Shape‐memory property and characterization of epoxy resin‐modified Mesua ferrea L. seed oil‐based hyperbranched polyurethane

Modification of existing polymers leads to enhancement of many desirable properties. So, a hyperbranched polyurethane (HBPU) of monoglyceride of Mesua ferrea L. seed oil, poly(ε‐caprolactone)diol (M_n = 3000 g mol^?1), 2,4‐toluene diisocyanate, and glycerol with 30% hard segment (NCO/OH = 0.96) has been modified with different amounts of bisphenol‐A based epoxy resin. The system is cured by poly(amido amine) hardener at 120°C for specified period of time. Improvement of thermostability, scratch hardness, and impact strength are observed by this modification of HBPU. The differential scanning calorimetry (DSC) results show improvement of melting temperature of the modified systems. The enhancement of tensile strength is about 2.4 times compared with that of the unmodified one. The morphology and structural changes due to variation of epoxy content was studied by scanning electron microscopy (SEM) analysis and Fourier transform infrared (FTIR) spectroscopy. The rheological properties of the epoxy‐modified HBPU show the dependence on the amount of epoxy resin. Shape memory study of the crosslinked HBPUs shows 90–98% thermoresponsive shape recovery. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comprehensive high‐performance epoxy nanocomposites co‐reinforced by organo‐montmorillonite and nano‐SiO2

Comprehensive high‐performance epoxy nanocomposites were successfully prepared by co‐incorporating organo‐montmorillonite (o‐MMT) and nano‐SiO₂ into epoxy matrix. Because of the strong interaction between nanoscale particles, the MMT layers were highly exfoliated, and the exfoliated nanoscale MMT monoplatelets took an interlacing arrangement with the nano‐SiO₂ particles in the epoxy matrix, as evidenced by X‐ray diffraction measurement and transmission electron microscopy inspection. Mechanical tests and thermal analyses showed that the resulting epoxy/o‐MMT/nano‐SiO₂ nanocomposites improved substantially over pure epoxy and epoxy/o‐MMT nanocomposites in tensile modulus, tensile strength, flexural modulus, flexural strength, notch impact strength, glass transition temperature, and thermal decomposition temperature. This study suggests that co‐incorporating two properly selected nanoscale particles into polymer is one pathway to success in preparing comprehensive high‐performance polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of epoxy resin–silica nanocomposites provided from perhydropolysilazane as a curing reagent and the precursor of silica domain

Epoxy resin–silica nanocomposites with spherical silica domains with 29.0 nm in diameter in an epoxy resin matrix were synthesized from Bisphenol‐A type epoxide monomer, 2,2‐bis(4‐glycidyloxyphenyl)propane (DGEBA), and perhydropolysilazane (PHPS, ? [Si₂? NH]_n? ). The volume fraction of silica domain in the composite varied from 5.4 to 37.8 vol % by varying the feed ratio of PHPS to the epoxide monomer. The reaction mechanism of epoxy group and PHPS was investigated by using glycidyl methacrylate as a model compound of the epoxy monomer by ¹H‐nucular magnetic resonance and Fourier transform infrared spectrometry. Ammonia gas provided by the decomposition of PHPS with moisture converted PHPS to silica and cured the epoxy monomer. The curing of epoxy monomer preferably proceeded than the conversion of silica. The addition of 1,4‐diaminobutane drastically accelerated the rate of curing; white and hard epoxy resin–silica nanocomposites were obtained. The good thermal stability of the composite prepared with DGEBA/PHPS/1,4‐diaminobutane was observed by thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Organic–inorganic hybrid materials. II. Preparation and properties of higher silica containing polycarbonate–silica hybrid materials

The sol–gel reaction of a polycarbonate (PC) oligomer having triethoxysilyl groups at both ends of the PC chain (PCS) with a tetraethoxysilane or tetramethoxysilane oligomer provided transparent or semitransparent films of higher silica containing organic–inorganic hybrid materials (HSPC‐HMs). The films were superior to those from PC and from PCS in terms of the morphological homogeneity, heat resistance, and surface hardness. The HSPC‐HM films had minimum oxygen permeability at a PCS/tetraethoxysilane ratio of 3/7. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4273–4279, 2006     

Synthesis and characterization of polyimide–silica nanocomposites using novel fluorine‐modified silica nanoparticles

Polyimide–silica nanocomposites were synthesized with 4,4′‐oxydianiline, 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride), and fluorine‐modified silica nanoparticles. Fluorinated precursors such as 4″,4?‐(hexafluoroisopropylidene)bis(4‐phenoxyaniline) (6FBPA) and 4,4′‐(hexafluoroisopropylindene)diphenol (BISAF) were employed to modify the surface of the silica nanoparticles. The microstructures and thermal, mechanical, and dielectric properties of the polyimide–silica nanocomposites were investigated. An improvement in the thermal stability and storage modulus of the polyimide nanocomposites due to the addition of the modified silica nanoparticles was observed. The microstructures of the polyimide–silica nanocomposites containing 6FBPA‐modified silica exhibited more uniformity than those of the nanocomposites containing BISAF‐modified silica. The dielectric constants of the polyimide were considerably reduced by the incorporation of pristine silica or 6FBPA‐modified silica but not BISAF‐modified silica. The addition of a modifier with higher fluorine contents did not ensure a lower dielectric constant. The uniformity of the silica distribution, manipulated by the reactivity of the modifier, played an important role in the reduction of the dielectric constant. Using 6FBPA‐modified silica nanoparticles demonstrated an effective way of synthesizing low‐dielectric‐constant polyimide–silica nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 882–890, 2007     

Synthesis and evaluation of liquid amine‐terminated polybutadiene rubber and its role in epoxy toughening

Epoxy resin is widely used for coatings, adhesives, castings, electrical insulation materials, and other applications. However, unsolved problems still remain in its applications. The main problem is low toughness: cured epoxy resin is rather brittle, with poor resistance to the propagation of cracks derived from the internal stress generated by shrinkage in the cooling process from cure temperature to room temperature. The objective of this study was to improve the flexibility and toughness of diglycidyl ether of bisphenol A based epoxy resin with a liquid rubber. For this purpose, amine‐terminated polybutadiene (ATPB) was synthesized. The product was characterized by Fourier transform infrared and NMR spectroscopy and elemental analysis. ATPB‐modified epoxy networks were made by curing with an ambient‐temperature curing agent, triethylene tetramine. We varied the epoxy/liquid rubber compositions to study the effect of toughener concentration on the impact and thermal properties. Higher mechanical properties were obtained for epoxy resins toughened with 1 phr ATPB. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2446–2453, 2005     

Study on the modification of epoxy resin by a phosphorus‐ and silica‐containing hybrid

A novel phosphorus‐ and silica‐containing hybrid (DPS) was synthesized by the reaction between diethyl phosphate (DEP) and polyhedral oligomeric siloxanes (POS) formed by hydrolysis condensation of 3‐glycidoxypropyltrimethoxysilane (GPTMS). The novel phosphorus‐ and silica‐containing hybrid was characterized by the flourier transform infrared spectroscope (FT‐IR), silicon nuclear magnetic resonance, and gel permeation chromatography (GPC). Then, the determination of the activation of the reaction between epoxy resin and phosphorus‐, and silica‐containing hybrids was studied by differential scanning calorimeter (DSC). In the presence of catalyst, the activation energies of the curing reaction were 63.3 and 66.7 kJ/mol calculated by Kissinger model and Ozawa model respectively. The thermal and flame retardant properties of the cured epoxy modified by DPS were determined by differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA), and limited oxygen index (LOI). The results revealed that those properties were improved in comparison with unmodified epoxy resin. In addition, scanning electron microscopy (SEM) was used to investigate the morphology of the cured epoxy resin modified by DPS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of polychloroprene–silica composites by sol‐gel method in the presence of modified polychloroprene containing triethoxysilyl group

Triethoxysilyl‐modified polychloroprene (CR) latex was synthesized by the emulsion copolymerization of 2‐(3‐triethoxysilylpropyl)‐1,3‐butadiene with chloroprene. This latex was mixed with unmodified CR latex and tetraethoxysilane to obtain CR–silica composites by sol‐gel reaction in the latex. SEM observation showed that the silica particles in unvulcanized composites have various diameters ranging from 0.1 to 0.6 μ m, and their size became larger with the decrease of the silica content. Vulcanized CR–silica composites showed that the tensile modulus and tear strength improved with an increase of the amount of modified CR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1545–1552, 2005     

Synthesis,properties and pyrolysis of siloxane‐ and imide‐modified epoxy resin cured with siloxane‐containing dianhydride

Hydrosilylation of nadic anhydride with tetramethyl disiloxane yielded 5,5′‐(1,1,3,3‐tetramethyl disiloxane‐1,3‐diyl)‐bis‐norborane‐2,3‐dicarboxylic anhydride (I), which further reacted with 4‐aminophenol to give N,N′‐bis(4‐hydroxyphenyl)‐5,5′‐bis‐(1,1,3,3‐tetramethyl disiloxane‐1,3‐diyl)‐bis‐norborane‐2,3‐dicarboximide (II). Epoxidation of II with excess epichlorohydrin formed a siloxane‐ and imide‐modified epoxy oligomer (ie diglycidyl ether of N,N′‐bis(4‐hydroxyphenyl)‐5,5′‐bis(1,1,3,3‐tetramethyl disiloxane‐1,3‐diyl)‐bis‐norborane‐2,3‐dicarboximide) (III). Equivalent ratios of III/I of 1/1 and 1/0.8 were prepared and cured to produce crosslinked materials. Thermal mechanical and dynamic mechanical properties were investigated by TMA and DMA, respectively. It was noted that each of these two materials showed a glass transition temperature (T_g) higher than 160 °C with moderate moduli. The thermal degradation kinetics was studied with dynamic thermogravimetric analysis (TGA) and the estimated apparent activation energies were 111.4 kJ mol^?1 (in N₂), 117.1 kJ mol^?1 (in air) for III/I = 1/0.8, and 149.2 kJ mol^?1 (in N₂), 147.6 kJ mol^?1 (in air) for III/I = 1/1. The white flaky residue of the TGA char was confirmed to be silicon dioxide, which formed a barrier at the surface of the polymer matrix and, in part, accounted for the unique heat resistance of this material. Copyright © 2005 Society of Chemical Industry     

Polyurethane‐modified epoxy resin: Solventless preparation and properties

A polyurethane‐modified epoxy resin system with potential as an underfill material in electronic packaging and its preparation procedure were studied. The procedure enabled the practical incorporation of an aliphatic polyurethane precursor, synthesized from poly(ethylene glycol) and hexamethylene diisocyanate without a solvent, as a precrosslinking agent into a conventional epoxy resin. With a stoichiometric quantity of the polyurethane precursor added to the epoxy (ca. 5 phr), the polyurethane‐modified epoxy resin, mixed with methylene dianiline, exhibited a 36% reduction in the contact angle with the epoxy–amine surface, a 31% reduction in the cure onset temperature versus the control epoxy system, and a viscosity within the processable range. The resultant amine‐cured thermosets, meanwhile, exhibited enhanced thermal stability, flexural strength, storage modulus, and adhesion strength at the expense of a 5% increase in the coefficient of thermal expansion. Exceeding the stoichiometric quantity of the polyurethane precursor, however, reduced the thermal stability and modulus but further increased the coefficient of thermal expansion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of UV‐cured hybrid coatings by triethoxysilane‐modified dimethacrylate based on bisphenol‐s epoxy

Novel hybrid oligomers based on a UV‐curable bisphenol‐S epoxy dimethacrylate (DBSMA) were synthetized. DBSMA was modified with various amount of (3‐isocyanatopropyl)triethoxysilane coupling agent. The modification degree of the hybrid oligomer was varied from 0 to70 wt %. The photopolymerization kinetics was monitored by a real‐time infrared spectroscopy. The conversion and rate of hybrid coatings increased with the increase in modification degree. UV‐curable, hard, and transparent organic–inorganic hybrid coatings were prepared. They were performed by the analyses of various properties such as surface and mechanical properties. Results from the mechanical measurements showed that the properties of hybrid coatings improved with the increase in modification degree. The thermal behavior of coatings was also investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of epoxy film cured with phosphorous‐containing phenolic resin

Through the electrophilic addition reaction of ? P(O)? H and C?C, a series of novel phosphorus‐containing phenolic resins bearing maleimide (P‐PMFs) were synthesized and used as curing agent for preparing high performance and flame retardancy epoxy resins. The structure of the resin was confirmed with FTIR and elemental analysis. Thermal properties and thermal degradation behaviors of the thermosetted resin was investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The epoxy resins exhibited high glass transition temperature (143–156°C), goof thermal stability (>330°C) and retardation on thermal degradation rates. High char yields (700°C, 52.9%) and high limited oxygen indices (30.6–34.8) were observed, indicating the resins' good flame retardance for the P‐PMFs/CNE cured resins. The developed resin may be used potentially as environmentally preferable products in electronic fields. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3813–3817, 2007     

Electrostatic deposition of silica nanoparticles between E‐glass fibers and an epoxy resin

The achievement of optimum adhesion between a thermoset and an inorganic material is an important goal for the composites and coatings industries. There is a growing interest in the use of structural surface modifiers, such as nanotubes, nanoparticles, and whiskers, to improve this adhesion. Here, a method for electrostatically depositing poly(ethylene imine)‐functionalized silica nanoparticles onto E‐glass fibers was developed. The deposition of 26‐nm functionalized particles onto glycidyloxypropyltrimethoxysilane (GPS)‐functionalized E‐glass fibers and then their embedding in a resin of diglycidyl ether of bisphenol A and m‐phenylene diamine increased the interfacial shear strength (IFSS) 35% over that of bare fibers and 8% over that of GPS‐functionalized fibers. IFSS was highly dependent on the particle size; the 16‐nm functionalized particles had little effect on the IFSS. When the particles size was increased to 71 and 100 nm, this led to increasingly poor IFSS values, whereas the 26‐nm particles produced the best results. Similar results were seen with the transverse flexural strength of the unidirectional composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41516.     

Thermal and mechanical properties of tetra‐functional mesogenic type epoxy resin cured with aromatic amine

A novel tetra‐functional epoxy monomer with mesogenic groups was synthesized and characterized by ¹H‐NMR and FTIR. The synthesized epoxy monomer was cured with aromatic amine to improve the thermal property of epoxy/amine cured system. The glass transition temperature (T_g) and coefficient of thermal expansion (CTE) of the cured system were investigated by dynamic mechanical analysis and thermal mechanical analysis. The properties of the cured system were compared with the conventional bisphenol‐A type epoxy and mesogenic type epoxy system. The storage modulus of the tetra‐functional mesogenic epoxy cured systems showed the value of 0.96 GPa at 250 °C, and T_g‐less behavior was clearly observed. The cured system also showed a low CTE at temperatures above 150 °C without incorporation of inorganic components. These phenomena were achieved by suppression of the thermal motion of network chains by introduction of both mesogenic groups and branched structure to increase the cross linking density. The temperature dependency of the tensile property and thermal conductivity of the cured system was also investigated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46181.     

Study of high thermal conductive epoxy resins containing controlled high‐order structures

Heat is transported by phonons through dielectric solids such as ceramics and organic insulating resins. Especially in organic insulating resins, phonons scatter intensely mainly by their amorphous structure, which affects their thermal conductivities, usually 1 to 3 orders lower than those of ceramics and metals. Here, we show that by the thermosetting resin system with a crystal‐like structure that is microscopic anisotropy, the thermal conductivities of the resin themselves can be improved while keeping their macroscopic isotropy. We studied four kinds of diepoxy monomers with a biphenyl group or two phenyl benzoate groups as mesogens, and cured them thermally with an aromatic diamine curing agent. These thermal conductivities were maximally 5 times higher than that of conventional epoxy resins because mesogens were highly ordered to form crystal‐like structures to suppress phonon scattering. We also succeeded in the direct confirmation of the existence of crystal‐like structures in the epoxy resins by TEM observation. These results suggest a novel strategy to improve thermal conductivities of insulating resins themselves by controlling the high‐order structures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2464–2467, 2003     

Structure‐property relationship of substituted pyrrolidine functionalized CNT epoxy nanocomposite

Carbon nanotubes (CNTs) based polymer nanocomposites hold the promise of delivering exceptional mechanical properties and multifunctional characteristics. However, the realization of exceptional properties of CNT based nanocomposites is dependent on CNT dispersion and CNT‐matrix adhesion. To this end, we modified MWCNTs by Prato reaction to yield aromatic (phenyl and 2‐hydroxy‐4‐methoxyphenyl) substituted pyrrolidine functionalized CNTs (fCNT1 and fCNT2) and aliphatic (2‐ethylbutyl and n‐octyl) substituted pyrrolidine functionalized CNTs (fCNT3 and fCNT4). The functionalization of CNTs was established by Thermogravimetric analysis (TGA), Raman Spectroscopy, and XPS techniques. Optical micrographs of fCNT epoxy mixture showed smaller aggregates compared to pristine CNT epoxy mixture. A comparison of the tensile results and onset decomposition temperature of fCNT/epoxy nanocomposite showed that aliphatic substituted pyrrolidine fCNT epoxy nanocomposites have higher onset decomposition temperature and higher tensile toughness than aromatic substituted pyrrolidine fCNT epoxy nanocomposites, which is consistent with the dispersion results of fCNTs in the epoxy matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42284.     

Preparation and evaluation of nano‐epoxy composite resins containing electrospun glass nanofibers

In this study, electrospun glass (structurally amorphous SiO₂) nanofibers (EGNFs) with diameters of ～ 400 nm were incorporated into epoxy resin for reinforcement and/or toughening purposes; the effects of silanization treatment (including different functional groups in silane molecules) and mass fraction of EGNFs on strength, stiffness, and toughness of the resulting nano‐epoxy composite resins were investigated. The experimental results revealed that EGNFs substantially outperformed conventional glass fibers (CGFs, with diameters of ～ 10 μm) in both tension and impact tests, and led to the same trend of improvements in strength, stiffness, and toughness at small mass fractions of 0.5 and 1%. The tensile strength, Young's modulus, work of fracture, and impact strength of the nano‐epoxy composite resins with EGNFs were improved by up to 40, 201, 67, and 363%, respectively. In general, the silanized EGNFs with epoxy end groups (G‐EGNFs) showed a higher degree of toughening effect, while the silanized EGNFs with amine end groups (A‐EGNFs) showed a higher degree of reinforcement effect. The study suggested that electrospun glass nanofibers could be used as reinforcement and/or toughening agent for making innovative nano‐epoxy composite resins, which would be further used for the development of high‐performance polymer composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and performance of a novel nitrogen‐containing cyclic phosphate for intumescent flame retardant and its application in epoxy resin

A novel nitrogen‐containing cyclic phosphate (NDP) was synthesized and well characterized by ¹H, ¹³C, ³¹P NMR, mass spectra and elemental analysis. NDP was used as an additive intumescent flame retardant (AIFR) to impart flame retardancy and dripping resistance for diglycidyl ether of bisphenol‐A epoxy resin (DGEBA) curied by 4,4′‐diaminodiphenylsulfone (DDS) with different phosphorus content. The flammability, thermal stability, and mechanical properties of NDP modified DGEBA/DDS thermosets were investigated by UL‐94 vertical burning test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Izod impact strength and flexural property tests. The results showed that NDP modified DGEBA/DDS thermosets exhibited excellent flame retardancy, moderate changes in glass transition temperature and thermal stability. When the phosphorus content reached only 1.5 wt %, the NDP modified DGEBA/DDS thermoset could result in satisfied flame retardancy (UL‐94, V‐0). The TGA curves under nitrogen and air atmosphere suggested that NDP had good ability of char formation, and there existed a distinct synergistic effect between phosphorus and nitrogen. The flame retardant mechanism was further realized by studying the structure and morphology of char residues using FT‐IR and scanning electron microscopy (SEM). It indicated that NDP as phosphorus‐nitrogen containing flame retardant worked by both of the condensed phase action and the vapor phase action. Additionally, the addition of NDP decreased slightly the flexural strength of the flame retarded DGEBA epoxy resins, and increased the Izod impact strength of these thermosets. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41859.     

Temperature effects on rigid nano‐silica and soft nano‐rubber toughening in epoxy under impact loading

The rigid nano‐silica and soft nano‐rubber toughening effects on neat epoxy under impact loading in a range of ?50 to 80 °C were investigated. Nanosilica particles (20 nm) toughened neat epoxy at all temperatures with a maximum toughening efficiency at ?50 °C and lower efficiency at elevated temperatures. In contrast, except at ?50 °C, nano‐rubber particles (100 nm) showed the deterioration effect on the impact fracture toughness of epoxy resin. Scanning electron microscopy examinations revealed that the crack pinning and local epoxy deformation induced by rigid particles in term of nano‐silica/epoxy and nano‐rubber/epoxy interfacial debonding (at ?50 °C) led to positive toughening efficiency on neat epoxy. However, at 20 and 80 °C, the rubber cavitations/void plastic growth was significantly suppressed under the impact loading, which led to the negative toughening efficiency on epoxy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45319.     

Preparation and properties of polyimide/silica hybrid composites based on polymer‐modified colloidal silica

A new type of polyimide/silica (PI/SiO₂) hybrid composite films was prepared by blending polymer‐modified colloidal silica with the semiflexible polyimide. Polyimide was solution‐imidized at higher temperature than the glass transition temperature (T_g) using 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐diaminodiphenyl ether (ODA). The morphological observation on the prepared hybrid films by scanning electron microscopy (SEM) pointed to the existence of miscible organic–inorganic phase, which resulted in improved mechanical properties compared with pure PI. The incorporation of the silica structures in the PI matrix also increased both T_g and thermal stability of the resulting films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2053–2061, 2006