Kinetic study by FTIR,TMA, and DSC of the curing of a mixture of DGEBA resin and γ‐butyrolactone catalyzed by ytterbium triflate

A mixture of diglycidylether of bisphenol A (DGEBA) and γ‐butyrolactone (γ‐BL) was cured in the presence of ytterbium triflate as a catalyst. The kinetics of the various elemental processes that occur in the curing process were studied by means of isothermal curing in the FTIR spectrometer. The kinetics of the contraction during the curing was also evaluated by TMA. In both cases, the kinetics was analyzed by means of isoconversional procedure and the kinetic model was determined with the so‐called compensation effect (isokinetic relationship). The isothermal kinetic analysis was compared with that obtained by dynamic curing in DSC. We found that all the reactive processes and the contraction follow a surface‐controlled reaction type of kinetic mechanism, R₃. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 381–393, 2004     

Dynamics and thermal properties of epoxy resin cured by new diamino disiloxanes

Two disiloxane compounds, 3,3′‐(1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediyl)bis(benzenamine) ( C1 ) and 4,4′‐(1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediyl)bis(benzenamine) ( C2 ) were synthesized and used as new curing agents of DGEBA epoxy resin with an epoxy value of 0.51 ( E‐51 ). The curing kinetics of E‐51/C1 and E‐51/C2 systems was investigated by non‐isothermal differential scanning calorimetry (DSC) analyses. The activation energy (ΔE) and the characteristic cure temperatures of the two systems were determined. The two systems have the similar activation energy. The reactivity of E‐51/C1 is higher than that of E‐51/C2 . The reaction orders of E‐51/C1 and E‐51/C2 are 0.88 and 0.87, respectively, illustrating that curing reaction between the epoxy resin and curing agent ( C1 or C2 ) is complicated. The DSC result shows that E51 cured by C2 has higher Tg; whereas thermogravimetric analysis results indicate that E51 cured by C1 has higher thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42385.     

Synthesis and properties of ultraviolet/moisture dual‐curable polysiloxane acrylates

Ultraviolet (UV)/moisture dual‐curable polysiloxane acrylates (PSAs) were prepared from N,N‐bis[3‐(triethoxysilyl)propyl]amine (G402) and ethoxylated trimethylolpropane triacrylate (EB160) through Michael addition. The obtained prepolymers were characterized by ¹H‐NMR and FTIR. The rheological behavior of the prepolymers exhibited the properties of a Bingham fluid and the apparent viscosity was directly correlated with molecular weight. The photocuring kinetics of PSA were studied using photo‐DSC and all the polymerization conversions were high. With increasing content of tertiary amine in the prepolymer, the photocuring rate in air increased as well. The moisture‐curing kinetics of the prepolymers was studied using FTIR. It was found that the curing mechanism may be described as the transforming of Si O C into Si O Si structure, which was consistent with the theoretical expectation. DSC and TGA were used to characterize the glass‐transition temperatures and the thermomechanical stability of the prepolymers. Measurements of physical properties showed excellent gloss, impact strength, and high electric resistance for both UV‐ and moisture‐cured films, but poor adhesion for UV‐cured films and lower hardness for moisture‐cured films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 846–853, 2005     

New thermosets obtained by copolymerization of DGEBA with 1,5,7,11-tetraoxaspiro[5,5]undecane catalyzed by lanthanide triflates

DGEBA epoxy resin was cured with different proportions of 1,5,7,11-tetraoxaspiro[5,5]undecane (TOSU) with ytterbium and lanthanum triflates as catalysts. The curing was studied by differential scanning calorimetry (DSC) and Fourier transform infrared in the attenuated-total-reflexion mode (FTIR/ATR).FITR/ATR was used to monitor the competitive reactive processes and to quantify the evolution of the epoxide, orthocarbonate, linear carbonate and other groups formed in the curing process. The T_g of the cured materials decreased when the proportion of TOSU increased. The kinetics were studied by DSC experiments and analyzed with iso-conversional procedures. The systems catalyzed by ytterbium triflate had a higher curing rate and reached a higher degree of cross-linking. The addition of TOSU reduced the degree of overall shrinkage and even led to one material expanding. The flexibility and the degradability of these materials were improved by introducing higher proportions of TOSU.     

Preparation and characterization of high char yield polybenzoxazine/polyarylacetylene blends for resin‐transfer molding

Benzoxazine precursors (BOZP), 6,6′‐bis(2,3‐dihydro‐3‐(3‐ethynylphenyl)‐4H‐1,3‐ benzoxazinyl)ketone and 6,6′‐bis(2,3‐dihydro‐3‐(3‐ethynylphenyl)‐4H‐1,3‐benzoxazinyl)ether were synthesized and characterized by Proton nuclear magnetic resonace (¹H‐NMR) and Fourier transform infrared spectroscopy (FTIR). The polyarylacetylene (PAA) was synthesized through thermal polymerization of diethynylbenzene, and characterized by ¹H‐NMR, FTIR, and Differential Scanning Calorimetry (DSC). The BOZP/PAA blends were prepared with different contents of PAA, and their viscosity was measured using NDJ‐79 rotating visometer. The curing behavior of BOZP/PAA blends was characterized by DSC. The thermal stability of cured BOZP/PAA blends was studied using Thermogravimetric Analysis, the results show char yield at 800°C was in the range of 78–84%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Curing behavior and network formation of cyanate ester resin/polyethylene glycol

The mechanism and kinetics of the curing reaction of cyanate ester (CE) resin modified with polyethylene glycol were investigated by means of differential scanning calorimetry (DSC) and Fourier‐transform infrared spectroscopy (FTIR). The relationship of heat flow versus conversion rate was used to evaluate the effects of polyethylene glycol (PEG) on the curing reaction of CE. DSC results showed that the addition of PEG decreased the curing temperature of CE effectively when its content was less than 20 wt %. The curing behavior of CE/PEG still complies with the self‐catalytic kinetic model proposed by Kamal. The effects of PEG content on the kinetics parameters and conversion rate of the curing reaction were discussed. FTIR results indicated that the –OH groups in PEG participated in the polymeric reaction of CE and formed –O–C (=NH) –O– structure through block copolymerization, which extended the chain length between triazine rings and reduced the density of triazine rings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41841.     

Curing of mixtures of epoxy resins and 4‐methyl‐1,3‐dioxolan‐2‐one with several initiators

Diglycidyl ether of bisphenol A or 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexane carboxylate were mixed with different proportions of 4‐methyl‐1,3‐dioxolan‐2‐one and cured using lanthanide triflates as initiators. In order to compare the materials obtained, conventional initiators such as boron trifluoride complexes and N,N‐dimethylaminopyridine were also tested. The curing process was followed by differential scanning calorimetry (DSC) and Fourier transform IR in attenuated total reflectance mode. This technique proved that the carbonate accelerates the curing process because it helps to form the active initiating species, although it was not chemically incorporated into the network and remained entrapped in the material. The DSC kinetic study was also reported. © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2086–2093, 2006     

Influence of oxidation treatment of carbon powders on the cure kinetics of amine cured tetrafunctional epoxy resins

A tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) type tetrafunctional epoxy resin containing carbon powders was cured with the stoichiometric amount of a tetrafunctional curing agent, namely m-phenylenediamine (mPDA). Carbon powders were oxidised with air or nitric acid. The influence of carbon powders on curing of the resin was followed by dynamic mechanical analysis, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Gelation and vitrification times were determined as a function of the variations of dynamic properties. The evolution of viscoelastic modulus during curing of the different mixtures showed that untreated carbon powder clearly accelerated the kinetics of curing whilst oxidation of carbon powders could remove their catalysing effect. These results were confirmed by monitoring the changes in conversion of epoxy and amine groups during cure using the FTIR technique. DSC experiments also showed the influence of carbon powder as a catalyst and the loss of the catalysing effect as a consequence of chemical treatment.     

Curing behavior and thermal properties of multifunctional epoxy resin with methylhexahydrophthalic anhydride

The curing behavior and thermal properties of bisphenol A type novolac epoxy resin (bisANER) with methylhexahydrophthalic anhydride (MHHPA) at an anhydride/epoxy group ratio of 0.85 was studied with Fourier‐transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry. The results showed that the FTIR absorption intensity of anhydride and epoxide decreased during the curing reaction, and the absorption peak of ester appeared. The dynamic curing energies were determined as 48.5 and 54.1 kJ/mol with Kissinger and Flynn–Wall–Ozawa methods, respectively. DSC measurements showed that as higher is the curing temperature, higher is the glass transition. The thermal degradation of the cured bisANER/MHHPA network was identified as two steps: the breaking or detaching of ? OH, ? CH₂? , ? CH₃, OC? O and C? O? C, etc., taking place between 300 and 450°C; and the carbonizing or oxidating of aromatic rings occurring above 450°C. The kinetics of the degradation reaction was studied with Coats–Redfern method showing a first‐order process. In addition, vinyl cyclohexene dioxide (VCD) was employed as a reactive diluent for bisANER (VCD/bisANER = 1 : 2 w/w) and cured with MHHPA, and the obtained network had a higher T_g and a slight lower degradation temperature than the undiluted system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2041–2048, 2007     

Curing of epoxy resin with poly(m‐phenylene methylphosphonate)

The mechanism and kinetics of curing of epoxy resin with poly(m‐phenylene methylphosphonate) (PMP) was studied by extraction and swelling experiments, DSC, ³¹P NMR, and FTIR. It was shown that at linear heating of 20°C/min PMP cures bisphenol A type epoxy resin at 230–300°C, whereas in the presence of catalytic amount of 2‐methyl imidazole the curing occurs at 200–230°C. Under isothermal conditions, epoxy resin was cured with PMP after 40–70 min at 150°C. An unusual mechanism of curing due to opening and insertion of epoxy into the phosphonate bond was suggested. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4011–4022, 2006     

Synthesis,characterization of new carboxylic acid‐containing benzoxazine and its cocuring behaviors with bisoxazoline

A new benzoxazine‐benzoic acid (BBA) was synthesized and the structure was conformed by ¹H‐NMR, ¹³C‐NMR, FTIR, etc. The cure behavior of BBA and cocure behavior of BBA with phenylene bisoxazoline (1,3‐PBO) were investigated by differential scanning calorimetry (DSC). It was found that BBA showed a single curing exothermic peak at about 217°C. However, all BBA/1,3‐PBO systems exhibited two exothermic peak. One may be attributed to the reaction between carboxyl groups of BBA and 1,3‐PBO. And the other was attributed to the ring‐opening polymerization of oxazine rings and the reaction between phenolic hydroxyl groups generated by the ring opening of benzoxazine ring and 1,3‐PBO. The curing temperature of benzoxazine containing carboxyl groups could be lowered by the copolymerization of 1,3‐PBO. Thermogravimetric analysis showed that the incorporation of ester–amide groups had a significant effect on decreasing thermal stability and char yield of the cured resin. SEM results indicated that 1,3‐PBO could toughen BBA benzoxazine resin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Curing of DGEBA epoxy resin by low generation amino‐group‐terminated dendrimers

Low generation amino‐group‐terminated poly(ester‐amine) dendrimers PEA1.0 (NH₂)₃ and PEA1.5 (NH₂)₈, and poly(amido‐amine) dendrimer PAMAM1.0 (NH₂)₄ were used as diglycidyl ether of bisphenol A (DGEBA) epoxy resin hardeners. Thermal behavior and curing kinetics of dendrimer/DGEBA systems were investigated by means of differential scanning calorimetry (DSC). Compared with ethylene diamine (EDA)/DGEBA system, the dendrimer/DGEBA systems gradually liberated heat in two stages during the curing process, and the total heat liberated was less. Apparent activation energy and curing reaction rate constants for dendrimer and EDA/DGEBA systems were estimated. Thermal stabilities and mechanical properties of cured thermosetting systems were examined as well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3902–3906, 2006     

Synthesis of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine and its application as latent curing agents

A kind of new compound of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine was successfully synthesized by addition–condensation reaction of phenyl aldehyde and β‐hydroxylethanolamine and purified by vacuum distillation. Its purity was examined by gas chromatographic analysis. Its structure was confirmed by ¹³C NMR and FTIR. When this compound was added as a latent curing agent in single‐component moisture‐curable polyurethane system (SPU), bubbles of SPU formed during curing was obviously restrained, and the elongation at break of the cured SPU contained a certain content of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine was increased to 16 times when compared with that uncontained this oxazolidine derivative. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Kinetics and thermal properties of epoxy resin cured with Ni(II)‐tris‐(O‐pheneylendiamine) bromide

Diglycidyl ether of bisphenol A (DGEBA) is cured with a nickel complex of O‐phenylendiamine (OPD) as a ligand. The structure of the synthesized curing agent is confirmed through IR and elemental analysis. The curing kinetics of DGEBA/Ni(OPD)₃Br₂ system is studied by the dynamic DSC and isothermal FTIR techniques. In all cases, we have observed at least two exothermic peaks during DSC traces up to 350°C. Dynamic activation energies are calculated by using the two isoconversional, Kissinger and Ozawa, methods applied to peak maximum. A two‐parameter (m, n) autocatalytic model (Sestak–Berggren equation) is found to be the most adequate model to describe the cure kinetics of the observed thermal events. Isothermal kinetic parameters are estimated using the Horie model. The onset decomposition temperature and char yield (at 700°C) of the crosslinked material were 290°C and 27%, respectively. The activation energy of the solid‐state thermal degradation process is evaluated by Ozawa approach, resulting in 95–138 kJ/mol on a range of 2–20% decomposition conversion. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1257–1265, 2006     

Effects of inhibitors and retarders on low temperature free radical crosslinking polymerization between styrene and vinyl ester resin

Many composite manufacturing methods are room temperature processes, which require the resins to be cured at low temperatures. Examples are Seemann Composite Resin Infusion Molding Process (SCRIMP)—a vacuum assisted resin transfer molding (VARTM) process, hand lay‐up and spray‐up. Vinyl ester resins have been widely used in this type of processes because of their versatility as a composite matrix. Low temperature polymerization between styrene and vinyl ester tends to be complex because of the presence of different curing agents. This paper reports on (1) the effects of a promoter (cobalt naphthenate) on the initiatin at low temperatures, and (2) the effects fo a retarder (2,4‐pentanedione) and an inhibitor (1,4‐benzoquinone) on the pot life, gel time, and cure kinetics. A differntial scanning calorimeter (DSC) and a Fourier transform infrared (FTIR) spectrometer were used to investigate the reaction kinetics of vinyl ester resins. The influence of the retarders and inhibitors on the rheological changes of the resin during curing was also studied using a Rheometris Dynamic Analyzer (RDA).     

DSC study on the effect of cure reagents on the lignin base epoxy cure reaction

The cure reactions of liquid lignin base epoxy resin (LEPL) with three different curing agents, viz., methylhexahydrophthalic anhydride, maleic anhydride, and 2‐methyl‐4‐methylimidazole (EMI‐2,4), were investigated by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry. Cure kinetics was evaluated using the multiple heating rate Kissinger method. The reactivities of the three curing agents were compared based on kinetics results obtained by DSC. FTIR spectra of these curing systems were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Use of epoxy–phenolic lacquers in food can coatings: Characterization of lacquers and cured films

Liquid and cured epoxy–phenolic lacquers used as can coatings were characterized. Tinplate was used as the base material, which was coated with lacquers of different epoxy to phenolic ratios (EPRs) from a commercial source. Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) were used together to obtain helpful information about the degree of curing and the composition of the lacquers. From FTIR analysis, we were able to infer that the lacquers were composed of a high‐molecular‐weight diglycidyl ether of bisphenol A type epoxy resin and a resol‐type phenolic resin. In addition, from FTIR spectra, we estimated the EPRs of lacquers applied on the tinplate and detected if they had been overcured. The EPRs of the applied lacquers were estimated also from DSC analysis. From TGA, we detected undercuring in the applied lacquers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1448–1458, 2005     

The effect of curing cycles on curing reactions and properties of a ternary system based on benzoxazine,epoxy resin,and imidazole

A ternary blend (BEM) of benzoxazine (BA‐a), epoxy resin (E44), and imidazole (M) was prepared to study the effect of different curing cycles on curing reactions and properties of cured resins. Reactivity of two binary blends, E44 and BA‐a, with the catalyst M, was first investigated based on the curing kinetics. Results suggest that E44/M has lower reaction activation energy than BA‐a/M meaning the reaction of E44/M easily proceeds. To further figure out the sequences of the curing reactions of E44, BA‐a, and M in BEM, the curing behaviors of three BEM gels at 80, 140, and 180°C (defined as BEM‐80g, BEM‐140g, and BEM‐180g) were studied by DSC and FTIR techniques. For BEM‐80g, E44/M cured before BA‐a/M. For BEM‐180g, both curing reactions occurred simultaneously and the copolymerization of BA‐a and E44 was promoted. The crosslinked structures of cured BEM with different initial curing temperatures were strongly influenced by the reaction sequences. The T_gs, flexural properties and thermal stability of the copolymers with different curing cycles were compared. Good performance of this ternary system can be obtained by choosing suitable curing cycles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

DSC analysis of epoxy molding compound with plasma polymer–coated silica fillers

Silica fillers were modified by plasma‐polymerization coating of 1,3‐diaminopropane, allylamine, pyrrole, 1,2‐epoxy‐5‐hexene, allylmercaptan, and allylalcohol using RF plasma (13.56 MHz). Modified fillers were then mixed with biphenyl epoxy resin, phenol novolac (curing agent), and optionally triphenylphosphine (catalyst) to prepare samples for DSC analyses. Some samples were also prepared from uncoated silica fillers and monomers used in plasma polymerization coating, instead of plasma polymer–coated silica fillers. Plasma polymer–coated silica fillers were characterized by FTIR, XPS, and water contact angle measurements. In DSC analyses, all samples with plasma polymer–coated silica fillers showed a large peak and an additional one or two small exothermic peaks when catalyst was added, compared to only one large peak with as‐received silica fillers. The large peak could be from epoxy–phenol novolac reaction in the presence of catalyst, whereas small reaction peaks were attributed to the chemical reaction between epoxy resin and functional moieties in the plasma polymer coating, such as amine, OH, and/or SH groups, as evidenced by FTIR and XPS analysis and contact angle measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2508–2516, 2003     

TG-siloxane改性BPFER/mXDA体系固化反应动力学与热性能

以1,3-二氨丙基-1,1,3,3-四甲基二硅氧烷(DSX)和环氧氯丙烷(ECH)为原料,利用相转移催化剂,合成双酚F环氧树脂(BPFER)改性剂N,N,N',N'-四缩水甘油基-1,3-二氨丙基-1,1,3,3-四甲基二硅氧烷(TG-siloxane),并用FTIR、¹³C NMR谱图对其结构进行了表征。对TG-siloxane改性BPFER/mXDA(间苯二甲胺)体系的固化动力学进行了研究。根据DSC曲线和Starink方程,得该体系表观固化活化能为51.52 kJ·mol^-1。用Šesták-Berggren模型求得不同升温速率下的表观因子、反应级数。动力学方程表明,升温速率对固化反应影响明显;所得方程用于预估反应进程时,与实测值吻合程度高。TG分析表明,TG-siloxane改性BPFER/mXDA体系固化物的耐热性能优于单纯BPFER/mXDA固化物。