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The kinetics, thermal and mechanical properties of epoxy-polycarbonate blends cured with aromatic amine
(1998-04-01)
Lu, MS
;
Chen, JL
;
Li, YS
;
Chang, FC
;
Li, MS
PC-DER331 blends are transparent and homogeneous due to the transesterification taking place during hot melting process. This transesterification reaction does not occur or occurs insignificantly during the preparation of PC-DER332 blends. PC is separated from the PC-DER332 melt mixture by slow cooling to room temperature but the mixture remains a single phase by quenching with an ice bath. Two systems of PC-epoxy blends, PC-DER331 blends and PCDER332 blends are cured by the m-phenylene diamine (MPDA) in a stoichiometric ratio. Curing kinetics have been carried out by differential scanning calorimeter (DSC). The presence of PC accelerates the curing reaction. Infrared spectroscopy (IR) indicates the occurrence of transesterification in the PC-DER331/MPDA blends during curing. The flexural modulus increases with the increase of the PC content while the notched Izod impact strength decreases with the increase of the PC content for all the blending systems. The fracture surfaces of the PC-DER331/MPDA blends are smooth, an indication of a homogeneous morphology. The fracture surfaces of the PC-DER332/MPDA blends are rough, an indication of a heterogeneous morphology.
Polymer blends of polyamide-6 (PA6) and poly(phenylene ether) (PPE) compatibilized by a multifunctional epoxy coupler
(1998-08-01)
Chiang, CR
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A tetrafunctional epoxy monomer, N,N,N'-N' -tetraglycidyl-4,4'-diaminodiphenyl methane (TGDDM),has demonstrated to be a highly efficient reactive compatibilizer in compatibilizing the immiscible and incompatible polymer blends of polyamide-6 (PA6) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE). This epoxy coupler can react with both PA6 and PPE to form various PA6-co-TGDDM-co-PPE mixed copolymers. These interfacially formed PAG-co-TGDDM-co-PPE copolymers tend to anchor along the interface to reduce the interfacial tension and result in finer phase domains and enhanced interfacial adhesion. A simple one-step melt blending has demonstrated to be more efficient in producing a better compatibilized PA6/PPE blend than a two-step sequential blending. The mechanical property improvement of the compatibilized blend over the uncompatibilized counterpart is very drastic, by considering the addition of a very small amount, a few fractions of 1%, of this epoxy coupling agent. (C) 1998 John Wiley & Sons, Inc.
Transesterification in homogeneous poly(epsilon-caprolactone)-epoxy blends
(1999-01-03)
Chen, JL
;
Huang, HM
;
Li, MS
;
Chang, FC
;
應用化學系
Transesterification has been investigated in poly(epsilon-caprolactone) (PCL)-epoxy blends. In the hot melt process, the hydroxyl on diglycidyl ether of bisphenol-il (DGEBA) monomers is too low to give a noticeable transesterification reaction. In the postcure process, model reactions reveal that the hydroxyls from a ring-opening reaction are able to react with the esters of PCL. In the meantime, the PCL molecular weight decrease and its distribution becomes broader. Nuclear magnetic resonance spectra reveal that fraction of the tertiary hydroxyls converts to secondary hydroxyls. In the cured DGEBA-3,3'-dimethylmethylene-di(cyclohexylamine)-PCL blend, a homogeneous morphology is achieved. PCL segments are grafted onto the epoxy network after postcuring and result in the lower T-g observed in the differential scanning calorimetry thermogram. A higher transesterification extent also results in broader transition peaks by dynamic mechanical analysis. (C) 1999 John Wiley & Sons, Inc.
Synthesis, characterization, thermal and flame-retardant properties of silicon-based epoxy resins
(1999-08-15)
Hsiue, GH
;
Wang, WJ
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A new silicon-containing oxirane triglycidyl phenyl silane oxide (TGPSO) and its corresponding silicon-containing epoxy resins are synthesized and characterized. The activation energies of TGPSO curing reaction with various curing agents, including 4,4-diaminodiphenylmethane, 4,4-diaminodiphenylsulfone, and dicyanodiaminde, are found to be 180, 196.5, and 154 kJ/mol. The curing reaction of TGPSO with diamines is determined to be a first-order reaction through means of Arrhenius plots. The introduction of the silicon-containing group results in higher curing reactivity. This silicon-containing resin possesses higher char yield as well as higher limiting oxygen index (LOI = 35) than the commercial epoxy resins, confirming the usefulness of these silicon-containing epoxy resins as flame retardants. Char yields and LOI measurements demonstrate that incorporating silicon into epoxy resins is able to improve their flame retardancy. (C) 1999 John Wiley & Sons, Inc.
Kinetics and curing mechanism of epoxy and boron trifluoride monoethyl amine complex system
(1999-09-15)
Li, YS
;
Li, MS
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The kinetics of cationic polymerization of epoxy resin has been studied. Due to multiple reaction exotherms and irregular baselines involved in this system, the ASTM E 698 method was chosen to determine the kinetic parameters of this epoxy/BF3-MEA system. The DER 332/BF3-MEA system follows the first order active chain end (ACE) reaction mechanism. The adding of the hydroxyl group into the system is prone to decrease the activation energy and shifts the curing into the activated monomer (AM) mechanism due to the stronger nucleophilicity of the hydroxyl group than the epoxide group. On the other hand, the DER 331/BF3-MEA system possesses lower activation energy because the DER 331 contains more hydroxyl groups-alpha-glycol and secondary alcohol. The former is the major contributor in lowering the activation energy. The hydroxyl group also can act as a chain transfer agent by retarding the propagation process, thus the reaction rate of the DER 332/BF3-MEA system is higher than the DER 331/BF3-MEA system. The DER 332/BF3-MEA system shows good correlation between the experimental data (FT-IR, DSC, and GPC) and the simulation curve based on ASTM E 698 before gelation, while a larger deviation is observed in the DER 331/BF3-MEA system. After gelation, the hydroxyl group also acts as an active site to react with residual epoxy monomers and obtain a more condense matrix. (C) 1999 John Wiley & Sons, Inc.
In-situ measurement of the crystallization process of polycarbonate/epoxy resin by a photoresistor
(2000-03-01)
Li, YS
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The PC crystallization process is measured by the photoresistor, by which the reciprocal relationship is obtained between the illumination of transmission light and the resistance. In the beginning of annealing the change of resistance is insignificant when the crystallization is still at the induction stage. Then the increasing number and size of spherulites scatter the incoming light and the resistance increases quickly. Finally the concentration of amorphous PC decreases and the increasing rate of resistance slows down. The X-ray pattern shows an ordered PC structure of 2 theta = 11 degrees in the induction period, then converts to amorphous (broad peak at 20 degrees) and spherulite (17.2 degrees) structure. The dissolving heat of PC spherulite, analyzed by differential scanning calorimetry, shows a linear relationship to the resistance. Thus the relative crystallinity can be obtained by measuring the resistance of the photoresistor from both primary and secondary crystallization. The experimental results show good correlation to the Avrami model and the highest crystallization rate is obtained at 80 degrees C. The thermodynamic factor controls the crystallization rate at higher annealing temperature while the kinetic factor dominates the crystallization rate at lower annealing temperatures. (C) 1999 Elsevier Science Ltd. All rights reserved.
Electrostatic dissipation and flexibility of poly(oxyalkylene)amine segmented epoxy derivatives
(2000-04-01)
Lin, JJ
;
Tseng, FP
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A family of hydrophilic and flexible epoxy polymers was prepared from the reaction of poly(oxyalkylene)amines and diglycidyl ether of bisphenol-A (DGEBA) at 1:1 molar ratio of N-H to epoxide. The use of a high molecular weight (M-W = 1000-6000) poly(oxyethylene-oxypropylene)amine and a low M-W amine as curing agents provided epoxy materials with good properties in toughness and hydrophilicity. The hydrophilicity, probed by surface resistivity of these cured materials, was found to be affected by the nature and weight content of poly(oxyethylene) segment in the polymer backbone, and also by the degree of crystallinity. Specifically, in the presence of a water-soluble poly(oxyethylene-oxypropylene)diamine of M-W 2000 the cured epoxies can reach surface resistivity as low as 10(8.6-9.6) Omega/square. In comparison, the water-insoluble poly(oxypropylene) diamine of M-W 2000 afforded a higher surface resistivity of 10(10.5) Omega/square because of the difference in hydrophilicity between oxyethylene and oxypropylene functionalities. Poly(oxypropylene)diamine of M-W 230 as the sole curing agent generated an epoxy with even higher surface resistivity of 10(13) Omega/square due to a highly crosslinking structure. With proper selection of mixed poly(oxyethylene-oxypropylene)diamine (25 wt%) and 2-aminoethanol (9 wt%), the DGEBA cured polymer had an appropriate surface resistivity of 10(9.8) Omega/square for antistatics. Moreover, this material was extremely ductile in appearance and showed over 500% elongation at break during mechanical tests. The high flexibility is rationalized by the balanced chemical structure of poly(oxyalkylene) segments and bisphenol-A distributed in a slightly crosslinked system. (C) 2000 Society of Chemical Industry.
Curing kinetics and viscosity change of a two-part epoxy resin during mold filling in resin-transfer molding process
(2000-09-06)
Lee, CL
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The curing kinetics and the resulting viscosity change of a two-part epoxy/amine resin during the mold-filling process of resin-transfer molding (RTM) of composites was investigated. The curing kinetics of the epoxy/amine resin was analyzed in both the dynamic and the isothermal modes with differential scanning calorimetry (DSC). The dynamic viscosity of the resin at the same temperature as in the mold-filling process was measured. The curing kinetics of the resin was described by a modified Kamal kinetic model, accounting for the autocatalytic and the diffusion-control effect. An empirical model correlated the resin viscosity with temperature and the degree of cure was obtained. Predictions of the rate of reaction and the resulting viscosity change by the modified Kamal model and by the empirical model agreed well with the experimental data, respectively, over the temperature range 50-80 degrees C and up to the degree of cure alpha = 0.4, which are suitable for the mold-filling stage in the RTM process. (C) 2000 John Wiley & Sons, Inc.
Effect of material and process variables on the performance of resin-transfer-molded epoxy fabric composites
(2000-09-06)
Lee, CL
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The effects of material and process variables on glass fabric-reinforced epoxy composites by the resin-transfer molding (RTM) process were studied. It was found that the molded aged resin with 55% fiber exhibited twice the mold-filling time and caused a 7-15% deterioration in the interlaminar shear strength (ILSS) and in the flexural strength of the composites as compared to those of the composites molded with fresh resin. At a 55% fiber volume fraction, composites molded with aged resin resulted in a 35% longer filling time and a 4-12% decreased ILSS and flexural strength as compared to those of the composites at a 44% fiber volume fraction. Moldings with a perimeter inlet exhibited a 65% shorter mold-filling time, 28% reduced void content, and 6% improved flexural strength as compared to those of the composites molded with the center inlet. (C) 2000 John Wiley & Sons, Inc.
Temperature-dependent phase behavior in poly(epsilon-caprolactone)-epoxy blends
(2001-03-01)
Chen, JL
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The cured morphologies of poly(epsilon -caprolactone)/epoxy (PCL/epoxy) blends are examined by SEM micrographs. The phase separation mechanism of the blend can be deduced from cured morphologies influenced by the blend compositions and curing conditions. The LCST phase diagram is proposed for the system and the location of the critical point shifts with the curing temperature, which results in the change of phase separation mechanism. The curing rate promoted by higher curing temperature also influences the morphologies of the blends. The fraction of the epoxy-rich macrophase resulted from the long-distance diffusion decreases with the increase of the curing temperature. In contrast, the domain size of the epoxy microphase increases with the curing temperature, which cannot be dominated by the epoxy curing rate. (C) 2000 Elsevier Science Ltd. All rights reserved.

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