Synthesis,thermal properties,and flame retardance of the epoxy‐silsesquioxane hybrid resins

Epoxy/silsesquioxane‐OH (EP‐SDOH, ED) hybrid resins were prepared from cyclohexyl‐disilanol silsesquioxane (SDOH) and diglycidyl ether of bisphenol A via the reaction between silanol and the oxirane group, with the cobalt naphthanate as a catalyst. It was found that incorporation of SDOH allows the reaction between oxirane ring and Si? OH, and the silsesquioxane cage structure can be the main chain or as the side chain of the hybrid resin. The EP‐SDOH hybrid resins with various SDOH contents were cured by 4,4′‐diaminodiphenylsulphone, and the curing reaction was investigated by differential scanning calorimetry. The curing characteristics of EP‐SDOH hybrids had been observed to be influenced by the content of SDOH in the hybrid. The differential scanning calorimetry thermograms indicated that the EP‐SDOH hybrid exhibited a higher initial temperature, peak temperature, as well as final temperature than those of the pure epoxy resin when cured by the same curing agent 4,4′‐diaminodiphenylsulphone. The curing kinetic parameters were calculated by using the Ozawa method and the results indicated that EP‐SDOH hybrids possess the same curing mechanism as the pure epoxy resin. The properties of the cured EP‐SDOH hybrid resins such as the glass transition temperature (T_g), dynamic mechanical analysis, thermal stability, as well as the flame retardance were also investigated, and the results showed that introducing silsesquioxane‐OH unit into epoxy resin successfully modified the local structure, made the chain stiffness, restrict the chain mobility, and eventually improved thermal stability and flame retardance of epoxy resin. POLYM. ENG. SCI., 47:225–234, 2007. © 2007 Society of Plastics Engineers.     

Phosphorous‐containing epoxy resins from a novel synthesis route

The ? P(O)‐H in 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was used as an active group to react with the carbonyl group in 4,4′‐dihydroxybenzophenone (DHBP) to result a novel phosphorous‐containing biphenol compound (DOPO‐2OH). Phosphorous‐containing epoxy resins were therefore obtained from reacting DOPO‐2OH with epichlorohydrin or with diglycidylether bisphenol A. The synthesized compounds were characterized with FTIR, ¹H and ³¹P NMR, elemental analysis, and epoxide equivalent weight titration to demonstrate the their chemical structures. Cured epoxy resins were prepared via thermal curing the epoxy resins with various curing agents. Thermal analysis results (differential scanning calorimetry and thermogravimetric analysis) revealed that these cured epoxy resins exhibited high glass transition temperatures and high thermal stability. High char yields at 700°C and high LOI (limited oxygen index) values were also found for the cured epoxy resins to imply that the resins were possessing high flame retardancy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1697–1701, 2002     

Low dielectric and flame‐retardant properties of thermosetting redistributed poly(phenylene oxide)

A curable low‐molecular‐weight poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) was prepared by the redistribution of regular PPO with maleic anhydride (MA) in toluene, using benzoyl peroxide as an initiator. The redistributed PPO (MA‐PPO), which contained alkene groups, was characterized by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. The redistributed PPO oligomers with reactive double bonds were cured with triallylisocyanurate (TAIC) and/or a phosphorus‐containing allyl‐functionalized monomer (allyl‐DOPO). Electrical properties of cured resins were studied by using a dielectric analyzer. The glass transition temperatures were measured by dynamic mechanical analysis. The flame retardancy was determined by the UL‐94 vertical test. The effects of curing accelerator and the amounts of TAIC and allyl‐DOPO incorporated into the network on the dielectric properties, glass transition temperature, and flame retardancy of the resulting systems were investigated. The results indicated that MA‐PPO cured with TAIC exhibited low dielectric constants (2.23–2.58 at 1 GHz) and dissipation factors (0.0034–0.0039 at 1 GHz) but had high glass transition temperatures (171–197°C)_. The MA‐PPO/TAIC copolymerized with allyl‐DOPO could achieve a flame retardancy rating of UL‐94 V‐0 at about 1.35 wt % of phosphorus. The redistributed PPO/TAIC resins have potential applications in the fabrication of printed circuit boards. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers.     

Novel phosphorus‐containing hardeners with tailored chemical structures for epoxy resins: Synthesis and cured resin properties

A comparative evaluation of systematically tailored chemical structures of various phosphorus‐containing aminic hardeners for epoxy resins was carried out. In particular, the effect of the oxidation state of the phosphorus in the hardener molecule on the curing behavior, the mechanical, thermomechanical, and hot‐wet properties of a cured bifunctional bisphenol‐A based thermoset is discussed. Particular attention is paid to the comparative pyrolysis of neat cured epoxy resins containing phosphine oxide, phosphinate, phosphonate, and phosphate (with a phosphorus content of about 2.6 wt %) and of the fire behavior of their corresponding carbon fiber‐reinforced composites. Comparatively faster curing thermosetting system with an enhanced flame retardancy and adequate processing behavior can be formulated by taking advantage of the higher reactivity of the phosphorus‐modified hardeners. For example, a combination of the high reactivity and of induced secondary crosslinking reactions leads to a comparatively high T_g when curing the epoxy using a substoichiometric amount of the phosphinate‐based hardener. The overall mechanical performance of the materials cured with the phosphorus‐containing hardeners is comparable to that of a 4,4′‐DDS‐cured reference system. While the various phosphorus‐containing hardeners in general provide the epoxy‐based matrix with enhanced flame retardancy properties, it is the flame inhibition in the gas phase especially that determines the improvement in fire retardancy of carbon fiber‐reinforced composites. In summary, the present study provides an important contribution towards developing a better understanding of the potential use of such phosphorus‐containing compounds to provide the composite matrix with sufficient flame retardancy while simultaneously maintaining its overall mechanical performance on a suitable level. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Flame retardant epoxy resin for electrical and electronic applications

Amine‐cured epoxy resins were prepared at 2% by weight phosphorus content using four halogen‐free flame retardants; poly(m‐phenylene methyl phosphonate) (Fyrol PMP); 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide; red phosphorus; and aluminum diethylphosphinate (OP1230). The effect of these additives on the properties of cured epoxy, including glass transition temperature, thermal stability, and fire retardancy (cone calorimetry), were studied and were compared with the conventionally used flame retardant, tetrabromobisphenol‐A (TBBA). All properties are improved for the non‐halogenated materials compared with TBBA. Further, the stoichiometric amounts of Fyrol PMP and TBBA (without an external curing agent) were reacted with epoxy to determine if they could be used as a flame retardant and as a curing agent; Fyrol PMP effectively acts as a flame retardant and as a curing agent. Evolved gas analysis is also discussed through thermogravimetric analysis/Fourier transform infrared spectroscopy. Copyright © 2013 John Wiley & Sons, Ltd.     

Epoxy/POSS organic–inorganic hybrids: Viscoelastic,mechanical properties and micromorphologies

A series of epoxy resin (EP)/octa(aminpropyl)silsesquioxane (POSS‐NH₂) organic–inorganic hybrid composites (EP/POSS‐NH₂ 100/0, 95/5, 90/10, and 80/20 wt/wt) were prepared by melt casting and then curing. Viscoelastic and mechanical properties of these composites were studied by dynamic mechanical analysis and mechanical testing, respectively. Scanning electron microscopy was used to study of the micromorphologies of the composites and to elucidate the toughening mechanisms of POSS‐NH₂. POSS units incorporated into the epoxy network showed good compatibility with the resin matrix. Phase separation was not observed even at high POSS content (20 wt%). Incorporation of POSS macromer into the epoxy network after curing increased the glass transition temperature, slightly narrowed the temperature range widths of the glass transition, and lowered the intensities of their loss moduli peaks of the resultant composites. The glass transition temperature of EP/POSS‐NH₂ composites increased significantly with increasing POSS content at lower POSS content (<10 wt%), while increased slightly at higher POSS content. Both impact and flexural strengths of the hybrids reached their optimum values when 10 wt% content of POSS was introduced. POLYM. COMPOS., 28:175–179, 2007. © 2007 Society of Plastics Engineers.     

Flame retardancy and dielectric properties of dicyclopentadiene‐based benzoxazine cured with a phosphorus‐containing phenolic resin

A dicyclopentadiene‐based benzoxazine (DCPDBZ) was prepared and separately copolymerized with melamine–phenol formaldehyde novolac or phosphorus‐containing phenolic resin (phosphorus‐containing diphenol) at various molar ratios. Their curing behaviors were characterized by differential scanning calorimetry. The electrical properties of the cured resins were studied with a dielectric analyzer. The glass‐transition temperatures were measured by dynamic mechanical analysis. The thermal stability and flame retardancy were determined by thermogravimetric analysis and a UL‐94 vertical test. These data were compared with those of bisphenol A benzoxazine and 4,4′‐biphenol benzoxazine systems. The effects of the diphenol structure and cured composition on the dielectric properties, moisture resistance, glass‐transition temperature, thermal stability, and flame retardancy are discussed. The DCPDBZ copolymerized with phosphorus‐containing novolac exhibited better dielectric properties, moisture resistance, and flame retardancy than those of the melamine‐modified system. The flame retardancy of the cured benzoxazine/phosphorus‐containing phenolic resins increased with increasing phosphorus content. The results indicate that the bisphenol A and 4,4′‐biphenol systems with a phosphorus content of about 0.6% and the dicyclopentadiene system with a phosphorus content of about 0.8% could achieve a flame‐retardancy rating of UL‐94 V‐0. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and properties of optically clear silicone resin/epoxy resin hybrids

Optically clear silicone/epoxy hybrid resins were synthesized. The silicone resin (SiR) carrying Si? H, Si? CH?CH₂ and Si? OH groups was prepared by hydrolytic condensation. The blends of SiR and diglycidyl ether of hydrogenated bisphenol A (DGEHBA) were cured through platinum‐catalyzed hydrosilylation and aluminium acetylacetonate‐catalyzed polymerization. The curing process was studied using differential scanning calorimetry and rigid‐body pendulum rheometry. It was found that the ratio of SiR to DGEHBA plays a major role in the curing process. The Si? OH groups of SiR assist polymerization of DGEHBA, and react with the epoxy resin to prevent phase separation. The cured hybrid resins are single‐phase materials with a transmittance of about 87% at 400 nm for a thickness of 3 mm using air as reference. UV resistance and thermal stability of the hybrids are largely dependent on the composition. The adhesive strength of the SiRs can be significantly improved by a small fraction of DGEHBA, with a marginal influence on UV resistance. However, increasing the epoxy proportion has a marked negative influence on thermal stability. Compounding stabilizers, especially thermal stabilizers, are essential, in particular for high epoxy content, if the hybrids are to be used for high‐brightness light‐emitting diode packaging. Copyright © 2011 Society of Chemical Industry     

Preparation of silicon‐/phosphorous‐containing epoxy resins from the fusion process to bring a synergistic effect on improving the resins' thermal stability and flame retardancy

Epoxy resins containing both phosphorous and silicon were prepared via the fusion process of reacting a phosphorous diol and a silicon diol with a bisphenol‐A‐type epoxy. With various feeding ratios of the reactants, epoxy resins with different phosphorous and silicon contents were obtained. Through curing the epoxies with diaminodiphenylmethane, the cured epoxy resins exhibit tailored glass transition temperatures (159–77°C), good thermal stability (>320°C), and high char yields at 700°C under air atmosphere. The high char yield was demonstrated to come from the synergistic effect of phosphorous and silicon, where phosphorous enriches char formation and silicon protects the char from thermal degradation. Moreover, high flame retardancy of the epoxy resins was found by the high LOI value of 42.5. The relationship of the char yields at 700°C under air atmosphere (ρ) and the LOI values of the epoxy resins could be expressed as LOI = 0.62ρ + 19.2. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 404–411, 2003     

Thermal Properties of Organic-inorganic Hybrid Composites Based on Multi-Epoxy Silsesquioxane and Epoxy Resin

The multi-epoxy cubic silsesquioxane (SSQE) was successfully introduced into epoxy resin (EP) and formed the organic-inorganic EP-SSQE hybrids. The hybrids were cured by 4,4′-diaminodiphenylsulphone (DDS) and the Fourier transformation infrared (FTIR) spectra were used to monitor the cured reaction of the hybrid, and the results showed that the hybrids could be cured thoughtfully without influence the cubic silsesquioane structure. The thermal properties of the hybrid such as the heat distortion temperature (HDT), the glass transition temperature Tg and the thermal decomposing property were studied. The results showed that the hybrids had the higher thermal properties than that of the pure epoxy resin for the introducing of multi-epoxy cubic silsesquioxane.     

Synthesis,Morphology and Viscoelastic Properties of Epoxy/Polyhedral Oligomeric Silsesquioxane (POSS) and Epoxy/Cyanate Ester/POSS Nanocomposites

TriSilanolPhenyl-polyhedral oligomeric silsesquioxane (POSS-1) (C₄₂H₃₈O₁₂Si₇), 1–15 wt%, was incorporated into aliphatic epoxy resin (Clearstrem Products, Inc.) with aliphatic diamine curing agents and cured. This epoxy resin was also blended with an equal weight (50/50 w/w) of aromatic cyanate ester resin, Lonza’s PT-15, and 1–15 wt% of POSS-1 and cured. These composites were characterized by FT-IR, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (X-EDS), dynamic mechanical thermal analysis (DMTA) and three-point bending flexural tests. XRD and X-EDS measurements were consistant with partial molecular dispersion of the POSS units in the continuous matrix phase, together with POSS aggregates. TEM and SEM show that POSS-1-enriched nanoparticles are present in the matrix resins of both the epoxy/POSS and epoxy/cyanate ester/POSS-1 composites. The storage bending moduli, E′, in the rubbery region and the glass transition temperatures, T_g, of epoxy and epoxy/cyanate ester 1-5% POSS-1 composites are higher than those of the reference resins. Small amounts (≤5 wt%) of POSS-1 improved E′ and T_g of both systems and raised flexural strengths and moduli.     

Preparation of epoxy resin/silica hybrid composites for epoxy molding compounds

Phenolic novolac/silica and cresol novolac epoxy/silica hybrids were prepared through in situ sol‐gel reaction of tetraethoxysilane (TEOS). The formed hybrids were utilized as a curing agent and an epoxy resin in epoxy curing compositions, respectively. Via the two‐step preparation route, the resulting epoxy resin/silica hybrid nanocomposites exhibited good thermal stability, high glass transition temperatures, and low coefficients of thermal expansion. High condensation degree of the condensed silica was observed with a high content of siloxane bridges, p > 85%, measured by ²⁹Si NMR. The two‐step route also provides feasibility of preparation of epoxy resin/silica hybrid nanocomposites compatible with the current processes of manufacturing of epoxy molding compounds. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4047–4053, 2003     

Synthesis of a novel phosphorus‐containing dicyclopentadiene novolac hardener and its cured epoxy resin with improved thermal stability and flame retardancy

A novel phosphorus‐containing dicyclopentadiene novolac (DCPD‐DOPO) curing agent for epoxy resins, was prepared from 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and n‐butylated dicyclopentadiene phenolic resin (DCPD‐E). The chemical structure of the obtained DCPD‐DOPO was characterized with FTIR, ¹H NMR and ³¹P NMR, and its molecular weight was determined by gel permeation chromatography. The flame retardancy and thermal properties of diglycidyl ether bisphenol A (DGEBA) epoxy resin cured with DCPD‐DOPO or the mixture of DCPD‐DOPO and bisphenol A‐formaldehyde Novolac resin 720 (NPEH720) were studied by limiting oxygen index (LOI), UL 94 vertical test and cone calorimeter (CCT), and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. It is found that the DCPD‐DOPO cured epoxy resin possess a LOI value of 31.6% and achieves the UL 94 V‐0 rating, while its glass transition temperature (T_g) is a bit lower (133 °C). The T_g of epoxy resin cured by the mixture of DCPD‐DOPO and NPEH720 increases to 137 °C or above, and the UL 94 V‐0 rating can still be maintained although the LOI decreases slightly. The CCT test results demonstrated that the peak heat release rate and total heat release of the epoxy resin cured by the mixture of DCPD‐DOPO and NPEH720 decrease significantly compared with the values of the epoxy resin cured by NPEH720. Moreover, the curing reaction kinetics of the epoxy resin cured by DCPD‐DOPO, NPEH720 or their mixture was studied by DSC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44599.     

Synthesis and properties of a phosphate ester as curing agent in an epoxy resin system

Phosphate ester compounds display good flame retardancy effect in epoxy resin systems. In this paper, several novel phosphate esters, used as curing agents for epoxy resins, were synthesized based on P₂O₅, phosphoric acid, and different types of alcohol. The structures of phosphate esters were characterized by ³¹P nuclear magnetic resonance (³¹P NMR). Then, a series of flame retardant epoxy composites were prepared by curing the epoxy resins (E-44) with the phosphate esters. The flame retardancy and thermal degradation behaviors of flame retardant epoxy composites were investigated by cone calorimeter test (CCT) and thermogravimetric analysis (TGA), respectively. The results of CCT indicated that phosphate esters can significantly decrease heat release rate, total heat release (THR), and smoke production rate. The sample cured by butyl phosphate ester from phosphorus pentoxide, phosphoric acid and butanol showed the best flame retardant performance among all samples. The TGA results showed that phosphate esters could enhance char residues of flame retardant epoxy composites when compared with those of a composite using T31 as a curing agent at high temperature. It may be concluded that good flame retardant properties of flame retardant epoxy composites are related to the formation of a protective phosphorus-rich char layer. These phosphate esters have a good future on flame retardant epoxy composites.     

Highly thermally stable novolac derivatives and their properties in epoxy composites

Two diazo‐coupling novolac derivative resins (carbonyl phenyl azo novolac resin and carbonyl phenol–biphenylene azo novolac resin) were used as flame retardants. The cured resins exhibited elevated glass‐transition temperatures from 115°C (blank) to 195 and 167°C, respectively. The char yield at 800°C was increased, which elaborated the effectiveness of flame retardancy with evaluated limiting oxygen indices around 36 to 40. This was mainly attributed to the increased crosslink densities and highly aromatic contents in the modified phenol novolac derivative resins, which exhibited higher thermal degradation energies. Furthermore, the more effective flame retardancy was expected because of the loss of nitrogen during combustion. Through the evaluation of the cooperative flame retardancy in the organic/inorganic hybrid with char yield and increasing limiting oxygen index percentage, the effects of the filler showed cooperative flame retardancy only with the appropriate addition and with a difference in the crosslinking densities. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cold‐cured epoxy‐silica hybrids: Effects of large variation in specimen thickness on the evolution of the Tg and related properties

Experimental organic–inorganic hybrid systems, based on silane functionalized difunctional and trifunctional epoxy resins and an alkoxysilane precursor mixture, containing small amounts of ammonium molybdate, are evaluated for potential use as adhesives cured at ambient temperatures. The precursor resin mixtures are found to exhibit a large increase in viscosity with a pseudoplastic behavior. Scanning electron microscopy (SEM) analysis shows the existence of siloxane domains with nanometric dimensions, except for the presence of microscopic molybdate particles. By monitoring the evolution of the glass transition temperature (T_g) during curing, varying the thickness of the specimens between 0.2 and 4.5 mm, it is found that the organic–inorganic hybrids display a significant increase in the final T_g over the parent unmodified epoxy resins, particularly in thin specimens and when ammonium molybdate is added. Small‐angle X‐ray scattering (SAXS) spectra show that the dimensions and typographic features of thick and thin specimens are similar, both containing an agglomeration of primary particles of 5–6 nm. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Novel flame retardant thermosets from nitrogen‐containing and phosphorus‐containing epoxy resins cured with dicyandiamide

A novel phosphorus‐containing epoxy resin (EPN‐D) was prepared by addition reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) and epoxy phenol‐ formaldehyde novolac resin (EPN). The reaction was monitored by epoxide equivalent weight (EEW) titration, and its structure was confirmed by FTIR and NMR spectra. Halogen‐free epoxy resins containing EPN‐D resin and a nitrogen‐containing epoxy resin (XT resin) were cured with dicyandiamide (DICY) to give new halogen‐free epoxy thermosets. Thermal properties of these thermosets were studied by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), thermal mechanical analyzer (TMA) and thermal‐gravimetric analysis (TGA). They exhibited very high glass transition temperatures (T_gs, 139–175°C from DSC, 138–155°C from TMA and 159–193°C from DMA), high thermal stability with T_{d,5 wt %} over 300°C when the weight ratio of XT/EPN‐D is ≥1. The flame‐retardancy of these thermosets was evaluated by limiting oxygen index (LOI) and UL‐94 vertical test. The thermosets containing isocyanurate and DOPO moieties showed high LOI (32.7–43.7) and could achieve UL‐94 V‐0/V‐1 grade. Isocyanurate and DOPO moieties had an obvious synergistic effect on the improvement of the flame retardancy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

High‐performance thermosetting films based on an amino‐functionalized poly(ether sulfone)

We have developed a sequence‐dependent synthesis of the amino‐functionalized poly(ether sulfone) P2 . The amino groups of P2 act as reactive sites toward epoxy resins. After curing P2 with diglycidyl ether of bisphenol A (DGEBA) and cresol novolac epoxy (CNE), we obtained the flexible, light‐yellow, transparent, epoxy thermosetting films P2 /DGEBA, and P2 /CNE, respectively, having glass transition temperatures (T_g) of 258 and 274°C, respectively. In addition, we also prepared a flexible film after condensation of the amino groups of P2 with the anhydride groups of 4,4′‐oxydiphthalic anhydride (ODPA); after imidization at 300°C for 1 h, the resulting P2 /ODPA thermosetting film possessed a value of T_g of 340°C. These three thermosetting films also exhibited flame retardancy with a UL‐94 VTM‐0 grade. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40980.     

Development of a DOPO‐containing melamine epoxy hardeners and its thermal and flame‐retardant properties of cured products

In this study, a novel Schiff base of melamine used as flame‐retardant curing agent for epoxy resins, was synthesized via condensation reaction of 4‐hydroxybenzaldehyde with melamine, followed by the addition of 9,10‐dihydro‐9‐oxa‐10‐phosphaphen‐anthrene 10‐oxide (DOPO) to the resulting imine linkage. The structure of DOPO‐containing melamine Schiff base (P‐MSB) was characterized by Fourier transformed infrared spectroscopy, ¹H‐nuclear magnetic resonance (¹H‐NMR) and ³¹P‐NMR. The compound (P‐MSB) was used as a reactive flame retardant in o‐cresol formaldehyde novolac epoxy resin (CNE) to prepare flame‐retardant epoxy resins for electronic application. The thermal and flame‐retardant properties of the epoxy resins cured by various equivalent ratios phenol formaldehyde novolac (PN) and P‐MSB were investigated by the nonisothermal differential scanning calorimetry, the thermogravimetric analysis, and limiting oxygen index test. The obtained results showed that the cured epoxy resins possessed high T_g (165°C) and good thermal stability (T_5%, 321°C). Moreover, the P‐MSB/CNE systems exhibited higher limiting oxygen index (35) and more char was maintained in P‐MSB/CNE systems than that in PN/CNE system and the effective synergism of phosphorus–nitrogen indicated their excellent flame retardancy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and properties of trifluoromethyl groups containing epoxy resins cured with amine for low Dk materials

The study synthesized a trifluoromethyl (CF₃) groups with a modified epoxy resin, diglycidyl ether of bisphenol F (DGEBF), using environmental friendly methods. The epoxy resin was cured with 4,4′‐diaminodiphenyl‐methane (DDM). For comparison, this study also investigated curing of commercially available diglycidyl ether of bisphenol A (DGEBA) with the same curing agent by varying the ratios of DGEBF. The structure and physical properties of the epoxy resins were characterized to investigate the effect of injecting fluorinated groups into epoxy resin structures. Regarding the thermal behaviors of the specimens, the glass transition temperatures (T_g) of 50–160°C and the thermal decomposition temperatures of 200–350 °C at 5% weight loss (T_d5%) in nitrogen decreased as amount of DGEBF increased. The different ratios of cured epoxy resins showed reduced dielectric constants (D_k) (2.03–3.80 at 1 MHz) that were lower than those of pure DGEBA epoxy resins. Reduced dielectric constant is related to high electrronegativity and large free volume of fluorine atoms. In the presence of hydrophobic CF₃ groups, the epoxy resins exhibited low moisture absorption and higher contact angles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012