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Vinyl‐substituted hydridopolycarbosilane (VHPCS) is widely studied for its low viscosity, abundance of active functional groups, rapid curing, and high ceramic yield. The curing reactions mainly involve the free radical polymerization of vinyl and hydrosilylation reactions, but these reactions typically require high temperatures such as 160–250°C. The curing behavior of VHPCS‐17 with a tert‐butyl peroxybenzoate/Nickel acetylacetonate (TBPB/NIAA) system is investigated using differential scanning calorimetry and in situ Fourier transform infrared. The properties of VHPCS‐17 with different initiator systems and VHPCS with different vinyl contents (under TBPB/NIAA system) are studied using thermogravimetric analysis and x‐ray diffraction. The results demonstrate that the TBPB/NIAA system can facilitate the free radical polymerization of vinyl; moreover, this system decreases the peak temperature of the curing reaction from 251 to 141°C and increases the ceramic yield from 80.49% to 89.88%. The ceramic yield of cured VHPCS increases gradually, reaching 89.88% when the vinyl content is 17%. The grain size of β‐SiC decreases continuously with the increase in vinyl content, while the high‐temperature oxidation‐resistant properties of SiC ceramics obtained from different VHPCSs are not negatively affected. [ABSTRACT FROM AUTHOR]

Three nitrile functional benzoxazine monomers (PH-bn, mPH-bn, aPH-bn) were synthesized based on phenols containing different substituents and m-aminobenzonitrile, and their cured products (poly(PH-bn)、 poly(mPH-bn)、poly(aPHbn)) were obtained. The structures and compositions of benzoxazine monomers were characterized by Fourier Transform Infrared spectroscopy (FT-IR), Nuclear Magnetic Resonance spectroscopy (¹H-NMR) and Gel Permeation Chromatography (GPC). The effect of the substituents on curing behaviors was compared by differential scanning calorimetry (DSC), and the curing reaction mechanism was further discussed. In addition, thermogravimetric analysis (TGA) and TGA-FTIR were used to compare the thermal stability and pyrolysis mechanism of the three cured products. The results showed that the crosslinking reactions of the oxazine rings and a part of nitrile groups occurred simultaneously during the curing process. Due to the presence of the electric-donating methyl group, the peak temperature of the curing reaction increased and the thermal stability decreased. However, the electric-absorbing aldehyde group made the curing peak temperature decrease. Moreover, the thermal stability significantly increased because of the crosslinking reaction of the aldehyde groups. The 5% mass loss temperature of poly(aPH-bn) was 380 ℃, and its char yield was as high as 67.3% in N2 atmosphere at 800 ℃. [ABSTRACT FROM AUTHOR]

With the appearance of new epoxy resins and amines, which are widely used for hardening epoxy compositions using energy-saving technology (at «ordinary» temperatures), on the world market, the targeted selection of these materials to provide the desired technological and operational properties becomes relevant. In order to predictively choose amine hardeners for epoxy resins, their quantum-chemical calculations were performed using the semi-empirical parameterized 3 (PM3) method. The energy value of the highest occupied molecular orbital (HOMO) of amines and the absolute value of the energy gap |Δ| (the absolute difference in energies between the HOMO of amines and the lower vacant molecular orbital (LUMO) of epoxy resins) were used. The relationships between the absolute value of the energy gap |Δ| and the main technological parameters of the curing process of dian epoxy resin ED-20 with individual amines were established with pairwise correlation coefficients of not less than 0.977. The evaluation of the activity of modified polyamines and their mixtures in hardening epoxy resins is proposed to be carried out based on the maximum temperature of the exothermic reaction of interaction between the epoxy groups of resins and the amine groups of hardeners. The possibility of adjusting the temperature of the exothermic hardening reaction of epoxy compositions and their «viability» time by introducing epoxy-containing diluents with different values of the LUMO energy was shown. [ABSTRACT FROM AUTHOR]

Epoxy resin is a thermosetting resin with excellent mechanical properties. It has been pointed out that there are problems on its mechanical properties due to poor polymerization of the epoxy ring caused by water and chlorine impurities during resin production. In this study, we focused on the electrochemical behavior during curing reaction of epoxy resin. To investigate the electrochemical reaction, galvanostat meter was used to measure the voltage behavior during chemical reaction. Molecular Orbital (MO) method was used to understand the mechanisms of voltage behavior during curing reaction. Furthermore, the effect of water existence during curing reaction was investigated by experimentally and analytically. As a result of experimental electrochemical reaction, we successfully measured the voltage behavior associated with the curing reaction. In the case of MO analysis, the epoxy and curing agent models were prepared. Before the reaction, each molecule had zero charge, but after the reaction, it was confirmed that the epoxy had a positive charged and the amine had a negative charged. It is thought that the voltage could be observed due to the movement of this charge during curing reaction. It has been also demonstrated through experimentation and analysis that water accelerates the curing reaction. It was observed that the accelerating effect amplifies as the quantity of water increases. Building upon these results, it was confirmed that the factor leading to the increase in voltage is due to the amount of water. To examine the presence of chlorine impurities during the production of epoxy resin, MO analysis was conducted on the production reaction of epoxy prepolymers. The findings indicated that as the water content increases, the reaction that results in the production of by-products is amplified. This outcome suggested that by-products were already incorporated during the formation of the epoxy. In conclusion, this study provides significant insights into the electrochemical behavior during the curing reaction of epoxy resin, the role of water in accelerating the reaction, and the impact of chlorine impurities during resin production. The findings pave the way for further research to optimize the production process and enhance the mechanical properties of epoxy resin. [ABSTRACT FROM AUTHOR]

Liquid hydridopolycarbosilanes (LHPCS) with vinyl or allyl groups have attracted significant research interest due to their low curing temperature and high ceramic yield. In this study, allyl-terminated hydridopolycarbosilane (AHPCS) and vinyl-terminated hydridopolycarbosilane (VHPCS) were prepared by the Grignard coupling reaction and characterized by NMR and Fourier infrared spectroscopy (FTIR). And the curing reactions of AHPCS and VHPCS with or without initiators (dicumyl peroxide [DCP], tert-Butyl peroxybenzoate [TBPB]) or Karstedt catalyst were investigated using differential scanning calorimetry and in-situ FTIR. The main curing reactions of VHPCS and AHPCS are the double bond free radical polymerization and hydrosilylation reaction, respectively. The addition of initiators and Karstedt catalyst could promote the corresponding curing reaction and increase the weight residual at 1000°C. The thermal properties of the cured resins were investigated by thermogravimetric analysis. The addition of initiators and catalyst could significantly increase the weight residual of VHPCS and AHPCS, respectively. The addition of the Karstedt catalyst increased the weight residual of AHPCS from 75.6% to 83.1%. In addition, the addition of TBPB and DCP increased the weight residual of VHPCS from 74.2% to 81.2% and 80.2%, respectively. [ABSTRACT FROM AUTHOR]

Resin transfer molding（RTM）process is a major molding process in the manufacture of resin-based composites, and the simulation of this process can play a key role in the process of optimization for the design of RTM parts. This paper independently developed a three-dimensional non-isothermal RTM simulation model based on the control volume/ finite element method（CV/FEM）on the basis of two-dimensional isothermal RTM program. Based on the Darcy equation, the continuity equation, the energy conservation equation, the curing reaction equation and multiple rheological curing models, the simulation model adopts semi-discrete method and three convergence criteria to effectively solve the problems of mold preheating and resin non-isothermal in the non-isothermal RTM simulation process. For the simulation problems such as viscosity changing and curing heat release during the filling process, the simulation function has reached the level of similar international products. After the application verifications of the flat plate test piece and casing simulation, this simulation model can simulate filling time, velocity and pressure of RTM process that is the same as the products in the world. This simulation model basically has the ability of simulation for the actual complex structure parts.

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To decrease the curing temperature and achieve excellent binding strength of BN coatings on graphite substrates, a proper Al(H 2 PO 4) 3 binder has been carefully designed where MgAl 2 O 4 and poly vinyl alcohol (PVA) were used as the curing agent and the dispersant, respectively. XRD, SEM, TEM and DSC showed that the desired binding phase AlPO 4 had been successfully obtained, where MgAl 2 O 4 and PVA worked synergistically to lower the curing temperature down to 70–100 °C and promote the formation of AlPO 4. Such optimized binder might have formed hydrogen bond with –NH 2 and –OH groups on the BN flakes. It might also form hydrogen bond with-OH and –COOH groups on graphite substrates to ensure an optimal binding strength of 5.5 N (∼22 MPa) as suggested by the scratch tests. This work affords a better understanding on the curing chemistry of Al(H 2 PO 4) 3 and the binding mechanism between BN flakes, AlPO 4 binding phases and graphite substrates. [ABSTRACT FROM AUTHOR]

Considering the poor cohesiveness of the joint between pothole repair materials on asphalt pavement and old pavement, epoxy resin (EP) was toughened in this study, and a new composite resin material applicable to pavement repair was proposed. In particular, epoxy acrylic resin was prepared through the blending modification of acrylic resin and EP. The rheological properties of the composite resin were analyzed, and the influence of different acrylic acid contents on the toughness of the composite resin was discussed. Subsequently, the curing reaction process of the composite resin was explored via differential scanning calorimetry, and the theoretical curing process was determined. On this basis, the thermal stability of the composite resin was analyzed through thermogravimetric analysis. Results show that the tensile strength, elongation at break, and impact strength of the optimal composite resin are increased by 88.43%, 4202%, and 103.14%, respectively compared with those of EP alone, indicating that acrylic resin exerts a remarkable toughening effect on EP. The construction process parameters of the resin can be effectively predicted by measuring the curing reaction degree. The onset temperature of the resin is 101 ℃, and its thermal stability is favorable and can meet the application requirements of the resin in high-temperature weather during summer. The conclusions provide an important reference for follow-up research on pavement maintenance materials. [ABSTRACT FROM AUTHOR]

In this paper, the structures and properties of PBT binder and TDI model compound were studied by density functional theory (DFT) method. The structures of PBT binder and TDI were optimized. The possible reaction sites of curing reaction were explored by calculating and analyzing the electrostatic potential energy diagram related to the electrostatic potential distributions of PBT and TDI. There are many reaction sites between PBT and TDI, which is easy to form network structures. Based on the model compounds, four possible curing reaction products were predicted, and the structures and energies of these products were calculated. The thermodynamic stable structure of the curing reaction was determined, and the most probable reaction pathway and activation free energy of the curing reaction were obtained by calculating the transition state of the most probable product reaction path. This study can provide a basis for further analysis of the aging reaction involved in PBT propellants. [ABSTRACT FROM AUTHOR]

• Thermal behavior of a newly synthesized epoxy-imides was investigated using TGA. • In epoxy-imide systems, degradation mechanisms of epoxy or polyimide can coincide. • Epoxy-imide resins have a multistep degradation process and lower degradation rate. • The effect of chemical structure is more pronounced in the last stage. • The curing temperature only affects the 1st stage of the degradation process. The dynamic thermogravimetric analysis of a new series of aliphatic, cycloaliphatic, and aromatic trimellitimide-based epoxy-imide (EI) resins, compared to diglycidyl ether of bisphenol-A (DGEBA) and triglycidyl isocyanurate (TGIC) resins, in uncured and cured states, revealed that the EI resins/ systems, unlike DGEBA ones, have a multistep thermal degradation process with two chief steps corresponding to the degradation of the DGEBA and the imide moieties. Evaluating the influences of isothermal curing temperature (T Cure) on their degradation behavior ascertained that, generally, the 1st stage of the thermal degradation processes is more affected by T Cure. Furthermore, the competition between epoxide-amine reactions with etherification/ homopolymerization plays the most crucial role in the impact of T Cure on the systems' stability and decomposition behavior. Therefore, the most considerable changes can be observed in the thermograms of the cycloaliphatic system due to the highest difference between the melting temperature of its resin and T Cure. [Display omitted] [ABSTRACT FROM AUTHOR]

Considering its great industrial potential, epoxidized linseed oil (ELO) was crosslinked with different agents, both natural and synthetic: citric acid (CA, in the presence of water—W, or tetrahydrofuran—THF, as activator molecules) and Jeffamine D230, respectively, resulting bio-based polymeric matrices, studied further, comparatively, in terms of their properties, through different methods. Thermal curing parameters were established by means of Differential Scanning Calorimetry (DSC). Fourier transform Infrared Spectroscopy (FTIR) and DSC were used to identify the reactivity of each ELO-based formulation, discussing the influence of the employed curing systems under the conversion of the epoxy rings. Then, the obtained bio-based materials were characterized by different methods, establishing the structure–properties relation. Thermogravimetric analysis revealed higher thermal stability for the ELO_CA material when THF was used as an activator. Moreover, a higher glass transition temperature (Tg) with ~12 °C was registered for this material when compared with the one that resulted through the crosslinking of ELO with D230 conventional amine. Other important features, such as crosslink density, storage modulus, mechanical features, and water affinity, were discussed. Under the loop of a comprehensive approach, a set of remarkable properties were obtained for ELO_CA_THF material when compared with the one resulting from the crosslinking of ELO with the synthetic Jeffamine. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The irreversible curing reaction of thermosetting epoxy asphalt mixture (EAM) brings challenges to the construction of epoxy asphalt concrete (EAC) on the steel bridge deck, and the curing reaction degree (CRD) of EAM before compaction has a great influence on the compaction quality. The objective of this study is to investigate the effects of excessive CRD condition and uneven CRD condition of warm mix EAC on its field compaction. To achieve this goal, a field compaction model for EAC on a steel bridge deck was developed using discrete-element method (DEM) first. In the DEM model, a two-stage contact model that combined Burges model with the parallel bond model was used to characterize the thermosetting and viscoelastic behaviors of EAM, and the values of the contact model's parameters under different CRDs were determined by a trial calculation method based on Superpave gyratory compaction test. Subsequently, the field compaction process of cured EAM with different CRDs was simulated by changing the contact parameters' value, and the effects of excessive CRD condition and uneven CRD condition on the compaction quality were analyzed. Results show that the highly cured EAM is hard to be compacted unless larger compaction loads are adopted in the repeated compaction. Uneven CRD of EAM is prone to generate the mixture agglomeration, and it has negative effects on the compaction quality of the surrounding EAM. [ABSTRACT FROM AUTHOR]

The recycling of zinc compound from waste tires and the negative impact of zinc oxide on environment have been major challenges in rubber industry. In this study, the components and microstructure of recovered carbon black (rCB) from waste tires pyrolysis are analyzed, in which the content of the ash and zinc element is 20 % and 6.1 %, and zinc sulfide is the main zinc compound. Zinc sulfide and zinc oxide could crosslink brominated butyl rubber (BIIR), and the crosslinking effect becomes more effective in the presence of carbon black N660. BIIR can be crosslinked and reinforced by rCB in the absence of other additives. BIIR/rCB composites have similar curing behavior and mechanical properties to the BIIR composites filled with N660 and cured by zine oxide. Therefore, rCB could replace commercial carbon black N660 and zinc oxide in BIIR, and this replacement will realize the effective use of carbon black and zinc compound in rCB from waste tires and promote the sustainable development of tire industry. [Display omitted] • The content of Zn was 6.1 %, and rCB contains Nano-sized zinc-containing compound. • ZnS was the main zinc-containing compound in rCB, and rCB can be used to effectively crosslink BIIR. • ZnS could play a similar role as ZnO in BIIR/N660 compound. • BIIR/rCB composite without adding ZnO had good performances. [ABSTRACT FROM AUTHOR]

Epoxy asphalt mixtures are renowned for their exceptional road performance. In this study, the simultaneous application of a rejuvenator and epoxy polymer in asphalt rejuvenation, comparing it with using only epoxy polymer were explored. Approaches were evaluated from the perspectives of tensile performance, low-temperature performance, viscosity properties, microscopic phase morphology, and molecular structure. Results reveal that the addition of the rejuvenator enhances the tensile toughness of the aged asphalt-epoxy system while significantly reducing viscosity under identical temperature and curing conditions. Microscopic analysis indicates that the rejuvenator weakens the uniformity of the dispersed phase, resulting in a less tightly interlocked structure between aged asphalt and the epoxy system. Molecular simulations demonstrate that the compatibility of aged asphalt with the rejuvenator and epoxy system is comparable to that of aged asphalt and the epoxy system alone. Furthermore, a small amount of rejuvenator increases the conversion degree of the epoxy system, whereas an excessive amount inhibits the curing reaction. These findings not only shed light on the mechanisms underlying rejuvenated epoxy asphalt systems but also hold promise for enhancing the competitiveness of such systems throughout their service life cycle. • The performance enhancement of rejuvenator on epoxy polymer-rejuvenated asphalt is investigated. • The rejuvenator enhances the tensile toughness and low-temperature performance of the asphalt-epoxy system. • The dosage of rejuvenator is a factor that affects the curing reaction of epoxy resin. [ABSTRACT FROM AUTHOR]

In this study, curing of BPA-based epoxy resins Araldite®GY-2600 and Araldite®GY-240 by low-molecular-weight amines EDA, TETA and Jeffamine D-230, and bio-based phenalkamines Cardolite®NX-6019, Cardolite®Lite-2002 and Cardolite®GX-6004 was studied by differential scanning calorimetry (DSC) and rheology measurements. DSC provided quantitative information on the overall reaction kinetics (the enthalpy of curing reaction, Î"HR; cure degree, α; curing reaction rate, dα/dt) and the glass transition temperature (Tg) of the cured product. It was demonstrated that the DSC curing of epoxy resins by phenalkamines started at lower temperature, and the curing rates were slightly lower compared to those cured by low-molecular-weight amine hardeners. The enthalpy of the curing by phenalkamines was lower, especially in the case of more viscous epoxy resin GY-2600. Tg of the cured epoxy resins varied from 50 to 98°C and was slightly lower when cured with cardanol-based phenalkamines. The results demonstrate that curing of epoxy resins by bio-based phenalkamines proceeds in a similar temperature interval like using low-molecular-weight amines as hardeners but with less exothermic effect, which could be an advantage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A multiscale simulation strategy was proposed to study the curing reaction on the network formation and corresponding mechanical properties of a bio-based epoxy resin composite. The crosslinking process of the system to form an epoxy network structure was reproduced on the mesoscopic scale by the dissipative particle dynamics simulation coupled with a curing reaction model. The density functional theory (DFT)-based method, IRC and relaxed potential energy surface scanning calculations were combined with the reverse mapping operations in order to improve the overall quality the reverse mapped structures. Finally, molecular dynamics simulations were performed on the atomistic level to analyze the mechanical properties, the volume shrinkage and the glass transition of the bio-based epoxy resin system, etc. This multiscale simulation strategy can provide as a possible investigation scheme for the subsequent improvement and design of bio-based epoxy resin composite materials.

Considering its great industrial potential, epoxidized linseed oil (ELO) was crosslinked with different agents, both natural and synthetic: citric acid (CA, in the presence of water—W, or tetrahydrofuran—THF, as activator molecules) and Jeffamine D230, respectively, resulting bio-based polymeric matrices, studied further, comparatively, in terms of their properties, through different methods. Thermal curing parameters were established by means of Differential Scanning Calorimetry (DSC). Fourier transform Infrared Spectroscopy (FTIR) and DSC were used to identify the reactivity of each ELO-based formulation, discussing the influence of the employed curing systems under the conversion of the epoxy rings. Then, the obtained bio-based materials were characterized by different methods, establishing the structure–properties relation. Thermogravimetric analysis revealed higher thermal stability for the ELO_CA material when THF was used as an activator. Moreover, a higher glass transition temperature (Tg) with ~12 °C was registered for this material when compared with the one that resulted through the crosslinking of ELO with D230 conventional amine. Other important features, such as crosslink density, storage modulus, mechanical features, and water affinity, were discussed. Under the loop of a comprehensive approach, a set of remarkable properties were obtained for ELO_CA_THF material when compared with the one resulting from the crosslinking of ELO with the synthetic Jeffamine.

The isothermal curing behavior of an epoxy–imidazole system was investigated through thermal, mechanical, and compositional analyses. Precise control over temperature and time afforded the monitoring of the progression of the curing reaction and enthalpy relaxation via fast scanning calorimetry. The real-time tracking of the glass transition temperature (T g) during isothermal curing revealed a temperature-dependent relationship between T g and thermally estimated conversion, distinct from epoxy–amine systems. Unlike previous research suggesting plasticization through cyclic-compound formation in epoxy–imidazole systems, such compounds were not detected in the early curing stages in this study. Furthermore, an endothermic reaction from imidazole regeneration was suggested to overlap with the main exothermic reaction of polymerization. Therefore, assessing thermally estimated conversion in the intermediate curing stage through differential scanning calorimetry was deemed practically impossible for epoxy–imidazole systems. The T g values of resins with different thermal histories were equal after complete curing under high-temperature/long-duration conditions. [Display omitted] • The glass transition temperature – conversion curve depends on curing temperature. • An endotherm from imidazole regeneration overlap with the main exothermic polymerization. • During imidazole regeneration, cyclic compounds derived from N-dealkylation was not detected. • The conversion of intermediate stage of curing cannot determined by conventional DSC. • The glass transition temperatures were finally equal after complete curing. [ABSTRACT FROM AUTHOR]

Liquid crystalline epoxy resins have been reported to show superior mechanical and thermal properties. This high functionality is attributed to their meso- or macroscopic layered domain structure and their molecular scale ordering; hence, elucidation of the mechanism of layer formation during curing reactions is necessary for material development. In this study, the layer formation process has been investigated by the reactive coarse-grained molecular dynamics method. A mesogenic liquid crystalline epoxy and a typical non-mesogenic epoxy (diglycidyl ether of bisphenol A), mixed with a curing agent 4,4′-DDS (diaminodiphenyl sulfone), were considered. The results clearly showed that the mesogenic epoxy molecules formed a layer structure, whereas the non-mesogenic epoxy molecules remained as the amorphous structure even after the curing reactions. This difference was assumed to be caused by the straight structure of the mesogenic epoxy molecules and the strong attractive interactions between mesogenic parts. The interlayer spacing calculated by the simulation was in close agreement with the X-ray measurement. The details of the curing reaction process, e.g. the conversion and the molecular size in the mesogenic epoxy system, were also investigated. A large layer structure covered the simulation system after the stage in which the first reaction of the amine group was dominant, but the molecules were not large: the molecules were mainly attracted by the non-bond interactions. With the progress of the second reaction of the amine group, by which the tertiary amine was formed from the secondary amine, the molecular size became large and a rigid layer structure was formed over the whole simulation system. These results clearly indicated the role of the curing reactions: the first reaction produced small molecules from monomers and made them align in a layer form, and the second reaction connected them by cross-linking bonds and that produced rigid and large domains.

Natural fibers and particularly flax fibers have a great potential to replace glass fibers in composite materials. However, the interaction between these fibers and thermoset matrices remains unclear and results in a weak interface affecting the mechanical properties of the composite. This study was carried out to investigate the impact of natural fibers on the chemical reaction between the resin and the hardener, studying the interaction of fibers with each component separately to understand more precisely the phenomena involved. The results show that the contact with the fibers involves a change of the matrix properties that has been attributed to the water absorbed on their surface. On the one hand, water could modify amine functions of the hardener leading to a decrease of 40°C of matrix glass transition temperature (Tg). This issue could be corrected by adding a 16% excess of hardener. On the other hand, the water added to the resin could also accelerate the epoxide/amine reaction increasing slightly the Tg of the matrix and also generating weaker distinct networks of lower Tg by post-modification of the hardener. Therefore, the control of the water content in flax fibers is a crucial parameter for composite manufacturing. [ABSTRACT FROM AUTHOR]

In order to eliminate the deficiencies of the solvent-based cold patch asphalt mixture, this paper presented the cold patch asphalt mixture modified with waterborne epoxy resin (WER). Firstly, the new evaluation method were put forward based on its technical features and application requirements. Then the influence of different compositions and contents of WER on the cold patch asphalt liquid was evaluated by laboratory tests. Further, the pavement performance and workability of WER modified cold patch asphalt mixture were systematically evaluated. The results show that (i) WER can significantly improve strength, moisture susceptibility, high temperature performance and cohesion. However, the inappropriate addition may lead to poor storability and low temperature performance. So the optimal WER content is recommended 1.2–1.8 wt%, and its component ratio of epoxy resin to curing agent is 3:1. (ii) Different WER components produce different performances of mixture. The EP-20 + HGC brings about higher curing strength, excellent high temperature performance and storability. In comparison, the mixture modified with EP-20 + HGA owns preferable initial strength and moisture susceptibility. In the practical project, it is necessary to choose suitable WER considering the performance deficiency of cold patch materials and maintenance needs. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the curing process of hydroxyl‐terminated polyether (HTPE) with different curing agents, aliphatic triisocyanate (N100) and toluene diisocyanate (TDI), the crosslink density (XLD) and chemical processes of the curing reactions have been investigated by low‐field NMR spectroscopy and FTIR spectroscopy, respectively, while the mechanical properties of those two cure systems were studied as well. The results show that, for either HTPE/N100 or HTPE/TDI, the higher curing temperature leads to the shorter curing time to reach stability of XLD, while the final XLD decreases by increasing the temperature. The XLD and tensile strength of HTPE/TDI are both lower than those of HTPE/N100, although curing reaction of the HTPE/TDI system is faster and more complete, as seen from FTIR spectra. Besides, the tensile strength of HTPE/N100 based propellant attains the maximum value of 0.64 MPa at NCO/OH ratio of 1.4, while the maximum XLD value of 6.5× 10−5 mol⋅cm−3 was obtained at the same time. The XLD is well correlated in tensile strength with the variation of NCO/OH, that suggests regulation of XLD value may be an effective way to optimize the curing conditions for improving mechanical properties of HTPE/isocyanate‐based propellants. [ABSTRACT FROM AUTHOR]

Epoxy/polysufone (PSF) composites cured with 4,4'‐diaminodiphenyl sulfone (DDS) and 4,4'‐diaminodiphenyl methane (DDM) were fabricated, and the effect of dual curing reaction of diamines with epoxy on morphology, mechanical, and thermal performance was investigated. DSC results indicated that DDM was more reactive than DDS and the activation energy decreased with the rising of DDM content. Structures with small domain size at the early stage of phase separation were fixed by the fast epoxy‐DDM reaction. When the DDM content was elevated to a high level, large dual structures were changed to fine bicontinuous structures, which was favorable to improve the mechanical property. The mechanical performance of epoxy composites was enhanced and the maximum values were achieved when the DDM/DDS ratio was located at 75/25 (PSF/DDS0.25‐DDM0.75). The flexural and tensile strength relative to epoxy/DDM system were enhanced more than those relative to epoxy/DDS, while the increase in toughness was the opposite. TGA measurement showed that thermal stability of epoxy/PSF composites was improved because of the restricting effect of continuous PSF domains on thermal motion of epoxy. DMA analysis exhibited two relaxation peaks for PSF/DDS0.25‐DDM0.75, which could be attributed to the formation of phase separated morphology and epoxy network with different cross‐link density. [ABSTRACT FROM AUTHOR]

To answer the question “How does lanthanide doping in iron oxide affect cure kinetics of epoxy-based nanocomposites?”, we synthesized samarium (Sm)-doped Fe3O4 nanoparticles electrochemically and characterized it using Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray analysis (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy analyses (XPS). The magnetic particles were uniformly dispersed in epoxy resin to increase the curability of the epoxy/amine system. The effect of the lanthanide dopant on the curing reaction of epoxy with amine was explored by analyzing differential scanning calorimetry (DSC) experimental data based on a model-free methodology. It was found that Sm3+ in the structure of Fe3O4 crystal participates in cross-linking epoxy by catalyzing the reaction between epoxide rings and amine groups of curing agents. In addition, the etherification reaction of active OH groups on the surface of nanoparticles reacts with epoxy rings, which prolong the reaction time at the late stage of reaction where diffusion is the dominant mechanism.

The paper presents the curing of diglycidyl ether of bisphenol A (DGEBA) with two natural hydroxy acids and the thermal behavior of the cured products. The kinetics of the curing reactions were evaluated from the differential scanning calorimetry (DSC) curves using Ozawa, Kissinger methods and "Thermokinetics-3" software (Netzsch). Thermal decomposition behavior of the cured products up to 600 °C (in nitrogen) was made using simultaneous TG/FT-IR/MS technique. The kinetic parameters were obtained using the same software which shows that the thermal degradation takes place in three or four consecutive steps. The chemical composition of gases evolved at the thermal decomposition has been identified using FT-IR and MS techniques. The main products are: water, carbon dioxide, acids, anhydrides, aliphatic and aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Thermosetting resins like polyfurfuryl alcohol (PFA) tend to get prematurely cured and viscous during storage. Understanding a resin shelf-life is very helpful but no definite and validated method could be found in both scientific literature and standard methods. Cure kinetics of PFA was determined through tracing the complex viscosity changes as a function of time at elevated temperatures of 160, 170, 180, 190 and 200 °C. Adopting an empirical statistical approach, shelf-life of PFA resin at ambient temperature was estimated using the accelerated cure profiles. To this end, two functions were fitted on experimental results and then the empirical cure reaction rate constants at different temperatures were extrapolated to 25 °C. Subsequently, the viscosity versus time profiles were built for curing the resin at ambient temperature. The time interval corresponding to a viscosity range of 10–12.5 Pa.s was considered as the practical shelf-life of the resin at ambient conditions. The findings were validated by comparing the model results to the real-time, experimentally-obtained values. [ABSTRACT FROM AUTHOR]

N, N, N′, N′ -tetrapropargyl-p, p'-diaminodiphenylmethane (TPDDM) was synthesized and used to prepolymerized with 4,4′-bismaleimide diphenylmethane (BDM) in molten state to obtain a new TPDDM modified bismaleimide (BTP) resin by addition reaction. The BTP resin displays a good solubility and meltability with process window of 90 °C. The self-polymerization of TPDDM and BDM and further free radical polymerization of the unsaturated groups construct the cross-linked networks to obtain the cured BTP resin. The apparent activation energy of cure reactions for BTP resin decreases slowly with conversion of reactions, and declines clearly with the conversion of above 60%. The residual yield at 600 °C in nitrogen and air of the cured BTP resin are 60.5% and 60%, respectively, and the glass transition temperature of the cured resin can reach 371 °C. The impact and flexural strengths of the cured BTP resin can increase with increase of BDM content in the BTP resin. The flexural strength of the cured BTP resin can reach 60.8 MPa at 300 °C for 30 min, which retains 94% of that at room temperature. The cured BTP resin displays better non-halogen and non‑phosphorus intrinsic flame retardancy based on its excellent thermal stability. [Display omitted] • Tetrapropargyl diaminodiphenylmethane modified 4,4′-bismaleimide diphenylmethane (BTP resin) has excellent processability. • The cured BTP resin has a high glass transition temperature of 371 °C. • The flexural strength of the cured BTP resin can reach 64.8 MPa at 300 °C for 30 min with retention of 94%. • The cured BTP resin is an intrinsic flame retardancy with the lower heat release capacity during combustion. [ABSTRACT FROM AUTHOR]

Here, we propose a novel attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method for simultaneously monitoring the curing reaction and the diffusion behavior of curing agents at the surface of rubber in real-time. The proposed scheme was demonstrated by fluorine rubber (FKM) and FKM/carbon nanotube (CNT) nanocomposites with a target curing agent of triallyl-isocyanurate (TAIC). The broadening and the evolution of the C=O stretching of TAIC were quantitatively analyzed to characterize the reaction and the diffusion. Changes in the width of the C=O stretching indicated the reaction rate at the surface was even faster than that of the bulk as measured by a curemeter. The diffusion coefficient of the curing agent in the course of heating was newly calculated by the initial increase in the absorbance and our model based on Fickian diffusion. The diffusion coefficients of TAIC during curing were evaluated, and its temperature and filler dependency were identified. Cross-sectional ATR-FTIR imaging and in situ ATR-FTIR imaging measurements supported the hypothesis of the unidirectional diffusion of the curing agent towards the heated surface. It was shown that our method of in situ ATR-FTIR can monitor the degrees of cure and the diffusion coefficients of curing agents simultaneously, which cannot be achieved by conventional methods, e.g., rheological measurements.

Unsaturated polyester resin (UP) is a critical polymer material in applications of many fields, such as the chemical industry, military, and architecture. For improving the mechanical properties, some hardeners, such as methyl ethyl ketone peroxide (MEKPO) or tert-butyl peroxy-2-ethylhexanoate (TBPO), can trigger the curing reaction in UP polymerization, which causes that UP changes the structure from monomer to polymer. However, polymerization is a strong exothermic reaction, which can increase the risk of thermal runaway reaction in UP. Therefore, the mechanisms and characteristics in the thermal runaway reaction of UP mixed with hardeners should be studied for preventing and controlling UP explosion. The thermal hazards of UP mixed with hardeners were determined by thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC) analysis. According to the results, UP mixed with MEKPO exhibited a more violent mass loss and exothermic reaction than UP mixed with TBPO. Furthermore, the thermal runaway reactions of UP mixed with MEKPO or TBPO with different mixing proportions of 1:1, 3:1, and 5:1 were determined. Irrespective of MEKPO or TBPO, the mixing proportions of 3:1 exhibited a high onset temperature and low enthalpy of curing reaction (ΔHexo). This demonstrated that this proportion was safer during UP polymerization. The results of this study can provide useful information for preventing UP explosion and developing polymerization technology.

Superhydrophobicity of alloy surfaces is generally determined by the low-energy chemical composition and geometric structure of the surface. The appropriate geometry on alloy surfaces can be easily constructed via chemical etching methods. However, the subsequent low-energy modifications for pre-etched alloys are time-consuming or expensive, thus preventing their further application. Here, we prepared superhydrophobic alloy surfaces based on combining wet chemical etching and room temperature vulcanized (RTV) silicone treatment. Compared to traditional immersion methods, RTV silicone treatment for superhydrophobic 6061 Al alloy surfaces needs only 30 s, which is several thousand times faster than stearic acid or polymethyl triethoxy silane solution treatment. Mechanisms of RTV silicone treatment were investigated. The results show that dip-coating modification is different from these traditional methods. We found that the optimized proportion for RTV silicone rubber is HPDMS, PMTSi, and DBTDL with hexane solvent (HPDMS:PMTSi:DBTDL:hexane = 4:3:1:46, weight ratio), and the water contact angles of treated surfaces of pre-etched 6061 Al alloy, pure Al, and steels are 159° ± 2.7°, 168° ± 1.2°, and 169° ± 1.5°, respectively. Herein, our results demonstrate a facile, low-cost strategy to fabricate superhydrophobic alloy surface that is notable and easy to scale up for industrial applications. [ABSTRACT FROM AUTHOR]

Abstract Liquid crystalline epoxy resins (LCERs) have been reported as a promising polymeric material with a high thermal conductivity. Among them, 4,4′-diglycidyloxybiphenyl (BP) epoxy with the simplest molecular structure for the formation of a liquid crystal (LC) phase appears most suitable for practical applications. In particular, it is known that BP epoxy cured by 4,4′-diaminodiphenylsulfone (DDS) exhibits a high thermal conductivity of 0.34 W/m K; however, their detailed curing reaction mechanism and kinetics have not been reported yet. Herein, the detailed mechanism and kinetics of the curing reaction between BP and DDS are reported. The curing reactions in the temperature range of 150–230 °C are investigated with the mixed model of the n th order and autocatalytic mechanism. The reaction order (m and n), reaction rate (d α /d t), rate constant (k 1 and k 2), and degree of conversion (α) are analyzed at several temperatures, where subscripts 1 and 2 represent the n th order and autocatalytic reaction, respectively. The kinetic parameters, activation energy, and pre-exponential factor, were determined as E a1 = 60.76 kJ/mol, E a2 = 57.20 kJ/mol, A 1 = 4.08 × 104 min−1, and A 2 = 101.22 × 104 min−1, which are in good agreement with the experimental data. Furthermore, the kinetic data could be utilized to predict and control the curing behaviors and the properties of the LCER for further application. Graphical abstract Image Highlights • Curing kinetics of liquid crystalline BP epoxy with DDS is comprehensively investigated by DSC analyses. • The reaction order, reaction rate, rate constant, and degree of conversion are analyzed at five different temperatures. • The activation energies of the curing reaction are determined as E a1 = 60.76 kJ/mol, and E a2 = 57.20 kJ/mol. • The pre-exponential factors are assigned as A 1 = 4.08⋅104 min−1, and A 2 = 101.22⋅104 min−1. • The kinetic parameters provide information to optimize curing reaction for improving the properties. [ABSTRACT FROM AUTHOR]

Featured Application: Microcapsule based self-healing system is developed for intelligent repair of microcracks or/and damage in cementitious composites. Self-healing cementitious composites have been developed by using microcapsules. In this study, the effect of the healing agent on the crosslinking and curing reaction kinetics was analyzed. The effect of the diluent n-butyl glycidyl ether (BGE) on the reaction was investigated for five fractions, namely 10.0%, 12.5%, 15.0%, 17.5%, and 20.0% mass fractions to epoxy resin. The Kissinger and Crane equations were used to obtain the activation energy and reaction order with different mass fractions of diluent, as well as the kinetic parameters of the curing reaction. The optimal fraction of BGE was determined as 17.5%. Likewise, the effect of the curing agent MC120D on the reaction kinetics was investigated for 10%, 20%, 30%, 40%, and 50% mass fractions to the diluted epoxy resin. The optimal fraction was determined as 20%. The mechanism of the curing reaction with the healing agent was investigated. The infrared spectra of the cured products of 20% MC120D with BGE/E51 (0.0%, 12.5%, 15.0%, 20.0%, 100%) were analyzed. It is shown that not only the epoxy resin E-51 was cured, but also that the BGE was involved in the cross-linking reaction of the epoxy resin E-51 with MC120D. [ABSTRACT FROM AUTHOR]

Recent experimental results showed that the Tg of cured resin scarcely decreased and the impact strength of resins increased by over 50% when a tetrafunctional epoxy named N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether (TGDDE) was introduced to an appropriate flexible chain from a dimer fatty acid (DFA). In order to understand the reason for this phenomenon, the modification and the chemical structure of the prepolymer together with the curing reaction and the viscoelasticity of the cured resins were studied in detail in the present work. The results indicated that the modification would help the prepolymer improve its molecular mobility. As a result, the resins could be further cured, resulting in the cross-linking density increasing. This is because the curing efficiency was increased, but the tetrafunctional epoxy was not cured completely due to its large steric hindrance. Moreover, the flexibility of some parts of the networks was improved, which was beneficial for the toughness of the cured resins. Therefore, the toughness of the tetrafunctional resin was improved with little influence on the thermal properties when the epoxies were modified with an appropriate content of DFA.

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Multivariate curve resolution (MCR) was applied to a hetero-spectrally combined dataset consisting of mid-infrared (MIR) and near-infrared (NIR) spectra collected during the isothermal curing reaction of an epoxy resin. An epoxy monomer, bisphenol A diglycidyl ether (BADGE), and a hardening agent, 4,4′-diaminodiphenyl methane (DDM), were used for the reaction. The fundamental modes of the N H and O H stretches were highly overlapped in the MIR region, while their first overtones could be independently identified in the NIR region. The concentration profiles obtained by MCR using the hetero-spectral combination showed good agreement with the results of calculations based on the Beer-Lambert law and the mass balance. The band assignments and absorption sites estimated by the analysis also showed good agreement with the results using two-dimensional (2D) hetero-correlation spectroscopy. [ABSTRACT FROM AUTHOR]

Self-healing cementitious composites have been developed by using microcapsules. In this study, the effect of the healing agent on the crosslinking and curing reaction kinetics was analyzed. The effect of the diluent n-butyl glycidyl ether (BGE) on the reaction was investigated for five fractions, namely 10.0%, 12.5%, 15.0%, 17.5%, and 20.0% mass fractions to epoxy resin. The Kissinger and Crane equations were used to obtain the activation energy and reaction order with different mass fractions of diluent, as well as the kinetic parameters of the curing reaction. The optimal fraction of BGE was determined as 17.5%. Likewise, the effect of the curing agent MC120D on the reaction kinetics was investigated for 10%, 20%, 30%, 40%, and 50% mass fractions to the diluted epoxy resin. The optimal fraction was determined as 20%. The mechanism of the curing reaction with the healing agent was investigated. The infrared spectra of the cured products of 20% MC120D with BGE/E51 (0.0%, 12.5%, 15.0%, 20.0%, 100%) were analyzed. It is shown that not only the epoxy resin E-51 was cured, but also that the BGE was involved in the cross-linking reaction of the epoxy resin E-51 with MC120D.

The mechanical and thermal performance of wood flour composites (WFCs) containing thermoset resin is known to be strongly dependent on the curing reaction. In the present work, WFCs were prepared based on either unsaturated polyester, vinylester or epoxy reinforced by oil palm shell (OPS) flour with a major focus being the preferential reaction of the curing initiator with the natural fiber cells instead of the thermoset resin. Increasing the loading of OPS was found to delay the curing reaction of all thermoset resins by decreasing the peak exothermic temperature and increasing the time to peak. Selecting a suitable surface treatment for the OPS was observed to play a significant effect on the rate of curing reaction. Thermal degradation (in an inert atmosphere) and linear shrinkage of the WFCs was found to decrease with an increase in filler load. In terms of the mechanical performance, the flexural modulus increased steadily with filler load whereas the tensile modulus reached its maximum value of 2.74 GPa (30% improvement) at a filler content of 23 wt% for the hot alkali treated OPS reinforced polyester composite. Increasing the filler load was found to decrease the tensile strength whilst the flexural strength experienced an optimal value of 70.6 MPa (28% improvement) for a filler load of 9 wt%. Furthermore, the OPS filler exhibited improved interfacial bonding with the polyester matrix when compared to vinylester and epoxy. [ABSTRACT FROM AUTHOR]

• Rheological kinetics of urushiol/MDI system was studied by rheology. • Isothermal rheological parameters were used to obtain the curing degree curve of the system. • Kamal-Sourour autocatalytic kinetic model well described the curing behavior. • The predicted model fits well with the experimental data. The gelation and curing process of urushiol and MDI system were studied by dynamic rheology. Rheometer was used to monitor the changes of rheological parameters (storage modulus G' , loss modulus G" , complex viscosity η* and loss tangent tan δ) during continuous heating, isothermal aging and high-frequency heat treatment. And track the gelation and structural evolution of the curing process system. The results showed that the combination of isothermal aging, heating and high frequency were expected to be a simple strategy for low temperature curing or shortening the curing time of resin. The conversion α of the curing process was described by the evolution of storage modulus G'. The curing process can be described by autocatalytic model, and the fitting data are in good agreement with the experimental data. The model can be used for process optimization and further development of urushiol based materials. [ABSTRACT FROM AUTHOR]

Phthalonitrile resin is a kind of high-performance thermosetting resins. Decreasing the curing temperature and accelerating the curing reaction rate have become the focus of research on phthalonitrile modification. Based on the reactivity, thermal and mechanical properties of diamine-type benzoxazine, a monocyano-functionalized diamine-type benzoxazine (MD-cn) was synthesized and applied to modify bisphthalonitrile resin containing bisphenol-type benzoxazine/nitrile phenylenediamine (BA-ph/BAB). Curing reaction properties and curing mechanism of BA-ph/BAB/MD-cn were studied by gelation time, DSC, DRA and in-situ IR. Results showed that MD-cn could significantly boost the curing reaction rate and reduce its curing temperature of BA-ph/BAB. Meanwhile, glass fiber reinforced composites (BA-ph/BAB/MD-cn/GF) was prepared and their properties were studied. Results showed that MD-cn improved the crosslinking density and curing degree of BA-ph/BAB could make the BA-ph/BAB/MD-cn resin matrix possess higher stiffness. Therefore, BA-ph/BAB/MD-cn/GF composites exhibited higher flexural strength (494 MPa, increased 40%) and flexural modulus (26 GPa, increased 13%) as well as good dimensional stability. Compatibility between MD-cn and BA-ph/BAB was investigated by DMA and SEM. Moreover, with the increase of MD-cn content, the good thermal stabilities (T 5% >404.5 °C, Y c, 800 °C >66%) of cured BA-ph/BAB/MD-cn were obtained. Besides, interfacial adhesion properties of BA-ph/BAB/MD-cn/GF composite laminates were also studied. [Display omitted] • A novel highly active monocyano-functionalized diamine-type benzoxazine (MD-cn) is prepared by molecular design. • A new method of modifying the bisphthalonitrile resin containing bisphenol-type benzoxazine (BA-ph) with MD-cn is proposed. • MD-cn reduces the initial reaction temperature of BA-ph/BAB and significantly improves the curing reaction rate. • MD-cn improves crosslinking density and curing degree of BA-ph/BAB, also perfects interfacial compatibility of composites. • MD-cn makes BA-ph/BAB/MD-cn/GF composites exhibit good thermal stability and its flexural strength increased by 40%. [ABSTRACT FROM AUTHOR]

Curing activity in the preparation of solid composite propellants determines the performance of solid rocket motors in operation. Limited by the lack of effective monitoring tools, the complete curing behavior and thermal-induced curing kinetics are rarely disclosed. It is still a challenge to monitor in situ and in real-time the physical and chemical cross-linking reaction during the curing of propellant. Herein, we demonstrate a promising approach based on optical fiber capable of being implanted inside the propellant to monitor the internal stress evolution during the curing process, by taking hydroxyl-terminated polybutadiene propellant as an example. Attributed to the strain and temperature sensitivity of a pair of optical fiber gratings, the thermal-assisted physico-chemical cross-linking states of curing process have been demonstrated in detail. By tracking the stress-induced wavelength shifts of fiber gratings and calculating the curing mechanism function, the complete curing roadmap, including the viscous flow stage, gel stage, hardening stage can be clearly revealed, and the curing completion times are obtained as 154, 81, and 40 h, at the curing temperatures of 60, 70, and 80 °C, respectively. The apparent activation energy of this curing system obtained by calculation is 73.88 kJ/mol. This flexible fiber-based sensor provides an effective tool for unraveling the cure kinetic mechanism, and paves a universal pathway to guide the preparation and applications of versatile composite materials for solid rocket motors.

Gels were obtained from resol type phenolic resins, with resorcinol, formaldehyde and lignin as precursors. Thermal response was evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and curing kinetics were determined from the SDTA curves using Flynn-Wall-Ozawa and Friedman iso-conversional models. Additionally, it was used Fourier transform infrared spectroscopy (FTIR) to evaluate the progress of the curing reaction. These analyzes were performed for two gels, one of them prepared with lignin (lignin resin), and a reference (resorcinol resin). Lignin resins tend to be more thermally stable than resorcinol resins. Average values found for activation energy of the curing processes are 55.07 kJ mol−1 and 60.60 kJ mol−1 for resorcinol resin and lignin resins respectively using Flynn-Wall-Ozawa method; values of 51.94 kJ mol−1 and 53.14 kJ mol−1 were obtained using Friedman method. It was possible to conclude that the lignin affects positively the thermal stability of the resin; the curing reaction takes place in the first six hours and the Flynn-Wall-Ozawa model fits better. [ABSTRACT FROM AUTHOR]

The paper presents the synthesis and thermal behavior of an epoxy matrix from diglycidyl ether of bisphenol A (DGEBA) and epoxidized hemp oil crosslinked with two hydroxy carboxylic acids (HAc). Epoxidized hemp oil (EHO) was obtained via epoxidation in situ with peroxyacetic acid. The chemical structures of hemp oil (HO), EHO and epoxy matrix were confirmed using FT-IR and 1 H NMR spectroscopy. The kinetics of the curing reactions were studied by differential scanning calorimetry (DSC) using multivariate non-linear regression method from the “Thermokinetics-3” software (Netzsch). Also, the thermal decomposition behavior of network has been studied in nitrogen atmosphere up to 600 °C using simultaneous TG/FT-IR/MS technique. Using the above software, the global kinetic parameters of thermal decomposition were determined and was found that the thermal decomposition process occurs in three steps. A good correlation was observed between experimental and simulated data. The chemical composition of gases that arise in the process of thermal decomposition was assessed using FT-IR and MS techniques. [ABSTRACT FROM AUTHOR]

4,4′-Diphenylmethane bismaleimide (BMI)/2,2′-diallylbisphenol A (DABPA) resin was modified with a multifunctional thiol containing isocyanuric ring and long-chain aliphatic unit (tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (TEMPIC)). To investigate the relationship of the curing reaction and properties of cured BMI/DABPA resin modified with TEMPIC, the temporal change in the functional groups during the curing reaction process was analyzed using Fourier transform infrared analysis. Despite the decreased cross-link density with increasing TEMPIC concentration, the glass transition temperature of BMI/DABPA resin was not decreased by modification with TEMPIC. The storage modulus of BMI/DABPA/TEMPIC resin maintained a value on the order of 109 Pa in the rubber region, which is similar to that of the unmodified resin. The fracture toughness and flexural strength were also improved by modification with TEMPIC. Moreover, the observation of the fracture surface of BMI/DABPA/TEMPIC resin using scanning electron microscopy showed a uniform structure with no phase separation. These results were consistent with the single α-relaxation peak in the loss tangent curve of the dynamic viscoelastic behavior. [ABSTRACT FROM AUTHOR]