Cured Epoxy Resin Research Articles

Computational modeling and simulation of temperature field evolution during the chemical foaming of epoxy foams

AbstractThe evolution and control of the temperature field during the chemical foaming of epoxy resin are of paramount importance because the foam structure results from the competition of resin crosslinking and foaming, both of which are highly dependent on temperature distributions. Herein, the epoxy foams, consisting of diglycidyl ether of bisphenol A, glycidyl amine‐type epoxy resin, and 4,4′‐diamino diphenyl sulfone hardener, are prepared using azodicarbonamide and 4,4′‐oxydibenzenesulfonyl hydrazide as a chemical foaming agent (CFA). Kinetic models for heat release and CFA decomposition are established using the auto‐catalytic and n‐th order models, respectively. By integrating the transient flow of resin during the foaming process, numerical simulations of the temperature field evolution within the self‐expanding geometry are conducted to investigate the effects of foaming temperature, heat transfer coefficient, and mold diameter on spatial temperature distributions. A comparison of the kinetic parameters of epoxy curing and CFA decomposition at various foaming temperatures (433, 443, and 453 K) reveals that the acceleration of the curing rate is consistent with that of the decomposition rate as the foaming temperature increases, then the foam structure remains largely unchanged across different foaming temperatures. However, local overheating is unavoidable for the foams at 443 and 453 K. This study offers a method for optimizing the processing parameters in preparing epoxy foams.Highlights Auto‐catalytic model for predicting heat released rate is well established. The decomposition kinetics of the chemical foaming agent is described by n‐th model. Nonisothermal simulation is implemented to study the self‐expanded process of epoxy foam. The foam structure is predicted by comparing the kinetic between the curing and expansion processes.

Recyclable epoxy resins with different silyl ether structures: structure–property relationships and applications in diverse functional composites

In this work, three liquid silyl ether-containing cycloaliphatic epoxides (CESI1, CESI2 and CESI3) with different numbers of pendent phenyl groups were synthesized and cured by methylhexahydrophthalic anhydride. The high glass transition temperatures of the cured epoxy resins range from 150 to 184 °C, which increase with the increasing number of pendent phenyl groups. However, the tensile strengths of the cured epoxy resins decrease as the number of pendent phenyl groups increase. Incorporating dynamic silyl ether bonds enables the cured epoxy resins to be reprocessable and degradable. It is demonstrated that the pendent phenyl groups have a significant impact on the dynamic behaviors and degradation rates of cured epoxy resins. The reprocessing efficiencies and degradation rates of the three epoxy resins monotonously decrease with increasing the number of pendent phenyl groups. Finally, the CESI1 resin with the lowest viscosity was used as the polymer matrix for carbon fiber reinforced composites, electromagnetic wave absorbing coatings and silver-filled conductive adhesives. Notably, non-destructive recovery of carbon fibers, ferromagnetic particles and silver flakes can be achieved through the degradation of the epoxy matrix.

Investigation of the isothermal curing and glass transition behaviors of epoxy–imidazole systems

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 (Tg) during isothermal curing revealed a temperature-dependent relationship between Tg 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 Tg values of resins with different thermal histories were equal after complete curing under high-temperature/long-duration conditions.

Low viscosity and low temperature curing reactive POSS/epoxy hybrid resin with enhanced toughness and comprehensive thermal performance.

The mechanical and high-temperature resistance properties of epoxy resins cured at low temperatures (Tcuring ≤ 100 °C) are often inferior, and the most toughening modification methods for epoxy resins tend to compromise thermal resistance, which significantly limit the practical applications of it. Therefore, this work reported a low viscosity and low-temperature curing epoxy hybrid resin system (OPEP), adopting E-51 as a resin matrix, liquid anhydride (MHHPA) as a curing agent, tertiary amine (DMBA) as a curing accelerator, and reactive octa-epoxy terminated polyhedral oligomeric silsesquioxane (OG-POSS) as a toughening modifier. Results demonstrated that the OPEP system has excellent processability with low viscosity and long processing window period and satisfies the practical requirements of low-temperature curing. The OG-POSS exhibits superior compatibility and reactivity with the resin matrix, and its addition slightly reduces the Eα of the curing reaction and has a certain promotive effect on the curing of epoxy resin. In addition, the curing reaction rate of the OPEP resin complies with the Šesták-Berggren autocatalytic kinetics model. The impact strength, flexural strength, tensile strength, and elongation at break of the OPEP resin reached a maximum of 15.55 kJ m-2, 121.65 MPa, 90.36 MPa, and 2.48%, representing increases of 55.97%, 3.1%, 64.68%, and 26.51% compared to those of the pure resin, respectively. Notably, due to the heat-resistant inorganic silicon cage structure of OG-POSS, the thermal decomposition temperature (Td5), glass transition temperature (Tg), and heat distortion temperature (THDT) of the OPEP0.02 resin were 313.2 °C, 123.7 °C, and 102.0 °C, showing increases of 13.0 °C, 2.3 °C, and 6.8 °C compared to the pure resin, respectively, which is difficult to achieve for the general thermosetting resin toughening modification method. This research utilized organic-inorganic nanohybrid materials (POSS) to optimize the toughness and thermal stability of the resin in a coordinated manner, providing guidance for the preparation of high-performance epoxy resins that cure at low temperatures.

Sustainable Composite of Cardanol Based Phenalkamine Cured Epoxy Systems: Fabrication, Characterization and Mechanical Performance Evaluation for Emerging Applications

Sustainable Composite of Cardanol Based Phenalkamine Cured Epoxy Systems: Fabrication, Characterization and Mechanical Performance Evaluation for Emerging Applications

Enter the multifunctional trifluoromethylated epoxy Resin: Excellent flame retardant, better dielectric, low thermal expansion, etc

In order to obtain epoxy resins with flame retardant, dielectric properties, and easier industrialization, thus meeting the future development requirements in the field of electronic encapsulation, a trifluoromethylated epoxy resin (DGEBAF) was synthesized by using a two-step method, and the cured epoxy resin (DGEBAF/DDM) was prepared with DDM as the curing agent. Detailed studies of DGEBAF/DDM including curing kinetics, mechanical properties, and dielectric properties, etc. were conducted by using DGEBA/DDM (with dimethyl structure in DGEBA) and DGEBF/DDM (with dihydrogen structure in DGEBF) as the comparative samples. The results indicate that DGEBAF/DDM has higher storage modulus and strength, better dielectric properties, and hydrophobicity, and lowest thermal expansion coefficient, due to the existence of trifluoromethyl. Importantly, deeply study about the flame retardancy and its mechanism of DGEBAF/DDM was processed, which was of great significance for its application in the field of electronic packaging. Its vertical combustion level reaches UL-94 V-0. The limiting oxygen index of DGEBAF/DDM is 34.5 %, which is improved by 35.8 % and 30.2 % compared to DGEBA/DDM and DGEBF/DDM, respectively. The thermal decomposition mechanism of DGEBAF was explored by Py-GC/Mass, XPS, and FTIR analysis. It can be inferred that trifluoromethylated epoxy resin releases •CF3 at high temperatures and effectively enhances the flame retardant of the epoxy resin through radical trapping. The smoke toxicity of DGEBAF/DDM combustion was detected in real time by conical thermal method combined with gas infrared analysis. In addition, we have found that DGEBAF/DDM decomposes at first but produces most residual carbon among the three epoxy resins. Based on the characteristics, an intelligent fire alarm system was designed.

Surface Degradation of DGEBA Epoxy Resins Cured with Structurally Different Amine Hardeners: Effects of UV Radiation.

In this study, the effects of three diamine curing agents (aromatic, cycloaliphatic, aliphatic) on the photochemical behavior of bisphenol A diglycidyl ether networks were comparatively examined. In order to monitor structural changes and study the curing agents' action mode, the cured epoxy resins were characterized before and after photoirradiation by means of Fourier-transform infrared spectroscopy, contact angle, differential scanning calorimetry, scanning electron microscopy, and energy-dispersive X-ray analysis, mass loss, and color modification measurements. Water absorption tests were also conducted. The cured epoxy resins are to be used in different multicomponent polymer materials for outdoor protection. The presence of the cycloaliphatic hardener led to reduced water absorption, and after UV irradiation, an increase in the glass transition temperature and lowest mass loss of the corresponding cured epoxy resin compared to the ones cured with aromatic and aliphatic hardener.

A facile and efficient solvothermal degradation route for carbon fiber reinforced epoxy resin composite waste

Carbon fiber reinforced epoxy resin composite (CF/EP) is widely used in aerospace applications, automotive industry, construction engineering and many other important sectors, for it has excellent mechanical properties and corrosion resistance. However, the three-dimensional cross-linked structure of the cured epoxy resin determines its insolubility and non-melting characteristics, which makes it challenging to efficiently degrade CF/EP waste and recycle the high-value carbon fibers. In this study we propose a strategy that degrades the CF/EP waste via a facile and efficient solvothermal degradation route. The results showed that the degradation ratio of the resin increased significantly with the rise in reaction temperature. When the reaction temperature reached 180 °C there were no obvious resin residues on the surface of the recycled carbon fibers. It was found that the recycled carbon fibers were not obviously damaged during the solvothermal degradation process, as shown by the scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman analyses.

Novel rich aromatic and phosphorus-containing compound cured epoxy resins toward outstanding comprehensive performances

Epoxy resin (EP) is quite flammable, which limits its application in areas such as coatings and electronic and electrical materials. In this study, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (or diphenylphosphine oxide (DPO)) 3-cyclohexene-1-formaldehyde (CC) and 4,4’diaminodiphenylmethane (DDM) were selected for the synthesis of two rich aromatic and phosphorus-containing compounds (DOPO-CC and DPO-CC). DOPO-CC and DPO-CC were introduced into epoxy pre-polymers to prepare epoxy thermosets with flame retardancy. When 5 wt% DOPO-CC (P content of 0.50 wt%) or DPO-CC (P content of 0.52 wt%) was added, the LOI values of the epoxy thermosets increased from 25.5% (pure EP) to 33.5% (EP added DOPO-CC) and 31.0% (EP added DPO-CC), respectively, and these epoxy thermosets also achieved the UL-94 V-0 rating. Additionally, cone calorimeter tests showed that the peak heat release rate (PHRR) and total heat release (THR) of epoxy thermoset containing 5 wt% DPO-CC reduced by 42.0% and 39.7% compared to those of pure EP, respectively. By reducing the thermal degradation rate (condensed phase) and combining and quenching free radicals (gaseous phase), the introduction of DOPO-CC or DPO-CC can efficiently improve the flame retardancy of epoxy thermosets. More importantly, the epoxy thermosets containing DOPO-CC or DPO-CC exhibited better mechanical properties than pure EP, which could be proven by the storage modulus and tensile strength. This study provided a new class of rich aromatic and phosphorus-containing compounds that can serve as co-curing agents for epoxy thermosets with outstanding comprehensive performances.

Dynamic reversible mechanism of phenol-carbamate bonds and their potential for the development of thermo-healing, recyclable and high-performance epoxy thermosets

In this paper, a series of small monomers were synthesized to explore the dynamic reversible properties of phenol-carbamate bonds (PCBs), and the bimolecular exchange mechanism of PCBs was verified. Based on this mechanism, a novel thermo-healing recyclable epoxy resin with high mechanical performance and shape memory function was successfully developed. Meanwhile, the number of reversible phenol-carbamate bonds in this system was increased by molecular structure design, which increased the chance of reversible cleavage and recombination of the dynamic covalent bonds. Compared with our previous work, the thermo-healing efficiency of the epoxy thermosets was greatly increased, and the target polymer achieved an excellent balance between high thermo-healing efficiency and good mechanical performance. Further post-treatment experiments show that the cured epoxy resin can also be well recycled by solvent degradation or hot-pressing process. What's more, a novel carbon fiber (CF) reinforced polymer composite material was synthesized by taking that prepared epoxy thermoset as a matrix, which greatly improve the mechanical properties of epoxy resin, and the CF cloths can be recycled when the epoxy resin is removed by chemical degradation. In addition, due to the existence of reversible crystallizable switching segments in the epoxy resin system, when the temperature is above its Tg, it can be triggered by thermal energy, so that the film can rapidly recover from the temporary shape to the permanent shape. This study also provides a new direction for the development of novel multifunctional intelligent polymers.

Synchronously Improving Mechanical and Thermal Performances of Cured Epoxy Resins by Epoxidized Polyether Sulphones as Modifiers

AbstractAs an effort to improve toughness of epoxy resins without scarifying their heat resistance, four novel polyether sulphones (PESs) with epoxy groups (PES‐Es) are developed as efficient toughness modifiers of epoxy resins. The influences of PES‐E on the mechanical property, curing kinetics, thermal, and mechanical properties of the diglycidyl ether with bisphenol‐A (DGEBA) are investigated. The impact strength of PES‐E/DGEBA composites is significantly improved from 16.6 to 28.9 kJ m−2 with optimal content of PES‐E. Different from the composites of typical PES and epoxy which have two‐phase structure, PES‐E/DGEBA composites exhibit a single‐phase structure owing to the participation of PES‐E in the curing reaction of epoxy groups and good solubility of PES‐E in DGEBA. Furthermore, the thermal stability of the PES‐E/DGEBA composites is slightly increased compared to the neat epoxy resin due to the formation of crosslinked semi‐interpenetrating polymer networks. The glass transitionnal temperature (Tg) of PES‐E/DGEBA composites is up to about 184 °C, 46 °C higher than the neat epoxy resin with the same hardener, which have great potential in high‐performance composites. The method developed in this seminal report makes it possible to improve the toughness of epoxy resins without trading‐off the Tg and tensile strength.

Prospects in the application of a frontally curable epoxy resin for cured‐in‐place‐pipe rehabilitation

AbstractPhotocurable acrylates and vinyl esters are among the most commonly used resins in cured‐in‐place‐pipe (CIPP) rehabilitation technology, as they impart excellent thermomechanical properties in composite pipes. In the quest for achieving a higher energy efficiency of the photo‐curing process in CIPP, the frontal polymerization technique is a viable alternative that requires a lower irradiation dosage coupled with exceptionally high curing speeds and depths. Herein, for the first time, we report the application of frontal polymerization in the rehabilitation of underground pipes using a newly developed frontally curable epoxy‐based resin (Trelleborg Self‐Curing*). The neat resin is characterized for degree of cure, glass transition temperature, and mechanical properties via FTIR, DMA, and tensile tests, respectively. In a comprehensive way, the properties are benchmarked against commercially available acrylate (Trelleborg Light Cure*) and vinyl ester (Trelleborg Rapid Cure*) resins to evaluate their applicability for CIPP. The results show a higher glass transition temperature and final monomer conversion for the frontally cured resin, which cures significantly faster than the reference resins under the same irradiation conditions. In proof‐of‐concept trials, the newly developed resin successfully cures polymeric liners in a PVC host pipe with 100% water tightness and without losing its structural integrity. Results from ring stiffness tests for cured composite pipes additionally show that liners cured with Trelleborg Self‐Curing* resin pass the minimum required Young's modulus for non‐pressure drainage pipes as per ASTM F1216. Thus, frontally curable epoxy‐based resins are a promising and competitive alternative to acrylates and vinyl esters in CIPP.

UV light leads to the formation of reduced graphene oxide and silver nanoparticles in waterborne coating

Ultraviolet (UV)-curable waterborne epoxy acrylic resin (EB) containing silver nitrate and graphene oxide (GO) was prepared. A new waterborne epoxy acrylate-based coating (rGO/AgNP/CEB) containing reduced graphene oxide (rGO) and silver nanoparticles (AgNPs) was obtained by the in situ crosslinking of EB and the reduction of GO and silver ion (Ag+) via UV curing. The experimental results showed that UV irradiation combined with glucose effectively reduced GO and Ag+ to rGO and AgNP. Moreover, AgNPs with a diameter of approximately 60 nm were uniformly distributed in the coating. This material can be used for the antifouling of the inner wall of fishponds in mariculture.

Covalent adaptable network offers “sustainable” closed‐loop circularity in epoxy vitrimers

AbstractTraditional Epoxies take hours to cure before their properties can be realized and this restricts its use in applications where quick turn‐around time is imperative. Herein, we developed fast curing Epoxies (which cure within 2 h) using Vitrimer chemistries. A unique dynamic curing agent (bio‐based Schiff motif) consisting of an aldehyde (here, cinnamaldehyde) and an amine (here, mussel inspired dopamine) is used to facilitate imine exchange during the curing process and maintains the network integrity‐ a key requirement to achieve excellent structural properties in epoxy based components. By incorporating this covalent adaptable network, various epoxies were designed which can cure within 2 h. The resulting epoxy vitrimers exhibited high tensile strength (68 MPa), exceptionally high Tg (128°C), fast stress relaxation (a relaxation time of 15.2 s at 180°C) and an activation energy of 105 kJ/mol. This associative covalent adaptable network (imine exchange) also rendered the epoxies re‐processable and re‐usable and offers closed‐loop circularity in plastics. The resulting epoxy also exhibited self‐healing property triggered by the exchangeable bonds. The self‐healing behavior of this epoxy was manifested from the surface conductivity measurements wherein the conducting pathway (facilitated by spraying conducting particles on the vitrimer epoxy substrate) was restored post self‐healing in substrates containing epoxy vitrimers. In addition, the epoxies cured using this Schiff based motif dissolves in a specific solvent and can be recovered and re‐purposed. The excellent mechanical properties achieved by retaining the network integrity together with the self‐healing properties offers myriad applications for the designed epoxy cured using bio‐based Schiff motif.Highlights Developed fast curing Epoxies that cures in 2 h using Vitrimer chemistries. Fully bio‐based hardener was used to realize the network topology. The dynamic exchange reaction results in re‐processability, reusable, recyclable and self‐healable that is not possible in the case of traditional epoxy. It exhibited high tensile strength, exceptional Tg, fast stress relaxation and an activation energy of 105 KJ/mol.

3D printed epoxy/acrylate hybrid polymers with excellent mechanical and shape memory properties via UV and thermal cationic dual-curing mechanism

Fabricating shape memory polymers with complex configurations and high mechanical performance for application as structural materials remains a significant challenge. Here, an epoxy/acrylate hybrid material with remarkable mechanical properties and excellent shape memory performance is fabricated using vat photopolymerization printing technology through photo-thermal dual curing mechanism. The UV-curing component comprises of a polyurethane acrylate and a rigid active diluent to ensure robustness and toughness. Meanwhile, the thermal curing epoxy constituent utilizes a benzylanilinium salt as the cationic initiator for its storage and handling stability throughout the UV curing stage. The interpenetrating polymer network and the unique two-phase molecular microstructure impart the hybrid material with good shape memory and high mechanical properties. Many complex objects are fabricated using vat photopolymerization printing technology and employed in self-deploying antennas, intelligent mechanical grippers, and switches. Combining with excellent printability, mechanical and shape memory properties, the hybrid materials have great potential applications in various fields.

The Design, Synthesis, and Characterization of Epoxy Vitrimers with Enhanced Glass Transition Temperatures.

A series of epoxy vitrimers (EVs) with enhanced glass transition temperatures (Tgs) were synthesized by curing epoxy resin E51 with different ratios of phthalic anhydride and sebacic acid as curing agents, and 1,5,7-triazabicyclic [4.4.0] dece-5-ene as a transesterification catalyst, and their curing dynamics, rheological properties, mechanical properties, and thermal stability were comprehensively investigated. By adjusting the molar ratio of the anhydride to the carboxylic acid in the curing agent, the Tgs of the EVs increased from 79 to 143 °C with the increase in the anhydride content. In particular, the material EV-5.5 with a high usable Tg of 98 °C could undergo stress relaxation through the transesterification reaction when exposed to high temperatures (160 to 200 °C), and the correlation between the relaxation time and temperature follows the Arrhenius equation. Moreover, EV-5.5 exhibited elastomeric behavior, where brittle fractures occurred before yielding, which demonstrated a tensile strength of 52 MPa. EV-5.5 also exhibited good thermal stability with a decomposition temperature (Td5) of 322 °C. This study introduces new possibilities for practical applications of thermoset epoxy resins under special environmental conditions.

Cure characterisation and prediction of thermosetting epoxy for wind turbine blade manufacturing

In the wind industry, the increasing length of turbine blades and the use of thick composite sections make it vital to understand the thermoset and the underlying curing process. In this study, the curing of a specific thermoset epoxy for application in wind turbine blades is characterised by differential scanning calorimetry. The thermoset is analysed under dynamic and isothermal conditions to determine the complex cure behaviour under these various conditions. The data is fitted to determine firstly; the cure kinetics of the material through a kinetic model. Secondly; the phenomenon of the glass transition temperature Tg is studied to predict the development of Tg as a function of the degree of cure. Thirdly, a Diffusion-Kinetic model was utilised to make more accurate cure predictions based on the interaction between kinetic chemical reactions and diffusion control affecting the reaction rate through the incorporation of the glass transition temperature. A simple experimental framework for validating the diffusion-kinetic model was used to make a final validation of the model predictions on a larger scale. A set of final parameters is presented for application in a full diffusion-kinetic model for cure predictions and simulations beyond this study.

Research on the formulation and performance of high-strength resin matrix T1 for wet winding

Aiming at the higher requirements on the performance of composite materials put forward by new specialized equipment, the development of new high-performance winding resin is carried out. First, basing on the epoxy curing system, the selection of the main resin has been completed, we select the appropriate curing agent according to the characteristics of the screened trifunctional glycidylamine epoxy resin and trifunctional alicyclic epoxy resin, the ratio is calculated and optimised, the curing system is established, and the design of the resin formulation system is completed. Second, according to the nature of the resin curing system, the toughening method is screened, and the synergistic enhancement of heat resistance and toughness of the resin is accomplished through the core-shell nano-toughening method. Finally, the glass transition temperature of the new high-performance winding resin T1 is 165.12°C, and the fracture toughness of the resin KIC can reach 1.74MPa-m1/2, and the annular tensile strength of the T1 resin-based T700 carbon fibre composites can reach 3500MPa, which meets the requirements of the design indexes of specialized equipment.

A multi‐element flame retardant for rail transit to improve the flame retardant performance of epoxy resin while reducing smoke density

AbstractA P/N/Si structure flame retardant DTBD was successfully synthesized by 3,5‐diaminobenzoic acid, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), triphenylsilanol, and benzaldehyde. The chemical structure of DTBD was analyzed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectra, which showed that DTBD was successfully synthesized. By analyzing the curing behavior, the addition of DTBD promoted the curing of epoxy resin (EP). According to the limited oxygen index (LOI) and UL‐94 vertical combustion tests, it can be shown that the introduction of DTBD makes the epoxy resin have good self‐extinguishing properties. Py‐GC/MS analysis showed that the phosphorus free radicals and ammonia generated in the gas phase of DTBD could quench and dilute by capturing reactive free radicals and refractory gases. DTBD could improve the tensile and flexural properties of epoxy resin. According to the European flame retardant standard EN45545‐2, the Ds of EP‐15 and EP‐20 obtained HL1 grade. With the increase in DTBD content, the VOF4 of modified EP also gradually decreased, and both EP‐15 and EP‐20 obtained HL2 grade.

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

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