Bio-based vanillyl alcohol epoxy thermoset with high mechanical properties and its applications for high- performance natural fiber-reinforced composites

doi:10.21203/rs.3.rs-3132839/v1

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Bio-based vanillyl alcohol epoxy thermoset with high mechanical properties and its applications for high- performance natural fiber-reinforced composites

https://doi.org/10.21203/rs.3.rs-3132839/v1

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With the massive usage of fossil-based resources and net-zero missions, developing bio-based epoxy resin and sustainable composites with excellent comprehensive properties from biomass resources as an alternative to commercial petroleum-based epoxy is still a crucial challenge. Herein, taking advantage of the mono and diepoxy cross-linking network structure, a lignin-derived novel cross-linked vanillyl alcohol epoxy (VAE) thermoset-containing mono and di (m&d) epoxy structure is prepared by the epoxidation of the vanillyl alcohol, followed by curing with hardener. The synthesized m&dVAE containing mono and di-epoxidized (m&d) aromatic rings, when cured with 4, 4´-diaminodiphenyl methane (DDM) hardener, exhibits higher record tensile strength ~ 124.0 ± 8.43 MPa and tensile modulus ~ 2.88 ± 0.35 GPa compared to a commercial petroleum-based epoxy, diglycidyl ether bisphenol A (DGEBA) thermoset. Additionally, it demonstrated higher adhesion shear strength (~ 19.16 ± 0.58 MPa) with cellulose nanofibers film than DGEBA. Further, the synthesized m&dVAE-DDM resins are used for bio-based natural fiber-reinforced composites for the first time. The green composite possesses excellent flexural strength of ~ 203.72 ± 2.08 MPa and stiffness of ~ 11.58 ± 0.38 GPa than the petroleum-based thermoset composite. Moreover, the green composite showed good hydrophobicity and an excellent heat-resistant index of 144.4^°C. The m&dVAE resin can be an alternative to petroleum-based resins, and its environment-friendly green composite could be a promising candidate to replace synthetic materials for high-performance structural applications.

Bio-based

Vanillyl alcohol epoxy

Interfacial adhesion

Thermal stability

Mechanical properties

High-performance green composites

The demand for sustainable materials derived from biosources is growing due to economic and increasing environmental concerns, especially in reducing harmful petroleum chemicals usage [1–3]. Thermosets and their composites have been widely used in adhesives, electronics, coatings, and structures, owing to their high strength, high glass transition temperature (T_g), excellent chemical resistance, and adequate compatibility with polymers and fibers [4, 5]. The most common thermoset (or epoxy resin) is diglycidyl ether bisphenol A (DGEBA), used as adhesives and structural material coatings [6, 7]. Since it is a petroleum-derived material, carcinogenic, and endocrine anarchist, it contributes to diminishing fertility of the agriculture field [8]. Thus, bio-based thermosets have been derived from bio-resources, e.g., vanillin, furan, tannins, cardanol, lignin, fatty acid, and eugenol, as alternatives to DGEBA [6, 7, 9–11].

Exploring bio-based and high-performance thermosets is essential to improve biomass-derived composites' strength and stiffness without degrading their intrinsic properties. Lignin is the second most abundant and high molecular weight natural phenolic polymer from plant tissues [12]. It has been used in limited industrial applications due to its complex structure with amphiphilic nature. Vanillin is the most well-known monoaromatic compound extracted from lignin using its chemical depolymerization in the presence of waste sulfite liquor [7]. It is widely used in various applications such as cosmetics, pharmaceuticals, food flavorings, and as additive building blocks for polymer composites [13–15]. Vanillin-based thermosets have been studied for high-performance applications in recent decades [16–21]. Despite those studies, limited effort has been paid to develop bio-based thermosets from vanillyl alcohol (VA). Generally, VA is synthesized by the reduction procedure of the –CHO group of lignin-derived vanillin, which has an aromatic and aliphatic –OH group. Due to VA's bio-based origination, vanillin and its derivative as biomass-based synthons are mainly used to develop bio-based epoxy resins [4]. For instance, Hernandez and co-workers synthesized a VA-based epoxy resin, showing a T_g of 100^°C and storage modulus around 3.02 GPa [8]. Wang et al. prepared a similar VA epoxy resin and cured it with a triethylenetetramine (TETA) hardener [4]. This resin was reinforced with lignin-containing cellulose nanofibers to develop environmentally friendly materials. The cured VA epoxy resins′ tensile strength and stiffness reached around ~ 32.94 MPa and ~ 2.47 GPa, respectively. Recently, the same groups investigated the effect of aliphatic-based hardeners on the mechanical and thermomechanical properties of VA-based epoxy resins [22]. VA epoxy resins cured with different aliphatic hardeners showed a tensile strength and storage modulus lower than 32.94 MPa and 3.76 GPa, respectively.

Because of environmental and health issues, vanillin epoxy resins have been explored for high-performance fiber-reinforced composites [18, 23]. However, most studies dealt with fabricating carbon fiber (CF)-reinforced epoxy resin composites and natural fiber-reinforced composites [17, 24–27]. For instance, thermoplastic polyethersulfone (PES) with CF-reinforced epoxy composites [28], poly(ether ether ketone) (PEEK)/CF [29], toughened by polyphenylene oxide CF-reinforced epoxy composites [24, 26, 30], epoxy/modified natural fibers composites [31], bacterial cellulose nanofiber (CNF)/bio-based epoxy composites [5], and bio-based epoxy vitrimer/CF composites [17] have been reported for high-performance applications with less use of petroleum-based resins. The bio-based CF-reinforced epoxy resin composites were recently fabricated using a low carbon footprint with epoxy amine resin, diminishing the dependency on non-renewable resources [32]. As a result, the flexural modulus of composites reached around 13.9 GPa, and T_g was 119^°C.

Natural fibers are a good candidate for fully bio-based natural fiber-reinforced thermoset composites because they are economical, lightweight, renewable, and biodegradable [5, 29, 33, 34]. This paper focused on fully bio-based natural fiber-reinforced thermoset composites to further increase composites' renewable and environmentally friendly characteristics. Few studies on natural fibers considered replacing CF and glass fibers [35]. Limited studies on natural jute fiber-reinforced bio-based thermoset composites have also been published with encouraging results of the flexural properties and interaction of fiber and bio-based epoxy thermosets [36–40]. For instance, Militky et al. fabricated the jute fiber-reinforced green epoxy composites, and they found less creep deformation at higher temperatures due to a good interface interaction between jute fibers and matrix [38]. Rehman and his workers investigated the effect of microcrystalline cellulose (MCC) particles on the mechanical properties of treated jute fiber (TJF)-reinforced bio-based epoxy composites. They found that composites' flexural strength and modulus reached around 70 MPa and 3.7 GPa at 5 and 7%wt of MCC [41]. Recently, Torres-Arellano et al. reported the bio-based jute fiber/epoxy composites with a fiber fraction of 25.55 and 29%, and they evaluated the flexural properties [42]. In contrast to the bio-based matrix, green composites were fabricated using fifteen plies of alkali-treated jute fibers with epoxy, and the composites showed their flexural strength in the range of 98–162 MPa [43]. Our previous reports presented a fabrication of a bio-based composite using vanillin-based epoxy and natural fibers; it showed flexural strength of ~ 122.9 ± 6.7 MPa, strain-at-break of 0.7%, and flexural modulus of 15.5 ± 0.5 GPa [44]. Recently, we have used the imine-bond containing vanillin epoxy resin with natural fibers to obtain the treated jute fibers (TJF)-reinforced composites, which presented a flexural strength of ~ 138.72 ± 3.81 MPa, flexural strain (2.12 ± 0.03%) and modulus ~ 8.01 ± 0.11 GPa [45]. Nevertheless, owing to the average mechanical properties of resins and their composites, they are still challenging to utilize for high-performance applications.

Thus, to overcome these limits, we report a new type of high-performance cross-linked network structure of VAE-based resin for the natural fibers composite, where the mixture of mono and diepoxy forms based on the vanillyl alcohol’s reactivity of aliphatic and aromatic –OH groups. The m&dVAE was synthesized through the epoxidation of vanillyl alcohol (VA); a mixture of m&dVAE was cured with 4, 4´-diaminodiphenyl methane (DDM) hardener to obtain the m&dVAE-DDM thermoset. The prepared resin's chemical structure, cross-linking, adhesion, thermal stability, and mechanical properties were examined. By embedding the cross-linking of the DDM hardener and the –OH groups, the cross-linked m&dVAE-DDM networks demonstrated high mechanical and thermomechanical properties. A diluted m&dVAE-DDM resin-solvent mixture was used to develop fully bio-based and high-performance natural fiber-reinforced composites. No studies have been published on the cured m&dVAE-DDM thermoset and its direct use for fully-bio-based alkali-treated jute fiber (TJF)-reinforced composites until now. The fully bio-based TJF-m&dVAE composites were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and flexural properties. Notably, the bio-based m&dVAE thermoset and its environment-friendly composites′ performance was compared with a commercial epoxy resin, DGEBA composites.

2.1 Materials

Vanillyl alcohol (VA ≥ 98%), Epichlorohydrin (ECH, 99%), 4, 4´-diaminodiphenyl methane (DDM, ≥ 97%), tetrabutylammonium bromide (TBAB, ≥ 99%), Hydrochloric acid, bisphenol A diglycidyl ether (DGEBA, trade name DER331) and Acetic acid were obtained from Sigma Aldrich. Cellulose nanofibers (CNF, 2.0 wt%) were obtained from Moorim Paper MFG Co., Ltd., South Korea. The jute fiber mat was procured from JOY elegant fabrics, South Korea, and anhydrous sodium sulfate was purchased from Yakuri Pure Chemicals Co., Ltd., Japan. Sodium hydroxide and acetone were obtained from Daejung Chemical and Metals Co., Ltd., South Korea. Dichloromethane was received from Samjung, South Korea.

2.2 Synthesis of lignin-derived m&dVAE

Lignin-derived m&dVAE was synthesized according to the following procedure. VA (1.0 mol) and TBAB (0.1 mol) were solubilized in ECH (10.0 mol), and the reaction mixture was introduced in three necks round bottom flask equipped with a stirrer and condenser. The reaction mixture is stirred at 50^°C for 3h in a nitrogen environment. After that, the reaction mixture was kept in the ice bath and maintained at around 5 ºC, then 40 wt % NaOH (0.1 mol NaOH) aqueous solution was added dropwise to the reaction mixture within 10 min and continued overnight. Afterward, dichloromethane was added to the reaction mixture, and the organic phase was washed with distilled water, separated, and dried on anhydrous sodium sulfate. A rotary evaporator evaporated the solvent and excess ECH. A mixture of m&dVAE of mono-epoxidized VAE (mVAE) and di-epoxidized VAE (dVAE) was obtained, as shown in Fig. 1, yielding 92%.

2.3 Preparation of cured m&dVAE-DDM thermoset

m&dVAE (2.0 g) and DDM (1.48 g) were dissolved in acetone to obtain the homogeneous mixture of m&dVAE-DDM resin and heated at 60^°C to remove the acetone. After being completely mixed, the remaining solvent was evaporated at 80^°C. Afterward, the epoxy mixture was heated at 100^°C for 1 h and 140^°C for 1 h until the air bubble was removed to obtain a pre-cured epoxy resin. Further, the pre-cured epoxy resin was cured in a hot press at 180^°C for 10 min, and after that, it was post-cured at 140^°C for 50 min and 160^°C for 50 min to obtain a cured m&dVAE thermoset film (thickness around ~ 0.45 mm). DGEBA was cured with the DDM hardener using the 1:1 equal ratios of epoxy and –NH to get a cured DGEBA thermoset.

2.4 Preparation of Single Lap Joint specimens

A single lap joint (SLJ) test investigated the adhesion shear strength of the prepared bio-based m&dVAE-DDM resin with cellulose. The adhesive area of the resins was 1 mm x 10 mm for SLJ specimens, and the thickness was around 2 µm. CNF film (thickness, 200 µm) was cut into a length of 40 mm and a width of 10 mm, as shown in (Fig. S1, Supplementary Information) [44]. Afterward, the CNF-m&dVAE specimens were cured in an oven as the m&dVAE-DDM resin was cured to obtain the thermoset. CNF-DGEBA SLJ specimens were also prepared by the same methodology and cured like DGEBA-DDM resin.

2.5 Preparation of fully bio-based TJF-m&dVAE composites

m&dVAE (5.0 g) and DDM (3.75 g) were solubilized in 50 mL acetone and concentrated at 80^°C to get the viscous m&dVAE resin (around ~ 98% solvent was evaporated in the oven). Subsequently, the solvent-epoxy resin was infused in three TJF mats through the vacuum-assisted resin transfer molding (VARTM) process under a reduced pressure of around ~ 4 MPa. Further, it was kept at 60^°C for 6 h to evaporate the remaining solvent. Afterward, the curing and post-curing of the TJF-m&dVAE composite were performed under the same condition as the cured m&dVAE-DDM thermoset, as shown in Fig. S2. The fiber weight percent in the prepared TJF-m&dVAE composite was around ~ 40%, and the thickness of the composite was around 1.48 mm. The same procedure was also followed for fabricating the TJF-DGEBA composite. The jute fiber surface was treated with the alkali-treating methodology (see Supplementary Information) [44].

2.6 Characterization

FTIR spectra of the prepared VA, m&dVAE, and the cured m&dVAE-DDM resins were recorded using FTIR spectroscopy (Cary 630, Agilent Technologies, USA) with Attenuated Total Reflectance (ATR) mode in the wavelength range of 4000 to 500 cm^− 1. The ¹H and ¹³C NMR spectra of m&dVAE were taken using a Bruker NMR spectrometer using the DMSO-d6 as solvents to confirm the chemical structure.

A single lap joint (SLJ) test was performed to examine the adhesive shear properties of the lignin-derived m&dVAE-DDM and the commercial DGEBA-DDM resins with CNF film: a tensile test machine (TEST ONE, TO-100-IC, South Korea) was used with a 1 mm/min pulling speed, a 5 kgf load cell, and a span length of 20 mm at room temperature. The tensile properties of m&dVAE-DDM and commercial-based DGEBA-DDM thermosets (Dimension: length 50 mm, width 3 mm, thickness 0.45 mm) were examined using the tensile test machine at room temperature with a gauge span length of 20 mm. The flexural properties of two thermosets (m&dVAE-DDM and DGEBA-DDM) and the prepared composites (TJF-m&dVAE and TJF-DGEBA) were examined according to the ASTM D790 using the tensile test machine.

Dynamic mechanical analysis (DMA) of m&dVAE-DDM and DGEBA-DDM thermosets was examined using a DMA Q800 instrument (Multi-Frequency-Strain TA Instruments) in a temperature range of room temperature to 220°C with a heating rate of 3°C/min and frequency 1 Hz. The DMA specimen dimension was 30 mm (length) × 3 mm (width) × 0.45 mm (thickness).

A scanning electron microscope (SEM) characterized the fracture surface morphology of two thermosets and the prepared composites using an SEM (S-4000, Hitachi, Japan) operated at 10.0 kV.

The prepared thermosets and composites' water contact angles (WCAs) were measured using WCA equipment (GSA, Surfacetech Co., South Korea).

T _g of two resins and the prepared composites were analyzed using a DSC instrument (200 F3 Maia, Netzsch, Selb, Germany) with a heating rate of 5^°C/min from room temperature to 250^°C in a nitrogen environment. The thermal stability of two thermosets and the prepared composites was examined with the help of thermogravimetric analysis (TGA, TG 209F3, Netzsch, Selb, Germany). All samples were heated from room temperature to 800^°C with a constant heating rate of 10^°C/min under nitrogen flow.

3.1 Synthesized m&dVAE monomer

The epoxidation of VA with ECH produces two types of structural epoxies, such as mono-epoxidized (mVAE) and di-epoxidized (dVAE) product, as shown in Scheme 1. dVAE is a major product due to its more acidic nature of aromatic –OH than the aliphatic hydroxyl (-CH₂-OH) group, resulting in aromatic –OH shows higher reactivity with ECH [8].

The chemical structure and ratios of the m&dVAE monomer were examined by the ¹H NMR and ¹³C NMR spectroscopy. As presented in Scheme 1, the proton NMR confirms the mixture of mVAE and dVAE structures (Fig. 2a). The signal H10 at 5.06 ppm and H9 at 4.40 ppm corresponds to the –OH and –CH₂ of aliphatic hydroxyl (-CH₂OH), and H8 at 4.42 ppm belongs to the epoxidized aliphatic hydroxyl (-CH₂-O-) [46]. H8, H9, and H10 signals represent the formation of mVAE and dVAE. Signals (H1 and H2) and (H′1 and H′2) are assigned to the oxirane ring in the mVAE and dVAE. The signals H3, H′3, and H7 appeared at 4.29–4.20, 3.73–3.67, and 3.76 ppm, which were attributed to the –O-CH₂-CH and –OCH₃. The H4, H5, and H6 signals belong to the aromatic protons. The ratio of dVAE and mVAE was around 80:20, calculated by integrating the area of signals H8 and H9, as shown in Fig. 2a. Further, the ¹³C NMR characterization was performed to confirm the mixture of mVAE and dVAE (Fig. 2b). The characteristic chemical shift at 63.24 ppm corresponds to the –CH₂-OH, indicating unreacted aliphatic hydroxyl moiety. The twelve carbon signals appeared in the region (111.25 ppm to 149.38 ppm) due to the benzene carbon, confirming the mixture of mVAE and dVAE.

Furthermore, the epoxidation of VA was confirmed by ATR-FTIR analysis. After the epoxidation of VA, a new band at 910 cm^− 1 appeared due to the oxirane ring, as shown in Fig. 2c. Moreover, the m&dVAE monomer's band intensity at 1611 cm^− 1 was partially decreased after the epoxidation of VA [23]. However, the band of aromatic –OH at 3163 cm^− 1 has disappeared, and the aliphatic –OH group′ band has broadened, indicating the existence of the aliphatic–OH group. This change also indicates the preparation of mVAE and dVAE monomers. After curing, the stretching vibration peaks of the oxirane ring in the epoxidized m&dVAE at 910 cm^− 1 disappeared, demonstrating the successful curing of the m&dVAE thermoset.

3.2 Adhesion properties of m&dVAE-DDM thermoset

To evaluate the interfacial adhesion properties of a bio-based m&dVAE-DDM resin with CNF film, we performed the SLJ test. Figure 3a shows stress-displacement curves of the CNF-m&dVAE and CNF-DGEBA SLJ specimens. The CNF-m&dVAE SLJ specimen presents a lap shear strength of 19.16 ± 0.58 MPa, while for CNF-DGEBA was 12.56 ± 0.22 MPa (Table 1). Higher adhesion properties of CNF-m&dVAE are attributed to the etherification reaction and more –OH groups in the cured m&dVAE-DDM, resulting in a robust cross-linking network between m&dVAE and CNF film compared to DGEBA resin, as shown in Fig. 3b-c. In previous literature, VDE-DDM, VDE-IPDA, and VE-DDM achieved adhesion shear strength with natural fibers around ~ 16.2 ± 0.5 MPa, 10.5 ± 0.6 MPa, and 13.93 ± 0.26 MPa, respectively [44, 45]. Thus, CNF-m&dVAE demonstrated excellent adhesion shear strength than the reported literature. The adhesion results indicate that m&dVAE-DDM resin can be applied to natural fibers to make fully bio-based composites for high-performance applications.

3.3 Tensile properties m&dVAE-DDM thermoset

Figure 4a delineates the stress-strain curves of bio-derived m&dVAE-DDM and petroleum-based DGEBA-DDM thermosets. The m&dVAE-DDM thermoset presents its tensile strength ~ 124.00 ± 8.43 MPa, elastic modulus ~ 2.88 ± 0.35 GPa, toughness ~ 5.96 ± 0.13 MJ/m³, and elongation-at-break ~ 6.94 ± 0.30%. However, the DGEBA-DDM thermoset shows its tensile strength, modulus, toughness, and elongation-at-break to be 66.00 ± 2.50MPa, 1.81 ± 0.11 GPa, 2.80 ± 0.20 MJ/m³, and 6.50 ± 0.60%, respectively. m&dVAE-DDM thermoset displayed higher tensile strength and elastic modulus than the DGEBA-DDM. The higher tensile strength is attributed to the increasing cross-linking density of the cured mVAE and dVAE networks in the m&dVAE-DDM thermoset. The rigid network structure and hydrogen bonding between –OH and –OCH₃ groups in the cured m&dVAE-DDM resulted in a higher elastic modulus than DGEBA-DDM [47]. Compared to DGEBA-DDM, m&dVAE-DDM presents higher elongation-at-break due to the eight-membered ring formation through the hydrogen bonding in the cured amine-epoxy thermoset network, as shown in Fig. 4b. The higher toughness is related to the higher tensile strength and the elongation-at-break of the cured m&dVAE-DDM [18]. Few studies have reported the preparation of di-epoxidized VAE thermosets with different hardeners, namely diethylenetriamine (DETA), 4,4’-methylenebiscyclohexanamine (PACM), Tris(2-aminoethyl) amine (TREN), triethylenetetramine (TETA), and ethylenediamine (EDA) [4, 8, 22]. They reported tensile strength around ⁓ 32.94 Mpa, 23.80 MPa, 18.92 MPa, and 12.62 MPa when epoxy monomer was cured with TETA, TREN, DETA, and EDA, respectively. In this work, we prepared the cured epoxy thermoset of mVAE and dVAE with outstanding mechanical properties, which was cured with the DDM hardener. In contrast to TETA, TREN, DETA, and EDA, the higher mechanical properties of m&dVAE-DDM might be due to the rigid aromatic structure and functionality of DDM and the degree of curing. Owing to the unique cross-linked network structure, bio-based m&dVAE-DDM thermoset presented the highest tensile strength and modulus compared to the previously reported bio-based vanillin epoxy thermosets [4, 16, 49, 50, 17–21, 24, 45, 48], as delineated in Fig. 4c.

Table 1

Mechanical properties of m&dVAE-DDM and DGEBA-DDM thermosets
Samples	Tensile strength (MPa)	Strain-at-break (%)	Toughness (MJ/m³)	Tensile Modulus (GPa)	Shear Strength (MPa)
m&dVAE-DDM	124.00 ± 8.43	6.94 ± 0.3	5.96 ± 0.13	2.88 ± 0.35	19.16 ± 0.58
DGEBA-DDM	66.00 ± 2.5	6.50 ± 0.60	2.80 ± 0.20	1.81 ± 0.11	12.56 ± 0.22

3.4 Glass transition temperature (T_g) of m&dVAE-DDM and DGEBA-DDM thermosets

The prepared m&dVAE and DGEBA thermosets′ T_g are presented in Fig. 5, and the results are summarized in Table 2. The m&dVAE was cured with the DDM hardener (1:1 equivalent ratio). As delineated in the DSC curves, the m&dVAE-DDM thermoset exhibited the T_g around 116^°C, and the petroleum-based DGEBA-DDM was 141^°C. Despite the higher cross-linking density and rigid structure, m&dVAE-DDM showed lower T_g than DGEBA-DDM. The low T_g of m&dVAE-DDM might be ascribed to the broken hydrogen bonding of –OCH₃ groups in the cured network at the heating process, creating the flexible network segment resulting in low T_g [18]. Note that the aliphatic –CH₂ of bio-based epoxy resin makes a space between hydroxylamine and aromatic ring, resulting in chain mobility in the cured thermosets network and reducing the T_g [51]. Nevertheless, the cured m&dVAE (mono and di-epoxides) with DDM hardener achieved higher T_g than the previously reported VAE thermosets cured with different hardeners [8, 52].

3.5 Dynamic mechanical properties m&dVAE-DDM and DGEBA-DDM thermosets

The thermo-mechanical properties such as E′, T_g, and v_e of m&dVAE-DDM and DGEBA-DDM thermosets were analyzed using a DMA, as shown in Fig. 6. The E′ of the prepared thermosets was taken at T_g + 60^oC in the rubbery plateau region and found to be 18.36 MPa and 2.63 MPa for m&dVAE-DDM and DGEBA-DDM thermoses, respectively. The cross-linking density (v_e) was calculated using Eq. 1, followed by the rubbery elasticity′ theory.

$${v}_{e} = E{\prime }/RT$$

where E′, T, and R denote the storage modulus at T_g + 60^oC, absolute temperature, and gas constant, respectively. Compared to DGEBA-DDM, m&dVAE-DDM thermoset demonstrated a higher v_e (Table 2). Moreover, the m&dVAE-DDM thermoset exhibited a higher E′ ~ 4.04 GPa at RT than DGEBA-DDM (2.52 GPa), indicating robust stiffness (Fig. 6a). The m&dVAE monomer structure has three epoxy rings with a hydroxyl group, contributing to the cross-linked network structure and higher v_e. In contrast, the two epoxy rings of the DGEBA monomer contribute to the cross-linked network structure, resulting in lower v_e. Despite higher cross-linking, bio-based m&dVAE-DDM thermoset showed lower T_g than DGEBA-DDM due to the weak hydrogen bonding and space between hydroxylamine and aromatic ring (Fig. 6b). It results in chain mobility in the cured thermoset network, leading towards the lower T_g [51]. The results of tensile strength and modulus of bio-based m&dVAE-DDM thermoset exhibited consistency with E′.

Table 2

Thermal-mechanical properties of m&dVAE-DDM and DGEBA-DDM thermosets
Samples	T_g (^oC)	Tan δ (^oC)	E′ (MPa) at RT	E′ (MPa) at T_g + 60^oC	v_e x 10³ (mol / m³)
m&dVAE-DDM	116	119	4035.2	18.36	1.87
DGEBA-DDM	141	154	2519.6	2.63	0.24

3.6 Flexural properties of TJF-m&dVAE composite

The bio-based m&dVAE-DDM resin was infused into TJF mats to obtain the fully bio-based TJF-m&dVAE composite. Flexural properties of the composite were tested to investigate the effect of the functional interaction of m&dVAE-DDM with jute fibers in the composite. Figure 7 delineates the flexural stress-strain curves of the cured m&dVAE-DDM thermoset and the prepared TJF-m&dVAE composite. The TJF-DGEBA composite was included for comparison. As a result, the TJF-m&dVAE composite exhibits higher flexural strength and modulus than the TJF-DGEBA composite and even the m&dVAE-DDM thermoset. Table 3 summarizes the results. The higher flexural strength (203.72 ± 2.08 MPa) of the TJF-m&dVAE composite is attributed to the hydrogen bonding between –OCH₃ and -OH groups and excellent interfacial interaction of the matrix with fibers. m&dVAE-DDM thermoset shows a higher cross-linking ability with natural fibers due to more than two epoxidized groups, resulting in a close tie network and a rigid segment structure TJF-m&dVAE composite and; thus, the high mechanical properties (Fig. S3a) [53]. The higher flexural modulus (11.58 ± 0.38 GPa) of the TJF-m&dVAE composite is related to the higher cross-linking and rigid network structure. Conversely, since DGEBA resin has two epoxy groups (Fig. S3b), it provides less cross-linking than VAE resin after curing, reducing the mechanical properties.

Table 3

Flexural properties of m&dVAE-DDM thermoset, TJF-m&dVAE, and TJF-DGEBA composites
Samples	Flexural strength (MPa)	Flexural strain (%)	Flexural Modulus (GPa)
m&dVAE-DDM thermoset	136.11 ± 2.82	3.71 ± 0.09	5.34 ± 0.31
TJF-m&dVAE composite	203.72 ± 2.08	1.84 ± 0.05	11.58 ± 0.38
TJF-DGEBA composite	104.79 ± 2.71	2.44 ± 0.07	4.56 ± 0.18

3.7 Fracture surface morphology of TJF-m&dVAE composite

The fracture surface morphology of TJF-m&dVAE and TJF-DGEBA composites was examined with SEM images. The composites' mechanical properties depend on the mechanism of the interfacial bonding of the fiber-matrix network. Figure 8 shows the fractured surface morphology of the TJF-DGEBA composite, representing that the fibers are separated from the resin matrix in several places due to the weak interfacial adhesion of DGEBA with TJF, resulting in debonding, void, and cracking in the fiber-matrix. This interfacial debonding and cracking are responsible for the failure of mechanical properties [54]. In contrast, the m&dVAE-DDM exhibited smooth fracture surface morphology without voids and cracks (Fig. 8). It is noteworthy that m&dVAE-DDM is more effective in enhancing the bending properties of the composites than DGEBA-DDM due to its excellent adhesion strength (Fig. 3a). As presented in Fig. 8, the m&dVAE-DDM thermoset bounded TJFs properly, and no interfacial debonding and voids are seen on the fractured surface of the TJF-m&dVAE composite. It means that m&dVAE-DDM exhibits excellent interfacial adhesion with natural fibers. However, the fiber-broken phenomenon was observed in the fractured surface morphology of the composite. It might appear after the composite is fractured due to the highly cross-linked network between the resin and the natural fibers, indicating a high-performance composite.

Natural fibers are highly hydrophilic, and their hydrophilicity is a crucial challenge for advanced materials for structural applications. Thus, we examined natural fiber-reinforced composites' water contact angle (WCA) to explore the hydrophobicity for structural applications. As delineated in Fig. 8, the m&dVAE-DDM thermoset showed a WCA of 96.0 ± 1.5^o, almost near the WCA of the DGEBA-DDM thermoset (95.9^o) [44]. The WCAs of TJF-reinforced composites were slightly decreased compared to the DGEBA-DDM and m&dVAE-DDM thermosets, as shown in Fig. 8. It might be due to the hydrophilic nature of the TJF, resulting in lower WCAs. Interestingly, the TJF-m&dVAE composite presented a higher (~ 94 ± 1^o) than TJF-DGEBA (~ 91 ± 2^o). The m&dVAE-DDM thermoset shows excellent adhesion with natural fibers (Fig. 3a), resulting in robust interfacial interaction with TJF without any voids than DGEBA-DDM resin (see the SEM images in Fig. 8). That is why the TJF-m&dVAE composite leads to a higher WCA. The WCA results indicate that the TJF-m&dVAE composite is hydrophobic and is favorable for water-resistance characters.

3.8 Thermal properties of TJF-m&dVAE and TJF-DGEBA composites

Figure 9a represents the T_g of TJF-m&dVAE and TJF-DGEBA composites obtained from DSC curves. Besides the superior bending properties, bio-based TJF-m&dVAE composites exhibited a comparable T_g (127^°C) with the petroleum-based TJF-DGEBA composite (138^°C). The slightly low T_g of TJF-m&dVAE composite is related to the –OCH₃ and aliphatic –CH₂ groups, which provide a free volume in the cured network structure, resulting in a flexible segment structure. However, the TJF-m&dVAE composite exhibited higher T_g than the cured m&dVAE-DDM thermoset (116^°C). It might be due to the increased number of hydrogen bonds between the bio-based resin and jute fibers, resulting in a higher degree of cross-linking and rigid network structure. In contrast, the T_g of the TJF-DGEBA composite was reduced by 14.49% from the T_g of the DGEBA-DDM thermoset. This T_g reduction in TJF-DGEBA composite is related to the lower adhesion strength and weak interfacial interaction of DGEBA resin with jute fibers (Fig. 8).

The thermal stability of the m&dVAE-DDM thermoset, TJF-m&dVAE, and TJF-DGEBA composites was evaluated using the TGA analysis, as presented in Fig. 9b. TJF-m&dVAE composite′s main degradation appeared at 242^°C with a weight loss of 2.72%, and the m&dVAE-DDM thermoset was at 202^°C with a weight loss of 3.85%. The main degradation of the m&dVAE-DDM thermoset might be due to the rupture of the cross-linked network. The petroleum-based TJF-DGEBA composite showed its main degradation at 237^°C. The higher thermal stability of the TJF-m&dVAE composite is ascribed to forming of a robust cross-linking network between the functional groups of TJF and m&dVAE-DDM resin [22]. Table 4 summarizes the evaluated thermal properties. The statistic heat resistant index, T_s, also describes the thermal stability of the composites, reflecting the material's heat resistance tolerance abilities [35]. T_s can be calculated using the following equation [7]:

$${T}_{s}=0.45\left[{T}_{d5\%}+0.6\left({T}_{d30\%}-{T}_{d5\%}\right)\right]$$

Here, T_d5% and T_d30% are at the 5wt% and 30wt% loss in the TGA curves. Temperatures at T_d5% and T_d30% determine the T_s. Table 4 shows T_s values. TJF-m&dVAE composite's T_s reached slightly higher up to 144.4^°C than the TJF-DGEBA composite (142.6^°C) and m&dVAE-DDM thermoset (131.3^°C). It might be due to the better cross-linking of m&dVAE-DDM with TJF than DGEBA-DDM. Additionally, the char residue of TJF-m&dVAE composite at 800^°C was around 35% against TJF-DGEBA composite (22%) and m&dVAE-DDM thermoset (11%). The higher char residue of TJF-m&dVAE composite indicates better thermal stability. The fully bio-based TJF-m&dVAE composite shows better thermal stability than the petroleum-based TJF-DGEBA composite, owing to the good interfacial bonding between matrix and fiber and higher cross-linking in the TJF-m&dVAE composite.

Table 4

Thermal properties of m&dVAE-DDM thermoset, TJF-m&dVAE, and TJF-DGEBA composites
Samples	T_g (^°C)	IDT^a (^°C)	T_d5% (^°C)	T_d30% (^°C)	T_s (^°C)	R^b (%)
m&dVAE-DDM	116	202	227	335	131.3	11
TJF-m&dVAE	127	242	276	351	144.4	35
TJF-DGEBA	138	237	272	347	142.6	22

A novel bio-based m&dVAE-DDM resin was designed to fabricate environment-friendly high-performance composites for natural fibers. The m&dVAE-DDM resin was successfully synthesized by the epoxidation reaction of a lignin-derived VA, followed by the reaction with a DDM hardener. The bio-based m&dVAE-DDM thermoset exhibited outstanding mechanical properties: tensile strength ~ 124.0 ± 8.43 MPa, tensile modulus ~ 2.88 ± 0.35 GPa, toughness ~ 5.96 ± 0.13 MJ/m³, and adhesion shear strength ~ 19.16 ± 0.58 MPa, which are higher than the petroleum-based DGEBA-DDM thermoset. The m&dVAE-DDM thermoset presented the record highest mechanical properties (especially tensile strength and modulus) than the vanillin-based thermosets with different hardeners. With the prepared bio-based m&dVAE-DDM resin, a fully bio-based environment-friendly TJF-reinforced composite was fabricated. The bio-based TJF-m&dVAE composite exhibited excellent flexural strength ~ 203.72 ± 2.08 MPa, and stiffness ~ 11.58 ± 0.38 GPa, which are higher than the m&dVAE-DDM thermoset (flexural strength: 136.11 ± 2.82 MPa and flexural stiffness: 5.34 ± 0.31 GPa). The SEM images of composites showed that the bio-based resin exhibited better interfacial bonding with TJF than the petroleum-based resin. Additionally, the TJF-m&dVAE composite possessed hydrophobic nature, higher thermal stability, and char residue than the TJF-DGEBA composite. The superior mechanical properties and thermal stability of m&dVAE-DDM thermoset and fully bio-based environment-friendly TJF-m&dVAE composite can be an alternative to petroleum-based epoxy resin and their composite for high-performance structural applications.

Supplementary Information

Supplementary data related to this article can be found at

Acknowledgments

This work was supported by National Research Foundation of Korea (NRF-2015R1A3A2066301).

Conflicts of interest

The authors declare no competing financial interest.

Data Availability

Data will be made available on request.

Author Contributions

Conceptualization, Jaehwan Kim and Bijender Kumar; Data curation and experiments, Samia Adil and Bijender Kumar; Writing—original draft preparation, Bijender Kumar; Visualization, Samia Adil; Writing— review and editing, Jaehwan Kim and Bijender Kumar; Supervision, Jaehwan Kim. All authors have approved the final version of the manuscript.. All authors have given approval to the final version of the manuscript.

More AP (2022) Flax fiber–based polymer composites: a review. Adv Compos Hybrid Mater 5:1–20. https://doi.org/10.1007/s42114-021-00246-9
Shen M, Robertson ML (2021) Degradation Behavior of Biobased Epoxy Resins in Mild Acidic Media. ACS Sustain Chem Eng 9:438–447. https://doi.org/10.1021/acssuschemeng.0c07621
A B, B K, J S (2019) Comparative mechanical, thermal, and morphological study of untreated and NaOH-treated bagasse fiber-reinforced cardanol green composites. Adv Compos Hybrid Mater 2:125–132. https://doi.org/10.1007/s42114-019-00079-7
Wang Z, Gnanasekar P, Sudhakaran Nair S, Farnood R, Yi S, Yan N (2020) Biobased Epoxy Synthesized from a Vanillin Derivative and Its Reinforcement Using Lignin-Containing Cellulose Nanofibrils. ACS Sustain Chem Eng 8:11215–11223. https://doi.org/10.1021/acssuschemeng.0c02559
Yue L, Liu F, Mekala S, Patel A, Gross RA, Manas-Zloczower I (2019) High Performance Biobased Epoxy Nanocomposite Reinforced with a Bacterial Cellulose Nanofiber Network. ACS Sustain Chem Eng 7:5986–5992. https://doi.org/10.1021/acssuschemeng.8b06073
Kumar B, Agumba DO, Pham DH, Kim HC, Kim J (2022) Recent progress in bio-based eugenol resins: From synthetic strategies to structural properties and coating applications. J Appl Polym Sci 139:51532. https://doi.org/10.1002/APP.51532
Kumar B, Agumba DO, Pham DH, Latif M, Dinesh, Kim HC, Alrobei H, Kim J (2021) Recent research progress on lignin-derived resins for natural fiber composite applications. Polymers (Basel) 13:1162. https://doi.org/10.3390/polym13071162
Hernandez ED, Bassett AW, Sadler JM, La Scala JJ, Stanzione JF (2016) Synthesis and Characterization of Bio-based Epoxy Resins Derived from Vanillyl Alcohol. ACS Sustain Chem Eng 4:4328–4339. https://doi.org/10.1021/acssuschemeng.6b00835
Tao Y, Fang L, Dai M, Wang C, Sun J, Fang Q (2020) Sustainable alternative to bisphenol A epoxy resin: High-performance recyclable epoxy vitrimers derived from protocatechuic acid. Polym Chem 11:4500–4506. https://doi.org/10.1039/d0py00545b
Nabipour H, Qiu S, Wang X, Song L, Hu Y (2021) Phosphorus-Free Ellagic Acid-Derived Epoxy Thermosets with Intrinsic Antiflammability and High Glass Transition Temperature. ACS Sustain Chem Eng 9:10799–10808. https://doi.org/10.1021/acssuschemeng.1c02434
Zheng Y, Liu T, He H, Lv Z, Xu J, Ding D, Dai L, Huang Z, Si C (2023) Lignin-based epoxy composite vitrimers with light-controlled remoldability. Adv Compos Hybrid Mater 6:1–10. https://doi.org/10.1007/s42114-023-00633-4
Kai D, Tan MJ, Chee PL, Chua YK, Yap YL, Loh XJ (2016) Towards lignin-based functional materials in a sustainable world. Green Chem 18:1175–1200. https://doi.org/10.1039/c5gc02616d
Huang W, Yang Y, Wen W, Luo Y, Wu J, Xiang L, Hu Y, Xu S, Chen S, Wang P (2020) Vanillin enhances the passive transport rate and absorption of drugs with moderate oral bioavailability: In vitro and in vivo by affecting the membrane structure. Food Funct 11:700–710. https://doi.org/10.1039/c9fo02846c
Cláudio AFM, Neves MC, Shimizu K, Canongia Lopes JN, Freire MG, Coutinho JAP (2015) The magic of aqueous solutions of ionic liquids: Ionic liquids as a powerful class of catanionic hydrotropes. Green Chem 17:3948–3963. https://doi.org/10.1039/c5gc00712g
Arya SS, Rookes JE, Cahill DM, Lenka SK (2021) Vanillin: a review on the therapeutic prospects of a popular flavouring molecule. Adv Tradit Med 21:415–431. https://doi.org/10.1007/s13596-020-00531-w
Wang S, Ma S, Xu C, Liu Y, Dai J, Wang Z, Liu X, Chen J, Shen X, Wei J, Zhu J (2017) Vanillin-Derived High-Performance Flame Retardant Epoxy Resins: Facile Synthesis and Properties. Macromolecules 50:1892–1901. https://doi.org/10.1021/acs.macromol.7b00097
Wang S, Ma S, Li Q, Xu X, Wang B, Yuan W, Zhou S, You S, Zhu J (2019) Facile in situ preparation of high-performance epoxy vitrimer from renewable resources and its application in nondestructive recyclable carbon fiber composite. Green Chem 21:1484–1497. https://doi.org/10.1039/c8gc03477j
Wang B, Ma S, Li Q, Zhang H, Liu J, Wang R, Chen Z, Xu X, Wang S, Lu N, Liu Y, Yan S, Zhu J (2020) Facile synthesis of “digestible”, rigid-and-flexible, bio-based building block for high-performance degradable thermosetting plastics. Green Chem 22:1275–1290. https://doi.org/10.1039/c9gc04020j
Xu X, Ma S, Wu J, Yang J, Wang B, Wang S, Li Q, Feng J, You S, Zhu J (2019) High-performance, command-degradable, antibacterial Schiff base epoxy thermosets: synthesis and properties†. J Mater Chem A 7:15420–15431. https://doi.org/10.1039/c9ta05293c
Memon H, Liu H, Rashid MA, Chen L, Jiang Q, Zhang L, Wei Y, Liu W, Qiu Y (2020) Vanillin-Based Epoxy Vitrimer with High Performance and Closed-Loop Recyclability. Macromolecules 53:621–630. https://doi.org/10.1021/acs.macromol.9b02006
Su X, Zhou Z, Liu J, Luo J, Liu R (2020) A recyclable vanillin-based epoxy resin with high-performance that can compete with DGEBA. Eur Polym J 140:110053. https://doi.org/10.1016/j.eurpolymj.2020.110053
Wang Z, Gnanasekar P, Nair SS, Yi S, Yan N (2021) Curing behavior and thermomechanical performance of bioepoxy resin synthesized from vanillyl alcohol: Effects of the curing agent. Polymers (Basel) 13:. https://doi.org/10.3390/polym13172891
Nabipour H, Wang X, Song L, Hu Y (2021) A high performance fully bio-based epoxy thermoset from a syringaldehyde-derived epoxy monomer cured by furan-derived amine. Green Chem 23:501–510. https://doi.org/10.1039/d0gc03451g
Liu YY, Liu GL, Li YD, Weng Y, Zeng JB (2021) Biobased High-Performance Epoxy Vitrimer with UV Shielding for Recyclable Carbon Fiber Reinforced Composites. ACS Sustain Chem Eng 9:4638–4647. https://doi.org/10.1021/acssuschemeng.1c00231
Chang BP, Gupta A, Muthuraj R, Mekonnen TH (2021) Bioresourced fillers for rubber composite sustainability: Current development and future opportunities. Green Chem 23:5337–5378. https://doi.org/10.1039/d1gc01115d
Wang B, Ma S, Yan S, Zhu J (2019) Readily recyclable carbon fiber reinforced composites based on degradable thermosets: A review. Green Chem 21:5781–5796. https://doi.org/10.1039/c9gc01760g
Aliyeva N, Sas HS, Saner Okan B (2021) Recent developments on the overmolding process for the fabrication of thermoset and thermoplastic composites by the integration of nano/micron-scale reinforcements. Compos Part A Appl Sci Manuf 149:106525. https://doi.org/10.1016/J.COMPOSITESA.2021.106525
Li C, Kang NJ, Labrandero SD, Wan J, González C, Wang DY (2014) Synergistic effect of carbon nanotube and polyethersulfone on flame retardancy of carbon fiber reinforced epoxy composites. Ind Eng Chem Res 53:1040–1047. https://doi.org/10.1021/ie403378w
Lu C, Wang J, Lu X, Zheng T, Liu Y, Wang X, Zhang D, Seveno D (2019) Wettability and Interfacial Properties of Carbon Fiber and Poly(ether ether ketone) Fiber Hybrid Composite. ACS Appl Mater Interfaces 11:31520–31531. https://doi.org/10.1021/acsami.9b09735
Huang Y, Liu W, Jiang Q, Wei Y, Qiu Y (2020) Interlaminar Fracture Toughness of Carbon-Fiber-Reinforced Epoxy Composites Toughened by Poly(phenylene oxide) Particles. ACS Appl Polym Mater 2:3114–3121. https://doi.org/10.1021/acsapm.0c00285
Zhao X, Li K, Wang Y, Tekinalp H, Larsen G, Rasmussen D, Ginder RS, Wang L, Gardner DJ, Tajvidi M, Webb E, Ozcan S (2020) High-Strength Polylactic Acid (PLA) Biocomposites Reinforced by Epoxy-Modified Pine Fibers. ACS Sustain Chem Eng 8:13236–13247. https://doi.org/10.1021/acssuschemeng.0c03463
Mattar N, Langlois V, Renard E, Rademacker T, Hübner F, Demleitner M, Altstädt V, Ruckdäschel H, Rios De Anda A (2021) Fully Bio-Based Epoxy-Amine Thermosets Reinforced with Recycled Carbon Fibers as a Low Carbon-Footprint Composite Alternative. ACS Appl Polym Mater 3:426–435. https://doi.org/10.1021/acsapm.0c01187
Khan FM, Shah AH, Wang S, Mehmood S, Wang J, Liu W, Xu X (2022) A Comprehensive Review on Epoxy Biocomposites Based on Natural Fibers and Bio-fillers: Challenges, Recent Developments and Applications. Adv Fiber Mater 4:683–704. https://doi.org/10.1007/s42765-022-00143-w
Li H, Tang R, Dai J, Wang Z, Meng S, Zhang X, Cheng F (2022) Recent Progress in Flax Fiber-Based Functional Composites. Adv Fiber Mater 4:171–184. https://doi.org/10.1007/s42765-021-00115-6
Dinu R, Montes S, Orange F, Mija A (2021) Reprocessable humins thermosets and composites. Compos Sci Technol 207:108655. https://doi.org/10.1016/J.COMPSCITECH.2021.108655
Zhang Z, Cai S, Li Y, Wang Z, Long Y, Yu T, Shen Y (2020) High performances of plant fiber reinforced composites—A new insight from hierarchical microstructures. Compos Sci Technol 194:. https://doi.org/10.1016/j.compscitech.2020.108151
Sarikaya E, Çallioğlu H, Demirel H (2019) Production of epoxy composites reinforced by different natural fibers and their mechanical properties. Compos Part B Eng 167:461–466. https://doi.org/10.1016/j.compositesb.2019.03.020
Militký J, Jabbar A (2015) Comparative evaluation of fiber treatments on the creep behavior of jute/green epoxy composites. Compos Part B Eng 80:361–368. https://doi.org/10.1016/j.compositesb.2015.06.014
Jawaid M, Abdul Khalil HPS, Hassan A, Dungani R, Hadiyane A (2013) Effect of jute fibre loading on tensile and dynamic mechanical properties of oil palm epoxy composites. Compos Part B Eng 45:619–624. https://doi.org/10.1016/j.compositesb.2012.04.068
Wang X, Shi X long, Meng Q kai, Hu Y cheng, Wang L hai (2020) Bending behaviors of three grid sandwich structures with wood facing and jute fabrics/epoxy composites cores. Compos Struct 252:112666. https://doi.org/10.1016/j.compstruct.2020.112666
Rehman MM, Zeeshan M, Shaker K, Nawab Y (2019) Effect of micro-crystalline cellulose particles on mechanical properties of alkaline treated jute fabric reinforced green epoxy composite. Cellulose 26:9057–9069. https://doi.org/10.1007/s10570-019-02679-4
Torres-Arellano M, Renteria-Rodríguez V, Franco-Urquiza E (2020) Mechanical properties of natural-fiber-reinforced biobased epoxy resins manufactured by resin infusion process. Polymers (Basel) 12:1–17. https://doi.org/10.3390/polym12122841
Kapatel PM (2021) Investigation of Green Composite: Preparation and Characterization of Alkali-Treated Jute Fabric-reinforced Polymer Matrix Composites. J Nat Fibers 18:510–519. https://doi.org/10.1080/15440478.2019.1636738
Kumar B, Roy S, Agumba DO, Pham DH, Kim J (2022) Effect of bio-based derived epoxy resin on interfacial adhesion of cellulose film and applicability towards natural jute fiber-reinforced composites. Int J Biol Macromol 222:1304–1313. https://doi.org/10.1016/j.ijbiomac.2022.09.237
Kumar B, Adil S, Kim J (2023) Adhesion Improvement of Bio ‐ Based Epoxy In Environmentally Friendly And High ‐ Performance Natural Fiber‐Reinforced Composites. Macromol Mater Eng 2300003:. https://doi.org/10.1002/mame.202300003
Zhang Y, Thakur VK, Li Y, Garrison TF, Gao Z, Gu J, Kessler MR (2018) Soybean-Oil-Based Thermosetting Resins with Methacrylated Vanillyl Alcohol as Bio-Based, Low-Viscosity Comonomer. Macromol Mater Eng 303:1–10. https://doi.org/10.1002/mame.201700278
Ma S, Webster DC, Jabeen F (2016) Hard and Flexible, Degradable Thermosets from Renewable Bioresources with the Assistance of Water and Ethanol. Macromolecules 49:3780−3788. https://doi.org/10.1021/acs.macromol.6b00594
Nikafshar S, Zabihi O, Hamidi S, Moradi Y, Barzegar S, Ahmadi M, Naebe M (2017) A renewable bio-based epoxy resin with improved mechanical performance that can compete with DGEBA. RSC Adv 7:8694–8701. https://doi.org/10.1039/c6ra27283e
Zhao S, Abu-Omar MM (2018) Recyclable and Malleable Epoxy Thermoset Bearing Aromatic Imine Bonds. Macromolecules 51:9816–9824. https://doi.org/10.1021/acs.macromol.8b01976
Mai V-D, Shin S-R, Lee D-S, Kang I (2019) Thermal Healing, Reshaping and Ecofriendly Recycling of Epoxy Resin Crosslinked with Schiff Base of Vanillin and Hexane-1,6-Diamine. Polymers (Basel) 11:293. https://doi.org/10.3390/polym11020293
Mora AS, Tayouo R, Boutevin B, David G, Caillol S (2018) Vanillin-derived amines for bio-based thermosets. Green Chem 20:4075–4084. https://doi.org/10.1039/c8gc02006j
Hernandez E, Hernandez ED (2015) Synthesis and characterization of vanillyl alcohol based thermosetting epoxy resins. Theses Diss 458. https://doi.org/https://rdw.rowan.edu/etd/458
Feghali E, Van De Pas DJ, Torr KM (2020) Toward Bio-Based Epoxy Thermoset Polymers from Depolymerized Native Lignins Produced at the Pilot Scale. Biomacromolecules 21:1548–1559. https://doi.org/10.1021/acs.biomac.0c00108
Amirabadi-Zadeh M, Khosravi H, Tohidlou E (2021) Preparation of silica-decorated graphene oxide nanohybrid system as a highly efficient reinforcement for woven jute fabric reinforced epoxy composites. J Appl Polym Sci 138:1–11. https://doi.org/10.1002/app.49653

Scheme 1 is available in the Supplementary Files section.

No competing interests reported.

SupplementaryInformationTJEVAEver03.docx
scheme1.jpg
Scheme 1 Synthetic route of m&dVAE monomer and m&dVAE-DDM thermoset

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Bio-based vanillyl alcohol epoxy thermoset with high mechanical properties and its applications for high- performance natural fiber-reinforced composites

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Abstract

Figures

1 Introduction

2 Experimental

2.1 Materials

2.2 Synthesis of lignin-derived m&dVAE

2.3 Preparation of cured m&dVAE-DDM thermoset

2.4 Preparation of Single Lap Joint specimens

2.5 Preparation of fully bio-based TJF-m&dVAE composites

2.6 Characterization

3 Results and Discussion

3.1 Synthesized m&dVAE monomer

3.2 Adhesion properties of m&dVAE-DDM thermoset

3.3 Tensile properties m&dVAE-DDM thermoset

3.4 Glass transition temperature (T_g) of m&dVAE-DDM and DGEBA-DDM thermosets

3.5 Dynamic mechanical properties m&dVAE-DDM and DGEBA-DDM thermosets

3.6 Flexural properties of TJF-m&dVAE composite

3.7 Fracture surface morphology of TJF-m&dVAE composite

3.8 Thermal properties of TJF-m&dVAE and TJF-DGEBA composites

4 Conclusions

Declarations

References

Scheme 1

Additional Declarations

Supplementary Files

Status:

Version 1

Bio-based vanillyl alcohol epoxy thermoset with high mechanical properties and its applications for high- performance natural fiber-reinforced composites

Status:

Version 1

Abstract

Figures

1 Introduction

2 Experimental

2.1 Materials

2.2 Synthesis of lignin-derived m&dVAE

2.3 Preparation of cured m&dVAE-DDM thermoset

2.4 Preparation of Single Lap Joint specimens

2.5 Preparation of fully bio-based TJF-m&dVAE composites

2.6 Characterization

3 Results and Discussion

3.1 Synthesized m&dVAE monomer

3.2 Adhesion properties of m&dVAE-DDM thermoset

3.3 Tensile properties m&dVAE-DDM thermoset

3.4 Glass transition temperature (Tg) of m&dVAE-DDM and DGEBA-DDM thermosets

3.5 Dynamic mechanical properties m&dVAE-DDM and DGEBA-DDM thermosets

3.6 Flexural properties of TJF-m&dVAE composite

3.7 Fracture surface morphology of TJF-m&dVAE composite

3.8 Thermal properties of TJF-m&dVAE and TJF-DGEBA composites

4 Conclusions

Declarations

References

Scheme 1

Additional Declarations

Supplementary Files

Status:

Version 1

3.4 Glass transition temperature (T_g) of m&dVAE-DDM and DGEBA-DDM thermosets