Oil-based Thermoset Research Articles

Photocurable Oil-Based Thermosets Containing Modifiers from Renewable Sources for Coating Applications

Photocurable Oil-Based Thermosets Containing Modifiers from Renewable Sources for Coating Applications

Development of Halloysite Nanotube-Infused Thermoset Soybean Bio-Resin for Advanced Medical Packaging.

The development of eco-friendly, mechanically stable, and biocompatible materials for medical packaging has gained significant attention in recent years. Halloysite nanotubes (HNTs) have emerged as a promising nanomaterial due to their unique tubular structure, high aspect ratio, and biocompatibility. We aim to develop a novel soybean oil-based thermoset bio-resin incorporating HNTs and to characterize its physical and functional properties for medical packaging. Soybean oil was epoxidized using an eco-friendly method and used as a precursor for preparing the thermoset resin (ESOR). Different amounts of HNTs (0.25, 0.50, and 1.0 wt.%) were used to prepare the ESOR/HNTs blends. Various characteristics such as transparency, tensile strength, thermal resistance, and water absorption were investigated. While incorporating HNTs improved the tensile strength and thermal properties of the ESOR, it noticeably reduced its transparency at the 1.0 wt.% level. Therefore, HNTs were modified using sodium hydroxide and (3-Aminopropyl) triethoxysilane (APTES) and ESOR/HNTs blends were made using 1.0 wt.% of modified HNTs. It was shown that modifying HNTs using NaOH improved the transparency and mechanical properties of prepared blends compared to those with the same amount of unmodified HNTs. However, modifying using (3-Aminopropyl) triethoxysilane (APTES) decreased the transparency but improved the water absorption of prepared resins. This study provides valuable insights into the design of HNT-based ESOR blends as a sustainable material for medical packaging, contributing to the advancement of eco-friendly packaging solutions in the healthcare industry.

High toughness plant oil-based epoxy resins simultaneous with low dielectric properties

Developing novel multifunctional polymeric materials from biomass to replace traditional electric encapsulation materials such as epoxy resins and polydimethylsiloxane is of great significance for energy consumption and sustainable development. Here, a series of bio-based epoxy thermosets were prepared using a solvent-free ring-opening polymerization-initiated process from different epoxidized plant oils. Key factors such as reactive sites and optimized curing conditions for this system were studied systematically. Moreover, the relative properties of the resulting products, including thermal, mechanical, and dielectric performance were investigated and discussed deeply in correlation with their structure and reactivity. The findings in this work demonstrated that the adjustable chain stiffness and cross-link density of cured networks, achieved through the use of different types of vegetable oils, allows for tailoring the comprehensive properties of these networks. Among the prepared samples, soybean oil-based thermoset exhibited superior tensile strength (7.5 ± 0.28 MPa), elongation at break (87.56 ± 4.80%), glass transition temperature (Tg) of approximately 23 °C, storage modulus of 5.84 MPa, and a dielectric constant of approximately 2.95 at 10 MHz. These properties endow soybean oil-based thermoset as a suitable candidate substrate for encapsulation materials, in comparison with commercial polydimethylsiloxane. The findings suggest that the functional materials designed in this study hold promise as alternatives to petroleum-based polymers and offer paramount potential for applications in diverse electronic device applications.

Sustainable biobased composites from norbornylized linseed oil and biomass sorghum fillers

Thermosets and composites sourced from environmentally benign natural sources are in huge demand. In that context, norbornylized linseed oil was used as the key sustainable polymer precursor for thermosets and glass fiber reinforced hybrid biocomposites via three different curing techniques. At first, norbornylized linseed oil was copolymerized by dicyclopentadiene whereas its epoxides were cured via latent cationic initiator, and copolymerization with disulfide containing acid moieties. Further, biomass sorghum fillers were incorporated into the epoxides to fabricate stronger, cheaper, light weight and more sustainable products. The activation energies and crosslink efficiency of the thermosets were calculated first. To evaluate the commercial significance of the products fabricated, synthetic bisphenol-A based epoxides and commercial standards of epoxidized linseed oil-based thermosets and composites were analyzed side by side. Finally, natural flax fiber reinforced composites were also fabricated to make green composites. The thermo-mechanical properties of the composites were investigated using universal testing machine and thermogravimetric analysis. Steric hindrance and ring strain energies seem to have tangible role in the curing process whereas the presence of ring structures increased the crosslink density and mechanical strength. Fine tunability of composite properties by the selection of a specific curing technique was demonstrated by virtue of different curing mechanisms. While outperforming commercial linseed oil epoxides, the norbornylized linseed epoxides-natural fiber composites exhibited comparable performance properties to synthetic bisphenol-A epoxy-glass fiber composites. Therefore, such biocomposites can be viable replacements of harmful bisphenol-A epoxides in the composite industry, especially in the non-structural automotive composite parts.

Plant oil-based branched polymer coatings enhanced with nucleobases for achieving strong adhesion and outstanding environmental tolerance

Plant oils as the most typical and widest available biomass feedstocks have been employed to construct organic coatings. In contrast to the conventional plant oil-based thermoset coatings, it is still challenging to fabricate robust supramolecular plant oil-based coatings with reversible and dynamic noncovalent interactions, overcoming the drawbacks of thermoset coatings. In this work, we have reported a series of strong nucleobase-enhanced plant oil-based coatings with multiple supramolecular interactions such as hydrogen bonding, π-π stacking, hydrophobic and coordination interactions. The nucleobase-functionalized supramolecular plant oil-based coatings display strong adhesion and outstanding environmental tolerance towards different pH conditions, the variation of temperatures, and UV irradiation. In order to optimize the polymerization of the plant oil-based monomer, the radical polymerization of methacrylate-type camellia oil monomer (MCO) was studied to understand the influence of the unsaturated carbon–carbon double bond in the appended long fatty chain on the polymerization of the methacrylate. The stable propagation radicals of methacrylate-type monomer result in the formation of branched plant oil-based polymers with high efficacy. The copolymerization of the plant oil-based and nucleobase-functionalized methacrylates and the supramolecular mixing achieves the maximum adhesion of 9.89 MPa, highlighting the potential of fabricating strong supramolecular plant oil-based coatings.

Flame-Retardant and Recyclable Soybean Oil-Based Thermosets Enabled by the Dynamic Phosphate Ester and Tannic Acid

The demands of safety and sustainability have driven the development of intrinsic flame-retardant biobased polymers from renewable materials. Herein, a mechanically robust, good flame-retardant, and recyclable thermoset was developed from renewable epoxidized soybean oil (ESO) by using 2-hydroxyethyl methacrylate phosphate (HEMAP) as the reactive flame retardant and tannic acid (TA) as the charring agent. The flame resistance of the obtained ESO-based thermoset achieved the highest UL-94 of V-0 rating and a limited oxygen index value of 26.7% due to the synergistic flame-retardant effect of phosphate and TA. The flame-retardant mechanisms of the gaseous phase and condensed phase were fully investigated by thermogravimetric infrared, scanning electron microscopy-energy-dispersive spectrometry, X-ray photoelectron spectroscopy, and Raman spectra. It is confirmed that the incorporation of phosphate and TA could effectively promote the formation of dense carbon layers and delay the pyrolysis of long aliphatic chains. The ternary crosslinking of ESO, HEMAP, and TA via free-radical polymerization and epoxy-ring opening reaction resulted in a rigid network with a high crosslink density, bestowing the thermoset with superior tensile strength (20.0 MPa), flexural strength (36.3 MPa), and bonding strength (16.7 MPa on steel). Moreover, the ESO-based thermoset exhibited a fast stress relaxation behavior due to the transesterification of dynamic β-hydroxyl phosphate esters, which enables the network with thermal-healing ability and recyclability. This study explores a feasible method to prepare an intrinsic flame-retardant polymer from commercially available and renewable vegetable oils and natural polyphenols.

Facile Approach for the Synthesis of Performance-Advantaged Degradable Bio-Based Thermoset via Ring-Opening Metathesis Polymerization from Epoxidized Soybean Oil

Design and synthesis of polymeric materials from sustainable feedstocks can partly mitigate environmental polymer pollution, and hence, it has received constant attention. This work aims to synthesize a degradable bio-based thermoset via ring-opening metathesis polymerization (ROMP) from epoxidized soybean oil (ESO). ESO was converted to norbornene-functionalized ESO first, and then, this functionalized ESO was rapidly generated to a thermoset via ROMP. The ESO-based thermoset exhibits promising thermal properties and mechanical performance, is available for fabrication of composites, and can be fully degraded into small molecules and oligomeric species under aqueous NaOH or KOH. Moreover, the functionalized ESO can copolymerize with norbornene to form partially degradable copolymers. This approach can be used to synthesize degradable vegetable oil-based thermosets for various applications and for environmental sustainability.

Effects of hydrogen bonds on soybean oil-based thermosets and their bamboo fibers composites

Biocomposites were fabricated from bamboo fibers (BFs) and acrylated epoxidized soybean oil (AESO) resins. Two reactive diluents (RDs), i.e., butyl methacrylate (BMA) and hydroxyethyl methacrylate (HEA), were used as comonomers for AESO, respectively. The effects of type and usage of RDs on the curing behavior, rheological and mechanical properties of AESO resins, the interfacial bonding between BFs and AESO matrix, and properties of the resulting BF/AESO composites were investigated. The formation of multimer induced by hydrogen bonds (H-bonds) in HEA-AESO resin greatly increased the free-radical polymerization rate of C=C bonds, hence reducing the curing temperature and activation energy. The H-bonds provide physical cross-linking points for the cured HEA-AESO network, which significantly increased the tensile strength, tensile modulus, storage modulus, and glass transition temperature of the thermoset. The polar groups of the resins form H-bonds with the hydroxyl groups of BFs, resulting in a good interfacial adhesion between fibers and matrix. The HEA-containing composites demonstrated significantly higher mechanical properties, storage modulus, and water resistance than BMA composites.

Photo-curing 3D printing of micro-scale bamboo fibers reinforced palm oil-based thermosets composites

Fiber-reinforced thermosets composites are widely used in engineering fields, but it is difficult to be customized for objects with complex shapes. Photo-curing 3D printing technique can achieve high precision and customization for polymer composites preparation. Herein, we demonstrate a simple and convenient strategy to manufacture biocomposites from micro-scale bamboo fibers (MBFs) and a vinyl palm oil-based resins via photo-curing 3D printing. To improve the dispersion and stability of MBFs in the inks and the interfacial adhesion between fibers and matrix, the MBFs were modified with methacrylic anhydride to endow the fibers with C=C bonds. The modified MBFs could participate in the crosslinking of the bio-based matrix, thus greatly enhancing the mechanical strength and modulus as well as glass transition temperatures of the composites. More importantly, the matrix of the printed bio-based composites can be degraded in a mild condition, which is conducive to the recycle and utilization of fibers.

Cellulose Nanocrystals vs. Cellulose Nanofibers: A Comparative Study of Reinforcing Effects in UV-Cured Vegetable Oil Nanocomposites.

There is an opportunity to use nanocellulose as an efficient renewable reinforcing filler for polymer composites. There have been many investigations to prove the reinforcement concept of different nanocellulose sources for thermoplastic and thermoset polymers. The present comparative study highlighted the beneficial effects of selecting cellulose nanofibers (CNFs) and nanocrystals (CNCs) on the exploitation properties of vegetable oil-based thermoset composite materials—thermal, thermomechanical, and structural characteristics. The proposed UV-light-curable resin consists of an acrylated epoxidized soybean oil polymer matrix and two different nanocellulose reinforcements. High loadings of up to 30 wt% of CNFs and CNCs in irradiation-cured vegetable oil-based thermoset composites were reported. Infrared spectroscopy analysis indicated developed hydrogen-bonding interactions between the nanocellulose and polymer matrix. CNCs yielded a homogeneous nanocrystal dispersion, while CNFs revealed a nanofiber agglomeration in the polymer matrix, as shown by scanning electron microscopy. Thermal degradation showed that nanocellulose reduced the maximum degradation temperature by 5 °C for the 30 wt% CNC and CNF nanocomposites. Above the glass transition temperature at 80 °C, the storage modulus values increased 6-fold and 2-fold for the 30 wt% CNC and CNF nanocomposites, respectively. In addition, the achieved reinforcement efficiency factor r value for CNCs was 8.7, which was significantly higher than that of CNFs of 2.2. The obtained nanocomposites with enhanced properties show great potential for applications such as UV-light-processed coatings, adhesives, and additive manufacturing inks.

A rigid plant oil-based thermoset with a furfural-derived cyclobutane cross-linker

Furfural-based hardener for cross-linking flexible epoxidized linseed oils leading to bulky biobased thermosets with high hardness and good ultimate strength.

Biocomposites from bamboo fibers and palm oil-based thermosets: Effects of natural phenolic cross-linkers

The development of highly biobased and robust thermosetting matrices using renewable feedstocks has become an interesting topic in the field of composites. A series of palm oil (PO)-based thermosets were prepared from a PO vinyl monomer and natural phenolic (NP) cross-linkers. The PO fatty acid-ethyl acrylamide (POFA-EA) was synthesized via a facile transesterification of PO with N-(2-hydroxyethyl)acrylamide (HEAA). NPs including eugenol, methyl gallate, and tannic acid were used to generate aromatic rings-containing cross-linkers via a solvent-free and ultrasonic-assisted esterification. The mechanical properties and processibility of the developed PO resins were closely associated with the chemical structures and unsaturation degrees of the incorporated NP cross-linkers. Besides, the thermosets were further used as the matrices for bamboo fibers-reinforced biocomposites. The resulting biocomposites showed comparable mechanical properties and Tgs toward those of petroleum-based counterparts. The biocomposites are anticipated to be fully decomposed because the PO matrices could be degraded in a mild alkali condition. This study provides insights to develop high performance and recyclable PO-based thermosets and their biocomposites.

Soybean Oil-Based Thermoset Films and Fibers with High Biobased Carbon Content via Thiol–Ene Photopolymerization

While a number of vegetable oil derivatives have been integrated with petroleum-based materials to prepare thermosetting polymers, existing examples usually incorporate low total biorenewable content into the final product. With the goal of generating thermosets with high biorenewable content, two different soybean oil derivatives with multifunctional thiol and acrylate groups were photocured via thiol–acrylate photopolymerization. For this purpose, l-cysteine, a nonhazardous amino acid, was coupled with epoxidized soybean oil to synthesize a mercaptanized soybean oil derivative containing multiple thiol groups. After being mixed with acrylate counterparts suitable for performing thiol–ene photopolymerizations, these monomer mixtures were processed into thermoset films (via monomer mixture film casting followed by photopolymerization) and fibers (via simultaneous electrospinning of the monomer mixture and photopolymerization in flight). The resulting materials possessed high biobased carbon content (BCC; ...

Soybean oil-based thermoset reinforced with rosin-based monomer

A full bio-based cured resin was synthesized by copolymerization of acrylated-epoxidized soybean oil (AESO) and 2-acrylamidoethyl dehydroabietic acid (DHA-HEMAA). The rigid rosin-based monomer 2-acrylamidoethyl dehydroabietic acid was first prepared from dehydroabietic acid and N-hydroxyethylacrylamide, which was characterized by nuclear magnetic resonance and Fourier transform infrared (FTIR) spectrometry techniques. The cured resin was then synthesized and characterized by FTIR spectroscopy, differential scanning calorimetry, dynamic thermomechanical analysis, and thermogravimetric analysis, as well as using a Kruss tensiometer and a universal testing machine. The results indicated that the resin cured with rosin-based monomer exhibited excellent thermomechanical properties. The crosslink density and thermal stability of cured samples containing DHA-HEMAA at molar ratio between 10 and 30% were higher than those of AESO/DHA-HEMAA0 sample. With increasing DHA-HEMAA content, the glass transition temperature (Tg), elongation-at-break, and tensile strength of samples increased, in the stated order, from 16 to 38 °C, from 24 to 45.8%, and from 1.7 to 6.5 MPa. Due to DHA-HEMAA with a hydrophenanthrene structure, the θ values increased with the increase of DHA-HEMAA molar ratios. The full bio-based rosin thermosetting resins may have great potentials in practical application fields, such as coating, adhesive, and packaging materials.

Optimisation of waste vegetable oil-based thermoset polymers

Bio-based thermoset polymers were produced from epoxidised waste vegetable oils (WVOs) cured with anhydrides at different molar ratios. Properties were compared to analogues produced with neat oil and diglycidyl ether of bisphenol A as a feedstock. The thermal stability proved to be affected by the molar ratio, and the use of feedstock from waste oil resulted in no effect on this property. A dynamic mechanical analysis has shown that higher concentrations of anhydride enhance the storage modulus, glass transition temperature (up to 42·5°C) and cross-link density. The frying process proved to play a minor role in tuning the dynamic mechanical properties. However, the contribution of the anhydride was demonstrated to be significant enough to mitigate the losses caused by the waste oil, as shown statistically in a design of experiment study. All formulations were chemically resistant to aqueous, organic and acidic media. The identification of the effects of critical parameters on the properties of WVO-based thermosets enables the further production of polymers from waste streams.

Synthesis of tung oil-based thermoset resin and its thermal·mechanical properties

Synthesis of tung oil-based thermoset resin and its thermal·mechanical properties

Effects of Catalyst Content, Anhydride Blending, and Nanofiller Addition on Anhydride-Cured Epoxidized Linseed Oil-Based Thermosets

A series of formulations based on epoxidized linseed oil, ELO cured with various anhydride hardeners, were investigated to assess the potential for enhanced elastic properties and thermal transitions through variations in catalyst concentration (1,8-diazabicyclo[5.4.0]undec-7-ene, DBU), hardener type (nadic methyl anhydride, NMA, methyltetrahydrophthalic anhydride, MTHPA, and their blends with phthalic anhydride, PA), and nanofiller (organically modified hydrotalcite, Perkalite F100S) content. To facilitate rapid screening, Shore D hardness was used as a proxy for Young’s modulus, and the limits of this approach were tested via comparisons with modulus measurements made via dynamic mechanical analysis (DMA). ELO cured with MTHPA at a 1:1 epoxy/anhydride molar ratio with 4.5 phr DBU gave a particularly attractive combination of rigidity, homogeneity, and alpha transition temperature rarely seen in thermosets composed of a 100% biobased epoxy component. Nanocomposite formation provided a modest increase in ...

Itaconic Acid as a Green Alternative to Acrylic Acid for Producing a Soybean Oil-Based Thermoset: Synthesis and Properties

In this paper, itaconic acid was monomethylated with methanol to produce monomethyl itaconate, and then monomethyl itaconated epoxidized soybean oil (IESO) was obtained by melt ring-opening esterification of monomethyl itaconate with ESO. For comparison, acrylated epoxidized soybean oil (AESO) was also synthesized from ESO and acrylic acid with the same synthetic method. The chemical structures of monomethyl itaconate, IESO, and AESO were characterized in detail by differential scanning calorimetry (DSC), FTIR, and 1H NMR. The isothermal thermogravimetric analysis at 30, 60, and 90 °C indicated that monomethyl itaconate exhibited extremely low volatility even at 90 °C, while acrylic acid volatilized very fast even at 30 °C, which suggested that monomethyl itaconate could be used as a green alternative to acrylic acid. Under UV radiation, IESO showed good copolymerization ability with reactive monomers such as glycidyl methacrylate modified itaconic acid (IG), trimethylolpropane triacrylate (TMPTMA), and s...

Soybean oil-based thermosets with N-vinyl-2-pyrrolidone as crosslinking agent for hemp fiber composites

Soybean oil-based thermosets from acrylated epoxidized soybean oil (AESO) with a highly reactive vinyl monomer, N-vinyl-2-pyrrolidone (NVP), as crosslinking agent to replace styrene (St) were formulated for the fabrication of hemp fiber composites. The theoretical miscibility of NVP–AESO and St–AESO systems were discussed based on the group contribution method. The AESO resin with 30wt% NVP exhibited a slightly higher viscosity than the counterpart with St, while the maximum curing temperature of the former was considerably lower than that of the latter. The composites from 20wt% NVP resin gained comparable mechanical properties and higher glass transition temperature (Tg) to the composites with 30wt% St. Further increase in NVP usage to 40wt% resulted in the composites with higher tensile strength, tensile modulus, flexural strength, flexural modulus, storage modulus, and Tg of 29.6%, 22.4%, 22.5%, 20.6%, 21.6%, and 47.2%, respectively, when compared to those of the St-based composites.

Effect of Microwave Cure on the Thermo-Mechanical Properties of Tung Oil-Based/Carbon Nanotube Composites

Tung oil is uniquely reactive among plant-based natural oils due to the series ofconjugated carbon-carbon double bonds in its fatty acid chains. These conjugatedcarbon-carbon double bonds impart a high reactivity towards cationic polymerization in thepresence of other reactive co-monomers, such as divinylbenzene and styrene. An impressivedecrease in the cure time of tung oil-based thermosets has been achieved when the resinsinvestigated were microwaved in the presence of carbon nanotubes (CNTs). However, thefast cure compromised the overall thermo-mechanical properties of the materialsinvestigated. Microwave power, exposure time, and CNT loading effects have been assessedby means of dielectric analysis (DEA), thermogravimetric analysis (TGA), differentialscanning calorimetry (DSC), dynamic mechanical analysis (DMA), and proton nuclearmagnetic resonance (1H NMR) spectroscopy of extracts obtained by Soxhlet extraction.Possible reasons were proposed to explain the overall inferior properties observed wheneverfaster cure rates were achieved.