Browsing by Author "Chiou, KC"

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Compatibilization and elastomer toughening of polyamide-6 (PA6)/poly(phenylene ether) (PPE) blends
(1999-10-03)
Chiou, KC
;
Wu, SC
;
Wu, HD
;
Chang, FC
;
應用化學系
In the elastomer-modified (polyamide-6/poly(phenylene ether) (PA6/PPE) = 50/50 blends, poly(styrene-co-maleic anhydride) (SMA) was demonstrated to be an efficient reactive compatibilizer. The G1651 elastomer was shown to be an effective impact modifier to result in superior toughness and heat-deflection temperature (HDT) than is the 1901X elastomer for the SMA-compatibilized blends because G1651 particles exclusively reside within the dispersed PPE phase but 1901X particles tend to distribute in the PA6 matrix and/or along the interface. The apparent average diameter of the dispersed PPE phase is insignificantly dependent on the elastomer content in the G1651-modified blend, whereas it increases with increase of the elastomer content in the 1901X-modified blend. Moreover, there exists a critical elastomer content, 15 phr, for the ductile-brittle transition of the G1651-modified SMA-modified PA6/PPE blends. (C) 1999 John Wiley & Sons, Inc.
Effect of temperature on fracture toughness of PC/ABS based on J-integral and hysteresis energy methods
(1996-11-07)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The critical fracture toughness J(1c) of the polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend at different temperatures was obtained from ASTM E813-81, E813-87, and the recently developed hysteresis energy methods, respectively. The J(1c) value increases with increase of the test temperature ranging from -60 to 70 degrees C. The hysteresis energy method and the ASTM E813-81 method result in comparable J(1c) values, while the ASTM E813-87 results in about 80-110% higher values. The critical initiation displacements determined from the plots of hysteresis energy and the true crack growth length vs. crosshead displacement are very close. This indicates that the critical initiation displacement deter mined by the hysteresis method is indeed the displacement at the onset of true crack initiation and the corresponding J(1c) represents a physical event of crack initiation. The fracture toughness, K-1c value, based on linear elastic fracture mechanics (LEFM), was determined by using K-Q analysis (ASTM E399-78), and the obtained K-Q value decreases with the increase of the test temperature. The K-Q value is not the real LEFM K-1c value because the criterion of P-max/P-Q < 1.1 has not been satisfied. However, the corresponding J(Q) obtained from the K-Q analysis is comparable to the J(1c) obtained from the E813-81 method at lower temperature (-45 or -60 degrees C), an indication of LEFM behavior at lower temperature. The various schemes and size criterion based on LEFM and the J-method are explored for the validity of J(1c) and K-1c values. (C) 1996 John Wiley & Sons, Inc.
Effect of temperature on fracture toughness of PC/ABS based on J-integral and hysteresis energy methods
(1996-11-07)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The critical fracture toughness J(1c) of the polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend at different temperatures was obtained from ASTM E813-81, E813-87, and the recently developed hysteresis energy methods, respectively. The J(1c) value increases with increase of the test temperature ranging from -60 to 70 degrees C. The hysteresis energy method and the ASTM E813-81 method result in comparable J(1c) values, while the ASTM E813-87 results in about 80-110% higher values. The critical initiation displacements determined from the plots of hysteresis energy and the true crack growth length vs. crosshead displacement are very close. This indicates that the critical initiation displacement deter mined by the hysteresis method is indeed the displacement at the onset of true crack initiation and the corresponding J(1c) represents a physical event of crack initiation. The fracture toughness, K-1c value, based on linear elastic fracture mechanics (LEFM), was determined by using K-Q analysis (ASTM E399-78), and the obtained K-Q value decreases with the increase of the test temperature. The K-Q value is not the real LEFM K-1c value because the criterion of P-max/P-Q < 1.1 has not been satisfied. However, the corresponding J(Q) obtained from the K-Q analysis is comparable to the J(1c) obtained from the E813-81 method at lower temperature (-45 or -60 degrees C), an indication of LEFM behavior at lower temperature. The various schemes and size criterion based on LEFM and the J-method are explored for the validity of J(1c) and K-1c values. (C) 1996 John Wiley & Sons, Inc.
Elastic-plastic fracture toughness of PC/ABS blend based on CTOD and J-integral methods
(1996-09-01)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The elastic-plastic fracture toughness of a PC/ABS blend has been investigated simultaneously by the conventional J-integral and the crack tip opening displacement (CTOD) methods for specimen thickness varying from 4 to 15 mm. The critical J (J(c)) and the critical CTOD (delta(c)) are-based on crack initiation. Another new method to determine J(c) based on the close relationship between the J-integral and CTOD has also been developed. Those three critical J(c) values, J(c-81), J(c-NEW), and J(c-BS) Obtained from the ASTM E813-81, the new J method, and the equation J(c) = m sigma(y) delta(c) (1-nu(2)) of the CTOD method, are comparable and are independent of the specimen thickness. The constraint factor m evaluated from the linear elastic fracture mechanics (LEFM) approach using the Dugdale model is about 1.5. A rotation factor r(g) of approximately 2 g was obtained which is also independent of the specimen thickness. The crack propagation resistance, J-curve (dJ/da) or delta-curve (d delta/da), decreases with increasing specimen thickness. A close relationship between CTOD and J-integral has been demonstrated in this study. Copyright (C) 1996 Elsevier Science Ltd.
Fracture toughness characterization of a PC/ABS blend under different strain rates by various J-integral methods
(1996-09-01)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A published, nonconventional J-integral method, based on the hysteresis energy and the ASTM E813 methods, has been employed to test the fracture toughness of a polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend. The critical J values (J(Ic)) at crosshead speeds ranging from 0.5 to 20 mm/min obtained from the hysteresis energy method are similar to 10 to 20% higher than those obtained from the E813-81 method and similar to 50 to 70% lower than those obtained from the E813-87 method. However, the hysteresis energy method results in comparable J(Ic) values with a modified ASTM E813-87 method when the 0.2 mm offset line is replaced with a 0.1 mm offset line. The critical displacements in terms of the onset of crack initiation, determined from the plots of hysteresis energy vs. displacement, hysteresis ratio vs. displacement, and the true crack growth length vs. displacement, are fairly close in value. This indicates the critical crack initiation and the corresponding J(Ic) obtained from this hysteresis energy method indeed represent the actual physical event of the onset of crack initiation.
Fracture toughness characterization of a PC/ABS blend under different strain rates by various J-integral methods
(1996-09-01)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A published, nonconventional J-integral method, based on the hysteresis energy and the ASTM E813 methods, has been employed to test the fracture toughness of a polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend. The critical J values (J(Ic)) at crosshead speeds ranging from 0.5 to 20 mm/min obtained from the hysteresis energy method are similar to 10 to 20% higher than those obtained from the E813-81 method and similar to 50 to 70% lower than those obtained from the E813-87 method. However, the hysteresis energy method results in comparable J(Ic) values with a modified ASTM E813-87 method when the 0.2 mm offset line is replaced with a 0.1 mm offset line. The critical displacements in terms of the onset of crack initiation, determined from the plots of hysteresis energy vs. displacement, hysteresis ratio vs. displacement, and the true crack growth length vs. displacement, are fairly close in value. This indicates the critical crack initiation and the corresponding J(Ic) obtained from this hysteresis energy method indeed represent the actual physical event of the onset of crack initiation.
Fracture toughness characterizations of compatibilized polyamide-6 (PA6)/poly(phenylene ether) (PPE) blends
(2001-03-01)
Chiou, KC
;
Chang, FC
;
Mai, YW
;
應用化學系
;
Department of Applied Chemistry
Under the plane-strain condition. the material properties. K-IC and G(IC), of the blends, brittle or with small-scale yielding, increase with increasing elastomer content. To evaluate the critical J-integral for the ductile blends, several methods have been compared to understand the influence of elastomer content and different thicknesses using single-edge notch-bend specimens. For a given thickness, the Fracture toughness increases with increasing elastomer content. Moveover, the slope of the R-curve becomes gradually steeper with increasing elastomer content and decreasing specimen thickness. J(IC) values determined from ASTM E813-89 and modified ASTM E813-81 methods always give the highest and the lowest values, respectively. J(IC) values determined from three other methods are comparable and can be employed to characterize the fracture toughness of the compatibilized PA6/PPE blends. it is noted that J(IC) values determined from the modified ASTM E813-89 and the hysteresis energy methods are apparently independent of thickness Therefore, these two methods may be considered as potential alternative techniques to evaluate the critical J-integral for toughened polymer blends.
Impact specific essential work of fracture of compatibilized polyamide-6 (PA6)/poly(phenylene ether) (PPE) blends
(2001-06-01)
Chiou, KC
;
Chang, FC
;
Mai, YW
;
應用化學系
;
Department of Applied Chemistry
The essential work of fracture (EWF) method has aroused great interest and has been used to characterize the fracture toughness for a range of ductile metals, polymers and composites. In the plastics industry, for purposes of practical design and ranking of candidate materials, it is important to evaluate the impact essential work of fracture at high-rate testing of polymers and polymer blends. In this paper, the EWF method has been utilized to determine the high-rate specific essential fracture work, w(e) for elastomer-modified PA6/PPE/SXM (50/50/5) blends by notched Charpy tests. It is found that w(e) increases with testing temperature and elastomer content for a given specimen thickness. Morphologically, there are two failure mechanisms: shear yielding and pullout of second phase dispersed particles. Shear yielding is dominant in ductile fracture, whereas particle pullout is predominant in brittle fracture.
In situ compatibilized polypropylene/liquid crystalline polymer blends
(1996-09-01)
Chiou, YP
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Ethylene-glycidyl methacrylate copolymer (EGMA) has been investigated as a reactive compatibilizer for the immiscible and incompatible blends of polypropylene (PP) and a liquid crystalline polymer (LCP). The epoxy functional groups of the EGMA copolymer can react with the carboxylic acid and/or hydroxyl end-groups of the liquid comptalline copolyester. The in situ-formed EGMA-g-LCP copolymer tends to reside along the interface of the PP-LCP and reduces the interfacial tension during melt processing. The compatibilized PP/LCP blends show finer disperse LCP domains and tend to shift the LCP fibrous structure near the skin region of the uncompatibilized blends into the droplet domains. The PP crystallinity in the compatibilized PP/LCP blends is lower than that of the corresponding uncompatibilized blends due to interference in the PP crystallization by the in situ-formed EGMA-g-LCP copolymers. The lower PP crystallinity of the compatibilized blends is reflected in a substantial reduction in stiffness (in terms of the tensile modulus). However, the improved adhesion of the compatibilized blends results in an improvement in the toughness (in terms of the tensile elongation and impact strength). Copyright (C) 1996 Elsevier Science Ltd.
Precrack hysteresis energy in determining polycarbonate ductile-brittle transition .4. Effect of strain rate
(1997-07-25)
Chiou, KC
;
Hsu, HC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Effect of deformation rate on the ductile-brittle transition behavior for polycarbonate (PC) with different molar mass, notch radius, and rubber content has been investigated. PC with higher molar mass, notch radius, or rubber-modification possesses a higher critical strain rate when the ductile-brittle transition occurs. Whether a notched specimen will fail in a ductile mode or a brittle mode is already decided before the onset of the crack initiation. If size of the precrack plastic zone exceeds a critical level prior to onset of crack initiation, the crack extension developed later will propagate within the plastic zone and result in a ductile mode fracture. The precrack elastic storage energy, the input energy subtracting the hysteresis energy, is the main driving force to strain the crack tip for crack initiation. The precrack hysteresis energy (directly related to the precrack plasticity) increases with the decrease of the applied strain rate. Therefore, the strain rate is also closely related to the size of the precrack plastic zone. If the strain rate is lower than the critical strain rate, the specimen is able to grow a precrack plastic zone exceeding the critical plastic zone and results in a ductile mode fracture. (C) 1997 John Wiley & Sons, Inc.
Precrack hysteresis energy in determining polycarbonate ductile-brittle transition .4. Effect of strain rate
(1997-07-25)
Chiou, KC
;
Hsu, HC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Effect of deformation rate on the ductile-brittle transition behavior for polycarbonate (PC) with different molar mass, notch radius, and rubber content has been investigated. PC with higher molar mass, notch radius, or rubber-modification possesses a higher critical strain rate when the ductile-brittle transition occurs. Whether a notched specimen will fail in a ductile mode or a brittle mode is already decided before the onset of the crack initiation. If size of the precrack plastic zone exceeds a critical level prior to onset of crack initiation, the crack extension developed later will propagate within the plastic zone and result in a ductile mode fracture. The precrack elastic storage energy, the input energy subtracting the hysteresis energy, is the main driving force to strain the crack tip for crack initiation. The precrack hysteresis energy (directly related to the precrack plasticity) increases with the decrease of the applied strain rate. Therefore, the strain rate is also closely related to the size of the precrack plastic zone. If the strain rate is lower than the critical strain rate, the specimen is able to grow a precrack plastic zone exceeding the critical plastic zone and results in a ductile mode fracture. (C) 1997 John Wiley & Sons, Inc.
Reactive compatibilization of polyamide-6 (PA 6)/polybutylene terephthalate (PBT) blends by a multifunctional epoxy resin
(2000-01-01)
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A multifunctional epoxy resin has been demonstrated to be an efficient reactive compatibilizer for the incompatible and immiscible blends of polyamide-6 (PA 6) and polybutylene terephthalate (PBT). The torque measurements give indirect evidence that the reaction between PA and PET with epoxy has an opportunity to produce an in situ formed copolymer, which can be as an effective compatibilizer to reduce and suppress the size of the disperse phase, and to greatly enhance mechanical properties of PA/PBT blends. The mechanical property improvement is more pronounced in the PA-rich blends than that in the PET-rich blends. The fracture behavior of the blend with less than 0.3 phr compatibilizer is governed by a particle pullout mechanism, whereas shear yielding is dominant in the fracture behavior of the blend with more than 0.3 phr compatibilizer. As the melt and crystallization temperatures of the base polymers are so close, either PA or PET can be regarded as a mutual nucleating agent to enhance the crystallization on the other component. The presence of compatibilizer and in situ formed copolymer in the compatibilized blends tends to interfere with the crystallization of the base polymers in various blends. (C) 2000 John Wiley & Sons, Inc.
Reactive compatibilization of the poly(ethylene terephthalate) liquid crystalline polymer blends by solid epoxy resin as a coupling agent
(1996-06-27)
Chin, HC
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A selected reactive coupling agent can be served as an effective compatibilizer for certain immiscible and incompatible blends should both blend constituents possess the necessary functional groups that can react with the coupling agent at comparable rates. Solid epoxy resin with two epoxide endgroups per molecule was demonstrated to be an efficient reactive compatibilizer for the incompatible blends of poly(ethylene terephthalate) (PET) and co-polyester liquid crystalline polymer (LCP) by functioning as a coupling agent. The main chain structure of the epoxy resin is neither identical nor miscible with PET and LCP and tends to reside at interface during melt mixing. This preferential residence gives the epoxy compatibilizer greater opportunity to react with both PET and LCP simultaneously to produce the in situ-formed epoxy-b-PET-b-LCP mixed copolymer. This in situ-formed mixed copolymer is highly effective in compatibilizing the PET/LCP blends. This reactive epoxy compatibilizer enhances the LCP fibril formation and results in substantial improvements on stiffness and toughness of the PET/LCP blends. (C) 1996 John Wiley & Sons, Inc.
Reactive compatibilization of the poly(ethylene terephthalate) liquid crystalline polymer blends by solid epoxy resin as a coupling agent
(1996-06-27)
Chin, HC
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A selected reactive coupling agent can be served as an effective compatibilizer for certain immiscible and incompatible blends should both blend constituents possess the necessary functional groups that can react with the coupling agent at comparable rates. Solid epoxy resin with two epoxide endgroups per molecule was demonstrated to be an efficient reactive compatibilizer for the incompatible blends of poly(ethylene terephthalate) (PET) and co-polyester liquid crystalline polymer (LCP) by functioning as a coupling agent. The main chain structure of the epoxy resin is neither identical nor miscible with PET and LCP and tends to reside at interface during melt mixing. This preferential residence gives the epoxy compatibilizer greater opportunity to react with both PET and LCP simultaneously to produce the in situ-formed epoxy-b-PET-b-LCP mixed copolymer. This in situ-formed mixed copolymer is highly effective in compatibilizing the PET/LCP blends. This reactive epoxy compatibilizer enhances the LCP fibril formation and results in substantial improvements on stiffness and toughness of the PET/LCP blends. (C) 1996 John Wiley & Sons, Inc.