Investigation of the postcure reaction and surface energy of epoxy resins using time‐of‐flight secondary ion mass spectrometry and contact‐angle measurements

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was used to investigate correlations between the molecular changes and postcuring reaction on the surface of a diglycidyl ether of bisphenol A and diglycidyl ether of bisphenol F based epoxy resin cured with two different amine‐based hardeners. The aim of this work was to present a proof of concept that ToF‐SIMS has the ability to provide information regarding the reaction steps, path, and mechanism for organic reactions in general and for epoxy resin curing and postcuring reactions in particular. Contact‐angle measurements were taken for the cured and postcured epoxy resins to correlate changes in the surface energy with the molecular structure of the surface. Principal components analysis (PCA) of the ToF‐SIMS positive spectra explained the variance in the molecular information, which was related to the resin curing and postcuring reactions with different hardeners and to the surface energy values. The first principal component captured information related to the chemical phenomena of the curing reaction path, branching, and network density based on changes in the relative ion density of the aliphatic hydrocarbon and the C₇H₇O⁺ positive ions. The second principal component captured information related to the difference in the surface energy, which was correlated to the difference in the relative intensity of the C_xH_yN_z⁺ ions of the samples. PCA of the negative spectra provided insight into the extent of consumption of the hardener molecules in the curing and postcuring reactions of both systems based on the relative ion intensity of the nitrogen‐containing negative ions and showed molecular correlations with the sample surface energy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Time‐of‐flight secondary ion mass spectrometry of wet and dry chemically treated display glass surfaces

Display glasses meet the demands of the flat panel display industry vis‐à‐vis their composition, flatness, and forming processes. Here, we report the high‐resolution time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) characterization of Corning^® EAGLE XG^®, a widely used display glass, and subsequent chemometric analyses of these data. Samples analyzed included the as‐formed glass, fracture surfaces from remelt bars, and as‐formed surfaces subsequently exposed to process‐relevant treatments, including strong acids and bases, two industrial detergents, and an atmospheric‐pressure plasma treatment. Elemental signals in the positive ion ToF‐SIMS spectra respond to surface treatments. Acidic conditions leach non‐silica components from the surfaces, while basic treatments extract these species less efficiently. The detergents leave residues of Na⁺ and K⁺. The atmospheric pressure (AP) plasma treatment had little effect on the surface composition, while the melt surface differs significantly from the bulk fracture surface. Above ca. 75 m/z, the negative ion spectra are dominated by two series of homologous cluster ions with compositions of Si_nO_2n+2Al^? and Si_mHO_2m+1H^?. The presence of these clusters suggests that analogous structures exist at the near surface regions of the samples. In a series of multivariate curve resolution (MCR) analyses, two or three MCR components captured >95% of the variance in the data for these samples.     

Comparative 13C‐NMR and matrix‐assisted laser desorption/ionization time‐of‐flight analyses of species variation and structure maintenance during melamine–urea–formaldehyde resin preparation

The preparation of an industrially used sequential formulation of a melamine–urea–formaldehyde resin was followed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and ¹³C‐NMR analysis. The analysis allowed us to identify and follow the appearance, increase, decrease, and disappearance of a multitude of chemical species during the preparation of both the initial urea–formaldehyde (UF) phase of the reaction and the subsequent reaction of melamine with the UF resin that formed. The analysis indicated that (1) the increase and decrease in the species that formed proceeded through a cycle of the formation and degradation of species occurring continuously through what appeared to be a series of complex equilibria, (2) even at the end of the reaction a predominant proportion of methylene ether bridges was still present, (3) some small proportion of methylene bridges already had formed in the UF reaction phase of the resin even under rather alkaline conditions, and (4) the addition of melamine to the UF prepolymer induced some noticeable rearrangement of methylene ether bridges to methylene bridges. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Molar mass distributions of polymers from size exclusion chromatography and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry: Methods for comparison

Equations are presented for calculating molar mass averages and molar mass distributions from matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) data and from size exclusion chromatography (SEC) data. The utility of polydispersity is examined as an indicator of the expectation of MALDI‐TOF MS mass discrimination effects. Cumulative distributions are found to be rich in information for comparing the two techniques and are easily obtained from both SEC and MALDI‐TOF MS data. Analyses of a series of narrow molar mass distribution poly(methyl methacrylate) (PMMA) standards and one polydisperse sample have been performed with both methods. MALDI‐TOF MS did not detect dimer and trimer in the PMMA samples, and it often indicated lower amounts of high‐molar‐mass polymers than did SEC. The results showed that the distribution breadth, as evidenced by the standard deviation of the distribution (calculated from the polydispersity and number‐average molar mass), correlated well with the molar mass range observed in the MALDI‐TOF MS spectra, whereas the polydispersity alone did not. Ratioing the extremes in the molar mass concentrations measured with the SEC differential refractometer, which were necessary to adequately define molar mass distributions, showed that detector dynamic range values as high as approximately 370,000 were required for the polydisperse samples. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 627–639, 2005     

One‐pot curing system of epoxy resin imines initiated with water

The curing and adhesive properties of one‐component epoxy resins containing Epikote 828 and diimines, derived from N,N′‐di(1‐ethylpropylidene)‐m‐xylylenediamine, N,N′‐di(1‐ethylpropylidene)‐1,3‐diaminomethylcyclohexane (2), and N,N′‐di(1,3‐dimethylbutylidene)‐m‐xylylenediamine, which were used as water‐initiated hardeners, were examined. Diethyl ketone‐based imines with a lower electron density on the C?N carbon were efficiently hydrolyzed and showed curing activity. 2, a novel diethyl ketone‐based diimine, served as an efficient latent hardener of the epoxy resin. A paste of the epoxy resin with 2 showed good storage stability at room temperature and good adhesive properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 878–882, 2003     

High‐performance liquid chromatography‐mass spectrometry of epoxy resins

The application of liquid chromatography coupled to mass spectrometry (LC‐MS) for the analysis of epoxy resins is shown in two examples. Electro spray (ESI) and atmospheric pressure chemical ionization (APCI) are compared with respect to the ionization of diglycidylether of bisphenol A‐based (DGEBA) epoxy resins. By‐products in a typical modified solid DGEBA‐based epoxy resin and in a new weatherable crosslinker for powder coating applications are characterized and discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 913–925, 1999     

Preparation and curing behavior of latent 2-PhIm-PS microcapsule curing agent for epoxy resin

A core–shell microcapsule latent epoxy curing agent (2-PhIm-PS) is obtained by solvent evaporation method with 2-phenyl imidazole (2-PhIm) as the core material and polystyrene (PS) as the wall material. The microcapsule parameters, morphology, structure, curing behavior, and the mechanic properties of cured epoxy resin with this microcapsule latent curing agent were characterized through comparing with 2-PhIm. The particle size distribution of the microcapsule is narrow, the average particle size is about 10.56 μm, and the core material content is 23%. The prepared 2-PhIm-PS microcapsule curing agent has excellent latent curing properties. It can completely cure epoxy resin E-51 within 10 min at 130°C, and its latent period can be more than 40 days at room temperature. In addition, the curing kinetics of one-component epoxy resin curing system (E-51/2-PhIm-PS) composed of 2-PhIm-PS microcapsules and epoxy resin E-51 is also studied by using Kissinger equation, Flynn–Wall–Ozawa and Crane formula. The results provide an outline for the evaluation on the applicability of the microcapsule curing agent of 2-PhIm-PS for epoxy resin.     

Ultraviolet‐curing behavior of an epoxy acrylate resin system

Ultraviolet (UV)‐curing behavior of an epoxy acrylate resin system comprising an epoxy acrylate oligomer, a reactive diluent, and a photoinitiator was investigated by Fourier transform infrared (FTIR) spectroscopy. The conversion changes of the resin system containing 20 phr of 1,6‐hexanediol diacrylate as a reactive diluent and 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one as a photoinitiator were measured under different UV‐curing conditions. The fractional conversion was calculated from the area of the absorption peak for the vinyl group vibration occurring at 810 cm^?1. The effects of photoinitiator concentration, total UV dosage, one‐step or stepwise UV irradiation, UV intensity, atmosphere, and temperature on the curing behavior of the resin system were investigated. The conversion of the resin system increased rapidly at the initial stage of the UV‐curing process but increased very slowly after that. The final conversion of the resin system was mainly affected by total UV dosage. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1180–1185, 2005     

Considerations on the macromolecular structure of chestnut ellagitannins by matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry

The rather novel picture of chestnut wood tannin, in situ in the wood, which emerges from matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) is that of a pervasive and extended random tridimensional macromolecular network, formed by pentagalloylglucose clusters linked to each other, to form chains and encrust the wood constituents matrix. Up to pentagalloylglucose trimers were identified in the MALDI‐TOF analysis of the commercial chestnut tannin extract, which were clearly degradation products of more extensive chains likely to be present in situ in the wood before extraction, in the network through polygallic/polyellagic chains or flavogallonic acid bridges. The hydrolyzable chestnut tannin network is capable of being extracted, to yield the commercial chestnut tannin extract exclusively by its degradation, a degradation that is possible only because of the susceptibility to hydrolysis of the ester bridges holding the network together. Internal rearrangements of the fragments formed by the extraction appear to occur readily and with ease, to yield a variety of structures characterized by the presence of ellagic acid residues, flavogallonic acid residues, and also, but less readily, nonahydroxytriphnoic acid residues. The other main constituents of the commercial tannin extract, castalagin and vescalagin, are shown to be simply the more stable degradation plus internal rearrangement products derived from the hydrolysis of polypentagalloylglucose chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 429–437, 2002     

Synthesis of rosin‐based imidoamine‐type curing agents and curing behavior with epoxy resin

Rosin is an abundantly available natural product. The characteristic fused ring structure of rosin acids is analogous to that of some aromatic compounds in rigidity, and makes rosin and its derivatives potential substitutes for those aromatic compounds. In the study reported, the synthesis of biobased curing agents containing imide structure using rosin and the cure reaction were investigated. Rosin‐based imidoamine‐type curing agents were synthesized, and the chemical structure was confirmed using ¹H NMR, Fourier transform infrared and electrospray ionization spectroscopy. The curing behavior with diglycidyl ether of bisphenol A epoxy was studied using differential scanning calorimetry. The thermal mechanical properties and thermal stability of the cured epoxy resins were evaluated using dynamic mechanical analysis and thermogravimetry, respectively. The results indicate that the curing behavior of the rosin‐based curing agents is similar to that of curing agents with analogous structures. Cured products have good thermal stability due to the presence of the imide group and the bulky hydrogenated phenanthrene ring structure. Rosin acids have a great potential in the synthesis of epoxy curing agents as replacements for some of the current commercial aromatic or cycloaliphatic analogues. Copyright © 2010 Society of Chemical Industry     

ToF‐SIMS investigation of epoxy resin curing reaction at different resin to hardener ratios

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and principal components analysis (PCA) were used to analyze diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) epoxy resin blend cured with isophorone diamine (IPD) hardener at different resin to hardener ratios. The aim was to establish correlations between the hardener concentration and the nature and progress of the crosslinking reaction. Insights into the cured resin structure revealed using ToF‐SIMS are discussed. Three sets of significant secondary ions have been identified by PCA. Secondary ions such as C₁₄H₇O⁺, CHO⁺, CH₃O⁺, and C₂₁H₂₄O₄⁺ showed variance related to the completion of the curing reaction. Relative intensities of C_xH_yN_z⁺ ions in the cured resin samples are indicative of the un‐reacted and partially reacted hardener molecules, and are found to be proportional to the resin to hardener mixing ratio. The relative ion intensities of the aliphatic hydrocarbon ions are shown to relate to the cured resin crosslinking density. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Promotion effect of bifunctional five‐membered cyclic dithiocarbonate on curing of one‐component epoxy resin by imines as latent initiator

This article deals with curing of a one‐component epoxy resin containing a bifunctional five‐membered cyclic dithiocarbonate 1 with an imine 2 as a latent initiator. When 1 was added to a mixture of epoxy resin and 2 , the curing rate and initial adhesive strength increased higher than that without 1 . It was supposed that the reaction of 1 and an amine released from 2 was much faster than the amine–epoxide reaction, and a thiol group formed by the reaction of 1 with the amine accelerated the amine–epoxide reaction. The adhesive strength of the one‐component epoxy resin containing 10 mol % of 1 exhibited the highest value. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 961–964, 2004     

B‐stage characterization of o‐cresol novolac epoxy resin system using raman spectroscopy and matrix‐assisted laser desorption/ionization mass spectrometry

The B‐stage of the o‐cresol novolac epoxy resin–phenol novolac hardener–triphenylphosphine (TPP) catalyst system was characterized using Raman spectroscopy and matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. The consistent decreasing intensities of characteristic epoxy resin peaks in MALDI mass and Raman spectra according to the melt mixing time were observed, which is due to the formation of the epoxy–phenol–TPP complex and the propagation reaction between them and with another epoxy resin. Our microscopic analysis method will provide a useful tool to control the optimum condition of the melt mixing process in the B‐stage. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1940–1946, 2000     

Adhesive properties of epoxy resin modified by end‐functionalized liquid polybutadiene

Adhesive properties of epoxy resin networks modified with different functionalized liquid polybutadiene were evaluated by using aluminum adherent. The end‐functionalized polybutadiene rubbers were hydroxyl‐ (HTPB), carboxyl‐ (CTPB), and isocyanate‐terminated polybutadiene (NCOTPB). The adhesive properties depend upon the morphology and the degree of interaction between the rubber–epoxy system. The most effective adhesive for Al–Al joint in both butt and single‐lap shear testing was epoxy resin–NCOTPB system. This system presents stronger rubber–epoxy interactions and a higher degree of rubber particle dispersion with particle size diameter in the nanoscale range. These characteristics were not important for improving the toughness of the bulk network but are fundamental for the improvement of adhesive strength. The effect of the pretreatment of the aluminum surface on the roughness was also evaluated by using profilometry analysis. The type of failure was also investigated by analyzing the adhered surfaces after fracture by scanning electron microscopy and profilometry. A proportion of cohesion failure higher than 90% was observed in all systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2370–2378, 2004     

Efficiently Detecting Metallodrug–Protein Adducts: Ion Trap versus Time‐of‐Flight Mass Analyzers

Modern mass spectrometry techniques have increasingly found use in studies on the binding of anticancer metallodrugs to potential cellular targets. In this context, investigations on the detection efficiency of adduct formation between antiproliferative Ru(arene) complexes and proteins in dependence of the mass analyzer used in the electrospray ionization (ESI) mass spectrometer are presented. The potential in detecting adducts between the metal center and the protein was found to be dependent on the mass analyzer and the denticity of the metal–protein interaction. This might be related to the design of the mass analyzers with different conditions in the ion travelling pathways, which affects adducts when the protein acts as a monodentate ligand more highly than in cases when the protein is a multidentate ligand. This could also impact the biological activity and indicate different pathways of metabolism of biomolecule adducts.     

Curing and post‐curing luminescence in an epoxy resin

A spontaneous luminescence is reported when epoxy resin samples are heated in air. This phenomenon is very sensitive to the nature of the atmosphere. The same treatment in nitrogen leads to an extinction of the luminescence. The emission process is restored when samples are kept for a sufficient time in air. To better understand this phenomenon, we have investigated the luminescence of the elementary constituents of the epoxy (resin and hardener), when heated in air and nitrogen, as well as during resin‐curing in the same atmospheres. It appears that the emission process is linked with the presence of oxygen. Although the kinetics of the luminescence can differ, depending on the nature of the sample (cured resin, resin during curing, liquid components), the emission spectra are the same during resin‐curing and upon heating of the cured resin and hardener. The emission spectrum of the base resin is different. It is concluded that the light results from a chemiluminescence process during oxidation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1899–1904, 2006     

Surface oxidation of styrene butadiene copolymers: Study by laser ablation and secondary ion mass spectrometry

The capabilities of ion bombardment and laser ablation coupled to mass spectrometry as independent techniques to investigate the surface thermooxidative stability of polystyrene, polybutadiene polymers, and styrene butadiene rubber (SBR) copolymers were investigated. Surface chemical modifications were detected according to the polymeric structure. The degradation products detected by static secondary ion mass spectrometry appeared at m/z 29, 43, and 55. Their compositions were related to the general formulae C_nH_mO⁺ with n = 1–3 and m = 1–3 for polybutadiene and styrene butadiene copolymers, whereas polystyrene was not affected by the aging treatment. The C_nH_mO⁺ ions result from butadiene unit degradation. The laser ablation ionization Fourier transform ion cyclotron resonance mass‐spectrometry results confirmed the detection of C_nH_mO⁺ ions. Finally, it may be considered that the surface thermooxidative process of SBR copolymers begins with butadiene unit degradation. The development of butadiene unit oxidation showed a dynamic oxidation phase, which coincided with a loss of unsaturation. The influence of the polymer conformation (blocked, branched, and random) on the surface oxidation for 30% styrene SBR compounds was also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1910–1917, 2003     

Superior real time method to evaluate photo‐curing resin by means of rigid‐body pendulum rheometer

The objective of this article is to establish a new method in evaluating photo‐polymerization resin reaction behavior, and to use the trends resulting from past evaluation methods and those already known to prove the feasibility of this method. Another objective is to compare the data gathered using the differential photo calorimeter (DPC) method and RPT on different photo‐polymerization resin systems to illustrate that the application of RPT on photo‐polymerization resin studies is more suitable. Experiment results show that the trends through the real time method using oxide series acrylate research through rigid‐body Pendulum Rheometer, the photo‐curing behavior under the various parameters of monomer functionality, and photo‐initiator concentration can all be observed. Comparing the DPC and RPT methods on polyester acrylate series, when the oligomer of tetra‐functional polyester acrylate is added with a different ratio of the monomer of propoxylated neopentyl‐glycol di‐acrylate, DPC evaluation methods show that the differences in observation are minimal. However, when RPT was applied, not only were the differences in reaction speed observed, but also the differences in crosslinking and other data in the hardening process when the balanced time was achieved during the oscillations procedure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3402–3407, 2006     

Ultraviolet/heat dual‐curable film adhesives with pendant‐acryloyl‐functional‐group‐modified epoxy resin

To facilitate the fabrication of a reliable semiconductor package, the UV/heat dual curing of film adhesives was investigated. The curing system of the epoxy resin affected the film adhesive properties. As the UV/heat dual‐curable epoxy resin, a modified o‐cresol novolak epoxy resin, in which half of the glycidyl groups were substituted by acryloyl groups (OCN‐AE), was applied to the film adhesive. The formulated film adhesive contained acrylic copolymer, OCN‐AE, phenolic aralkyl resin as a heat‐curing agent of the glycidyl groups, and 1‐hydroxycyclohexyl phenyl ketone as a photoinitiator of the acryloyl groups. The formulated reference film adhesive contained unmodified o‐cresol novolak epoxy resin (OCN‐E) in place of OCN‐AE. Formulated film adhesives containing a mixture of OCN‐E and o‐cresol novolak epoxy acrylate were also used as references. The morphology and the film adhesive properties were investigated. In these investigations, the film adhesive of OCN‐AE showed better adhesive properties, lower modulus, and a better stress‐relaxation ability than the referenced adhesives. As a result, a reliable film adhesive for semiconductor packages was successfully developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010