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Flammability of intumescent coatings at the materials-scale is “expected” to have an impact on their fire resistance offered to the steel member. However, to what extent and at what stage during the exposure to an imposed fire curve in a furnace are not thoroughly established. The role of different functionality of the flame-retardant additives in this process is also not clear despite a thorough understanding of their thermal decomposition mechanisms. In an effort to better understand some of these aspects, in this work, model systems based on different flame-retardant additives in epoxy are chosen to cover various strategies (like intumescent, radical quenching, and endothermic behavior) that are typically employed to reduce the flammability of a coating system. The flame-retardant additives chosen are ammonium polyphosphate, tetrabromobisphenol-A, 9,10-dihydro-9-oxa-10-phosphaphenanthrene oxide, and aluminum trihydroxide. The effects of flame-retardant additives on the curing, thermal decomposition, and flammability of epoxy resin are investigated. Reactive flame-retardant additives, in particular, are found to reduce the enthalpy associated with curing of epoxy by more than 45%. However, as the amount of hardener incorporated in these formulations is not controlled despite the presence of reactive flame-retardant additives, this had a negative effect on the thermal decomposition behavior of the epoxy/flame-retardant formulations, and consequently on the calculated decomposition activation energies. Heating rate seems to be a dominating parameter influencing the flammability of the formulations. Peak heat release rate values, irrespective of the formulation, increased by more than 1382%–1970% by changing the heating rate in a pyrolysis flow combustion calorimeter from 6°C/min to 100°C/min. As the flammable volatiles released per unit time are higher at high heating rates, ignition and subsequent flaming of the coating occurred in the furnace tests, where a cellulosic fire curve was simulated. This has significantly influenced the fire resistance times.

Multifunctional cotton fabric was prepared through a two-step layer-by-layer spray coating method, where the first layer of the coating comprising chitosan and ammonium phytate provided fire retardancy, and the second one with PDMS-ZnO composite imparted hydrophobicity to the fabric. A molecular dynamics (MD) simulation study was carried out to calculate interfacial adhesion of different components of the coating, based on which the sequencing of the coating layers was determined and used to prepare coated samples. The coated fabric demonstrated a significant improvement in fire retardancy through an increase in LOI from 18 % in control to 30 %, a reduction in char length from 30 cm to 7 cm, and a decrease in peak and total heat release rate values by 75 % and 33 %, respectively. The hydrophobicity of coated fabric was tested via water drop test where coated sample maintained a contact angle of 148° for up to 120 s, while the control sample showed 0°.

A phase change material (PCM) composite was prepared by impregnating propyl palmitate in expanded perlite (EP, as a support matrix), and its thermal buffering performance was tested in building app...

The emphasis on sustainability in materials related to the construction and transportation sectors has renewed interest in the usage of natural fibers. In this manuscript, a different perspective is taken in adopting oil palm fibers (OPF) to develop composite panels and understand their acoustic, mechanical, and water susceptibility (including warm water analysis) properties to provide an insight into the potential of these panels for further exploration. The binder for these composite panels is a water-based acrylic resin, and for reinforcement purposes, fly ash and other metal oxides are used. It is shown that the presence of fibers positively influences the acoustic absorption coefficient in the critical mid-frequency range of 1000–3000 Hz. Even the noise reduction coefficient values highlighting the octave band are higher by more than 50% in the presence of fibers as compared to traditional refractory boards. Quasistatic indentation and drop-weight tests have also highlighted the excellent performance of the composite panels developed in this work. Though the water immersion tests on composite panels and subsequent analysis showed relatively minor changes in their performance, the immersion of the panels in caustic warm water for 56 days has resulted in their severe degradation with a loss of more than 65% in flexural strength.

This review addresses the current potential of two-dimensional (2D) transition metal dichalcogenide (TMD) nanomaterials for multi-functional polymeric nanocomposites. The properties of TMDs, characterization techniques, the applicability of different synthesis methods along with the surface treatment/modification of TMDs, are comprehensively examined by largely focusing on TMD/polymer nanocomposite preparation. Moreover, a vast range of nanocomposite properties, including mechanical/tribological properties, thermal stability/flame retardancy, and electrical/electronic properties, was investigated. The incorporation of TMDs in both thermoplastic and thermoset matrices can lead to the improvement of the aforementioned properties as reported by many studies in the literature. TMDs can thus possibly be considered not only as a liable reinforcement for polymers to induce multi-functionalities to nanocomposites but also a good hybridizing agent for other types of nano reinforcements. Potential opportunities offered by TMDs in composites/nanocomposites have opened up new horizons in a vast range of applications in different fields, including transportation, electrical/electronic, filtration and biomedical. This review has also compiled publications on the research and developments of TMDs and TMD composites/nanocomposites, from 1970 to the present, with the special focus on molybdenum disulfide (MoS2) and tungsten disulfide (WS2).

Zinc nitrate hexahydrate, an inorganic phase change material, can store high latent heat during its phase change, but it has significant phase transition defects, including form instability, a high degree of supercooling, and phase separation issues. Zinc nitrate hexahydrate/expanded perlite (EP) composite was fabricated by impregnating zinc nitrate hexahydrate into expanded perlite and further 65 wt% PCM-EP composite was coated with paraffin to reduce phase transition imperfections. Scanning electron microscope (SEM) results confirmed that the zinc nitrate hexahydrate could be impregnated into expanded perlite, and paraffin successfully formed a coating layer on the expanded perlite surface. Fourier transform infrared spectroscopy (ATR-IR) confirmed no chemical interactions between zinc nitrate hexahydrate and expanded perlite. The melting and crystallization enthalpies of paraffin-coated PCM composites are 82.24 ± 2.93 kJ kg−1 and 73.32 ± 1.97 kJ kg−1 respectively. The supercooling was reduced from 7 °C to 1 °C owing to numerous nucleation sites on the surface of expanded perlite and coating effect of the paraffin. After the 500 thermal cycles, melting and crystallization enthalpy of coated composite PCM is 78.24 kJ kg−1 and 68.32 kJ kg−1 respectively. Electric radiant floor heating application studies of the coated composite phase change material were performed by varying heat transfer area of building model and amount of composite used. COMSOL Multiphysics 5.6 was used to simulate the thermal buffering performance of the composite in floor heating application. The temperature profile predicted by the simulation was found to be quite close to the experimental data. Financial support to execute the experimental work is gratefully acknowledged to MHRD (Ministry of Human Resources Development) Plan grant (2019-20) and IIT Roorkee (No. OH-35-71-142), IIT Roorkee, India.

Due to high energy storage densities and reduced requirement of maintenance or moving parts, phase change materials are believed to have great potential as thermal energy storage materials. Salt hydrate phase change materials have been relevant since the earliest commercial deployment of latent heat thermal energy storage solutions, however a deeper look into the present standing, commercial requirements and performance improvements of this class of materials indicates that their capabilities have remained underdeveloped, and their advantages, underleveraged. These phase change materials have better thermal performance, better flame retardance, lower manufacturing costs, and a more sustainable supply than their organic counterparts, although a few limitations still exist, often hampering a more widespread adoption. As such, much research in recent years has been focused on eliminating these shortcomings. Presently, all these challenges are critically reviewed, and relevant mitigation/enhancement strategies are also discussed. In the purview of this discussion, shape stabilized composites arise as a singular strategy to alleviate the performance properties of salt hydrate phase change materials across multiple dimensions. A detailed review on the advantages offered by shape stabilized phase change materials is presented along with relevant development studies reported in the literature. Altogether, the reported information provides a perspective towards commercial realization of salt hydrate phase change materials in a wide range of applications, spanning from cold chain logistics to textile incorporation and building materials to solar heating solutions. Financial support to execute the experimental work is gratefully acknowledged to MHRD (Ministry of Human Resources Development, India) Plan grant (2019–20) and IIT Roorkee (No. OH-35-71-142), India.

The combination of egg white proteins (W) and hypophosphorous acid (HA) was used for developing a flame retardant coating for cotton fabrics by adopting the layer-by-layer assembly technique. This has resulted in a novel phosphorous-nitrogen-based assembly due to strong electrostatic interactions between W and HA. Coated cotton fabrics were characterized by using a variety of microscopic, analytical and thermal/combustion tests. Flammability properties of the fabrics were evaluated as per widely recognized standards like BS EN ISO 15025:2016 for protective clothing and ASTM D6413 for flame resistance of textiles. Coated cotton fabric showed self-extinguishing property with significant but fragile residual char structure, whereas uncoated fabric completely burnt with a little ash as residue. Thermogravimetric analysis revealed that decomposition temperature of coated fabric was lowered compared to control fabric, but char residue increased at 800 °C. Forced combustion cone calorimeter tests on the coated and uncoated fabrics showed that peak heat release rate, total heat released, and average rate of heat emission values reduced by 80%, 38%, and 40%, respectively, for coated fabrics as compared to control fabric. Even the mass loss rate value of the coated fabric has reduced significantly (from 514 g/m2.s for the uncoated fabric to 2 g/m2.s for coated fabric). Wash durability of the coated fabrics, though showed a slight reduction in flame-retardant properties as a consequence of ~ 9.7 wt% coating loss during soaking, yet there was no after-glow.

Foam concrete is conventionally used in non-structural applications (e.g. thermal and acoustic insulation) due to its lightweight nature and poor mechanical properties. However, interest in adopting foam concrete as structural components has increased phenomenally in recent years due to its lightweight and sustainable feature. A new type of foam concrete termed as carbon nanofibers enhanced lightweight cementitious composite (CNF-LCC) was developed by blending micro-foam bubbles with carbon nanofibers enhanced ultra-high performance concrete; it has superior mechanical properties, long-term properties and bond performance with steel bar compared with conventional foam concrete. In this paper, thermal properties of CNF-LCC during heating were investigated and compared with normal weight concrete (NWC) and lightweight aggregate concrete (LWAC). From room temperature to 800 ℃, the thermal diffusivity of CNF-LCC was lower than NWC and similar to LWAC while the specific heat and thermal conductivity of CNF-LCC was lower than both NWC and LWAC. CNF-LCC showed better structural efficiency than NWC and LWAC in combination of mechanical and thermal insulation properties. The measured thermal insulation properties under high temperature were verified by conducting one-dimensional heat transfer tests and numerical analysis on CNF-LCC blocks. Furthermore, the thermal strain of CNF-LCC during heating is lower and more stable than NWC and LWAC. Dehydration reaction at isothermal elevated temperature was characterised for the analysis of experimental results. Foam bubbles could reduce both thermal insulation and strain properties while a low dosage of CNFs had minimum effect on the thermal insulation properties but could improve the mechanical properties and decrease the thermal shrinkage. CNF-LCC showed potential for fire resistant as a structural lightweight concrete due to the excellent thermal insulation and lower thermal strain properties. The authors would like to acknowledge financial and materials support from ceEntek Pte Ltd.

Microencapsulated phase-change material (ME-PCM) employing octadecane as a core material has been practiced for thermal-energy-storage (TES) applications in buildings. However, octadecane as a hydrocarbon-based PCM is flammable. Herein, silica-shelled microcapsules (SiO2-MCs) and poly(urea-formaldehyde)-shelled microcapsules (PUF-MCs) were successfully prepared, loaded with octadecane/tributyl phosphate (TBP) as hybrid core materials, which not only exhibited good TES properties but also high-effective flame retardancy. SiO2-MC (ΔHm = 124.6 J g-1 and ΔHc = 124.1 J g-1) showed weaker TES capacity than PUF-MC (ΔHm = 186.8 J g-1, ΔHc = 188.5 J g-1) but better flame retardancy with a lower peak heat-release rate (HRRpeak) of 460.9 W g-1 (556.9 W g-1 for PUF-MCs). As compared with octadecane (38.7 kJ g-1), the reduction in total heat release (THR) for SiO2-MC was up to 22% (30.1 kJ g-1) with combustion time shortened by 1/6. SiO2-MC had a typical diameter of 150-210 μm, shell thickness of ∼6.5 μm, and a core fraction of 84 wt %. SiO2-MC showed better thermal stability with a higher initial evaporation/pyrolysis temperature than PUF-MC. The thermal decomposition of MCs with its mechanism of flame retardancy was significantly studied using thermogravimetric analysis/infrared spectrometry (TG-IR). The strategy presented in this study should inspire the development of microcapsules with PCMs/flame retardants as hybrid core materials for structural applications. Agency for Science, Technology and Research (A*STAR) Ministry of National Development (MND) The authors would like to acknowledge financial support from the Agency for Science, Technology and Research (A*STAR) -- Ministry of National Development (MND), Singapore (SERC132 176 0014).

Polypropylene (PP) fibers are commonly used for the prevention of thermal spalling of ultra-high performance concrete (UHPC). In this work, the effect of fiber distribution on permeability and spalling resistance is investigated and an analytical model for permeability at 150 °C is proposed. This model, considering the parameters like fiber dimensions, dosage, and percolation, is based on Kozeny-Carman equation. It was found that the percolation of the interconnecting fiber network resulted in a significant increase in permeability of UHPC. X-ray tomography data on the three-dimensional spatial distribution of fibers reiterated that fiber aspect ratio and dosage (and fiber number density) were critical in increasing the fiber connectivity (percolation). It was also found that a vapor permeability of larger than 0.6 × 10⁻¹⁶ m² at 150 °C could eliminate spalling. Further, based on a semi-empirical approach, aspect ratio between 300 and 600 was recommended for spalling prevention with a fiber dosage of 0.3–0.4 vol%. Ministry of National Development (MND) National Research Foundation (NRF) This research work is supported by the Singapore Ministry of National Development and National Research Foundation under L2 NIC, Award No. L2NICCFP1-2013-4.

Material-scale tests involving milligrams of samples are used to optimize fire-retardant coating formulations, but actual applications of these coatings require them to be assessed with structural-scale fire tests. This significant difference in the scale of testing (milligrams to kilograms of sample) raises many questions on the relations between the inherent flammability and thermal characteristics of the coating materials and their &ldquo, performance&rdquo, at the structural scale. Moreover, the expected &ldquo, requirements and the definition of &ldquo, varies at different scales. In this regard, the pathway is not established when designing and formulating fire-retardant coatings for structural steel sections or members. This manuscript explores the fundamental relationships across different scales of testing with the help of a fire-protective system based on acrylic resin with a typical combination of intumescent additives, viz. ammonium polyphosphate, pentaerythritol, and expandable graphite. One of the main outcomes of this work dictates that higher heat release rate values and larger amounts of material participating in the pyrolysis process per unit time will result in a rapid rise in steel substrate temperature. This information is very useful in the design and development of generic fire-retardant coatings.

It has been established that the addition of synthetic fibers like polypropylene (PP) to ultra-high performance concrete (UHPC) enhances the latter's thermal spalling resistance. The key for this is the thermal mismatch between embedded fibers and matrix as a result of the expansion of PP fibers with temperature. This paper explores the effect of natural fibers (replacing traditional PP fibers) on compressive strength, hot permeability, and spalling resistance of UHPC. Different dosages (3, 5 and 10 kg/m3) of jute fibers are used for this purpose. The findings are critical as they oppose the mechanism of thermal spalling resistance established for synthetic fibers in UHPC. Natural fibers swell by absorbing water (during the casting of UHPC and during their service life) and shrink upon exposure to warm and high temperatures. The deswelling and shrinkage of natural fibers at high temperatures create spaces between fibers and matrix, which could influence permeability at those temperatures. This suggests that percolation of fibers is critical in the case of jute as opposed to PP fibers. It was found that a dosage of 10 kg/m3 of jute fibers is required for eliminating spalling of UHPC as opposed to 3 kg/m3 for PP fibers. Additionally, preliminary efforts are put in to investigate the short-term durability of the samples and changes in properties of UHPC with jute fibers. Ministry of National Development (MND) National Research Foundation (NRF) This research/work is supported by the Singapore Ministry of National Development and National Research Foundation under L2 NIC, Award No. L2NICCFP1-2013-4.

Cheetah skin carbon nanotube, a novel periodically patterned nanocarbon on CNT synthesized as a highly effective filler for fabrication of high performance composites. The advantage of newly developed morphology lies in the fact that the size of nanocarbon on CNT and their distance can be fully controlled based on the application requirements. Cheetah skin CNT shows an excellent thermal stability and dispersibility in a high density polyethylene (HDPE) compared to pristine CNT/HDPE composite, making cheetah skin CNT a suitable candidate for fabrication of high performance HDPE based composite. The addition of cheetah skin CNT into HDPE resulted in a composite with improved thermomechanical properties. Compared with the pure HDPE and HDPE/pristine CNT, storage modulus and loss modulus of HDPE/cheetah skin CNT improved significantly at low temperatures even with very low content of cheetah skin CNT. Also, the thermal stability of the cheetah skin CNT/HDPE was found to be significantly higher than that of pristine CNT/HDPE composite in both isothermal and non-isothermal degradation performed for composites.

In this Research Article, we report on the development of water-based flame retardant coating based on phospho-nitrogen combination for cotton fabrics. A one-step spray-on process was employed to coat the fabrics by taking advantage of the spontaneous reaction between para-phenylenediamine (PDA) and tetrakis (hydroxymethyl) phosphonium chloride (THPC) resulting in an instantaneous precipitation of poly[1,4-diaminophenylene-tris(dimethyl hydroxymethyl)phosphine] (PApP) on the fabric surface. The effectiveness of PApP in improving the flame retardant properties like ignition resistance and lateral flame spread were evaluated in accordance with ASTM D6413 and BS EN ISO 15025 flammability tests. Despite the early (thermal) decomposition onset for coated fabrics under both oxidative and pyrolytic conditions, remarkably, self-extinguishing behavior (

Highly porous graphene aerogels enhanced with phenolic resol resin are prepared by a hydrothermal synthesis followed by high-temperature annealing. The introduced phenolic resol resin and its pyrolysis derivative effectively combine the sheets together and thus the three-dimensional networks of the enhanced aerogels are well retained even after compounding with epoxy resin. The synthesized aerogels are highly efficient in endowing epoxy with high electrical conductivity, excellent electromagnetic interference (EMI) shielding efficiency and satisfactory mechanical reinforcement. With only 0.33 wt% of the annealed aerogel, its epoxy nanocomposite exhibits a high electrical conductivity of 73 S/m and an excellent EMI shielding effectiveness of 35 dB, which are among the best results for polymer nanocomposites with even higher loadings. Especially, the EMI shielding performance is comparable to or even higher than that of the nanocomposite filled with chemical vapor deposition-synthesized graphene foam. Furthermore, the aerogel also leads to notable 67% and 20.2% increases in flexural strength and flexural modulus, respectively. Therefore, the phenolic resin-enhanced graphene aerogel holds a great potential in producing high-performance polymer nanocomposites for EMI shielding application.

This work highlights the thermal decomposition and fire-protective behaviour of two polymer-based coatings for concrete. The coatings are entirely free of halogenated compounds. Although the combustion behaviour of the coatings is different from classical intumescence, their action is based on a condensed-phase mechanism, which creates a steep temperature gradient between the coating surface and the coating-concrete interface. When subjected to the ISO 834 heating curve, one of the coatings could prevent the temperature of the interface from rising above 345 °C even after 3 h (corresponding furnace temperature is 1114 °C). Heat transfer simulation corroborates the observed fire-protective behaviour and shows that it may have potential for use on structural members. Analysis of the concentration of several gases produced by the burning of the coatings shows that they do not pose an immediate danger to life and health.

This work explores the importance of varying the ratio of conventional flame-retardant additives and the scale of testing on the thermal and flammability/fire performance of acrylic-based coatings. Ammonium polyphosphate (APP), pentaerythritol (PER), and expandable graphite (EG) are used as intumescent additives by varying their ratios as 1:1:3 or 1:3:1 or 3:1:1. APP, PER and EG are used as acid source, carbonising agent and blowing agent, respectively. Despite the different roles of APP, PER, and EG, in all the compositions, the physical mechanism of exfoliation of graphite played an important role in offering the fire protection. With higher loadings of EG, the fire-resistance time was higher. However, there were clear differences in the protection extent when tested in a furnace under one-dimensional heat transfer conditions (bench-scale) as opposed to three-dimensional large-scale testing. Parameters that are not intrinsic to the coating system like char cohesion, cracking, delamination from the substrate, rapid and non-directional expansion, and even higher heat fluxes experienced by the edges of the I steel section affect the fire performance. Ministry of National Development (MND) Nanyang Technological University National Research Foundation (NRF) This material is based on research work supported by the Singapore Ministry of National Development and National Research Foundationunder L2 NIC Award No. L2NICCFP1-2013-4 and JTC through NTU-JTC I3C (RCAs 16/277 and 17/365).

Carbon nanotubes have considerable potential for use as reinforcements in high-performance polymer composites, but their large-scale application has been hindered by their poor processability. Here, we report an extremely simple and scalable method for the chemical treatment of single-wall carbon nanotubes (SWNTs) to enable easy dispersion in an epoxy matrix. The treatment involves stirring SWNTs in a concentrated solution of sodium hydroxide in ethanol. The chemicals used can be recovered and re-used. The treated SWNTs show greater ease of exfoliation into organic solvents without the need for high-intensity ultrasonic probe treatment. Raman spectroscopy shows that the treatment does not create any noticeable defects or functional groups on the SWNT walls. As a result of the treatment, the SWNTs could be dispersed in epoxy with minimal, low-power ultrasonic treatment. The resulting composites showed increased fracture toughness and tensile strength at SWNT loadings as low as 0.5 weight percent, when compared with neat epoxy. The enhancement in properties of the composites does not decrease with increased SWNT loading, implying that the SWNTs do not re-aggregate.

Simultaneous improvement of flame retardancy and physiological comfort of clothing fabrics has not been studied before. One of the probable reasons for this is the complexity of dynamic processes involved. This work is a preliminary effort to understand various parameters involved in combining these two facets of fabrics. For this purpose, polyester fabrics are coated with branched polyethylenimine (BPEI) and sodium montmorillonite (smectite clay) via electrostatic self-assembly approach. The effect of their concurrent presence in different concentrations (variation of number of bilayers) on thermo-oxidative properties and flame retardancy behavior as well as physiological comfort (in terms of wicking, moisture management, and air permeability) of polyester has been assessed. The obtained results have shown the efficiency of the electrostatic self-assembly process in improving both facets. This work provides the foundation and knowledge for further development of effective coating systems with a multi-functional approach in the textile industry. Keywords: Flame retardant textiles, Electrostatic self-assembly, Moisture management, Montmorillonite

It has been a common practice to use polymer fibers to reduce susceptibility of explosive spalling in ultra-high performance concrete (UHPC). However, to-date, despite the proposition of different mechanisms through which polymer fibers enhance gas permeability and reduce explosive spalling, there are many unanswered questions and unjustified claims on the proposed mechanisms. Therefore, the major emphasis of this work is to thoroughly re-examine and understand the exact role of polymer fibers in the prevention of explosive spalling of UHPC. A range of analytical and microscopic tools are used to realize this objective. It is concluded that melting of polymer fibers and creation of empty channels are not required for enhancing the permeability of gases or water vapor through concrete. In fact, it is the thermal mismatch between embedded fibers and matrix that is critical in obtaining an interconnected network of cracks in the matrix. This occurs even before melting of polypropylene (PP) fibers. The network of cracks is responsible for enhancing permeability, thereby reducing the susceptibility of explosive spalling of UHPC.

It is well known that when an unprotected steel structure is exposed to fire, depending on the section factor, the temperature of the steel increases rapidly. This increase affects the mechanical properties of the steel and could result in deformation/failure of the structure depending on the temperature, time, and applied load. Therefore, conventionally, intumescent-based coatings are used as protective coatings on steel. However, poor weathering resistance of these coatings is a major problem. Even the slightest changes in chemical composition due to weathering reduce the fire performance of these coatings. This review focuses on elaborating and exploring the protective coatings for steel, the environmental interaction of these polymer-based coatings, sorption kinetics of moisture/water, leaching of flame-retardant additives, subsequent changes in chemical composition of the coatings, and the resulting effect on fire performance of coatings. Discussions on UV degradation of polymeric materials, blister formation in weathered coatings, and corrosion susceptibility of the substrates are also incorporated in these topics. NRF (Natl Research Foundation, S’pore) Accepted version

A key parameter influencing ignition, heat of combustion and charring of polymer/clay (montmorillonite, MMT) nanocomposites during combustion is the catalytic activity of clay. This work explores the effect of metal ions (MIs) like Mg2+, Al3+ and Fe3+ that are inherent to clay in altering the kinetics of degradation of organic modifier, hexadecyltrimethylammonium bromide (HDTMA-Br). Based on Brønsted and Lewis acid characteristics associated with these metal ions, their catalytic activity varied; Brønsted acidity affected initial stages of organic modifier degradation, while Lewis acidity influenced oxidation stability of carbonaceous residue beyond dehydration temperatures. For example, OMgMMT yielded delayed peak degradation temperature for HDTMA+, while Fe3+ ions from OFeMMT significantly lowered the oxidation stability of carbonaceous content. Knowing the effect of each metal ion separately, correlation between clay structural chemistry and organic degradation onset has been established. Degradation mechanism for alkyl fragment (from organic modifier) was provided adding fundamental knowledge to the field that will help in the design and development of polymer/clay nanocomposites with superior fire retardancy. MOE (Min. of Education, S’pore) Accepted version

The key objective of this work is to highlight the effect of manufacturing-induced fiber waviness defects on the compressive failure of glass fiber-reinforced unidirectional specimens. For this purpose, in-plane, through-thickness waviness defects (with different waviness severities) are induced during the manufacturing of the laminate. Numerical and experimental results show that the compressive strength of the composites decreases as the severity of the waviness defects increases. A reduction of up to 75% is noted with a wave severity of 0.075. Optical and scanning electron microscopy observations of the failed specimens reveal that kink-bands are created in the wavy regions and lead to failure. NRF (Natl Research Foundation, S’pore) Published version

This paper examines the effect of surface treatment and filler shape factor on the fracture toughness and elastic modulus of epoxy-based nanocomposite. Two forms of nanofillers, polydopamine-coated montmorillonite clay (D-clay) and polydopamine-coated carbon nanofibres (D-CNF) were investigated. It was found that Young’s modulus increases with increasing D-clay and D-CNF loading. However, the fracture toughness decreases with increased D-clay loading but increases with increased D-CNF loading. Explanations have been provided with the aid of fractographic analysis using electron microscope observations of the crack-filler interactions. Fractographic analysis suggests that although polydopamine provides a strong adhesion between the fillers and the matrix, leading to enhanced elastic stiffness, the enhancement prohibits energy release via secondary cracking, resulting in a decrease in fracture toughness. In contrast, 1D fibre is effective in increasing the energy dissipation during fracture through crack deflection, fibre debonding, fibre break, and pull-out. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

This article reports the preparation of nylon 6/stacked-cup carbon nanofiber (CNF) nanocomposites via in situ anionic ring-opening polymerization partially initiated from caprolactam-functionalized CNFs. As a result of the successful functionalization of CNF surface, good dispersion of the CNFs was observed by transmission electron microscopy (TEM). Moreover, with the addition of a very small amount of CNFs, significant enhancements in tensile modulus and yield strength were achieved together with slightly improved impact resistance. The enhanced stiffness may be attributed to effective filler–matrix stress transfer induced by interfacial covalent bonds. On the other hand, SEM micrographs provided evidence for the possible unraveling of the stacked-cup CNF, which may allow the CNFs to bridge the matrix during crack propagation, hence resulting in the toughening of the nanocomposites. ASTAR (Agency for Sci., Tech. and Research, S’pore)

The article elucidates the mechanisms of formation of varying degrees of surface pores/pits on polylactic acid (PLA) fibers during electrospinning. The role of a combination of different parameters in governing pore formation was demonstrated. They include solvent vapor pressure (pv), solvent miscibility/interaction with water, solubility parameter, and relative humidity (RH) within the spinning unit. Our results indicated that traditional mechanisms like thermally induced phase separation (TIPS) and vapor induced phase separation (VIPS) were not responsible in the generation of surface porosity/pits. Instead, higher RH (water vapor, a non-solvent of the polymer), and its miscibility/interaction with solvent(s) were concluded to be relatively more important than the simple presence of a high pv solvent or a combination of high pv and low pv solvent system. Further, content of high pv solvent in solution determined the spherical or elliptical nature of pores/pits by affecting the level of saturation of nearby region of the interface between jet and air during the electrospinning process. Accepted version

Dispersion and spatial distribution of graphene sheets play crucial roles in tailoring mechanical and functional properties of their polymer composites. Anisotropic graphene aerogels (AGAs) with highly aligned graphene networks are prepared by a directional-freezing followed by freeze-drying process and exhibit different microstructures and performances along the axial (freezing direction) and radial (perpendicular to the axial direction) directions. Thermal annealing at 1300 °C significantly enhances the quality of both AGAs and conventional graphene aerogels (GAs). The aligned graphene/epoxy composites show highly anisotropic mechanical and electrical properties and excellent electromagnetic interference (EMI) shielding efficiencies at very low graphene loadings. Compared to the epoxy composite with 0.8 wt % thermally annealed GAs (TGAs) with an EMI shielding effectiveness of 27 dB, the aligned graphene/epoxy composite with 0.8 wt % thermally treated AGAs (TAGAs) has an enhanced EMI shielding effectiveness of 32 dB along the radial direction with a slightly decreased shielding effectiveness of 25 dB along the axial direction. With 0.2 wt % TAGA, its epoxy composite exhibits a shielding effectiveness of 25 dB along the radial direction, which meets the requirement of ∼20 dB for practical EMI shielding applications. Accepted version

Solvothermally reduced and functionalized graphene (SRFG) was obtained by refluxing graphene oxide in dimethyl formamide at 140 °C. The resultant simultaneous nitrogen-doping and presence of dangling bonds on SRFG prompted us to study the evolution of structural changes with refluxing time. It is shown that the removal of oxygen-containing functional groups leaves dangling bonds during the solvothermal reduction, which are responsible for the nitrogen-doping with longer refluxing time. The relationship between the defects of SRFGs and their lithium ion storage performances are also discussed.

Inspired by the radical scavenging function of melanin-like materials and versatile adhesive ability of mussel-adhesion proteins, dopamine-modified clay (D-clay) was successfully incorporated into polypropylene (PP) using an amine-terminated PP oligomer as the compatibilizer. Although the PP/D-clay nanocomposites exhibit intercalated morphology, the incorporation of D-clay greatly improves the thermo-oxidative stability and UV resistance of PP owing to the strong radical scavenging ability of polydopamine (PDA) and large contact area between PP and the PDA coating on clay mineral. Moreover, the reinforcement effect brought by D-clay is fairly significant at very low clay loadings probably owing to the strong interfacial interactions between the layered silicates and the compatibilizer as well as that between the compatibilizer and the PP matrix. The work demonstrates that D-clay is a type of promising nanofiller for thermoplastics used for outdoor applications since it stabilizes and reinforces the polymers simultaneously.

Novel clay/waterborne polyurethane (WPU) nanocomposites were synthesized in which the clay was acidmodified with hydrochloric acid. The molecular motion of nanocomposites was investigated using high resolution solid state 13C NMR technique. Addition of clay drastically decreased the molecular mobility of waterborne polyurethane in hard segment; but little in soft segment. Two-leg trouser studies revealed that introducing clay into waterborne polyurethane significantly enhanced the tearing toughness of the nanocomposites. Refereed/Peer-reviewed

In this monograph, basics and advanced knowledge of different facets of polymer nanocomposites will be reviewed. This understanding will take us a step closer towards achieving truely multi-functional polymer nanocomposites. This monograph also highlights our continuous and coherent research efforts over many years on these materials.