Fracture behavior–morphology relationships in an unsaturated polyester resin modified with a liquid oligomer

An unsaturated polyester (UP) resin modified with a liquid polymer, polyoxypropylenetriamine (POPTA), at a concentration of 10 wt% has been precured at several temperatures. Phase separation takes place before gelation at all precure temperatures used. The glass‐transition region has been analyzed by dynamic mechanical analysis. Mechanical properties have been related to microstructural features. With a precure temperature fixed, the unsaturated polyester (UP) resin has also been modified with different contents of POPTA. Fracture toughness of the mixtures has also been analyzed and results are compared to those for the unmodified mixture. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1677–1685, 1999     

Analysis of blends of poly(styrene‐co‐acrylonitrile) with an epoxy/aromatic amine resin using scanning thermal microscopy

Using a microthermal analyzer TA Instruments 2990 μTA, we have analyzed the morphologies developed for the resin tetraglycidyl‐4,4′‐diaminodiphenylmethane cured with an aromatic amine 4,4′‐diaminodiphenylsulphone modified with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic. The phase‐separation phenomenon induced by polymerization was also followed by scanning electron microscopy. Using the modulated local thermal‐analysis mode of μTA, the glass‐transition temperatures of different domains for each sample were evaluated. Dynamic mechanical analyzer experiments were made to evaluate the macroscopic thermal properties of the blends. A morphology was well established for all blends examined with these techniques showing a nodular structure, the epoxy‐rich phase, and a continuous phase, the SAN‐rich phase, that forms the matrix. From both microscopic and macroscopic thermal analyses, it is concluded that a phase separation exists for the blends investigated. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 284–289, 2002     

4-苯乙炔苯酐封端聚酰亚胺树脂的合成与性能研究

使用3,3′,4,4′-二苯醚四酸二酐(ODPA)、3,3′,4,4′-联苯四酸二酐(BPDA)、1,3-双(4-氨基苯氧基)苯(1,3,4-APB)、3,4′-二氨基二苯醚(3,4′-ODA)和反应性封端剂4-苯乙炔苯酐(4-PEPA)合成了设计分子量为5000的系列苯乙炔基封端的聚酰亚胺低聚物,并使用XRD、DSC、TGA、FT-IR、DMA和流变仪等对低聚物的化学结构、热性能和熔体性能,固化后树脂的热性能和力学性能进行了测试.研究结果表明基于ODPA的低聚物具有低的熔体粘度和良好的熔体粘度稳定性,固化后的树脂具有很高的热失重温度,较高的玻璃化转变温度以及良好的力学性能尤其是高的断裂伸长率(>10%);基于BPDA的低聚物具有一定的结晶性,其结晶熔融温度与苯乙炔基固化交联温度相近,影响了材料的成型工艺性能.     

Blends of an epoxy thermosetting polymer with aromatic liquid-crystalline polyesters

A series of aromatic liquid-crystalline polyesters with different composition have been synthesized to adjust transition temperatures and molecular weight. Miscibility of polyesters with bisphenol-A-diglycidyl ether (DEGBA), 4,4′-methylene-bis(3-chloro-2,6-dimethylaniline) (MCDEA) and the influence on transition temperatures has been studied. Miscibility of binary and ternary mixtures was found over the whole range of composition depending on the temperature. Thermoset formation by curing of LC-polyester / DEGBA / MCDEA mixtures containing different amounts of polyester resulted in reaction-induced phase separation with polyester content from 30 to 50 wt.%. Cloud point techniques, scanning electron microscopy (SEM) and dynamic mechanical thermal analysis (DMTA) have been applied.     

Tannic acid: A sustainable crosslinking agent for high glass transition epoxy materials

Epoxy thermosets have revolutionized the coating, adhesive, and composite industries but the chemicals from which they are synthesized have significant effects on the environment and human health not only precure but also after crosslinking has occurred. In this study, we propose tannic acid (TA) as an alternative epoxy hardening agent for commercially available epoxy resin, the diglycidyl ether of bisphenol A (DGEBA). The resulting thermosets were characterized by Fourier transform infrared spectroscopy, optical microscopy, dynamic mechanical analysis, differential scanning calorimetry, compression testing, and thermogravimetric analysis. The results from this study showed that at temperatures above 100 °C, the compatibility of TA in DGEBA was significantly increased for loading levels up to 37% weight of TA in DGEBA, something that has not been seen before in literature. It was also discovered that at high loading levels, the resulting materials had glass transition temperatures at and above 200 °C. The resulting material was proposed as a more sustainable alternative to amine or acid hardened epoxy thermosets and was particularly useful in high‐temperature applications. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1468–1480     

Highly regioselective hydroaminomethylation of terminal olefins to linear amines using Rh complexes with a Tetrabi phosphorus ligand

A highly regioselective hydroaminomethylation of terminal olefins catalyzed by Rh complexes with 2, 2′, 6, 6′‐tetrakis ((diphenylphosphino)methyl)‐1, 1′‐biphenyl (Tetrabi) ligand has been developed. Up to 99 % amine selectivity, 168 linear/branched amine product ratio (n/i), and 97.4 % linear amine yield has been obtained at a substrate/rhodium precursor ratio (S/Rh) of 1000 with this methodology. The turnover number was achieved 6930 at 10000 S/Rh ratio, and the n/i can reach up to >525. Several different olefins and secondary amines have been applied successfully with high chemoselectivity (99 %), yield (>98 %), and regioselectivity (>120).     

Curing properties of novel curing agent based on phenyl bisthiourea for an epoxy resin system

Phenyl bisthioureas: 4,4′-(bisthiourea)diphenylmethane (DTM), 4,4′-(bisthiourea)diphenyl ether (DTE), and 4,4′-(bisthiourea)diphenyl sulfone (DTS) were synthesized and used as curing agents for the epoxy resin diglydicyl ether bisphenol A (DGEBA). Synthesized phenyl bisthioureas were characterized using FT-IR and ¹H-NMR analysis. For comparison studies the epoxy system was also cured using the conventional aromatic amine 4,4′-diaminodiphenyl ether (DDE). Curing kinetics of epoxy/amine system was studied by dynamic and isothermal differential scanning calorimeter (DSC). Curing kinetic was evaluated based on model-free kinetics (MFK) and ASTM E 698 model, and the activation energy was compared with DDE. Curing system of phenyl bisthiourea link (DGEBA/DTM, DGEBA/DTE, and DGEBA/DTS) shows two exothermic peaks, while that of the conventional aromatic amines showed only a single peak. The initial exothermic peak is due to the primary nitrogen of the thiourea group, and the exotherm at higher temperature is due to the presence of thiourea groups. Glass transition temperature (T _g) of DGEBA/DTM, DGEBA/DTE, and DGEBA/DTS cured resins were lowered by 323 K when compared to the widely used diaminodiphenyl ether (DDE) cured resin. Oxidation induction temperature measurement performed on DSC suggests that the DGEBA/DTM, DGEBA/DTE, and DGEBA/DTS system cured resins has better oxidative stability when compared to cured DGEBA/DDE resin system.     

Synthesis and characterisation of epoxy-novolac/bismaleimide networks

Epoxy-novolac resin was modified with 1,1^′-(methylenedi-4,1-phenylene) bismaleimide (BMI), and cured with an aromatic amine. Cure behaviour of these blends was studied using differential scanning calorimetry (DSC). The thermograms indicated a unimodal exothermic peak for blends containing lower percentage of BMI. The cured blends showed much higher glass transition temperatures than that of the unmodified epoxy. Thermal stability of the cured epoxy resin was also improved with BMI addition. A homogeneous structure (with no phase separation) of the blends was confirmed both by DSC analysis and scanning electron microscopy (SEM).     

High resolution solid‐state 13C‐NMR study of as‐cured and irradiated epoxy resins

This article presents the effects of strong ionizing radiations on the physico‐chemical modifications of aliphatic or aromatic amine‐cured epoxy resins based on diglycidyl ether of bisphenol A (DGEBA). Such epoxy resins have a considerable number of applications in the nuclear industrial field and are known to be very stable under moderate irradiation conditions. Using extensively high resolution solid‐state ¹³C‐NMR spectroscopy we show that the aliphatic amine‐cured resin (DGEBA‐TETA) appears much more sensitive to gamma rays than the aromatic amine‐cured one (DGEBA‐DDM). On the one hand, qualitative analyses of the high resolution solid‐state ¹³C‐NMR spectra of both epoxy resins, irradiated under similar conditions (8.5 MGy), reveal almost no change in the aromatic amine‐cured resin whereas new resonances are observed for the aliphatic amine‐cured resin. These new peaks were interpreted as the formation of new functional groups such as amides, acids and/or esters and to alkene groups probably formed in the aliphatic amine skeleton. On the other hand, molecular dynamics of these polymers are investigated by measuring the relaxation times, T_CH, T_1ρH and T_1C , before and after irradiation. The study of relaxation data shows the formation, under irradiation, of a more rigid network, especially for the aliphatic amine‐cured system and confirms that aromatic amine‐cured resin [DGEBA‐4,4′‐diaminodiphenylmethane(DDM)] is much less affected by ionizing radiations than the aliphatic amine‐cured resin [DGEBA‐triethylenetetramine(TETA)]. Moreover, it has been shown that the molecular modifications generated by irradiation on the powder of the aliphatic‐amine‐cured resin appear to be homogeneously distributed inside the polymers as no phase separations can be deduced from the above analyses. Copyright © 2001 John Wiley & Sons, Ltd.     

Reactivity of common functional groups with urethanes: Models for reactive compatibilization of thermoplastic polyurethane blends

Two model urethane compounds, dibutyl 4,4′‐methylenebis(phenyl carbamate) (BMB) and dioctyl 4,4′‐methylenebis(phenyl carbamate) (OMO) were prepared by capping 4,4′‐methylenebis(phenyl isocyanate) with n‐butanol and n‐octanol, respectively. The reactions of the two model urethane compounds with several small monofunctional compounds as well as two model poly(ethylene glycols) were carried out with neat mixtures at elevated temperatures. The ranking of reactivity of the functional groups with the urethanes was determined as follows—primary amine > secondary amine ? hydroxyl ～ acid ～ anhydride ? epoxide. Nuclear magnetic resonance spectroscopy (NMR) was used for the quantitative analysis. Fourier transform infrared spectroscopy was used to complement the NMR analysis. Conversions of carbamate in each reaction were monitored over time at constant temperature (200 °C). The reactions between OMO and primary amine were conducted at 170, 180, 190, and 200 °C and best described with a second‐order bimolecular reaction model. The rate constant was estimated to be 1.8 × 10^?3 L · mol^?1 · s^?1 and activation energy 115 kJ · mol^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2310–2328, 2002     

Influence of substrate chemistry and the network homogeneity of ultra‐thin cross‐linked polymer films cured at their surface on the main relaxations temperatures probing by microthermal analysis

Thin 200‐nm epoxy–amine mixtures were cured on silicon wafers with different surface chemistry to quantify the effect of the chemistry on the glass transition temperature evolution in ultra‐thin thermosetting films. Two surface treatments were investigated: the first one only consisted in the activation of the silanols groups at the silicon surface, whereas the second one consisted in the grafting 3‐aminopropyltrimethoxysilane (APTMS) monolayer on the silicon wafers. The epoxy films were deposited on these chemistry modified wafers by spin coating a toluene solution of DGEBA–amine mixture at stoichiometric ratio. The same cure processing was used for both samples. Thin films were analysed not only using microthermal and thermomechanical analysis to determine the relaxation transitions temperatures of these films but also using FTIR in infrared reflection absorption spectroscopy mode to determine the curing rate of these networks. It was found that all these thin films showed two different glass transitions, the first one at 96 °C and was independent of the surface treatments, whereas the second one increasing from 142 °C for the oxidised wafers surface to 167 °C for the aminosilane grafted on the silicon wafer. The substrate chemistry extent on the film network structure, the interfacial bonds and interactions are discussed. This work also illustrates the interest in using microthermal analysis to obtain relevant temperature glass transition of thin film at sub‐micrometre scale, strongly dependant of local structure and chemistry composition. Copyright © 2009 John Wiley & Sons, Ltd.     

Selected fluorosubstituted phenyltolanes with a terminal group: NCS,CN, F,OCF3 and their mesogenic and dielectric properties and use for the formulation of high birefringence nematic mixtures to GHz and THz applications

Thirty laterally fluorosubstituted new 4-isothiocyanato-, 4-cyano-, 4-fluoro- and 4-(1,1,1-trifluorometoxy)-4′-(4-alkylphenyl)tolanes have been synthesised and their phase transition temperatures and enthalpies and electric permittivity have been measured. These data have been analysed together with data for earlier prepared similar compounds and with recently prepared analogously substituted 4″-alkyl-terphenyls. It was shown that some di-, tri- and tetra-fluorosubstituted 4-isothiocyanato- and 4-cyano-4′-(4-alkylphenyltolanes) are very useful components for the formulation of high birefringence (Δn up to 0.5 measured at 589 nm) and large temperature range nematic mixtures for photonic applications, especially in the infra-red, GHz and THz range of electromagnetic radiation. Three ways of formulation of high birefringence mixtures were proposed.     

Quaternary ammonium polymers from 1,4-diaza[2.2.2]bicyclooctane

Menschutkin reactions of 1,4-diaza[2.2.2]bicyclooctane with various α,α-dibromoalkanes and α,α′-dibromoxylenes have been studied in two solvent systems and at different temperatures. It was found that quaternary ammonium polymers could easily be prepared from this rigid, bicyclic, ditertiary amine.     

Low-birefringence liquid crystal mixtures for photonic liquid crystal fibres application

ABSTRACT

Series of low-birefringence liquid crystal mixtures composed of alkyl alkylbicyclohexyl carbonates and modified mixtures with other compounds have been formulated, their refractive indices and electric permittivity measured upon temperature. They exhibit the ordinary refraction index n_o lower than the refractive index of silica glass in a different range of temperature. This enables to observe in photonic liquid crystal fibres (PLCFs) a change in the light propagation mechanism from photonic band gap guiding to modified total internal reflection at different temperatures. Selected applications of PLCFs are also discussed.     

Evolution of structure and properties of a liquid crystalline epoxy during curing

The evolution of structure, and thermal and dynamic mechanical properties of a liquid crystalline epoxy during curing has been studied with differential scanning calorimetry (DSC), polarized optical microscopy, x-ray scattering, and dynamic mechanical analysis. The liquid crystalline epoxy was the diglycidyl ether of 4,4′-dihydroxy-α-methylstilbene (DGEDHMS). Two curing agents were used in this study: a di-functional amine, the aniline adduct of DGEDHMS, and a tetra-functional sulfonamido amine, sulfanilamide. The effects of curing agent, cure time, and cure temperature have been investigated. Isothermal curing of the liquid crystalline epoxy with the di-functional amine and the tetra-functional sulfonamido amine causes an increase in the mesophase stability of the liquid crystalline epoxy resin. The curing also leads to various liquid crystalline textures, depending on the curing agent and cure temperature. These textures coarsen during the isothermal curing. Moreover, curing with both curing agents results in a layered structure with mesogenic units aligned perpendicular to the layer surfaces. The layer thickness decreases with cure temperature for the systems cured with the tetra-functional curing agent. The glass transition temperature of the cured networks rises with increasing cure temperature due to the increased crosslink density. The shear modulus of the cured networks shows a strong temperature dependence. However, it does not change appreciably with cure temperature. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2363–2378, 1997     

One‐Pot Synthesis and Characterization of Some New Types of 5,5′‐Disubstituted Bis(imidazolidine‐2,4‐diones)

The synthesis and structural elucidation of some novel 5,5′‐disubstituted spiro and nonspiro‐bis‐hydantoins are reported. The Bucherer Burge's method has been modified for the preparation of some 5,5′‐substituted bis(imidazolidine‐2,4‐dione) derivatives starting with diketones ( 1–5 ) and dialdehydes ( 6 , 7 ). In some cases, diastereoisomeric mixtures of compounds were obtained. The resulting bis‐hydantoins ( 8–11 , 13 , 14 ) have not to our knowledge been previously reported in the literature.     

Synthesis and properties of conjugated enyne polysulfones

High-molecular-weight polysulfones that contained 1,3-enyne linkages in the polymer backbone were prepared by the reaction of potassium salts of (E)-1,3-bis(3-hydroxyphenyl)-1-buten-3-yne and 4,4′-dihydroxybiphenyl with 4,4′-dihalodiphenylsulfones in DMSO-sulfolane solvent mixtures. The polymers were soluble in methylene chloride and exhibited intrinsic viscosities as high as 0.74 (in DMAC at 30°C) with glass transition temperatures ranging from 179 to 214°C. It was postulated that on heating the polymers would cure via a intramolecular cycloaddition reaction to from a 2-phenylnaphthalene fused ring system along the polymer backbone. Thermal analytical data studies on cured polymer films and investigations of the products obtained from the thermal reactions of model compounds indicated that the primary curing reaction was intermolecular rather than intramolecular in nature. Additional data from testing fabricated composites indicated that the enyne polysulfones have suitable properties for use as high-temperature thermoplastic composite materials.     

Reaction‐induced phase separation in epoxy/polysulfone/poly(ether imide) systems. I. Phase diagrams

Epoxy–aromatic diamine formulations are simultaneously modified with two immiscible thermoplastics (TPs), poly(ether imide) (PEI) and polysulfone (PSF). The epoxy monomer is based on diglycidyl ether of bisphenol A and the aromatic diamines (ADs) are either 4,4′‐diaminodiphenylsulfone or 4,4′‐methylenebis(3‐chloro 2,6‐diethylaniline). The influence of the TPs on the epoxy–amine kinetics is investigated. It is found that PSF can act as a catalyst. The presence of the TP provokes an increase of the gel times. Cloud‐point curves (temperature vs. composition) are shown for epoxy/PSF/PEI and epoxy/PSF/PEI/AD initial mixtures. Phase separation conversions are reported for the reactive mixtures with various TP contents and PSF/PEI proportions. On the basis of phase separation and gelation curves, conversion–composition phase diagrams at constant temperature are generated for both systems. These diagrams can be used to design particular cure cycles to generate different morphologies during the phase separation process, which is discussed in the second part of this series. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3953–3963, 2004     

Dielectric Properties of Hyperbranched Polyesteramide with Long Alkyl Chain End Groups

Summary: Hyperbranched polyesteramides were prepared using phethalic anhydride (Ph An) or maleic anhydride (M An) as an A₂ monomer and diethanol amine (DEA) as B′B₂ monomer. Bulk condensation technique was used to synthesize polymers with both OH and modified polymers with long alkyl chain end groups. The prepared polymers were characterized using ¹H-NMR, FTIR and TGA. Solution viscosity for hyperbranched polyester amide with hydroxyl end groups was measured as well. Dielectric and electric properties of the modified samples were investigated over a range of frequency and temperatures. No relaxation peak is noticed in the dielectric spectrum ε(ν) at various temperatures. The illustration of the imaginary part of the electric modulus M″ versus frequency shows a peak which is shifted towards higher frequency in increasing temperature.     

Thermal Behavior of Bismaleimide-Amine/Vinyl Ester Resin-Styrene Blends

Abstract

Curing of 4,4′-bismaleimido-diphenyl methane-4,4′ -diaminodi-phenyl methane (1:0.3 molar ratios) (BM-A) was carried out in the presence of vinyl ester-styrene resin. The BM-A could be cured at lower temperatures. The char yields of the cured resins depended on the percentage of bismaleimide-amine in the blend.