Biobased epoxy resin derived from eugenol with excellent integrated performance and high renewable carbon content

Developing biobased epoxy resin with high renewable carbon content and outstanding integrated performance is beneficial for both sustainable development and applications in cutting‐edge fields. Herein, a biobased epoxy monomer (TEUP‐EP) with high renewable carbon content (100%) was synthesized from renewable eugenol with a sustainable process; TEUP‐EP was then blended with 4,4′‐diaminodiphenylmethane (DDM) to develop a new biobased epoxy resin (TEUP‐EP/DDM). The integrated performance of TEUP‐EP/DDM resin was studied and compared with that of petroleum‐based diglycidyl ether of bisphenol A (DGEBA)/DDM resin. Compared with DGEBA/DDM resin, TEUP‐EP/DDM resin has much better integrated performance and not only exhibits a glass transition temperature about 26 °C higher and a 24.4% or 57% increased flexural strength or modulus, but also shows outstanding flame retardancy. Specifically, the limiting oxygen index increases from 26.5% to 31.4% and the UL‐94 grade improves from no rating to the V‐0 level; moreover, the peak heat release rate and total heat release decreased by 63.1% and 57.4%, respectively. All these results fully prove that TEUP‐EP/DDM is a novel biobased high performance epoxy resin. The mechanism behind these attractive integrated performances is discussed intensively. © 2018 Society of Chemical Industry     

Hyperbranched polysiloxane‐based diglycidyl ether of bisphenol a epoxy composite for low k dielectric application

A new type of diglycidyl ether of bisphenol A (DGEBA) epoxy‐based hybrids has been developed by the incorporation of varying percentages of glycidyl‐terminated hyperbranched polysiloxane (HPSiE) into DGEBA resin and are characterized for their physicochemical, thermal, mechanical, and dielectric behaviors by modern analytical techniques. Data resulted from different studies indicate that the incorporation of HPSiE into DGEBA epoxy resin significantly improved the impact strength, thermal, and dielectric properties with an increase in the HPSiE loading. The contact angle [water and diiodomethane (DI)] increase with increases according to the weight percentages of HPSiE, which indicates the HPSiE‐modified DGEBA shows hydrophobic in nature. The resulting epoxy‐based hybrid composites can be used effectively for different industrial and engineering applications for better performance with improved longevity. POLYM. COMPOS., 34:904–911, 2013. © 2013 Society of Plastics Engineers     

Processing and chemorheology of epoxy resins and their blends with dendritic hyperbranched polymers

Toughened epoxy systems have found increasing applications in automotive, aerospace, and electronic packaging industries. The present article reported work done for elucidation of gelation and vitrification for various epoxy systems and their blends with dendritic hyperbranched polymers (HBPs) having epoxy and hydroxyl functionality. Gel time was found to increase with increasing functionality from diglycidyl ether of bisphenol A (DGEBA) to tetraglycidyl diaminodiphenyl methane (TGDDM). The vitrification point was clearly identified from rheological experiments for triglycidyl p‐amino phenol (TGAP) and TGDDM. In the case of DGEBA a clear display of vitrification was not observed. TGDDM underwent vitrification sooner than did TGAP. Hydroxyl‐functionalized HBP reduced the gel time of the blends because of the accelerating effect of –OH groups to the epoxy curing reaction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1604–1610, 2004     

Antimicrobial dual-cured photopolymers of vanillin alcohol diglycidyl ether and glycerol dimethacrylate

Considering the current efforts for to develop new antimicrobial polymers from renewable resources suitable for application in environmentally friendly light-based technologies, novel dual-cured photopolymers of vanillin alcohol diglycidyl ether and glycerol dimethacrylate are developed. The kinetics of the sequential and simultaneous dual-curing processes, combining free radical and cationic photopolymerizations, is investigated by real-time photorheometry. Comparison of dual-curing systems with different ratios of biobased epoxy and acrylate monomers revealed that the increase in the acrylate content increases the photocuring rate and improves the mechanical performance (Young's modulus increases from 76.64 to 190.71 MPa) and thermal stability (the 10% weight loss increases from 227 to 274°C) of the polymers, while the increase in the vanillin epoxy content results in better antimicrobial activity. Developed photopolymers create unfavorable conditions for the growth of microorganisms and reduce their population by up to 0% in 24 h. The excellent antibacterial and antifungal activity of new photopolymers allows them to be considered as biobased alternatives to petroleum-based antimicrobial coatings, films, or optical 3D printed objects.     

Epoxy networks for medicine applications: Mechanical properties and in vitro biological properties

This work describes the physicochemical, mechanical, and in vitro biological properties of three epoxy networks based on diglycidyl ether of bisphenol‐A (DGEBA) epoxy prepolymer cured with triethylenetetramine, 1‐(2‐aminoethyl)piperazine (AEP) and isophoronediamine. The mechanical properties were evaluated with respect to impact and flexural tests. Functionality rules the mechanical behavior of epoxy networks by increasing the crosslink density and the flexural modulus, increasing T_g and decreasing the chain flexibility and the impact resistance. The biological interactions between the obtained epoxy polymers and blood were studied by in vitro methods. Studies on the protein adsorption, platelet adhesion, and thrombus formation are presented. The protein adsorption assays onto polymeric surfaces showed that the epoxy networks adsorbed more albumin than fibrinogen. The results about platelet adhesion and thrombus formation indicated that DGEBA‐IPD and DGEBA‐AEP networks exhibits good hemocompatible behavior. The materials revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing a satisfactory cytocompatibility. In this way, we can assume that the epoxy polymers are biocompatible materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Homopolymerization of epoxy monomers initiated by 4‐(dimethylamino)pyridine

The anionic epoxy homopolymerization initiated by tertiary amines, imidazoles, and ammonium salts is a complex reaction exhibiting two undesired characteristics for practical applications: (a) slow reaction rates with long induction periods, and (b) short primary chains due to the high rate of chain transfer reactions. Therefore, these systems have not found an important place in commercial applications. In this study, it is shown that using 4‐(dimethylamino)pyridine (DMAP) as initiator of the polymerization of phenyl glycidyl ether (PGE) or diglycidyl ether of bisphenol A (DGEBA) enables to obtain high polymerization rates and longer primary chains than those generated using typical initiators. A critical molar ratio DMAP/epoxy groups was necessary to attain complete conversion. Networks resulting from the DMAP‐initiated homopolymerization of DGEBA exhibited a high crosslink density and corresponding high values of the glass transition temperature (T_g = 160°C) and of the rubbery elastic modulus (higher than 100 MPa). An intense brown color of reaction products, associated with an absorption band with a maximum at 360 nm, was ascribed to the presence of initiator fragments with conjugated double bonds in chain ends. These results might revalorize the anionic homopolymerization of epoxy monomers for commercial applications. POLYM. ENG. SCI. 46:351–359, 2006. © 2006 Society of Plastics Engineers     

Polymerization of an epoxy resin modified with azobenzene groups monitored by near‐infrared spectroscopy

New photosensitive materials containing photochromic azobenzene moieties were synthesized. For this purpose, an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) was reacted with an azobenzene chromophore (disperse orange 3, AZ) to satisfactorily synthesize an azo‐modified prepolymer, which was then used to generate series of epoxy‐based polymers containing azo groups. Three different amines were used as hardeners, with the aim of obtaining materials with different chemical structures. Understanding the epoxy resin polymerization kinetics is essential for intelligent processing of materials. Near‐IR (NIR) spectral analysis was used to follow the polymerization kinetics. The quality of the NIR spectra enables concentrations of individual chemical species to be measured in real time. Conversion of epoxy and primary amine groups, as well as the concentration of different groups, as a function of reaction time was therefore calculated by this spectroscopic technique. Samples containing azo units were compared to the pure DGEBA/amine systems. Results showed that the azo‐prepolymer incorporation has an accelerating effect on polymerization rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical characterization of woven carbon fiber composites with poly(methyl methacrylate)–modified epoxy matrices

The influence of the modification of epoxy matrices with poly(methyl methacrylate) (PMMA) on the fracture behavior of composite laminates based on woven carbon fibers has been investigated. Three‐point flexural, short beam shear (SBS) and end‐notched flexural tests (ENF) have been carried out. Microstructural features have been investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Dynamic mechanical thermal analysis of the different epoxy matrices and their corresponding composites shows the power of this technique for microstructural studies. Fracture behavior is compared with that shown by similar bifunctional (DGEBA) epoxy matrix composites. In spite of the two‐phase structure obtained in tetrafunctional (TGDDM) epoxy matrix‐based systems for all PMMA contents, only a small improvement in fracture toughness and interlaminar shear strength properties was obtained. In contrast, for DGEBA bulk matrices and composites, a higher enhancement of fracture toughness was obtained, as a consequence of the lower crosslink densities of bifunctional matrices.     

Mechanical and dynamic mechanical properties of jute fibers–Novolac–epoxy composite laminates

A study was done of jute composite using a polymer matrix of epoxidized Novolac resin (ENR), diglycidyl ether of bisphenol A (DGEBA)–based epoxy, and their blends with different weight percentages of the resins. It was found that on blending ENR with DGEBA, the storage modulii at room temperature are enhanced by about 100% or more in the case of 30 and 40% ENR‐containing matrices, whereas the enhancement in the case of 20 and 12% ENR‐containing matrices is only 50% that of the pure matrix. It was also observed that the tan δ peak heights of the composites containing 30 and 40% ENR are closer to that of 20% ENR‐containing composite. The probable explanation drawn on the basis of experimental findings of DMA and mechanical analysis is that by blending ENR with DGEBA epoxy it is possible to manufacture jute composites with increased stiffness without sacrificing their ductility. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2800–2807, 2002     

Malleable and recyclable thermoset network with reversible β-hydroxyl esters and disulfide bonds

By combining bifunctional diglycidyl ether of bisphenol A (DGEBA) and trifunctional tris(4-hydroxyphenyl) methane triglycidyl ether (TMTE) epoxy monomers, along with 4,4′-dithiodibutyric acid (DTDBA) as a carboxylic acid, a variety of novel reprocessable and recyclable thermoset polymers are synthesized. The crosslinked network structures with different crosslinking densities are produced by changing the mixing ratio between DGEBA and TMTE, resulting in changes in mechanical and thermal properties of the final products. The stress relaxation and self-healing experiments confirmed that all of these polymeric materials have covalent adaptable networks in their microstructures and perform reversible transesterification processes inside a polymer network. These thermoset polymers are completely decomposed in solution by disulfide-thiol reduction of DTDBA with reversible cleavage or coupling capability in the presence of reducing agent, allowing chemical recycling capability into the thermoset polymer network.     

New biobased carboxylic acid hardeners for epoxy resins

Soybean oil was modified into a novel biobased polyacid hardener by thiol‐ene coupling with thioglycolic acid. The structure of the initial soybean oil and polyacid triglyceride was carefully analyzed using ¹H NMR and titration. The thermal crosslinking reaction between acid hardener and epoxidized resin was studied by differential scanning calorimetry (DSC) and rheology. Then, the synthesized biobased acid hardener was employed as a novel curing agent for bisphenol A diglycidyl ether to elaborate new partially biobased materials. These materials, formulated in stoichiometry ratio, were characterized by DSC, thermogravimetry analyses, dynamic mechanical analyses and exhibit interesting properties for coatings. Practical applications: The products of the chemistry described in this contribution, i.e., polyacid from soybean oil and thioglycolic acid, provide biobased building blocks for further epoxy resin syntheses by reaction with epoxy groups. The obtained epoxy resins are partially biobased and may be applied as binders and coatings.     

Cationic photopolymerization of bisphenol A diglycidyl ether epoxy under 385 nm

The cationic photopolymerization of bisphenol A diglycidyl ether epoxy (DGEBA) at λ = 385 nm was conducted by the combination of a cationic photoinitiator PAG30201 (Bis (4‐isobutylphenyl) iodonium hexafluorophosphate) and a photosensitizer PSS303 (9,10‐dibutoxy‐9,10‐dihydroanthrance). The kinetic characterization was investigated by real‐time Fourier transform infrared spectroscopy. The enhancement of epoxy conversion of DGEBA was achieved by increasing temperature, adding alcohols, active monomers and radical photoinitiators. As a result, in the presence of 2 wt % PAG30201 and 1.2 wt % PSS303, the epoxy rings conversion of DGEBA has reached to more than 70% from 55.9% at room temperature; it could be increased to almost 80% if heated to 60°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3698–3703, 2013     

Toughening of epoxy resin systems using low‐viscosity additives

This study has evaluated three low‐viscosity epoxy additives as potential tougheners for two epoxy resin systems. The systems used were a lower‐reactive resin based upon the diglycidyl ether of bisphenol A (DGEBA) and the amine hardener diethyltoluene diamine, while the second epoxy resin was based upon tetraglycidyl methylene dianiline (TGDDM) and a cycloaliphatic diamine hardener. The additives evaluated as potential tougheners were an epoxy‐terminated aliphatic polyester hyperbranched polymer, a carboxy‐terminated butadiene rubber and an aminopropyl‐terminated siloxane. This work has shown that epoxy‐terminated hyperbranched polyesters can be used effectively to toughen the lower cross‐linked epoxy resins, i.e. the DGEBA‐based systems, with the main advantage being that they have minimal effect upon processing parameters such as viscosity and the gel time, while improving the fracture properties by about 54 % at a level of 15 wt% of additive and little effect upon the T_g. This result was attributed to the phase‐separation process producing a multi‐phase particulate morphology able to initiate particle cavitation with little residual epoxy resin dissolved in the continuous epoxy matrix remaining after cure. The rubber additive was found to impart similar levels of toughness improvement but was achieved with a 10–20 °C decrease in the T_g and a 30 % increase in initial viscosity. The siloxane additive was found not to improve toughness at all for the DGEBA‐based resin system due to the poor dispersion within the epoxy matrix. The TGDDM‐based resin systems were found not to be toughened by any of the additives due to the lack of plastic deformation of the highly cross‐linked epoxy network Copyright © 2003 Society of Chemical Industry     

Influence of the Bio‐Based Epoxy Prepolymer Structure on Network Properties

Three different bio‐based epoxy prepolymers are studied: one that is synthesized from isosorbide and two that are commercial prepolymers derived from sorbitol and cardanol. The chemical structures are analyzed by SEC, ESI–TOF MS, and FTIR analyses. The bio‐based prepolymers exhibit different structures, either aromatic with long aliphatic chains for the epoxy prepolymer derived from cardanol (DGECAR), with high functionality for the sorbitol polyglycidyl ether (SPGE) or a short and cyclic structure for the epoxy prepolymer derived from isosorbide (DGEDAS₀). A traditional petroleum‐based epoxy prepolymer, diglycidyl ether of bisphenol A (DGEBA) is also used for comparison. Gelation and reactivity of the different precursors with an isophorone diamine hardener are studied using rheological measurements and differential scanning calorimetry. Glass transition temperatures of the epoxy networks are evaluated and the thermal stability is also studied by thermo‐gravimetric analysis.

     

Novel Interacting Blends of Unsaturated Polyester-s-Triazine and Epoxy Resin

2-(4-ethyl-1-piperazinylo)-4,6-bismaleatedethylamino-1,3,5-triazine (EBT) was prepared by the reaction of 2-(4-ethyl-1-piperazinylo)-4,6-bishydroxyethylamino-1,3,5-triazine and maleic anhydride. The EBT derivative was characterized by elemental analysis, acid value and spectral studies.

EBT was then polycondensed respectively with three commercial epoxy resins, namely diglycidyl ether of bisphenol-A (DGEBA), diglycidyl ether of bisphenol-F (DGEBF) and diglycidyl ether of bisphenol-C (DGEBC). The resultant polymers are designated as unsaturated polyester-s-triazine (UPETs) and were characterized by elemental analysis, spectral study, molecular weight determination, differential scanning calorimeter (DSC)and thermogravimetry. The interacting blends of UPETs with DGEBA epoxy resin was made at stoichiometric ratio. The blending of these systems was monitored on a differential scanning calorimeter (DSC), and based on DSC data the glass-reinforced composites (GRC_s) were prepared and characterized by physical and mechanical properties.     

Toughening of aromatic epoxy via aliphatic epoxy copolymers

While aromatic diglycidyl ether of bisphenol A (DGEBA) based epoxy polymer matrix systems are important for high-performance applications, their brittle nature is an issue that needs to be addressed. In this paper the authors show that small additions of a more flexible aliphatic epoxy copolymers, both di- and tri-functional, can significantly increase the notched Izod impact strength (56–77%) over the neat DGEBA, while not detrimentally affecting other mechanical properties such as glass transition temperature and flexural properties. In fact, at 1 wt% concentrations, the tri-functional epoxy shows a slight increase (∼2%) in the glass transition temperature compared to neat DGEBA. The improvement in impact toughness is attributed to the more flexible backbone of the aliphatic epoxy molecules. The total miscibility of the aromatic and aliphatic epoxies within the investigated concentration range (up to 20 wt%) allows for this toughening approach to be directly applied to current composite production methods, such as resin transfer molding (RTM).     

Morphology control in polysulfone‐modified epoxy resins by demixing behavior

Polysulfone (PSu) was used as a modifier of epoxy/aromatic diamine formulations. Two epoxy monomers, based on diglycidyl ether of bisphenol A (DGEBA), were used. The cure agent was 4,4′‐diaminodiphenylsulfone. PSu was miscible with DGEBA, as shown by the existence of a single glass‐transition temperature within the whole composition range. The effect of PSu addition on the cure kinetics was investigated. The reaction rate of the epoxy–amine species was slightly lower in the presence of PSu. The morphology was analyzed by optical and scanning electron microscopy. A range of microstructures were obtained by control over the cure temperature, the amount of PSu incorporated, and the molecular weights of the epoxy resins. The variations in the morphology resulted from the different stages of demixing, which were arrested because of the different developments of the viscosity of the system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 405–412, 2003     

High‐performance liquid chromatography‐mass spectrometry of epoxy resins

The application of liquid chromatography coupled to mass spectrometry (LC‐MS) for the analysis of epoxy resins is shown in two examples. Electro spray (ESI) and atmospheric pressure chemical ionization (APCI) are compared with respect to the ionization of diglycidylether of bisphenol A‐based (DGEBA) epoxy resins. By‐products in a typical modified solid DGEBA‐based epoxy resin and in a new weatherable crosslinker for powder coating applications are characterized and discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 913–925, 1999     

Reaction and miscibility of two diepoxides with poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) was melt‐blended at 270°C with two epoxy monomers, diglycidyl ether of bisphenol A (DGEBA) and 3,4‐epoxycyclohexyl‐methyl‐3,4‐epoxycyclohexyl carboxylate (ECY). Intermediate proportions of the epoxy in the range of 20–0.5 wt % were used. If the epoxy monomers were added in a high proportion (10–20%), a large fraction did not react with PET. Calorimetric experiments showed that the unreacted fractions of both epoxies were miscible with the amorphous phase of the polyester. Only one glass‐transition temperature was detected. It was depressed as the epoxy content was increased. The transition was broad when the PET component was crystalline, and it was narrow when the PET component was made amorphous by quenching of the blend. These features were confirmed by dynamic thermal mechanical analysis. As is often the case for crystalline blends, the crystallization and melting temperatures decreased when the proportion of the epoxy was increased. Concerning the reactivity of the epoxy with PET, the behavior differed according to the nature of the epoxy. The DGEBA monomer showed a low reactivity. It was not effective for the chain extension of PET, and no increase in the intrinsic viscosity was observed under the experimental conditions. However, some functionalization of the chain ends may be possible at a high concentration of the epoxy. ECY was more reactive, and the molecular weight of the processed PET increased, although the value of the commercial untreated polyester was not attained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1995–2003, 2003     

Physical and Mechanical Interfacial Properties of Epoxy Copolymers Initiated by Latent Thermal Catalysts

Summary: The epoxy copolymers containing sulfone groups, diglycidyl ether of bisphenol‐A – Bisphenol‐S (DGEBA‐S) were synthesized by a hot‐melt method. The thermal properties of the epoxy systems initiated by two cationic latent catalysts, i.e., N‐benzylpyrazinium hexafluoroantimonate (BPH) and N‐benzylquinoxalinium hexafluoroantimonate (BQH), were investigated by using a dynamic DSC, DMA, and TGA. The mechanical properties were measured by single‐edge‐notched (SEN) beam fracture toughness tests. As a result, the thermal stability and mechanical interfacial properties of the DGEBA‐S/catalyst system were found to be higher than those of the DGEBA/catalyst. This was probably due to the fact that the introduction of sulfone groups with a polar nature to the main chain of the epoxy resins led to an improvement of thermal stability and toughness of the cured epoxy copolymers.

Conversion of the epoxy/catalyst systems as a function of curing temperature.