fire Performance of Flax Laminates and their Hybrids

In the current age of growing environmental awareness, natural fibre composites have gained wide acceptance in various facets of engineering. However, in industries, such as aerospace and mining, their acceptance is primarily dependent on them meeting the stringent fire test requirements. In this paper, symmetric laminates consisting of only glass, glass/flax hybrid and only flax as reinforcements in thermoset matrices were tested for their time to ignition, heat release rate and smoke constituents as per standard ASTM E 1354 in a cone calorimeter. Four fire retardant versions of resin systems, were used in this study. The laminates were manufactured using wet hand-layup technique that was vacuum bagged and cured between hot platens of a hydraulic press. A constant fibre volume fraction of 0.5 for all the laminates was obtained by maintaining a constant laminate thickness of 4mm. The results from the cone calorimeter tests were compared to examine the influence of natural fibres on the fire properties of the laminates. It was observed that the degree of fire retardance in the polyester based composites decreased with the increase in the flax fibre content; however, in the modified urethane composites, flax fibre composites performed better by exhibiting higher ignition time compared to the hybrid and glass fibre composites. Another important observation was that the carbon monoxide emissions during testing decreased with the increase in flax content in the composites, no matter what resin system was used. These preliminary tests suggest that, by judiciously incorporating natural fibres in a synthetic system, a hybrid system could be designed to sustain loads in environments with high fire risks.

Synthesis and evaluation of modified urethane dimethacrylate resins with reduced water sorption and solubility

Objectives New aliphatic and aromatic urethane dimethacrylate monomers containing pendant phenyl methoxy or ethyl substituents were synthesized in order to reduce the water sorption and solubility of urethane dimethacrylate systems. Selected properties including flexural strength, flexural modulus, water sorption and solubility, and water contact angle were evaluated. Hoy's solubility parameters were also calculated to rank copolymer hydrophilicity. Methods Filled (20%) composite resins were formulated with each of the newly synthesized dimethacrylates as well as the commercially available urethane dimethacrylate monomer, UDMA. Flexural strength, flexural modulus, water sorption and solubility of the urethane composites were evaluated after light-cured specimens were immersed in water for seven days. Water contact angles were measured on the surface of each material. Data were analyzed using ANOVA and Ryan–Einot–Gabriel–Welsch multiple range tests ( α = 0.05). Results A significant reduction of nearly 30% and 40% in water uptake was observed with composite polymers containing pendant ethyl and phenyl methoxy groups, respectively, compared to UDMA ( p < 0.05). Urethane copolymers containing pendant ethyl groups also showed a significant reduction in water solubility ( p < 0.05). A positive correlation was found between contact angle and water sorption as well as Hoy's δ h for hydrogen bonding forces. Significance The results of this study indicate that the incorporation of pendant hydrophobic substituents within the monomer backbone may be an effective method in reducing the water sorption and water solubility of urethane based dimethacrylate systems. The use of Hoy's solubility parameters to determine the relative hydrophilicity of a polymer may be limited by its three-dimensional chemical structure.

Characteristics of organosilicon urethane composite materials and coatings

We study the principles of modification of organosilicon materials aimed at improving their physicomechanical, engineering, and operating parameters. The efficiency of application of viscous-flow polyurethane compositions as modifiers is demonstrated. We analyze the structural, physicomechanical, and dielectric characteristics of the polyurethane elastomers, organosilicon urethane composites, and anticorrosive coatings based on these compounds.

Enhanced fibronectin adsorption on carbon nanotube/poly(carbonate) urethane: Independent role of surface nano-roughness and associated surface energy

The contribution of nanoscale surface roughness on the adsorption of one key cell adhesive protein, fibronectin, on carbon nanotube/poly(carbonate) urethane composites of different surface energies was evaluated. Systematic control of various surface energies by creating different nanosurface roughness features was performed by mixing two promising biomaterials: multi-wall carbon nanotubes and poly(carbonate) urethane. High ratios of carbon nanotubes coated with poly(carbonate) urethane provided for greater hydrophilic surfaces because of higher nanosurface roughness although pure carbon nanotube surfaces were extremely hydrophobic. Fabrication methods followed in this study generated various homogenous nanosurface roughness values (ranging from 2 to 20 nm root mean square (RMS) AFM roughness). With the aid of such nanosurface roughness values in composites, a model was developed that linearly correlated nanosurface roughness and associated nanosurface energy to fibronectin adsorption. Specifically, independent contributions of surface chemistry (70%) and surface nano-roughness (30%) were found to mediate fibronectin adsorption. The results of the present study showed why carbon nanotube/poly(carbonate) urethane composites enhance cellular functions and tissue growth by delineating the importance of their physical nano-roughness on promoting the adsorption of a protein well known to be critical for mediating the adhesion of anchorage-dependent cells.

Structural relaxation and morphology of the rubber-urethane composites

The supermolecular structures and structural relaxation of the waste rubber–urethane composites are discussed on the basis of results of calorimetric measurements and mechanical spectroscopy. The results give a broader understanding of the relationship between processing history and morphology in the resultant engineering products. The effect of different kinds of urethane prepolymer on the thermomechanical properties of commercial composite products is presented. The idea of reaction between rubber granulate and urethane prepolymer is under consideration. The shear and tensile modes were applied to better explore relaxations that occur in rubber grains and in an interphase area created by the urethane agents. The rubber waste management problem was taken into account also. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1186–1193, 2004

Interfacial contributions in lignocellulosic fiber-reinforced polyurethane composites

Whereas lignocellulosic fibers have received considerable attention as a reinforcing agent in thermoplastic composites, their applicability to reactive polymer systems remains of considerable interest. The hydroxyl-rich nature of natural lignocellulosic fibers suggests that they are particularly useful in thermosetting systems such as polyurethanes. To further this concept, urethane composites were prepared using both unused thermomechanical pulp and recycled newsprint fibers. In formulating the materials, the fibers were considered as a pseudo-reactant, contributing to the network formation. A di-functional and tri-functional poly(propylene oxide)-based polyol were investigated as the synthetic components with a polyol-miscible isocyanate resin serving as a crosslinking agent. The mechanical properties of the composites were found to depend most strongly on the type of fiber, and specifically the accessibility of hydroxy functionality on the fiber. Dynamic mechanical analysis, swelling behavior, and scanning electron micrographs of failure surfaces all provided evidence of a substantial interphase in the composites that directly impacted performance properties. The functionality of the synthetic polyol further distinguished the behavior of the composite materials. Tri-functional polyols generally increased strength and stiffness, regardless of fiber type. The data suggest that synthetic polyol functionality and relative accessibility of the internal polymer structure of the fiber wall are dominant factors in determining the extent of interphase development. Considerable opportunity exists to engineer the properties of this material system given the wide range of natural fibers and synthetic polyols available for formulation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 546–555, 2001

Biologically degradable fiber‐reinforced urethane composites from wheat straw

AbstractUrethane type adhesive mixtures containing poly(MDI) were used to prepare biodegradable urethane type composites containing wheat stalks. According to the mechanical properties, i.e., tensile strength, bending strength, and hardness of the composites, the ratio of wheat stalks to sticking mixtures, the technological pressure used, and the size of the wheat stalks were optimized. The mechanism of the possible chemical reaction is also discussed.