A novel biobased resin‐epoxidized soybean oil modified cyanate ester

Cyanate ester (CE) resin was modified with renewable resource, i.e. epoxidized soybean oil (ESO), and the effects of ESO content on the curing co‐reaction, morphologies, water absorption behaviors, thermal and mechanical properties of CE/ESO blends were studied. Differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA) were employed to characterize the ESO‐modified CE polymer networks. Homogeneous structures were observed for low‐content of ESO modified CE systems by SEM, while ESO‐rich particles were observed in the modified systems with ESO above 15 wt %. The blend of the CE and ESO resulted in an excellent combination as a new biobased thermoset material having relatively high mechanical properties with 15 and 20 wt % ESO as replacement of CE. Enhanced elongations at break were observed for the modified systems while the tensile strengths kept about the same level at the same time. The storage moduli and glass transition temperatures of the modified systems in the glassy state and rubber plateau were observed to be lower than those of neat CE with the increase of ESO weight percent. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Processing and mechanical properties of bio‐derived vinyl ester resin‐based composites

A “green” vinyl ester resin (GVER) is investigated for use in structural applications. The GVER was formulated using a monodisperse vinyl ester created via a novel synthetic route capable of using bio‐waste material from paper and biodiesel industries. The GVER was used either as a neat resin or as blended with a commercial vinyl ester resin. The processing viscosity and gel times are investigated. The GVER reaches a similar viscosity as the commercial resin with only half the styrene monomer content, thereby reducing the volatile organic compounds associated with manufacturing. Composites of the GVER matrix reinforced by carbon fabric were tested for their tensile and flexural properties. The mechanical performance of the GVER compares favorably with commercial resin and provide a route for composites manufacturing from sustainably sourced vinyl ester matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44642.     

Foam sandwich composites with cyanate ester based syntactic foam as core and carbon‐cyanate ester as skin: Processing and properties

Foam sandwich composites were processed using cyanate ester‐based syntactic foam as core and carbon fabric‐cyanate ester composite as skin. They were processed by a one‐step compression‐molding technique. The mechanical performance of the sandwich composites was evaluated in terms of flatwise tensile strength (FTS), flatwise compressive strength, and edgewise compressive strength. The dependency of these properties on the core composition was investigated. FTS initially increased with the increase in resin content of the syntactic foam core. However, higher resin content in the core led to a diminution in FTS due to high void content. The flatwise compressive strength and edgewise compressive strength and the corresponding moduli values showed an increasing trend with increase in resin content of the core despite the presence of voids at high resin content. The failure modes of the composites under different loading conditions have been examined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Blends of bisphenol A‐based cyanate ester and bismaleimide: Cure and thermal characteristics

A dicyanate ester, namely, 2,2‐bis‐(4‐cyanatophenyl)propane, and a bismaleimide, namely, 2,2‐bis[4‐(4‐maleimido phenoxy)phenyl]propane, possessing closely resembling backbone structures, were cured together to derive bismaleimide–triazine network polymers of varying compositions. The blend manifested a eutectic melting behavior at a 1 : 1 composition with a eutectic melting point of 15°C. The cure characterization of the blends was done by DSC and dynamic mechanical analyses (DMA). The near simultaneous cure of the blend could be transformed to a clear sequential one by catalyzing the dicyanate cure to lower temperature using dibutyl tin dilaurate. The two‐stage, independent cure of the components of the blend evidenced in DSC was confirmed by DMA. The cure profile of the bismaleimide component predicted from the kinetic data derived from nonisothermal DSC was found to be in league with the isothermal DMA behavior. Both techniques led to optimization of the cure schedule of the blends. The cured polymers were characterized by FTIR and TGA. The cured blends underwent decomposition in two stages, each corresponding to the polycyanurate and polybismaleimide. Enhancing the bismaleimide component did not alter the initial decomposition temperature, but led to reduced rate of thermal degradation at higher temperature. Interlinking of the two networks and enhancing crosslink density through coreaction of the blend with 4‐cyantophenylmaleimide unaffected the initial decomposition properties but was conducive for increasing the char residue significantly. Computation of activation parameters for the thermal decomposition of the polymers confirmed that the first step in the degradation of the blends is caused by the polycyanurate component. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3365–3375, 1999     

Preparation and properties of nano diamond/6F‐bisphenol A‐based cyanate ester composites

The aim of this study was to improve thermal conductivity, thermal stability, and mechanical properties of bisphenol A dicyanate ester (BADCy) by adding bisphenol A dicyanate ester containing fluorine (F‐BADCy) and nano diamond. The cyanate esters containing fluorine/nano diamond composites having various ratios of BADCy, F‐BADCy, and nano diamond were prepared. Thermal stability and thermal conductivity of the samples were evaluated by thermogravimetric analysis, differential scanning calorimetry and laser flash method, respectively. The samples were characterized with the following analysis; gel content, water absorption capacity, and stress‐strain test. Hydrophobicity of the samples was determined by the contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy (SEM). The obtained results prove that the cyanate ester containing fluorine/nano diamond composites have good thermal and mechanical properties and they can be used in many applications such as electronic devices, materials engineering, and other emergent. POLYM. COMPOS., 34:1977–1985, 2013. © 2013 Society of Plastics Engineers     

Novel high‐performance wave‐transparent aluminum phosphate/cyanate ester composites

Advanced wave‐transparent composites are the key materials for many cutting‐edge industries including aviation and aerospace, which should have outstanding heat resistance, low dielectric constant and loss as well as good mechanical properties. A novel kind of high‐performance wave‐transparent composites based on surface‐modified aluminum phosphate AlPO₄(KH‐550) and cyanate ester (CE) was first developed. The dielectric and dynamic mechanical properties of AlPO₄(KH‐550)/CE composites were investigated intensively. Results show that AlPO₄(KH‐550)/CE composites have decreased dielectric loss and higher storage moduli than pure CE resin; in addition, the composites with suitable AlPO₄(KH‐550) concentration remain the outstanding thermal property and low dielectric constant of pure CE resin. The reasons attributing to these results are discussed from the effects of AlPO₄(KH‐550) on the key aspects such as morphology, curing mechanism, and interfacial adhesion of composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Epoxy‐modified cyanate ester resin and its high‐modulus carbon‐fiber composites

Epoxy E51‐modified bisphenol A dicyanate (BADCy) and its high‐modulus carbon fiber (M40) reinforced composites were prepared in this research. The carbon‐fiber composites were prepared by autoclave molding. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy of BADCy‐E51 blend systems showed that polycyclotrimerization of BADCy primarily took place at low temperature. Epoxy group reacted with triazine ring group and produced oxazolidinone at high temperature. The data of mechanical properties, water absorption, and heat deflection temperature (HDT) of cured castings showed that the matrix system containing 95 wt% BADCy and 5 wt% E51 had optimum characteristics. Scanning electron microscopy (SEM) analysis of M40 fiber and the fracture surfaces of M40/BADCy‐E51 composite displayed that the adhesion between M40 fiber and BADCy was good though the surface of M40 was inert. The high retention of mechanical properties of M40/BADCy‐E51 composite after long‐term exposure to environmental conditions indicated that the M40/BADCy composite was suitable for space applications. POLYM. COMPOS., 27:402–409, 2006. © 2006 Society of Plastics Engineers     

Examining the thermal degradation behaviour of a series of cyanate ester homopolymers

A series of thermally stable dicyanate monomers was prepared containing different thermally stable structural units, namely 2,2′‐bis(4‐cyanatophenyl)propane, bis‐4‐cyanato‐biphenyl, bis‐4‐cyanato naphthalene, 3,3′‐bis(4‐cyanatophenyl)sulfide and 3,3′‐bis(4‐cyanatophenyl)sulfone, was prepared and the identity of the products was confirmed by Fourier transform infrared and NMR spectral methods. The corresponding cyanate homopolymers were prepared and their properties were evaluated and compared. The composites were analysed for their thermal stability and thermal degradation kinetics. The series of homopolymers exhibit excellent thermal characteristics, e.g. relatively high glass transition temperatures of at least 215 °C, which were inversely proportional to the molecular weight between the crosslinks, high thermal decomposition temperature and high activation energies for the decomposition of cured resins. Determination of their limiting oxygen indices indicates that all the homopolymers are characterized as ‘self‐extinguishing’ materials. © 2019 Society of Chemical Industry     

Biobased cyanate ester composites with epoxidized soybean oil and in situ generated nano‐silica

Biobased cyanate ester (CE) nanocomposites have been prepared from renewable resource, epoxidized soybean oil (ESO) and in situ generated nano‐silica via sol–gel process. The isothermal curing process was investigated by differential scanning calorimetry (DSC) and rheometry. The results indicate that the incorporation of silica accelerates the reaction at the beginning stage of curing process but descends the final isothermal curing conversion. The morphological study of nanocomposites by scanning electron microscope and transmission electron microscope suggests that the silica exists in the forms of both nanoparticles and silica networks, while the diameter of ESO‐rich phase diminished with the increase of silica loading. In addition, the thermal–physical and mechanical properties were evaluated by dynamic mechanical analysis, thermogravimetric analysis, and tensile mechanical test. The biobased CE nanocomposites show effectively improved properties compared to the systems without nano‐silica. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Preparation and characterization of POSS‐SiO2/cyanate ester composites with high performance

In this article, a hybrid filler based on polyhedral oligomeric silsesquioxane and silica, coded as POSS‐SiO₂, has been successfully synthesized. The structure of POSS‐SiO₂ was studied by Fourier‐transform infrared spectra, X‐ray diffraction, and scanning electron microscopy. Then the POSS‐SiO₂ was compounded with dicyclopentadiene bisphenol dicyanate ester (DCPDCE) resin to prepare composites. The effects of POSS‐SiO₂ on the curing reaction, mechanical, thermal, dielectric and tribological properties of DCPDCE resin were investigated systematically. Results of differential scanning calorimetry show that the addition of POSS‐SiO₂ can facilitate the curing reaction of DCPDCE and decrease the curing temperature of DCPDCE. Compared with pure DCPDCE resin, the impact and flexural strengths of the composites materials are improved markedly with up to 72 and 52% increasing magnitude, respectively. Meanwhile, the POSS‐SiO₂/DCPDCE systems exhibit lower dielectric constant and loss than pure DCPDCE resin over the testing frequency from 10 to 60 MHz. In addition, the thermal stability and tribological properties of POSS‐SiO₂/DCPDCE composites are also superior to that of pure DCPDCE resin. POLYM. COMPOS., 36:1840–1848, 2015. © 2014 Society of Plastics Engineers     

Modification of cyanate ester resin by hydroxyl‐terminated liquid butadiene‐acrylonitrile rubber and free volume properties of their composites

The toughness of cyanate ester resin (CE) matrix is improved significantly with addition of hydroxyl‐terminated liquid butadiene‐acrylonitrile rubber (HTBN). The impact strength increased from 4.4 KJ/m² (pure CE) to 13.3 KJ/m² (CE/HTBN, HTBN 10 wt %). The curing behavior of the system is studied by differential scanning calorimetric and Fourier transform infrared spectroscope. The results showed that hydroxyl groups on the HTBN chains have slight activation effect to CE curing reaction at the beginning of the cure process. The toughening mechanism is mainly caused by the flexibilizing effects of the homogeneously dispersed HTBN molecules in the CE matrix. The toughening mechanism was demonstrated from the aspect of free volume using positron annihilation lifetime spectroscopy. With addition of HTBN, the mean free‐volume size of the composite is smaller than pure CE. The decrease in the mean free‐volume size of the system is mainly related to the partition effects of the finely dispersed HTBN molecules to the free‐volume holes of CE matrix. A dramatic increase in the interfacial area occurs in this highly miscible system. Good interfacial adhesion is also reflected from the higher I₂ of the composite. Therefore, more positrons annihilation in their free state occurs in the composites containing HTBN than pure CE. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization

The aim of this study was to improve hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization for high performance applications such as aerospace and electronic devices. A novel 2,2′-diallylbisphenol A dicyanate ester (DA-BADCy) which is the allyl group containing cyanate ester was synthesized and characterized. DA-BADCy, silicon containing monofunctional thiol compound, trifunctional thiol compound and boron phosphate were cured using both ultraviolet (UV) and thermal methods. Using thiol-ene system, cyanate ester formulations, which are normally prepared at high temperatures, were prepared at room temperature. This study maintains ease of application for cyanate esters. Thermal stability, flammability and thermal conductivity of the samples were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI) and laser flash method, respectively. The samples were characterized with the following analysis; gel content, water absorption capacity and stress–strain test. Hydrophobicity of the samples was determined by the contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy (SEM–EDS). The obtained results prove that the composites have good thermal and mechanical properties and with the help of easier preparation techniques, they can be used in many applications such as aerospace, electronic devices, materials engineering.     

Experimental characterization of traditional composites manufactured by vacuum‐assisted resin‐transfer molding

The primary purpose of this study is to investigate the anisotropic behavior of different glass‐fabric‐reinforced polyester composites. Two commonly used types of traditional glass fabrics, woven roving fabric and chopped strand mat, have been used. Composite laminates have been manufactured by the vacuum infusion of polyester resin into the fabrics. The effects of geometric variables on the composite structural integrity and strength are illustrated. Hence, tensile and three‐point‐bending flexural tests have been conducted at different off‐axial angles (0, 45, and 90°) with respect to the longitudinal direction. In this study, an important practical problem with fibrous composites, the interlaminar shear strength as measured in short‐beam shear tests, is discussed. The most significant result deduced from this investigation is the strong correlation between the changes in the interlaminar shear strength values and fiber orientation angle in the case of woven fabric laminates. Extensive photographs of fractured tensile specimens resulting from a variety of uniaxial loading conditions are presented. Another aim of this work is to investigate the interaction between the glass fiber and polyester matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, are interpreted in an attempt to explain the interaction between the glass fiber and polyester. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Toughening of cyanate ester resin by N‐phenylmaleimide–styrene copolymers

The N‐phenylmaleimide–styrene copolymer (PMS) was prepared and used to improve the brittleness of the cyanate ester resin. PMS was an effective modifier for improving the brittleness of the resin. The morphologies of the modified resins depended on PMS molecular weight and content. The most effective modification of the cyanate ester resin was attained because of the cocontinuous phase structure of the modified resin. Inclusion of 10 wt % PMS (M_w 133,000) led to an 160% increase in the fracture toughness (K_IC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and the glass transition temperature, compared to the values for the unmodified resin. Low water absorptivity of the parent‐cured resin was not deteriorated by modification. The toughening mechanism was discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified cyanate ester resin system. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2931–2939, 1999     

Thermo‐physical,thermal degradation,and flexural properties of betel nut husk fiber reinforced vinyl ester composites

This study aims to investigate the thermo‐physical, mechanical, and thermal degradation properties of betel nut husk (BNH) fiber reinforced vinyl ester (VE) composites. These properties were evaluated as a function of fiber maturity, fiber content, and fiber orientation. Thermo‐physical properties were analyzed experimentally using a hot disk TPS method. The introduction of BNH was found to reduce the thermal conductivity of neat VE. The thermal conductivity and thermal diffusivity of BNH reinforced VE composites decreased with the increase in fiber content. Short fiber BNH reinforced VE composites showed the lowest thermal conductivity as compared to the unidirectional and random nonwoven composites. The TGA analysis shows lower resin transition peak for the BNH reinforced VE composites than the peak of neat VE. Fiber maturity had a notable effect on the flexural modulus of the BNH fiber reinforced VE composites. Incorporation of 10 wt% BNH fibers into the composite has increased the composites' flexural modulus by 46.37%. However, further increases in the fiber content reduced both flexural strength and modulus of the composites. POLYM. COMPOS., 37:2008–2017, 2016. © 2015 Society of Plastics Engineers     

Flammability and thermal degradation of intumescent flame‐retardant polypropylene composites

The flammability of polypropylene (PP) composites containing intumescent flame‐retardant additives, i.e., melamine pyrophosphate (MPP) and 1‐oxo‐4‐hydroxymethyl‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane (PEPA) was characterized by limiting oxygen index (LOI), UL 94 test, and cone calorimeter. In addition, the thermal degradation of the composites was studied using thermogravimetric analysis (TG) and real‐time Fourier transform infrared (RTFTIR). It has been found that the PP composite only containing MPP (or PEPA) does not show good flame retardancy even at 30% additive level. Compared with the PP/MPP binary composite, the LOI values of the PP/MPP/PEPA ternary composites at the same additive loading are all increased, and UL 94 rating of the ternary composite (PP3) studied is raised to V‐0 rating from no rating (PP/MPP). The cone calorimeter results show that the heat release rate of some ternary composites decreases in comparison with the binary composite. It is noted from the TG data that initial decomposition temperatures of ternary composites are lower than that of the binary composites. The RTFTIR study indicates that the PP/MPP/PEPA composites have higher thermal oxidative stability than the pure PP. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Morphological,mechanical and thermal properties of cyanate ester/benzoxazine resin composites reinforced by silane treated natural hemp fibers

This present study deals with the reinforcement of thermosetting resin blends composed of cyanate ester (CE) and benzoxazine (BOZ) resins with natural hemp fibers (NHFs). These NHFs were initially treated by using a silane coupling agent (SCA) in order to chiefly enhance their distributions as well as adhesions within the CE/BOZ resin matrix, then incorporated with various weight amounts ranging from 5 wt% to 20 wt% with a regular interval of 5 wt%. The obtained results showed that at the maximum treated fiber loading (20 wt%), distinctive enhancements in the mechanical properties in terms of flexural strength and microhardness were obtained. Besides, the thermal stability and glass transition temperature (T_g) were appreciably enhanced and were higher than those of the pure CE/BOZ resin properties. With respect to the astonishing properties of the NHFs, these enhancements could be possibly due to the good dispersion and adhesion of the treated NHFs inside the CE/BOZ resin achieved upon using the SCA. Therefore, we believe herein that these renewable and cheap NHFs have considerable potential to be used as reinfocer materials for CE/BOZ resin composites to be used in various industrial sectors.     

Thermal degradation study of interpenetrating polymer network based on modified bismaleimide resin and cyanate ester

Interpenetrating polymer networks (IPNs) based on different ratios of a modified bismaleimide resin (BMI/DBA) and cyanate ester (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic thermal degradation study of these new BMI/DBA‐CE IPN resin systems was conducted by thermogravimetric analysis at different heating rates both in N₂ (thermal stability) and in air (thermal‐oxidative stability). The cured BMI/DBA‐CE IPN resin systems show excellent thermal stability, which could be demonstrated by 5% weight loss temperature (T_5%) ranging between 409 and 423 °C, maximum decomposition rate temperature (T_max) ranging between 423 and 451 °C, and the char yields at 800 °C ranging from 37% to 41% in nitrogen at a heating rate of 10 °C min^?1. The apparent activation energy associated with the main degradation stage of the cured BMI/DBA‐CE IPN resin systems was determined using the Kissinger method. The obtained results provide useful information in drawing correlation between thermal properties and structure. © 2003 Society of Chemical Industry     

Structure and properties of multiwalled carbon nanotubes/cyanate ester composites

Two types of multiwalled carbon nanotubes (MW‐CNTs) with different structure and morphology were used to fabricate cyanate ester (CE) matrix composites. Mechanical, thermal, and transmission electron microscopy tests were performed to evaluate the different effects of the two types of MW‐CNTs on the structure and properties of MW‐CNT/CE composites. Results showed that the bundled MW‐CNTs were easier to be dispersed in CE matrix than single MW‐CNTs, and could improve the toughness and stiffness of CE material more significantly. Functionalization of the two types of MW‐CNTs, which was achieved by grafting triethylenetetramine groups onto the surface of MW‐CNTs, was helpful in improving the dispersion of the MW‐CNTs in CE, and thus in fabricating MW‐CNT/CE composites with improved mechanical and thermal properties. POLYM. ENG. SCI. 46:670–679, 2006. © 2006 Society of Plastics Engineers