New Epoxy-Anhydride Thermosets Modified with Multiarm Stars with Hyperbranched Polyester Cores and Poly(ϵ-caprolactone) Arms

Multiarm star polymers with hyperbranched aromatic or aromatic-aliphatic cores and poly(?-caprolactone) arms have been used as toughness modifiers in epoxy-anhydride formulations catalyzed by benzyldimethylamine. The curing process has been studied by dynamic scanning calorimetry, demonstrating little influence of the mobility of the reactive species and the hydroxyl content on the kinetics of this process. The obtained materials were characterized by thermal and mechanical tests and the microstructure by electron microscopy. Homogeneous thermosets have been obtained with a remarkable increase in impact strength without compromising glass transition temperature, thermal stability or hardness.     

Aromatic amino acids as latent,bio-based curing agents and toughening agents for epoxy resins

In the realm of bio-based curing agents, recent investigations have focused on amino acids owing to their distinctive attributes. Nevertheless, the suitability of thermosets cured with aromatic amino acids as latent matrix materials for fiber-reinforced composites remains to be empirically established. Consequently, this study is oriented toward assessing the mechanical properties of diglycidyl ether of bisphenol A when cured with either L-tryptophan or L-tyrosine, in the presence of a latent, urea-based accelerator. The investigated properties include glass transition temperatures, tensile, flexural, compression, and fracture toughness properties. The predominant variations in the mechanical characteristics of these thermosets are confined to their Young's moduli and fracture toughness properties. This divergence is attributed to the greater presence of crystals in the L-tyrosine-cured thermoset, resulting in enhanced reinforcement and toughening effects compared to the L-tryptophan-cured thermoset.     

Biobased thermosets from the free‐radical copolymerization of conjugated linseed oil

New polymeric thermosets were prepared through the bulk free‐radical copolymerization of 100% conjugated linseed oil, acrylonitrile, and divinylbenzene. Under the appropriate reaction conditions and with the appropriate curing sequence, 61–96 wt % of the oil was incorporated into the crosslinked thermosets. The resulting yellow, transparent thermosets varied from being soft and flexible to being hard and brittle. Dynamic mechanical analysis and thermogravimetric analysis showed that these thermosets had good mechanical properties and thermal stability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 979–985, 2007     

Unsaturated para-linked aromatic LC polyesters: Thermotropic and lyotropic systems

Liquid-crystalline thermosets (LCT) are a new class of materials which combine typical properties of LC polymers with those of conventional thermosets. This article reports on the development of a lyotropic LC thermoset (LLCT) in which the solvent is a vinyl monomer. Such an LLCT is expected to have several advantages compared to conventional unsaturated polyester resins. The synthesis and characterization of a variety of novel substituted para-linked aromatic polyesters and copolyesters containing unsaturated fumaroyl units is presented. The thermal and liquid crystal properties were investigated. It is demonstrated that it is possible to prepare a lyotropic LC solution in styrene. These lyotropic solutions are capable of thermal crosslinking by the addition of a free-radical initiator. © 1995 John Wiley & Sons, Inc.     

New UV-Curable Anticorrosion Coatings from Vegetable Oils

Bio-based epoxy resins are attracting widespread interest in the field of polymer thermosets as environmentally friendly building block. In the present study, the feasibility of applying UV-curable epoxidized vegetable oils (EVOs) as anti-corrosion coating is investigated. Rheological characterization of EVOs is carried out, and their viscosity-shear relationship is evaluated. The cationic UV-curing of EVOs successfully gives rise to crosslinked materials with a wide range of thermo-mechanical properties, evaluated by differential scanning calorimetric analysis and dynamic thermal mechanical analysis. A high epoxy-group conversion, ranging from 93% to 99%, is always obtained. The thermal stability and surface properties of the bio-based coatings, such as, pencil hardness, adhesion, solvent resistance, and contact angle, are analyzed. Moreover, the corrosion protection effectiveness of the coatings is characterized by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. In addition, field emission scanning electron microscopy is used to assess the samples morphology after corrosion tests.     

碳酸钙和芳烃油对CR硫化胶性能的影响

通过中心复合试验设计法研究了碳酸钙和芳烃油用量对氯丁橡胶硫化胶物理性能的影响。结果表明：随碳酸钙和芳烃油的用量变化，硫化胶的拉伸强度、撕裂强度、伸长率、硬度、３００ ％ 定伸应力和压缩永久变形均显示出规律性的变化。通过两者用量的变化可以调节硫化胶的某些物理性能。     

Ring-opening metathesis polymerization (ROMP) of norbornenyl-functionalized fatty alcohols

Novel biorenewable-based thermosets have been successfully synthesized by the ring-opening metathesis polymerization (ROMP) of norbornenyl-functionalized fatty alcohols derived from soybean oil (NMSA), Dilulin (NMDA), ML189 (NMMA) and castor oil (NMCA). The effects of the monomer structure on the polymerization process, and the thermal and mechanical properties of the resulting thermosets have been extensively investigated. The number of ROMP-reactive rings appended to the fatty acid chain and the viscosity play an important role in controlling the initiation and propagation processes of the polymerization and the final properties of the thermosets obtained. The thermosets have been characterized by Soxhlet extraction, DMA, TGA, and tensile tests. It has been found that polyNMDA and polyNMMA have best thermo-mechanical properties. Compared with polyNMSA, the polyNMDA and polyNMMA thermosets exhibit lower soluble fractions, and higher thermal stabilities and mechanical properties, because of more effective crosslinking; whereas, polyNMCA exhibits a higher soluble fraction, and lower thermal stability, resulting from incomplete polymerization of the more viscous NMCA monomer.     

Tannic acid-based tough hyperbranched epoxy thermoset as an advanced environmentally sustainable high-performing material

Bio-based resources are progressively replacing those of petroleum-based to address the detrimental impact on environment and health issues. In this regard, hyperbranched epoxy resins with three different compositions were synthesized by simple polycondensation reaction of bio-based branching reactant, diethanolamide of gallic acid with bisphenol-A, and epichlorohydrin. Diethanolamide of gallic acid was obtained from the reaction between tannic acid and diethanol amine in the presence of sodium methoxide catalyst. FTIR, ¹H NMR, and ¹³C NMR spectroscopic analyses were employed to confirm the structure of branching unit and hyperbranched resins. Poly(amido amine)-cured hyperbranched epoxy thermosets exhibited superior properties, such as tensile strength (45–57.2 against 38.5 MPa), elongation-at-break (16.3–24.2 against 5 %), scratch hardness (>10 against 7 kg), toughness (577.8–859.1 against 150.2 MPa), tensile adhesive strength (1647–2086 against 581 MPa), and biodegradability (17.6–31 against 2.2 %), compared with the conventional bisphenol-A-based epoxy, prepared under the same conditions. These results simply indicate the advantageous of the bio-based moiety and hyperbranched architecture on the overall performance of the thermosets. Moreover, good antioxidative response of these thermosets expands their applications as protective coatings and adhesive materials. Thus, diethanolamide of gallic acid-based hyperbranched epoxy thermoset can be used as potent ecofriendly advanced material in multifaceted applications.     

Synthesis of epoxy-terminated fluoropolymer via ATRP and the properties of epoxy thermosets modified with it

A novel fluoropolymer of epoxy-terminated poly(2,2,3,4,4,4-hexafluorobutyl methacrylate) (E-PHFMA) was synthesized and incorporated into epoxy resin to prepare thermosets. Gel permeation chromatography and ¹H nuclear magnetic resonance data obtained verified the synthesis and measured the structure of the polymer. In order to demonstrate the effect of epoxy group on the properties of the thermosets, the corresponding fluoropolymer without epoxy group was prepared and the properties of thermosets modified by two kinds of fluoropolymers were comparatively studied. The contact angle measurements indicated that the thermosets modified with E-PHFMA had a little worse hydrophobicity but better surface stability. Scanning electron microscopy revealed the surface morphologies of the modified thermosets before or after surface stability experiment. The results of differential scanning calorimetry and thermogravimetric analysis showed that the thermosets modified with E-PHFMA had higher thermal stability.     

Microstructure and performance of block copolymer modified epoxy coatings

The effects of two diblock copolymers, poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP–PEO) and poly(1,2-butadiene)-b-poly(2-vinyl pyridine) (PB–P2VP) on the mechanical properties of epoxy coatings were studied. Both modifiers self-assembled into spherical micelles of 10–20 nm diameter in cured bulk epoxy. This morphology was preserved in 15 μm thick coatings; however, micelle segregation to the coating/substrate interface was also observed. The critical strain energy release rate, G_1c, of bulk thermosets was enhanced by up to fivefold with the addition of block copolymers. Likewise, the abrasive wear resistance of thin coatings increased with modifier inclusion. The results showed that at 5 wt.% of loading, block copolymers were able to impart a 40% increase in abrasive wear resistance to modified coatings over neat ones. Block copolymer modifiers did not sacrifice the modulus and glass transition temperature of bulk thermosets and coatings, or the hardness and transparency of coatings.     

Preparation and investigation of flame‐retardant epoxy resin modified with a novel halogen‐free flame retardant containing phosphaphenanthrene,triazine‐trione,and organoboron units

In this article, a novel flame retardant (coded as BNP) was successfully synthesized through the addition reaction between triglycidyl isocyanurate, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and phenylboronic acid. BNP was blended with diglycidyl ether of bisphenol‐A to prepare flame‐retardant epoxy resin (EP). Thermal properties, flame retardancy, and combustion behavior of the cured EP were studied by thermogravimetric analysis, limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The results indicated that the flame retardancy and smoke suppressing properties of EP/BNP thermosets were significantly enhanced. The LOI value of EP/BNP‐3 thermoset was increased to 32.5% and the sample achieved UL94 V‐0 rating. Compared with the neat EP sample, the peak of heat release rate, average of heat release rate, total heat release, and total smoke production of EP/BNP thermosets were decreased by 58.2%–66.9%, 27.1%–37.9%, 25.8%–41.8%, and 21.3%–41.7%, respectively. The char yields of EP/BNP thermosets were increased by 46.8%–88.4%. The BNP decomposed to produce free radicals with quenching effect and enhanced the charring ability of EP matrix. The multifunctional groups of BNP with flame retardant effects in both gaseous and condensed phases were responsible for the excellent flame retardancy of the EP/BNP thermosets. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45291.     

Synthesis of a novel phosphonate flame retardant and its application in epoxy resins

A novel phosphonate flame retardant additive bis(2,6‐dimethyphenyl) phenylphosphonate (BDMPP) was synthesized from phenylphosphonic dichloride and 2,6‐dimethyl phenol, and its chemical structure was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H and ³¹P nuclear magnetic resonance. The prepared BDMPP and curing agent m‐phenylenediamine were blended into epoxy resins (EP) to prepare flame retardant EP thermosets. The effect of BDMPP on fire retardancy and thermal degradation behavior of EP/BDMPP thermosets was investigated by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter and thermalgravimetric analysis (TGA). The morphologies of char residues of the EP thermosets were investigated by scanning electron microscopy (SEM) and the water resistant properties of thermosets were evaluated by putting the samples into distilled water at 70°C for 168 h. The results demonstrated that the cured EP/14 wt % BDMPP composites with the phosphorus content of 1.11 wt % successfully passed UL‐94 V‐0 flammability rating and the LOI value was as high as 33.8%. The TGA results indicated that the introduction of BDMPP promoted EP matrix decomposed ahead of time compared with that of pure EP and led to a higher char yield at high temperature. The incorporation of BDMPP enhanced the mechanical properties and reduced the moisture absorption of EP thermosets. The morphological structures of char residue revealed that BDMPP benefited to the formation of a more compact and homogeneous char layer on the materials surface during burning, which prevented the heat transmission and diffusion, limit the production of combustible gases and then lead to the reduction of the heat release rate. After water resistance tests, EP/BDMPP thermosets still remained excellent flame retardancy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42765.     

Bismaleimide-bisvinylether copolymers: A new class of thermosetting resins

Summary The free radical network copolymerization of bismaleimides with bisvinylethers containing aromatic groups gives rise to a new class of thermally stable imide-containing thermosets. The chief assets of these thermosetting materials are their ability to cure rapidly at low temperatures without the evolution of volatile byproducts.     

Epoxy resin containing poly(ethylene oxide)-block-poly(?-caprolactone) diblock copolymer: Effect of curing agents on nanostructures

An amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(?-caprolactone) (PEO-b-PCL) was synthesized via the ring-opening polymerization of ?-caprolactone in the presence of a hydroxyl-terminated poly(ethylene oxide) monomethyl ether. The diblock copolymer was incorporated into epoxy thermosets. It is found that the formation of nanostructures of thermosetting blends is quite dependent on the uses of aromatic amine hardeners. For 4,4′-methylenebis(2-chloroaniline) (MOCA)-cured thermosetting system, the homogeneous morphology was obtained at the compositions investigated. Nonetheless, the nanostructured thermosets were obtained when the blends were cured with 4,4′-diaminodiphenylsulfone (DDS). The differential scanning calorimetry (DSC) showed that the nanostructured thermosets did not displayed any crystallinity although the subchains of the diblock copolymer are crystalline. The nanostructures were evidenced by means of atomic force microscopy (AFM), small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The dependence of morphological structures on the types of aromatic amines for epoxy and PEO-b-PCL thermosetting blends were interpreted on the basis of the difference in hydrogen bonding interactions resulting from the structure of curing agents. Considering the complete miscibility of the subchains (viz. PEO and PCL) with the precursors of epoxy resin before curing, it is judged that the formation of the nanostructures in the thermosets follows the mechanism of reaction-induced microphase separation, which is in marked contrast to the mechanism of self-assembly, i.e., micelle structures of block copolymers are formed prior to curing, followed by fixing these nanostructures via curing.     

Carboxylated Lignin as an Effective Cohardener for Enhancing Strength and Toughness of Epoxy

It is demonstrated that pristine or functionalized lignin can be used in epoxy as a cohardener or comonomer; however either unsatisfactory mechanical properties or low lignin content remains a challenge in utilizing the sustainable biomass to replace petrochemical product. In this study, carboxylic acid‐modified kraft lignin (lignin–COOH) is synthesized and used as a cohardener for epoxy with loading content of up to 10.0 wt%. With incorporation of 10.0 wt% of lignin–COOH, the resulting composite exhibits increments of 16%, 13%, 20%, and 95% on tensile modulus, flexural modulus, tensile strength, and toughness respectively, in contrast to neat epoxy. The good dispersion of lignin–COOH in epoxy, rigid aromatic structure of lignin, and the reduced crosslink density in the composite can simultaneously contribute to the high mechanical performance, which is verified by the thermal and mechanical analysis results. It suggests that lignin can be converted to effective alternative curing agents for epoxy thermosets.     

Rubber-toughening epoxy thermosets with epoxidized crambe oil

Epoxidized crambe oil and rapeseed oil were synthesized by reaction of the oils with m-chloroperoxybenzoic acid. Formulating the neat epoxidized oils with epoxy-amine systems gave two-phase thermosets with epoxidized crambe oil, but not with epoxidized rapeseed oil. Glass transition temperature, mechanical properties, and fracture toughness of the epoxidized crambe oil thermoset specimen were measured. Fracture toughness values of the epoxy thermosets were increased approximately 100% by both 5 and 10% epoxidized crambe oil. Glass transition temperature and mechanical properties were affected only modestly.     

“In Water” Fabricated and Recycled Covalent Adaptable Acylhydrazone Thermosets

Thermosetting resins play an increasingly important role in daily life due to their good mechanical properties. However, they can hardly be recycled and reused, leading to severe environmental pollution. A very promising solution to this dilemma is to develop sustainable thermosets from biomass that can be recycled and reprocessed on demand under environmentally friendly conditions. In this study, sustainable thermosets based on dynamic acylhydrazone bonds made from biomass acid derivatives is reported. The sustainability of the presented acylhydrazone biomass covalent adaptable networks (CANs) thermosetting resins is summarized as follows: 1) The raw materials are renewable resources; 2) the resins can be recycled to maintain their mechanical properties, which can considerably extend their service life; and 3) the material preparation and recycling can be conducted in the mixed solvent of water/ dimethyl sulfoxide (7/3), which excellent reduced the use of organic solvents. In addition, these acylhydrazone CANs thermosets have excellent mechanical performance and outstanding heat resistance. The acylhydrazone bonds in the thermoset networks can enhance the hydrophobicity and water resistance of the acylhydrazone CANs thermosets. Taken together, these acylhydrazone CANs thermosets which are fabricated and recycled in the mixed solvent provide a solution to developing sustainable materials.     

Carborane‐incorporated poly(silyleneethynylenephenyleneethynylene)s with different side groups

Carborane‐incorporated poly(silyleneethynylenephenyleneethynylene)s with different side groups were synthesized from corresponding poly(silyleneethynylenephenyleneethynylene)s and decaborane (B₁₀H₁₄) in the presence of acetonitrile through in‐situ reaction. The obtained polymers with o‐carborane units were characterized by using Fourier transform infrared and nuclear magnetic resonance spectroscopies, rheological measurements, differential scanning calorimetry, and thermogravimetric analysis. The results show that the properties of these carborane‐incorporated polymers vary with side groups in main chains. They possess good processability and can be crosslinked to form thermosets at temperatures less than 250°C. The thermosets exhibit excellent thermal and thermooxidative stabilities. The weight losses of the thermosets heated to 800°C in air are only 10% approximately. After pyrolysis of the thermosets in nitrogen at 1000°C, the pyrolytic products have no further weight losses up to 1000°C in air. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Formation of new thermosets by the reaction of cyanates with thiophenols

Sulfur‐containing aromatic thermosets, mainly consisting of aryloxy‐ and arylthio‐substituted 1,3,5‐triazines, have been prepared through the reaction of difunctional cyanates with mono‐ and difunctional aromatic thiols. A straightforward three‐step reaction scheme is proposed and verified by the identification of key substances: (1) the addition of thiol and cyanate groups, (2) the stepwise addition of (thio)imino carbonic esters with one another, and (3) the ring closure of chain‐extended (thio)imino carbonic esters to form 1,3,5‐triazines. Reactions of types 2 and 3 are associated with an abstraction of phenol or thiophenol, which can enter into reaction 1 again. Characterization of the curing behavior of dicyanate of bisphenol A with thiophenol as well as dimercaptodiphenyl sulfide by differential scanning calorimetry shows that the reaction rates are significantly enhanced by the admixture of thiols to the cyanate. Dynamic mechanical analysis of resulting thermosets showed that large amounts of comonomers can be incorporated into the network resulting in a decrease of glass temperature but increase of fracture toughness. Finally, the fully cured thermosets resulting from the reaction of dicyanate of bisphenol A with different admixtures of dimercaptodiphenyl sulfide were characterized by cone calorimetry to get information about flame retardancy. The flame retardancy is influenced by incorporation of dimercaptodiphenyl sulfide into the triazine network only slightly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure-property relationships of controlled epoxy networks with quantified levels of excess epoxy etherification

Epoxy thermosets are commonly formulated with an excess of epoxy resin to ensure complete reaction of co-reactive hardeners and to optimize performance. However, the degree to which the reaction of the excess epoxy resin contributes to the thermal and mechanical properties of the thermoset is incompletely understood. In this report, the preparation of controlled epoxy thermosets containing varying amounts of excess epoxy resin having essentially complete excess epoxy conversion is described. The extent of conversion was determined using a solid-state ¹³C NMR method with enhanced resolution due to solvent swelling of the thermosets. This etherification reaction increases the crosslink density of the epoxy thermosets but uniquely affects the thermal and mechanical properties of the materials. Significant property differences observed with respect to analogous thermosets made by varying crosslink density using different extender/hardener ratios are the sensitivity of T_g to the crosslink density and enhanced fracture toughness and tensile yielding with reduced bulk density.