Conventional Epoxy Research Articles

Mechanical behavior and composite action of two-wythe precast concrete sandwich beams via chemically hybridized intermediate layer

Composite action of two-wythe precast concrete sandwich beams are examined on the premise of an integrated thin intermediate layer that is suggested as a possible substitute candidate for industry-standard extruded polystyrene (XPS) in precast concrete sandwich panels (PCSP). Designable mechanical properties of a carbon-fiber reinforced interfacial epoxy-polyurea matrix (C-IEPM) may be tuned via the rate of reaction between epoxide and amine of a thermosetting epoxy network, controlled by the elapsed time of reaction tc, and its subsequent surface treatment via reaction with isocyanate and amine moieties, resulting in a thin covalently bonded IEPM layer. Thirteen concrete beams were tested under 4-point bending. A two-wythe beam with an intermediate C-IEPM layer (tc = 0.5 h) was compared to two-wythe beams that included the following intermediate layers: XPS, conventional carbon-fiber epoxy (CF/E), and no layer, where beams with a C-IEPM layer at lower tc showed substantial increase in peak strength and energy absorption: 54% and 97%; 47% and 143%; 27% and 46%, respectively. This indicates that C-IEPM that engenders a high-quality IEPM can substantially improve mechanical performance, energy absorption, and composite action. Finite element analysis of a two-wythe system with an assumed perfectly bonded C-IEPM intermediate layer (tc = 24) confirms that IEPM designed at tc ≤ 0.5 effectuates a perfect bond between wythes and also provides tremendous resiliency and strength sustainability in accordance with load-deflection response beyond the peak load, making C-IEPM a viable candidate as an intermediate layer in pre-cast multi-wythe constructions.

Mechanical property evaluation of alkali-treated jute fiber reinforced bio-epoxy composite materials

Natural fiber reinforced polymer composites have proved to be fit for use in several structural and functional applications. Jute fiber reinforced epoxy composites are one of the most preferred natural fiber-based polymer composites. The emerging need for high strength application while considering environmental sustainability and with the advent of bio-composites, the researchers, in recent times, started showing interest in incorporating the various bio-based resins in the composites. The present work thus aims at investigating the possibilities of making jute fiber reinforced epoxy composites with alkali-treated fibers and cashew nut shell liquid blended epoxy resins. The feasibility is tested through the mechanical properties, which is quantified using tensile strength and flexural strength. The modified matrix in the prepared composites is based on the variation in the weight percentage of cashew nut shell liquid (25 and 30%). The results indicate that it is possible to make better composites using the modified matrix and alkaline treated jute fibers as the mechanical properties outperform the jute fiber reinforced epoxy composites made using conventional epoxy resin and untreated jute fibers. The best amongst all the variants made, the one that proved to be the best JFRE composite is having alkaline treated fiber and blend 2, which exhibits an average tensile strength of 679 MPa, and flexural strength of 88.83 MPa.

Effect of Thiodiphenol-Based Epoxy Resin on the Thermal Properties of an Aluminum Oxide Composite

The effects of thiodiphenol based epoxy resin on the thermal property of the composites containing aluminum oxide were investigated. The thermal conductivities and thermal diffusivities of the composites were dependent on the polymer resin. At the same content of Al₂O₃, the thermal conductivity and thermal diffusivity of composites made by synthesized polymer resin exhibited higher than that of composite made by bisphenol-A resin. The obtained maximum thermal conductivity of the composite was 0.25 W/mK, which was 0.4 times as large as that of the conventional bisphenol-A epoxy resin which has an amorphous structure. It is supposed that the reason for the high heat conductivity obtained in thiodiphenol based epoxy resin is certain high packing structure.

The antibacterial activity of an epoxy resin-based dental sealer containing bioactive glass, hydroxyapatite, and fluorohydroxyapatite nanoparticles against Enterococcus Faecalis and Streptococcus mitis

Objective(s): The present study aimed to investigate the antibacterial properties of a conventional epoxy-based dental sealer modified with synthesized bioactive glass (BG), hydroxyapatite (HA), and fluorine-substituted hydroxyapatite (FHA) nano-fillers. Materials and Methods: The synthesized nano-fillers were incorporated into the conventional epoxy-based dental seaer at the concentration of 10%. The antimicrobial properties of the unmodified sealers (controls) and modified seaers with BG, HA, and FHA nanoparticles (NPs) were evaluated based on biofilm formation and using the direct contact test (DCT) of Enterococcus faecalis and Streptococcus mitis. Data analysis was performed using one-way analysis of variance (ANOVA) and Tukey’s post-hoc test at the significance level of 5%. Results: A significant reduction was observed in the biofilm formation and DCT of the microbial strains in the three modified groups compared to the unmodified conventional epoxy sealer (P<0.05). The addition of FHA NPs resulted in the most significant antibacterial effects against E. faecalis and S. mitis, as well as a statistically significant reduction compared to the unmodified and BG-modified groups (P≤0.001). Conclusion: According to the results of this preliminary study, nano-structured FHA, HA, and BG fillers incorporated into epoxy-based dental sealers could be potentially effective biomaterials for antibacterial approaches to root canal treatments.

Development of Epoxy with Nano and Micro Fillers for Core Insulation of Composite Insulators

Epoxy composites are extensively used in different applications in high voltage engineering. However, the use of these composites for outdoor insulators has been challenging due to complexities arising out of the conditions of operation of the insulators. Pollution performance of composite insulators is influenced by the nature of the pollution existing, in addition to the combination of stresses acting on the insulators. The use of nano and micro combination of fillers in the epoxy composites is an ideal choice for achieving a proper balance of electrical, thermal and mechanical properties. This paper considers the merits of using combination of micro and nano fillers in an epoxy matrix to demonstrate that such insulation systems would provide better alternatives to the conventional epoxy systems for use as central rod in composite insulation systems for severe contaminated conditions.

Facile one pot synthesis of strong epoxy/agar hybrid hydrogels

Epoxy biopolymer hybrid hydrogels have excellent potential for load bearing applications, despite limited studies in this area. In this paper, a facile one-pot synthesis of epoxy/agar hybrid hydrogels has been reported. Infrared spectroscopy, rheometry, thermal, mechanical properties and immersion studies have been reported. An advantage of the hydrogels synthesized here is that they can be prepared in a shorter timeframe than conventional epoxy biopolymer hydrogels. Diethylene triamine was used as the cross-linker which induces gelation within five minutes at 90 °C. The mechanical properties of epoxy hydrogels prepared using diethylene triamine are found to be comparable to that of hydrogels prepared using long chain amine terminated poloxamers. The compressive toughness of the hybrid hydrogels increases by ~380% via the addition of 3 wt% agar in comparison with epoxy hydrogels. These hybrid hydrogels are elastic and biodegradable.

Synthesis of Bisphenol A Based Phosphazene-Containing Epoxy Resin with Reduced Viscosity.

Phosphazene-containing epoxy oligomers (PEO) were synthesized by the interaction of hexachlorocyclotriphosphazene (HCP), phenol, and bisphenol A in a medium of excess of epichlorohydrin using potassium carbonate and hydroxide as HCl acceptors with the aim of obtaining a product with lower viscosity and higher phosphazene content. PEOs are mixtures of epoxycyclophosphazene (ECP) and a conventional organic epoxy resin based on bisphenol A in an amount controlled by the ratio of the initial mono- and diphenol. According to 31P NMR spectroscopy, pentasubstituted aryloxycyclotrophosphazene compounds predominate in the ECP composition. The relative content in the ECP radicals of mono- and diphenol was determined by the MALDI-TOF mass spectrometry method. The organic epoxy fraction, according to gas chromatograpy-mass spectrometry (GC-MS), contains 50–70 wt % diglycidyl ether of bisphenol A. PEO resins obtained in the present work have reduced viscosity when compared to other known phosphazene-containging epoxy resins while phosphazene content is still about 50 wt %. Resins with an epoxy number within 12–17 wt %, are cured by conventional curing agents to form compositions with flame-retardant properties, while other characteristics of these compositions are at the level of conventional epoxy materials.

Advanced anticorrosive coatings based on epoxy/functionalized multiwall carbon nanotubes composites

Anti-corrosion epoxy coatings are extensively used to protect the petroleum tanks. For anti-corrosion applications of such epoxy coatings, it is necessary to decrease the defects that are commonly observed in conventional epoxy coatings. Herein we report the new anti-corrosive coatings based on epoxy/functionalized multiwall carbon nanotubes (f-MWCNTs) composites. The electrochemical impedance spectroscopy (EIS), nanoindenter tests, transmission electron microscopy (TEM), Raman spectra, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) were conducted to investigate the performance of prepared composites. The results revealed that anti-corrosion performance of epoxy/ f-MWCNTs nanocomposite film was significantly improved compared to those of pure epoxy and epoxy/ p-MWCNTs. Our results confirm also that f-MWCNTs are able to promote the epoxy coating hardness and reduced modulus.

Fabrication and characterization of novel p-Phenylamine-N(4-chloro salicylaldenemine) ligand and its metal complexes and evaluation their anti-corrosion and chemical resistance properties in epoxy/SiO2 nanocomposite for steel surface coating

Schiff base metal complex/epoxy nanocomposite coating engineering is considered a vital corrosion protection model for steel surface applications. To support this concept, several metal (Cr(III), Co(II), Ni(II), Cu(II) and Zr(IV)) complexes of Schiff base ligand named p-Phenylamine-N(4-chloro salicylaldenemine) (HL) were synthesized. The HL was chelated with metal ions as a bidentate manner through NO donor atoms with 1:2 (metal:HL) molar ratio and it was detected by microanalytical procedure. The resulting metal chelates of HL were fully characterized using the conductivity and magnetic moment measurements, UV–Vis, FT-IR, 1H NMR, XRD and TG-DTG analysis. Transmission electron microscope (TEM) and X-ray diffraction (XRD) techniques were accomplished for the silica nanoparticles characterization. Different surface-modified epoxy/SiO2 nanocomposite coating formulations with HL and its metal complexes were prepared without any compatibility problems. The anti-corrosion behavior of the epoxy nanocomposite coated films versus unmodified conventional epoxy was clarified by salt spray accelerated corrosion test. The obtained results demonstrated a considerable improvement in the rust grade, size and frequency of blistering, and adhesion strength of surface modified Ni(II) and Cr(III) complexes nanocomposite coated steel films at the same loading level. To confirm the previous concept, SEM morphology survey and FT-IR chemical structure characterizations for the employed cured coated films after the direct exposure to salt spray aggressive fog were investigated. Chemical immersion strategy was performed to check the acids and alkali resistances of nanocomposite coated films against conventional epoxy. The perfect protective behavior of the Ni(II) and Cr(III) complexes may be attributed to their highly effective magnetic moment (μeff) which leads to enhancing the cross-linking density through the coating layer, thereby enhancing the adhesion between the steel substrate and epoxy matrix.

Curing behavior and properties of high biosourced epoxy resin blends based on a triepoxy monomer and a tricarboxylic acid hardener from 10-undecenoic acid

Renewable propane-1,2,3-triyl tris(9-(oxiran-2-yl) nonanoate) (EGU, 100 wt% biogenic) and a tricarboxylic acid triglyceride (CGTU) hardener (85.7 wt% biogenic) were synthesized from 10-undecenoic acid (10-UDA) and used to produce epoxy resins with 52–92 wt% biobased carbon. CGTU was prepared by thermally activated thiol-ene coupling of thioglycolic acid onto propane-1,2,3-triyl tris(undec-10-enoate), (GUD) in the absence of solvent. The characterized CGTU was used as a green hardener of blends based on EGU and a conventional bisphenol A-based epoxy pre-polymer (DGEBA) at various mass percentages (0–100 wt%) with an stoichiometric epoxy/acid equivalent ratio. Calorimetric studies revealed higher peak temperature, lower reaction heats, and longer gelation times in resins with high EGU proportion, evidencing the lower reactivity of aliphatic EGU compared with aromatic DGEBA. Cured resins were yellowish transparent rubber-like materials with glass transition temperatures (Tg) varying from −14 °C to −42 °C and tensile strength in the range of 1750 kPa–790 kPa, for 0 and 100 wt % EGU, respectively. The soluble fraction of all resins was less than 4.3%, reflecting a high level of crosslinking. Thermosets with high biobased content showed both UV-light protection and visible light transparency.

Determining the interphase thickness and properties in carbon fiber reinforced fast and conventional curing epoxy matrix composites using peak force atomic force microscopy

Quantitative analyses of the thickness and properties of the interphase in carbon fiber reinforced resin matrix composites, which play an important role in loading transfer, are essential and intuitive to accurately design the properties of the composites. In this study, to know the distinctions of the interphase between the carbon fiber reinforced fast and conventional curing epoxy matrix composites quantitatively and completely, in addition to modulus map, adhesion map by Peak Force Quantitative Nano-Mechanics technology was newly introduced and applied to determine the interphase thickness and properties. The interphase in the fast curing epoxy matrix composites in modulus image was found to be soft with an average thickness of 20.03 ± 2.04 nm, while it was 40.48 ± 4.17 nm in the conventional curing epoxy matrix composites, and the modulus of the interphase formed a depression between the fiber and the matrix. Consistent with the interphase thickness determined by the modulus, the average interphase thickness in the fast and conventional curing epoxy matrix composites were 19.45 ± 0.68 nm and 41.01 ± 3.98 nm, respectively, based on the adhesion contrast in the interphase, and the adhesion of the interphase reached a peak between the fiber and the matrix. Compared with the conventional curing epoxy matrix composites, the modulus and the adhesion of the interphase changed more sharply in the fast curing epoxy matrix composites. Obviously, numerous distinctions of the interfacial properties existed between the fast and conventional curing epoxy matrix composites.

E12 technique: Conventional epoxy resin sheet plastination.

Epoxy plastination techniques were developed to obtain thin transparent body slices with high anatomical detail. This is facilitated because the plastinated tissue is transparent and the topography of the anatomical structures well preserved. For this reason, thin epoxy slices are currently used for research purposes in both macroscopic and microscopic studies. The protocol for the conventional epoxy technique (E12) follows the main steps of plastination-specimen preparation, dehydration, impregnation and curing/casting. Preparation begins with selection of the specimen, followed by freezing and slicing. Either fresh or fixed (embalmed) tissue is suitable for epoxy plastination, while slice thickness is kept between 1.5 and 3mm. Impregnation mixture is made of epoxy E12 resin plus E1 hardener (100ppw; 28ppw). This mixture is reactive and temperature sensitive, and for this reason, total impregnation time under vacuum at room laboratory temperature should not last for more than 20-24hr. Casting of impregnated slices is done in either flat chambers or by the so-called sandwich method in either fresh mixture or the one used for impregnation. Curing is completed at 40°C to allow a complete polymerization of the epoxy-mixture. After curing, slices can be photographed, scanned or used for anatomical study under screen negatoscope, magnification glass or fluorescent microscope. Based on epoxy sheet plastination, many anatomical papers have recent observations of and/or clarification of anatomical concepts in different areas of medical expertice.

A renewable resveratrol-based epoxy resin with high Tg, excellent mechanical properties and low flammability

Preparing low-flammable biobased epoxy resins with a high glass transition temperature (Tg) and excellent mechanical properties is significant for the rapid growing electronics and microelectronics industry. In this research, a resveratrol-based epoxy resin (REEP) with well-designed chemical structures possessing trifunctional epoxy groups and rigid conjugate structures was prepared through the one-pot method and was then cured by methyl hexahydrophthalic anhydride (MeHHPA). The conventional petroleum-based epoxy resin (DGEBA) was cured by the same kind of curing agent. Results showed that Tg of REEP/MeHHPA was up to 210.8 °C, much higher than that of DGEBA/MeHHPA (only 146.5 °C). The tensile strength and modulus of REEP/MeHHPA were 73.5 MPa and 3.0 GPa, respectively. More importantly, REEP/MeHHPA exhibited exceptional low permittivity (about 3.5) and low flammability with high char yield of 19.0% (800 °C). Therefore, the resveratrol-based epoxy resin could be a promising candidate for DGEBA and has great potential application in electronics and microelectronics industry.

Advanced Low-K Polymer Dielectric Materials and Interfaces for Fine-Pitch Re-Distribution-Layer (RDL) to Enable 2.5D and Fan-out Packages

The rapid increase of devices with artificial intelligence (AI) and machine learning capabilities is driving the demand for growth in compute performance. With transistor scaling reaching physical limitations, the semiconductor industry is looking to system-scaling to deliver the performance improvements. Advanced packaging architectures capable of supporting these applications are 2.5D interposers, 3D IC stacking, chiplets and fan-out based packaging. All of these architectures require high-density interconnects capable of routing >200 IOs/mm/layer. This talk demonstrates advanced ultra-thin ( <10 µm), low-Dk (< 3.0) polymer dielectric material candidates capable of achieving I/O densities of 500 IOs/mm/layer. Current commercially available solutions based on silicon interposers suffer from conductor and dielectric losses because of restrictions on the dielectric material (SiO2). Polymer based dielectrics offer a compelling alternative because of the potential to reduce the capacitance of the traces and improve power efficiency alongside compatibility with low-cost panel-scalable processes. This idea is explored will be explored in this talk and we will demonstrate through modelling and characterization that low-Dk polymer dielectrics are a superior candidate to current dielectric material candidates The choice of polymer dielectric is driven by technology trends towards a)high-density fine-pitch routing b)system level thermo-mechanical reliability c)panel-scalable processing. This work examines four dielectric material candidates comprising of 3 material classes, namely photo-sensitive epoxy, non-photo-sensitive epoxy and BCB for next-generation interconnect technology. High-speed electrical simulations indicate that low-Dk materials can support data rates of >10Gbps which overcomes the limitations faced by conventional high Dk epoxy dielectrics and SiO2 alternatives. The biggest challenge in moving towards low-Dk materials is that these polymers are typically non-polar and do not adhere well which poses challenges in package integration. This work proposes a unique approach to improve polymer/metal interfacial adhesion by creating a hybrid layer with tailorable material properties using vapor-phase-infiltration (VPI). VPI exposes the polymeric material to a metal-organic reactant such as trimethyl aluminium (TMA) in a heated environment. Diffusional kinetics of the reactant are highly dependent on each step of the sequential process such as temperature, time of hold, exposure time, and co-reactants used. This process is superior compared to Atomic Layer deposition (ALD) in promoting the diffusion of organometallic precursors into the polymer subsurface because of a hold-period after exposure. VPI thereby provides a highly adaptable process to create tunable hybrid interfaces with target properties. VPI-treated polymers showed a 3X improvement in adhesion strength at the polymer/metal interface. This work dives into the kinetic factors required to achieve this adhesion improvement and characterizes the corresponding material structure changes. In summary, advanced low-Dk polymer dielectrics capable of meeting next-generation high-performance computing requirements are discussed. This work evaluates the key performance benefits from moving to low-Dk dielectric materials and tackles a critical challenge of integrating these materials as re-distribution layer (RDL) dielectrics by demonstrating 3X improvement in adhesion using VPI.

Evaluation the anti-corrosion behavior, impact resistance, acids and alkali immovability of nonylphenol ethoxylate/TiO2 hybrid epoxy nanocomposite coating applied on the carbon steel surface

Nanocomposite modifiers reinforce the whole characteristics of epoxy coatings for different steel surface applications. To support this concept, sol-gel synthesized TiO2 nanoparticles (TNPs) were mixed with nonylphenol ethoxylate (NPhE) to form nonylphenol ethoxylate/TiO2 nanocomposite (NPhE/TNC) as a modifier for epoxy coating applied on the C-steel surface. TNPs were characterized by XRD, SEM and HR-TEM techniques. Various modified NPhE/TNC epoxy coating formulations with different loading levels (0.5, 1, 1.5, 2 and 2.5%) by weight were prepared. FT-IR spectra were used for characterizing of the formed nanocomposites. The anti-corrosion behavior of surface-modified NPhE/TNC coated films versus unmodified conventional epoxy was studied by salt spray accelerated corrosion test. The obtained results demonstrated a considerable improvement in the rust grade, blistering size and frequency, and adhesion strength of modified NPhE/TNC epoxy nanocomposite coated films and affirmed by SEM morphology survey. The impact resistances of unmodified and modified NPhE/TNC epoxy coatings were measured where the best impact resistance was recorded for NPhE/TENC-E coated film at 51 J. Acids and alkali chemical immersion test was performed to check the chemical immovability for the surface-modified NPhE/TNC coated films against conventional epoxy where NPhE/TENC-E coating showed the suitable immovability levels.

Application insights of Schiff base metal complex/SiO2 hybrid epoxy nanocomposite for steel surface coating: Correlation the protective behavior and mechanical properties with material loading

Implementation of Schiff base metal complex/SiO2 nanocomposite as a multifunctional modifier in steel epoxy coating represents a novel engineering issue for surface treatment technology. The present work investigates the application of epoxy coating modified with several metal (Co(II), Zr(IV), Ni(II), Cu(II) and Cr(III)) complexes of Schiff base versatile ligand namely p-Phenylamine-N(4-chloro salicylaldenemine) (HL), composited with SiO2 nanoparticles to enhance its protective behavior and mechanical resistance on the C-steel surface. Characterizations of silica nanoparticles were demonstrated by using transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive of X-rays (EDX) and X-ray diffraction analysis for integral clarification. FT-IR discriminatory spectra for polyamine cured blank unmodified conventional epoxy and surface modified HL and its metal complexes epoxy/SiO2 hybrid nanocomposite cured coatings were checked. The protective behavior of the investigated modified epoxy nanocomposite coatings against unmodified blank conventional epoxy on the steel surface was clarified by studying the surface morphology of the cured coated films after the immediate exposition to corrosive salt spray cabinet for 500 h and employing 5% NaCl aggressive solution. Modified cured Cr(III) and Ni(II) complex epoxy/SiO2 nanocomposite coated films (NS/MCE-F3 and NS/MCE-F5) manifested the minimum corrosion rate (CR) at 0.00063 mm/y and a superb protection efficiency (PE) recorded at 99.80%. The mechanical resistance properties of the nanocomposite coatings were examined by adhesion cross-cut, bend, impact, and abrasion (film stiffness) coating tests to underline their enforcement efficiency. NS/MCE-F3 and NS/MCE-F5 coated films boosted an outstanding mechanical resistance behavior on the C-steel surface in contrast with complete deterioration for blank conventional epoxy. The main reason for the superior anti-corrosion and mechanical performance properties observed in case of the nanocomposite coatings modified with Cr(III) and Ni(II) complexes may be attributed to the higher magnetic dipole moment of these complexes than the others in which enhances their electronegativity, cross-linking density and chemical bonding with the steel surface via the donor-acceptor interactions.

TO/TMMP-TMTGE Double-Healing Composite Containing a Transesterification Reversible Matrix and Tung Oil-Loaded Microcapsules for Active Self-Healing.

Thermoset epoxies are widely used due to their excellent properties, but conventional epoxies require a complicated and time-consuming curing process, and they cannot self-healed, which limits their applications in self-healing materials. Extrinsic and intrinsic self-healing materials are applied in various fields due to their respective characteristics, but there is a lack of comparison between the two types of healing systems. Based on this, a thiol-epoxide click reaction catalyzed by an organic base was introduced to achieve the efficient preparation of thiol-epoxy. Furthermore, tung oil (TO)-loaded microcapsules were introduced into the thiol-epoxy matrix of dynamic transesterification to obtain a TO/TMMP-TMTGE self-healing composite with an intrinsic–extrinsic double-healing system. For comparison, a TMMP-TMTGE self-healing material with an intrinsic healing system was also prepared, which contained only thiol and epoxy curing chemistries. The effect of the core/shell ratio on the morphology, average particle size, and core content of TO-loaded microcapsules was studied. It was found that when the core/shell ratio was 3:1, the average particle size of the microcapsules was about 99.8 μm, and the microcapsules showed good monodispersity, as well as a core content of about 58.91%. The differential scanning calorimetry (DSC) results showed that the TO core was successfully encapsulated and remained effective after encapsulation. Furthermore, scanning electron microscopy (SEM), atomic force microscopy (AFM), tensile tests, and electrochemical tests were carried out for the two types of self-healing materials. The results showed that the TO/TMMP-TMTGE composite and TMMP-TMTGE material both had self-healing properties. In addition, the TO/TMMP-TMTGE composite was superior to the TMMP-TMTGE material due to its better self-healing performance, mechanical strength, and corrosion protection performance.

Self‐healing semi‐IPN materials from epoxy resin by solvent‐free furan–maleimide Diels–Alder polymerization

ABSTRACTNovel self‐healing Diels–Alder (DA) polymer and the corresponding semi‐interpenetrated polymer networks (semi‐IPNs) were synthesized and characterized. Initially, a furan‐functionalized resin (FFR) was synthesized through the ring‐opening reaction of a conventional epoxy resin [diglycidyl ether bisphenol A (DGEBA)] with furfuryl alcohol as a bio‐based compound. Subsequently, semi‐IPNs with different compositions were obtained through the blending of DGEBA, FFR, 4,4′‐diaminodiphenylmethane, and 1,1′‐(methylenedi‐1,4‐phenylene) bismaleimide in the molten state by following a predetermined time–temperature program. Fourier transform infrared and nuclear magnetic resonance analyses confirmed the successful synthesis of the materials. Thermoreversibility via retro‐DA (rDA) reaction was evidenced by differential scanning calorimetry (DSC) and sol–gel transition tests. Repeated DSC cycle was successfully performed thrice on the DA polyadduct which corroborated repeatability of the DA/rDA association/dissociation. Self‐healing and mechanical properties were preliminarily evaluated by scanning electronic microscopy and flexural testing analyses, respectively. The self‐healing efficiencies were around 80 and 95% for semi‐IPN and DA polyadduct, respectively, based on flexural strength. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48015.

Method for in situ analysis of volatiles generated during cure of composites

Conventional epoxies used in composites are formulated to release minimal amounts of volatiles during cure, aside from moisture, which is a perpetual concern. However, a variety of polymers are used in production of composite parts, including adhesives, prepregs, and non-epoxy polymers, and sources of volatilization during processing can be both difficult to determine and problematic. Here we demonstrate a general method for in situ analysis of volatile release during cure. The method improves upon traditional characterization techniques of TGA/MS and TGA/FTIR (thermogravimetric analysis, mass spectroscopy, and Fourier transform infra-red spectroscopy). We characterize a commercial epoxy prepreg typical of those used in aerospace, a benzoxazine/epoxy blended liquid resin intended for high-temperature service, and finally, a high-temperature polyimide. By understanding the identity, origin, and kinetics of volatile release in these three materials, we can prescribe additional pre-treatments and define process windows to minimize and even eliminate volatile-induced porosity. Finally, we demonstrate the utility of the reaction cell/FTIR approach for characterizing cure-induced volatiles and mitigating final part porosity.

Preparation of epoxy-based shape memory polymers for deployable space structures using diglycidyl ether of ethoxylated bisphenol-A

To develop epoxy-based shape memory polymers (ESMPs) with a high switching temperature and good mechanical and shape memory properties for deployable space structures, the crosslink density and chain flexibility of the conventional epoxy resin, diglycidyl ether of bisphenol-A, were controlled by adding a flexible epoxy resin, diglycidyl ether of ethoxylated bisphenol-A with six oxyethylene units (DGEEBA-6). With increasing DGEEBA-6 content, the crosslink density of the ESMPs increased, but their glass transition temperature (Tg) decreased. The ESMPs with suitable switching temperatures (120–135 °C) for deployable space structures showed enhanced toughness, modulus, tensile strength, elongation at break, and shape memory properties. The ESMPs had fast full recovery times of only 80 s at Tg + 20 °C. DGEEBA-6 was shown to be a good modifier of ESMPs for deployable space structures.