Cure Index Research Articles

Grass curing-driven fire danger index in a protected mountainous grassland using fused MODIS and Sentinel-2

ABSTRACT This study assessed the spatio-temporal variation of the degree of curing (DoC) in the Golden Gate Highlands National Park (GGHNP) from 2016 to 2020. The estimation of the degree of grass curing was carried out with the high spatial resolution fused remotely sensed data of MODIS and Sentinel-2 employing Index-then-Blend (IB) data fusion methods on Google Earth Engine (GEE) to compute Grassland Curing Index (GCI) using soil and vegetation moisture content indices-based grassland curing algorithm. Grassland curing indices were computed on Google Earth Engine and converted into Grassland Curing Maps (GCMs), which were then synthesized into fire danger maps. The study showed that all selected indices have the highest DoC in the month of September, with the minor time variation observed in MODIS and Sentinel 2-derived GCI estimated using Shortwave Infrared Water Stress (GCI_SIWSI) in the months of August and March, respectively. The analysis further revealed that GCI_SIWSI (44%) derived from Sentinel-2 data yielded the highest area of extremely high fire danger, followed by GCI estimated using Normalized Difference Moisture Index (GCI_NDMI) (25%) derived from fused data, MODIS-derived GCI_SIWSI and fused-derived GCI estimated using Global Vegetation Monitoring Index (GCI_GVMI) (both 16%). The GCI_SIWSI derived from Sentinel-2 data also showed that more than 95% of the entire landmass of the study area was within a high to extremely high fire danger zone, making the park’s vegetation susceptible to fire. Among all the four selected indices correlated against fire point, only SIWSI revealed a positive relationship across MODIS, Sentinel-2 and Fused data. It is also evident from the study that GCMs derived from Fused data outperformed MODIS and Sentinel-2 with the highest R2 and F values of 0.65 and 380, respectively. These results indicate that GCI derived from fused remotely sensed data is a promising GCI for accurately assessing the DoC over mountainous grassland environments. The study paved the way for increasing the spatial resolution for estimating the DoC for fire and fuel management of parks and other fire agencies within mountainous grassland environments.

Fluorinated‐polyhedral oligomeric silsesquioxane (F‐POSS) functionalized halloysite nanotubes (HNTs) as an antifouling additive for epoxy resin

AbstractAntifouling epoxy resin serves as a member of advanced nanocomposite coatings and engineered surfaces. Nevertheless, developing an antifouling epoxy composites is a state‐of‐the‐art technology. Herein, a complex nanostructure is tailored to be served as an advanced additive giving the antifouling characteristics to the epoxy resin. F‐POSS@HNT hybrid nanostructure, that is, halloysite nanotubes (HNTs) decorated with fluorinated polyhedral oligomericsil sesquioxane (F‐POSS), was synthesized and characterized. Chemical structure changes, thermal stability and morphology of hydroxylated HNTs (hHNTs) intermediate and F‐POSS@HNT ultimate nanostructures were analyzed by FTIR spectroscopy, TGA and TEM, respectively. The F‐POSS@HNTs catalyzed the epoxy‐amine crosslinking reaction, taking “Good” or “Excellent” crosslinking tags an quantified by the “Cure Index.” The apparent activation energy values were calculated for the epoxy (reference), epoxy/hHNTs, and epoxy/F‐POSS@HNTs systems (26, 51, and 47 kJ mol−1, respectively). Contact angle measurements were performed via dynamic tests demonstrating improved hydro‐ and oleophobicity of the thermoset composites. The advancing contact angle with diiodomethane increased 36% and 30% for nanocomposites containing 5 and 10 wt.% of the developed hybrid nanostructure, respectively, compared with the neat epoxy. Likewise, 54% and 67% reduction in paraffin fouling in the same order confirmed their antifouling ability. Regarding self‐cleaning characteristics, 24% and 33% surface recovery were observed, respectively.Highlights Antifouling surface was achieved in epoxy thermoset nanocomposites for potential industrial applications. Self‐cleaning behavior correlated with low wetting and antifouling properties. F‐POSS@HNT nanofillers were synthesized and successfully added to epoxy matrix. Both hHNT and F‐POSS@HNT showed a beneficial autocatalytic effect on epoxy‐amine reaction yielding satisfactory polymer crosslinking. Activation energy was reduced by incorporating F‐POSS@HNT compared with hHNT, signature of facilitated crosslinking.

Optimization of safflower oil-based polyester biocomposite reinforced with diatomite: An response surface methodology approach and assessment of artificial neural network findings

In this investigation, the examination revolves around the characterization of diatomite-enhanced modified safflower oil (MSO)-derived polyester biocomposites. The primary objective is to explore the feasibility of these biocomposites as a substitute for petrochemical-based unsaturated polyester (UP) materials, with the overarching goal of enhancing their economic sustainability. Experimental data analysis employed Response Surface Methodology (RSM) and Artificial Neural Network (ANN), uncovering the optimal composition for the polyester biocomposite to be 6.7 wt.% MSO and 4.5 wt.% diatomite. During the RSM analysis, it was noted that the response parameters exhibited quadratic p-values, specifically, for density ( p < .0001), thermal conductivity ( p < .0001), and Shore D hardness ( p < .0003). However, higher ratios of MSO lead to decreased hardness and increased curing time. SEM images reveal a detrimental impact on the surface morphology of the polyester biocomposite when the diatomite content reaches 8 wt.%. Additionally, Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) offer valuable insights into the chemical bond structure and thermal behavior of the biocomposite, respectively. The Cure Index (CI) value for the diatomite-enhanced composite was determined to be 0.925, indicating a favorable contribution to the polyester curing process. The study finds that diatomite contributes to a linear change in the thermal conductivity coefficient, making the biocomposite suitable for use in the insulation industry. Overall, the study suggests that diatomite reinforced MSO-based polyester biocomposites have the potential as an alternative to petrochemical unsaturated polyester.

Curing kinetics study of chemically modified pineapple leaf fiber/epoxy composite

Agricultural by-products have long hinder farmers, and subsequently, the food supply chain. Making use of their natural by-products will both reduce waste and increase industrial production. In particular, pineapple leaf fibers (PALF) can be extensively studied. Here, the curing kinetics of chemically modified PALF/epoxy resin crosslinked by an anhydride hardener was investigated by non-isothermal and isothermal methods with the differential scanning calorimetry technique. In this study, the Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods, as well as Kamal's model, were employed to analyze the curing behavior of epoxy in non-isothermal and isothermal processes, respectively. The highest activation energies for pure epoxy and PALF/epoxy composite calculated differ when using the methods. Additionally, a decreasing trend in the activation energy values during the late stages of epoxy curing was observed. The results from Kamal's model indicate that the k1 values of the PALF/epoxy composite are only greater than those of pure epoxy at 100°C and 110°C. However, all the k2 values of PALF/epoxy are greater than those of pure epoxy. Additionally, the m value of the PALF/epoxy composite is lower than that of pure epoxy only at 100°C, while the n and m+n values of the PALF/epoxy composite are all greater than those of pure epoxy. Moreover, the results reveal that the Cure Index of the PALF/epoxy composite was larger than ΔH* and smaller than ΔT*. With PALF, it was found that the epoxy resin’s curing rate was increased and the activation energy was reduced. Meanwhile, the degree of crosslinks was less than that of the virgin resin. It is speculated that the hydroxyl groups on the plant fibers and the amine groups on the coupling agent-modified fibers can promote the cross-linking reaction. However, the curing reaction of the composite is affected by steric obstacles and high viscosity resulting from the addition of PALFs.

Nigella sativa extract phytochemicals: Effective green/bio-active anti-corrosion agent for steel protection in saline media

This research aims to develop a low-VOC silane (sol-gel) coating functionally protected by novel non-toxic metal-organic networks (MONs) based on extracted Nigella sativa bio-molecules/Zinc nitrate. The effectiveness of the silane coating containing the MONs pigment was investigated via electrochemical (i.e., EIS) and accelerated (i.e., salt spray) corrosion experiments. Based on the electrochemical tests' results in the solution phase, an efficiency of 67.8% and a mixed-type corrosion mitigation mechanism were obtained for the hybrid pigment to protect the mild steel against the NaCl media. Moreover, adding the synthesized MONs into the silane coating matrix dramatically increased its protection performance. Fourier-transform infrared spectroscopy (FT-IR) results revealed that the coating’s curing index is affected after the MONs pigment’s inclusion in the silane matrix. The change in the coating curing index increases the silane film crosslinking density, improving coating adhesion to the metallic substrate and then enhancing its anti-corrosion protection performance. The electrochemical tests were employed in the presence of artificial defects to study the active protection performance of the silane layer. Results indicated that the active anti-corrosion protection performance of the silane coating was significantly improved after employing the synthesized MONs in its structure. Adsorbing the inhibitive species in the scratched region of the silane coating and fabricating the inhibitive film at this region is the main protection mechanism, which was illustrated via SEM/EDS analysis.

Toughing epoxy nanocomposites with graphene-encapsulated liquid metal framework

Multifunctional epoxy nanocomposites have long been pursued as the crucial component of future aerial vehicles, while their practical implementation is unfortunately restricted by the poor toughness and incapability of chemical activity derived from highly cross-linked networks. Here, inspired by “brittle–ductile” laminated architecture, a stress-induced graphene-encapsulated liquid metal framework was developed to enhance the fracture toughness of multifunctional epoxy nanocomposites and their electromagnetic interference shielding, outdoor deicing and crosslinking behaviors were discussed. The resulting “brittle-ductile” laminated structure enables effective crack deflection and unique fracture surface; the plane strain fracture toughness (KIC) of epoxy nanocomposites is 2.34 times higher than that of pure epoxy resin. Moreover, the reinforced epoxy nanocomposites exhibited high electromagnetic interference shielding effectiveness of 48.24 dB at X-band, about 20 times greater than that of the pure epoxy (∼2.4 dB), and its efficient solar de-icing capability enable spontaneously melting surface ice/frost within 3 min. The dimensionless Cure Index (CI) was used for qualitative analysis of epoxy crosslinking in the presence of graphene-encapsulated liquid metal framework performed by nonisothermal differential scanning calorimetry (DSC). This work shows for the first time to the best of our knowledge graphene encapsulated liquid metal framework as reinforced fillers in epoxy nanocomposite achieve a unification of high toughness, electromagnetic shielding capabilities, and solar deicing properties. Present work thus provides an alternative of constructing high-toughness multifunctional epoxy nanocomposites for aerial vehicles application.

A novel DOPO derivative containing multifunctional groups aiming to improve fire safety, thermal stability and curing state towards epoxy resin

A novel reactive flame retardant (PABO) was synthesized via a one-pot reaction from para-aminobenzonitrile, p-hydroxy benzaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and applied on epoxy resin (EP). The curing state of the EP mixture with the addition of PABO was excellent as detected by the cure index (CI). Thermogravimetric analysis showed that compared with DOPO, PABO possessed a higher degradation temperature, a lower thermal decomposition rate and the Char800 (char residues at 800°C) increased from 1.5 to 26.5 wt%. The EP/PABO-5 with only 5 wt% PABO content attained a limiting oxygen index of 32.7% and possessed the UL-94 V-0 level. The calculated flame retardant index (FIGRA) showed that the fire safety of EP/PABO-5 was superior to that of EP/DOPO-5. For flame retardant mechanism, in the gas phase, PABO possessed the function of retarding the thermo-oxidative decomposition of EP, the quenching effect of phosphorus radicals and the diluting effect of non-combustible nitrogen-containing gas. In the condensed phase, the trimerization reaction of nitrile groups happened and the existence of the phosphaphenanthrene group together promoted the formation of a stable char layer, which could obstruct the transfer of heat and oxygen.

Adhesive Films Based on Benzoxazine Resins and the Photoreactive Epoxyacrylate Copolymer

UV-cross-linkable and thermally curable self-adhesive structural tapes (SATs) were compounded using solid commercial benzoxazine resins (Araldite MT 35700 and Araldite MT 35910) and a photoreactive epoxyacrylate copolymer (EAC). As initiators of benzoxazine resin polymerization and epoxy component cationic polymerization, two kinds of latent curing agents (LCAs) were tested, i.e., amine type and ionic liquid type. The influence of the benzoxazine resin and the LCA type on the UV-cross-linking process, the self-adhesive features and thermal curing behavior of UV-cross-linked tapes, as well as the shear strength of cured aluminum/SAT/aluminum joints and thermal stability of adhesives were investigated. It was found that the amine additive and the benzoxazine resin take part in the UV-cross-linking process of the EAC as hydrogen donors, which is confirmed by an increase in cohesion (+86%) and a decrease in adhesion (−25%) of SATs. The highest results of adhesion to steel (47 N/25 mm) and overlap shear strength (11.1 MPa) values were registered for SATs based on Araldite MT 35910 and contained 7.5 wt. parts of the amine-type hardener. The formation of a polyacrylate-benzoxazine network has a significant impact on the course of the thermal curing process and the thermomechanical properties of adhesive joints, which was also confirmed by the Cure Index calculation.

Correlating thermal properties of polyurethane/clay nanocomposite coatings with processing

Phase morphology of polyurethane (PU) and its nanocomposites with Bentone 38 (B38) nano clay additive has been investigated and its effect on the thermal degradation behaviour has been evaluated. Two processing schemes were used to reinforce B38 into the matrix of PU in three different weight percentages (1, 2 and 3 wt%). The nanocomposite coatings show different formations (pyramid, sheet stacks etc.) of clay on the surface of the PU nanocomposite samples. The variable intensity of the key peaks in Fourier transform infrared spectroscopy (FTIR) confirms changes in the chemical interface between B38 clay-PU chains due to different processing schemes. The FTIR data was quantitatively derived to calculate the degree of phase separation (DPS) and the degree of phase mixing (DPM) and analyse the effect of this variation. “Cure index” calculations from differential scanning calorimetry (DSC) were used to analyse the cure state of the nanocomposites. The morphological studies through X-ray diffraction (XRD), atomic force microscopy (AFM) and optical microscopy (OM) highlight the variation in structures due to modified processing schemes. An improvement of around 34% (89 °C) is seen in the 20% weight loss temperature (Tg20) at a loading of just 1 wt% B38. DSC scans also show improved thermal properties. A shift of 14 °C (2 wt% B38) and 46 °C (1 wt% B38) respectively is observed in the degradation temperature from the heat flow scans w.r.t. the pristine PU. These results indicate that even at low clay loadings, properties can be significantly enhanced just by tweaking the processing scheme, thereby indicating the great sensitivity nanocomposites have to processing schemes.

Hydroxylated hexagonal boron nitride nanoplatelets enhance the mechanical and tribological properties of epoxy-based composite coatings

The relationship between microstructure and properties of hydroxylated hexagonal boron nitride nanoplatelets (denoted as OH-h-BN) reinforced epoxy composite coatings was still not clear. In this work, hexagonal boron nitride nanoplatelets (h-BN) were successfully hydroxylated to increase their dispersion and compatibility with the EP matrix, which was confirmed by the results obtained from FTIR, XPS, XRD and TEM. Subsequently, OH-h-BN reinforced epoxy resin (EP) composite coatings were prepared by means of a spraying process, and their curing characteristics, cross-linking density and mechanical and tribological properties were discussed. As a result, the EP/OH-h-BN composite coating took an excellent curing label in terms of the ‘Cure Index’ (CI) and had a cure enthalpy 1.5 times higher than that of the pure EP coating. Moreover, with the presence of OH-h-BN, the storage modulus (at 40 °C) and cross-linking density of the epoxy composite coating were enhanced by 56% and 43%, respectively. The tensile test outcomes presented approximately 16% and 138% improvements in the maximum tensile strength and elongation at break of the EP/OH-h-BN composite coating compared with pure EP coating. In addition, the friction coefficient and the wear rate were reduced by 27% and 58% because of the enhancement of mechanical strength of the EP/OH-h-BN composite coating and the formation of a continuous, dense and high load-carrying lubricating tribofilm on the dual steel ball.

Synthesis of graphene oxide functionalized by polyaniline coated alpha-zirconium phosphate to enhance corrosion resistance of waterborne epoxy coating

Graphene oxide (GO), a preeminent two-dimensional (2D) material, has great potential application for corrosion protection owing to its excellent barrier properties to gas and liquid. Unfortunately, the poor dispersion in waterborne epoxy resins and excessive surface defects limit the further application of GO. In this study, a novel GO-based nanofiller PZ-GO (GO modified by polyaniline-wrapped alpha-zirconium phosphate) was designed to endow waterborne epoxy coating (WEC) system with durable anti-corrosion performance. Among them, the modification of alpha-zirconium phosphate (α-ZrP) wrapped with polyaniline (PZ) for GO not only enhanced the dispersion of GO but also strengthened its barrier effect. Notably, as a linker between GO and α-ZrP, PANI could also endow the coating with active inhibition performance. Differential scanning calorimetry (DSC) was introduced to investigate the effect of adding nanofillers on ‘Cure Index’ of composites. The ‘Cure Index’ of epoxy resins doped with PZ-GO was 1.139, which was considered as ‘Excellent’ according to the evaluation criteria, proving that the addition of PZ-GO significantly reinforced the curing degree of epoxy resins. A more complete cure of the epoxy resins could provide a stronger barrier ability for the coatings, thus improving the corrosion resistance of the coatings. Furthermore, the anticorrosive behavior of PZ-GO/WEC was analyzed via electrochemical impedance spectroscopy (EIS) and salt spray tests. The results showed that PZ-GO/WEC exhibited great anticorrosive performance (the impedance value was maintained at 8.72 ×10 7 Ω.cm 2 after immersion in 3.5 wt% NaCl solution for 80 days). In particular, PZ-GO/WEC also demonstrated great active inhibition performance. In addition, the active inhibition mechanism of PZ-GO/WEC was revealed by X-ray photoelectron spectroscopy (XPS) analysis of the corrosion products. All results proved that the excellent corrosion protection properties of PZ-GO/WEC for carbon steels originated from the outstanding barrier ability of PZ-GO/WEC and the active inhibition of PANI. In this study, graphene oxide-based nano-fillers for anticorrosive reinforcement of waterborne epoxy coating were prepared by a facile process. In details, α-zirconium phosphate nanosheets with the size of 0.5μ to 1μ was fabricated by a simple hydrothermal reaction. Then, wrapping polyaniline on the surface of α-zirconium phosphate was achieved through in-situ polymerization. Further, graphene oxide was modified with smaller laminar polyaniline-coated alpha-zirconium phosphate via π-π interaction through facile ultrasonic vibration process. • A novel GO-based nanofiller PZ-GO with high barrier abilities and active inhibition properties. • PZ-GO endows waterborne epoxy coating with durable anti-corrosive performance. • PZ-GO/WEC exhibited great active inhibition performance.

Synthesis of a phosphaphenanthrene/triazole oligomer for simultaneous improvement of flame retardancy and smoke suppression of epoxy resins

In this work, a phosphaphenanthrene/triazole oligomer named PDTD was synthesized based on DOPO, 1, 4-phthalaldehyde and 3,5-diamino-triazolz, and used as flame retardant to solve the flammability of epoxy resin (EP). When only 7 wt% PDTD was added, limited oxygen index (LOI) of EP-7% composite greatly elevated to 36% from 22.5% of neat EP with a 60% of increment, and obtained a UL-94 V0 rating as well as showed good heat and smoke suppression properties. The results of flame retardant index (FRI) showed EP-7% was considered to have good flame retardance. The cure of epoxy/PDTD was qualitatively analyzed by cure index (CI), and the result exhibited EP/PDTD system (EP-3%, EP-5%) possessed excellent cure state at low concentration of PDTD. In addition, investigation of flame-retardant mechanism revealed that the improvement of flame retardancy was mainly due to the barrier effect of residual carbon in condensed phase, and dilution effect and free radical capture effect of gaseous phase.

Epoxy/Ionic Liquid-Modified Mica Nanocomposites: Network Formation-Network Degradation Correlation.

We synthesized pristine mica (Mica) and N-octadecyl-N’-octadecyl imidazolium iodide (IM) modified mica (Mica-IM), characterized it, and applied it at 0.1–5.0 wt.% loading to prepare epoxy nanocomposites. Dynamic differential scanning calorimetry (DSC) was carried out for the analysis of the cure potential and kinetics of epoxy/Mica and epoxy/Mica-IM curing reaction with amine curing agents at low loading of 0.1 wt.% to avoid particle aggregation. The dimensionless Cure Index (CI) was used for qualitative analysis of epoxy crosslinking in the presence of Mica and Mica-IM, while qualitative cure behavior and kinetics were studied by using isoconversional methods. The results indicated that both Mica and Mica-IM improved the curability of epoxy system from a Poor to Good state when varying the heating rate in the interval of 5–15 °C min−1. The isoconversional methods suggested a lower activation energy for epoxy nanocomposites with respect to the blank epoxy; thus, Mica and Mica-IM improved crosslinking of epoxy. The higher order of autocatalytic reaction for epoxy/Mica-IM was indicative of the role of liquid crystals in the epoxide ring opening. The glass transition temperature for nanocomposites containing Mica and Mica-IM was also lower than the neat epoxy. This means that nanoparticles participated the reaction because of being reactive, which decelerated segmental motion of the epoxy chains. The kinetics of the thermal decomposition were evaluated for the neat and mica incorporated epoxy nanocomposites epoxy with varying Mica and Mica-IM amounts in the system (0.5, 2.0 and 5.0 wt.%) and heating rates. The epoxy/Mica-IM at 2.0 wt.% of nanoparticle showed the highest thermal stability, featured by the maximum value of activation energy devoted to the assigned system. The kinetics of the network formation and network degradation were correlated to demonstrate how molecular-level transformations can be viewed semi-experimentally.

The correlated effects of polyetheramine-functionalized graphene oxide loading on the curing reaction and the mechanical properties of epoxy composites

In this study, the effects of polyetheramine (D230) functionalized graphene oxide loading on the curing reaction, thermal and mechanical properties of epoxy composites were studied and the correlation between structure and property of epoxy composite was established. In the functionalization of graphene oxide (GO), the effect of the mass ratio of D230 to GO on chemical properties of the functionalized GO was investigated. Results showed that D230 were successfully covalently grafted onto surface of two-dimensional functionalized GO sheet. The functionalized GO sheets prepared under optimal condition of D230/GO ratio of 1:1 dispersed evenly in epoxy composites, indicating the possibility of the epoxy composite fabrication by the solvent-free technique. The analysis of qualitative Cure Index suggested that epoxy composites were subjected to excellent curing. The quantitative evaluation of curing kinetics demonstrated that the functionalized GO exhibited a chemical facilitation on the curing reaction. However, the functionalized GO simultaneously physically restricted the curing reactivity, especially at high loading. These contributed to the improved interfacial properties and high toughness of the epoxy composites. Compared to neat epoxy, the epoxy composites showed effective tensile strength improvement of ∼10.0% (77.0 MPa), tensile modulus enhancement of ∼7.7% (3.34 GPa), flexural modulus increment of ∼12.1% (3.43 GPa), and flexural strength increment of ∼10.6% (124.3 MPa). This study demonstrated an effective and environment-friendly strategy to design GO reinforced epoxy composites with favorable dispersion and interfacial bonding, and it further clarified the relationship between the crosslinking network/interfacial structure and the mechanical properties of epoxy composites.

Correlating the Photophysical Properties with the Cure Index of Epoxy Nanocomposite Coatings

Transparency is a crucial factor in developing functional and decorative thin films and coatings, but incorporation of nanoparticles into organic resins for improving their properties quite often makes them opaque. In this work, photophysical properties of epoxy/layered double hydroxide (LDH) nanocomposite coatings were correlated with the dispersion state of LDH in the epoxy resin. The quality of solid epoxy network was assessed in terms of the Cure Index (CI) in relation to the transparency of the films containing 0.1, 0.5, 0.7, 1.0, and 3.0 wt% Mg–Al–LDH and Zn–Al–LDHs. At high loadings, direct transmittance (YDirect) decreased, while the light scattering in the coatings improved with respect to the neat epoxy. The highest Zn–Al–LDH loading (3.0 wt%) slightly deteriorated the transparency (YDirect = 93.3), but it was still higher than that of epoxy nanocomposite containing 0.5 wt% Mg–Al–LDH (YDirect = 89.8). A Good label was assigned to the epoxy nanocomposites containing up to 1.0 wt% Zn–Al–LDH, while epoxy/Mg–Al–LDH nanocomposites were Poor in terms of the CI labeling when Mg–Al–LDH content was more than 0.1 wt%. An increase of about 28 °C in the Tg value after the addition of 0.1 wt% Zn–Al–LDH indicated that Zn–Al–LDH can make strong the interaction between the epoxy matrix and nanoplatelets. However, decrease in the Tg of the epoxy/Mg–Al–LDH nanocomposites was a signature of the weak interactions between the Mg–Al–LDH nanoplatelets ‎and epoxy matrix due to inappropriate dispersion. In general, it was revealed for the first time that the CI enables correlating the chemical crosslinking with the photophysical properties of the epoxy/LDH nanocomposites.

Imidazole-functionalized nitrogen-rich Mg-Al-CO3 layered double hydroxide for developing highly crosslinkable epoxy with high thermal and mechanical properties

Ionic liquid-based N-octadecyl-N'-octadecyl imidazolium iodide functionalized layered double hydroxide (LDH-IM) was synthesized for manufacturing high-performance epoxy nanocomposites. Nonisothermal differential scanning calorimetry (DSC) was performed to study cure kinetics of epoxy reinforced قث with LDH and LDH-IM. Incorporation of Mg-Al-CO3 LDH into epoxy hindered the curing reaction, as detected by dimensionless Cure Index (CI). By contrast, epoxy/LDH-IM cured Good and Excellent due to imidazolium ionic liquid. Higher activation energy for completely cured epoxy/LDH-IM nanocomposite was obtained compared to epoxy and epoxy/LDH nanocomposites. The curing reaction rate was obtained by calculation of the orders of instantaneous autocatalytic and non-catalytic reactions, and optimal kinetic parameters based on isoconversional methods were in good agreement with experimental cure reaction rates. Lower value of Tg for epoxy/LDH nanocomposite compared to the neat epoxy signified weak interactions between Mg-Al-CO3-LDH and epoxy matrix, while a higher Tg was obtained for epoxy/LDH-IM. Network degradation kinetics of the samples was also investigated. The higher decomposition activation energy for epoxy/LDH-IM approved strong interfacial adhesion in the assigned system. The highly reactive nature of the developed LDH-IM gives reason for its usage for developing highly curable epoxy with high thermal and mechanical properties.

Bulk-Surface Modification of Nanoparticles for Developing Highly-Crosslinked Polymer Nanocomposites.

Surface modification of nanoparticles with functional molecules has become a routine method to compensate for diffusion-controlled crosslinking of thermoset polymer composites at late stages of crosslinking, while bulk modification has not carefully been discussed. In this work, a highly-crosslinked model polymer nanocomposite based on epoxy and surface-bulk functionalized magnetic nanoparticles (MNPs) was developed. MNPs were synthesized electrochemically, and then polyethylene glycol (PEG) surface-functionalized (PEG-MNPs) and PEG-functionalized cobalt-doped (Co-PEG-MNPs) particles were developed and used in nanocomposite preparation. Various analyses including field-emission scanning electron microscopy, Fourier-transform infrared spectrophotometry (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) were employed in characterization of surface and bulk of PEG-MNPs and Co-PEG-MNPs. Epoxy nanocomposites including the aforementioned MNPs were prepared and analyzed by nonisothermal differential scanning calorimetry (DSC) to study their curing potential in epoxy/amine system. Analyses based on Cure Index revealed that incorporation of 0.1 wt.% of Co-PEG-MNPs into epoxy led to Excellent cure at all heating rates, which uncovered the assistance of bulk modification of nanoparticles to the crosslinking of model epoxy nanocomposites. Isoconversional methods revealed higher activation energy for the completely crosslinked epoxy/Co-PEG-MNPs nanocomposite compared to the neat epoxy. The kinetic model based on isoconversional methods was verified by the experimental rate of cure reaction.

Reactive oxygen species explicit dosimetry to predict local tumor growth for Photofrin-mediated photodynamic therapy.

Although photodynamic therapy (PDT) is an established modality for cancer treatment, current dosimetric quantities, such as light fluence and PDT dose, do not account for the differences in PDT oxygen consumption for different fluence rates (ϕ). A macroscopic model was adopted to calculate reactive oxygen species concentration ([ROS]rx) to predict Photofrin-PDT outcome in mice bearing radiation-induced fibrosarcoma (RIF) tumors. Singlet oxygen is the primary cytotoxic species for ROS, which is responsible for cell death in type II PDT, although other type I ROS is included in the parameters used in our model. Using a combination of fluences (50-250 J∕cm2) and ϕ (75 or 150 mW∕cm2), tumor regrowth rate, k, was determined for each condition by fitting the tumor volume versus time to V0 *exp(k*t). Treatment was delivered with a collimated laser beam of 1 cm diameter at 630 nm. Explicit dosimetry of light fluence rate on tissue surface, tissue oxygen concentration, tissue optical properties, and Photofrin concentration were performed. Light fluence rate at 3 mm depth (ϕ 3mm) was determined for the treatment volume based on Monte-Carlo simulations and measured tissue optical properties. Initial tissue oxygenation [3 O 2]0 was measured by an Oxylite oxygen probe before PDT and used to calculate [ROS]rx,calc. This value was compared to [ROS]rx,meas as calculated with the entire tissue oxygen spectrum [3 O 2](t), measured over the duration of light delivery for PDT. Cure index, CI = 1-k/kctr , for tumor growth up to 14 days after PDT was predicted by four dose metrics: light fluence, PDT dose, and [ROS]rx,calc, and [ROS]rx,meas. PDT dose was defined as the product of the time-integral of photosensitizer concentration and ϕ at a 3 mm tumor depth. These studies show that [ROS]rx,meas best correlates with CI and is an effective dosimetric quantity that can predict treatment outcome.

Fabrication and characterization of alumina-silica/poly(o-toluidine) nanocomposites as novel anticorrosive epoxy coatings films on carbon steel

Alumina-silica/poly(o-toluidine) (POT) nanocomposites were designed from o-toluidine monomer by in-situ polymerization in the existence of nano-Al2O3:SiO2 with a different ratio. The structure and the composition of the as-prepared nanocomposites were investigated in terms of Fourier-transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), zeta-potential and nonisothermal differential scanning calorimetry (DSC) methods. Epoxy resin (EP) was blended with the introduced-Al2O3:SiO2/POT composites using a solution combination technique. A qualitative evaluation provided using Cure Index (CI), Al2O3: SiO2/POT/EP nanocomposites can facilitate or hinder curing reaction depending on the different ratios of alumina to silica. The Al2O3:SiO2/POT/EP nanocomposites were painted onto the C-steel substrates, and its corrosion protection characteristics were examined by electrochemical (potential vs. time, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP)) measurements in 1.0 M HCl as corrosive medium and also compared with that of the composite POT/EP coating. The outcomes indicated that the coating systems containing Al2O3:SiO2/POT/EP nanocomposite has higher corrosion resistance than that of individual POT. The protection capacity values of coated systems POT/EP, Al: Si/POT/EP, 2Al: Si/POT/EP and Al: 2Si/POT/EP were 75.2, 91.2, 86.7 and 97.5%, respectively. The existence of Al2O3-SiO2 nanocomposites improved the quality of the POT/EP coating by decreasing the porosity of the painting matrix. FESEM observations before and after the corrosion test confirmed that the occurrence of Al2O3-SiO2 nanocomposites improve the protection features of POT/EP coating.

Curing kinetics and mechanical properties of epoxy resin/1-benzyl-2-methylimidazole/isophorone diamine system

The epoxy resin of diglycidyl ether of bisphenol A (DGEBA) diluted with allyl glycidyl ether (AGE) was mainly cured by 1-benzyl-2-methylimidazole (1B2MZ). Then, the effect of isophorone diamine (IPDA) on the properties of DGEBA-AGE-1B2MZ system was investigated. The differential scanning calorimetry (DSC) results revealed that when the content of 1B2MZ was small, the epoxy groups need to be completely cured by imidazole regeneration, which would be unnecessary with the introduction of IPDA thereby alleviating the burden of 1B2MZ. The variations of the activation energy with the degree of curing determined via Ozawa–Flynn–Wall were various for the studied systems. Calculations based on the Cure Index (CI) approved that the cure states of all the composite systems were affected by the heating rate. Finally, the resin of optimal formula could be cured in 20 min at 120 °C with the best mechanical properties and the glass transition temperature (Tg) of 100.61 °C.