Browsing by Author "CHANG, FC"

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A NEW APPROACH IN J-INTEGRAL METHOD BASED ON HYSTERESIS ON DUCTILE POLYMERIC MATERIALS
(1992-04-05)
LEE, CB
;
LU, ML
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
BLENDS OF POLYCARBONATE AND POLYACETAL
(1991)
CHANG, FC
;
YANG, MY
;
WU, JS
;
交大名義發表
;
應用化學系
Immiscible blends of polycarbonate (PC) and polyacetal (polyoxymethylene, POM) were investigated through rheological measurements, tensile, impact, TEM, SEM, FTi.r. and thermal analysis. The large difference in melt viscosities between these two matrix polymers makes this blending system extremely difficult to process and results in partial thermal degradation of POM. The formation of a strong interpenetrating interface in PC/POM blends significantly raises tensile yield strength, modulus and heat distortion temperature above the average values for the individual polymers. Thermoplastic polyurethane elastomer is not very efficient in toughening PC/POM blends because the elastomer distributes selectively in the PC phase. The rheological morphologies of the blends are interpreted through TEM and SEM photomicrographs.
BLOCK COPOLYETHERESTERS .3. PREPARATION OF BLOCK COPOLYETHERESTERS BY A TEREPHTHALIC ACID PROCESS IN THE PRESENCE OF SALTS
(1995-01-01)
CHANG, SJ
;
CHANG, FC
;
TSAI, HB
;
應用化學系
;
Department of Applied Chemistry
The block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolyetheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.
COEXISTENCE OF DUCTILE, SEMI-DUCTILE, AND BRITTLE FRACTURES OF POLYCARBONATE
(1992-03-25)
CHANG, FC
;
CHU, LH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The ductile-brittle transition behavior of polycarbonate and methylmethacrylate-butadiene-styrene (MBS) elastomer modified polycarbonate has been investigated in terms of notch radius and temperature. At -40-degrees-C and 21-mil notch radius, polycarbonate fractures in three possible modes, ductile (25%), semi-ductile (50%), and brittle (25%). This semi-ductile mode fracture has never been reported previously with brittle characterization, but to a greater extent in localized shear yielding on the fracture surface and intermediate toughness. A two-dimensional fracture mode diagram in terms of temperature and notch radius has been constructed to interpret the observed phenomena. This diagram can also predict the existence of other conditions under which the triplet fracture modes may also occur. Another unstable zone has also been identified where the fracture occurs in either ductile mode or brittle mode over a broad temperature range, instead of the narrow temperature range typically observed for polycarbonate. A model based on the excessive precrack strain just below yielding due to the greater notch radius is proposed to explain such observed semi-ductile mode fracture.
COEXISTENCE OF DUCTILE, SEMIDUCTILE, AND BRITTLE FRACTURES OF ELASTOMER-MODIFIED POLYCARBONATES
(1995-05-02)
LIU, WB
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
Phenomenologically, coexistence of ductile, semiductile, and brittle fractures in an apparently identical impact testing condition for the elastomer-modified polycarbonates containing a sharper notch and at high test temperatures has been found. At the ductile-brittle transition temperature, approximately 10% of specimens fractured in the semiductile mode with impact strength about the average of the ductile and brittle modes. The fracture surface of this semiductile mode shows ductile tearing flow in the plane-stress regions near the edges and brittle crack in the plane-strain central region. This unusual semiductile fracture occurs only on the thicker specimens with a sharper notch where clear plane-stress and plane-strain are present. (C) 1995 John Wiley and Sons, Inc.
DETERMINATION OF J(C) FOR A POLYCARBONATE (PC) POLY(BUTYLENE TEREPHTHALATE) (PBT) BLEND-BASED ON THE ANALYSES OF MULTIPLE-SPECIMEN J-R CURVES
(1995-11-01)
LU, ML
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
Various regression models and data windows have been used to examine the multiple-specimen J integral analysis to provide the best estimate of fracture toughness. The linear regression model (similar to ASTM E813-81) results in the least accuracy in the data fitting and is highly sensitive to the data window. The power law model (similar to ASTM E813-87) gives a better data fitting and is less sensitive to the data window. The polynomial regression models with higher orders (n = 3 and 4) give the best data fitting. True crack initiation occurs gradually rather than as an abrupt event, and therefore the critical J strictly based on initiation could be in error. ASTM E813-81 based on the theoretically predicted blunting line tends to give an underestimated J(c). The power law approach of ASTM E813-87 indeed provides a better data fitting but suffers the disadvantage of an overestimated J(c) owing to the 0.2 mm offset line. The 0.1 mm offset line approach proposed here results in the most consistent J(c) regardless of the regression models and data windows selected.
DUCTILE BRITTLE TRANSITION BEHAVIOR OF POLYCARBONATE - EFFECT OF MOLECULAR-WEIGHT, TEMPERATURE, STRAIN RATE, AND ELASTOMER
(1989-04-09)
CHANG, FC
;
CHU, LH
;
應用化學系
;
Department of Applied Chemistry
EFFECT OF POLYCARBONATE MOLECULAR-WEIGHT ON POLYMER BLENDS OF POLYCARBONATE AND ABS
(1993-11-20)
WU, JS
;
SHEN, SC
;
CHANG, FC
;
交大名義發表
;
應用化學系
The melt viscosity of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends relative to PC is significantly lower, even lower than that of pure ABS in some compositions. Annealing above the T(g) of PC coalesces and coarsens phase structure in core and skin regions. Increase in the molecular weight of PC in PC/ABS blends results in low-temperature fracture toughness improvement but suffers from the disadvantage of higher melt viscosity. The selection of PC in PC/ABS blends must be a compromise between the toughness advantages of higher PC molecular weight and the disadvantages of higher melt viscosity. (C) 1993 John Wiley & Sons, Inc.
EFFECT OF POLYCARBONATE MOLECULAR-WEIGHT ON PRECRACK HYSTERESIS ENERGY IN DETERMINING ITS DUCTILE-BRITTLE TRANSITION
(1991-09-20)
CHANG, FC
;
HSU, HC
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The distinctive ductile-brittle transition behavior of pseudoductile polymeric materials such as polycarbonate (PC) has been discovered to be closely related to the precrack hysteresis loss energy. The higher molecular weight (MW) PC with higher ductility also results in higher precrack hysteresis energy and therefore greater precrack plastic volume under condition of constant loads. If the precrack plastic volume exceeds a critical value, crack initiation thereafter will propagate within the domain of the plastic zone and results in ductile fracture. The deformation displacement is closely related to the precrack plastic volume, and the critical displacement actually determines the critical plastic volume. The higher molecular weight polycarbonate with higher entanglement density is able to withstand earlier crack initiation more effectively. Toughening plastics, such as rubber modification, is simply the result of delaying or retarding the crack initiation and allows the precrack plastic zone to grow over its critical value. A model of crack criterion based on precrack plastic zone is proposed to interpret the ductile-brittle transition phenomenon.
EFFECT OF PRECRACK PLASTIC ZONE ON PSEUDODUCTILE MATRICES DUCTILE-BRITTLE TRANSITION
(1990-04-22)
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
EFFECT OF RUBBER CONTENT IN ACRYLONITRILE-BUTADIENE-STYRENE AND ADDITIONAL RUBBER ON THE POLYMER BLENDS OF POLYCARBONATE AND ACRYLONITRILE-BUTADIENE-STYRENE
(1994)
WU, JS
;
SHEN, SC
;
CHANG, FC
;
交大名義發表
;
應用化學系
Higher ABS rubber content in the polycarbonate (PC)/acrynitrile-butadiene-styrene (ABS) blend resulted in toughness improvement in terms of tensile, Izod impact and strain energy release rate at a cost of higher melt viscosity. The extra-added core-shell rubber particles with poly(methyl methacrylate) (PMMA) or acrylonitrile-styrene (SAN) outer shell resided mainly in the ABS phase and further improved the resulted blends toughness. The addition of styrene-maleic anhydride (SMA) copolymer in the PC/ABS blends caused severe coagulation of the rubber particles in the ABS phase and left a greater fraction of the SAN phase without presence of rubber. The toughness improvement by increasing rubber content must be compensated by the increase of melt viscosity and this fact has to be taken into consideration in selecting the starting materials of the PC/ABS blends.
FRACTURE AND IMPACT PROPERTIES OF POLYCARBONATES AND MBS ELASTOMER-MODIFIED POLYCARBONATES
(1992-01-25)
CHANG, FC
;
WU, JS
;
CHU, LH
;
交大名義發表
;
應用化學系
Mechanical properties of polycarbonates (PCs) and elastomer-modified polycarbonates with various molecular weights (MW) are investigated. Higher MW PCs show slightly lower density, yield stress, and modulus. The ductile-brittle transition temperature (DBTT) of the notched impact strength decreases with the increase of PC MW and with the increase of elastomer content. The elastomer-modified PC has higher impact strength than does the unmodified counterpart if the failure is in the brittle mode, but has lower impact strength if the failure is in the ductile mode. The critical strain energy release rate (G(c)) measured at -30-degrees-C decreases with the decrease of PC MW. The extrapolated zero fracture energy was found at M(n) = 6800 or MFR = 135. The G(c) of the elastomer-modified PC (MFR = 15, 5% elastomer) is about twice that of the unmodified one. The presence of elastomer in the PC matrix promotes the plane-strain localized shear yielding to greater extents and thus increases the impact strength and G(c) in a typically brittle fracture. Two separate modes, localized and mass shear yielding, work simultaneously in the elastomer-toughening mechanism. The plane-strain localized shear yielding dominates the toughening mechanism at lower temperatures and brittle failure, while the plane-stress mass shear yielding dominates at higher temperatures and ductile failure. For the elastomer-modified PC (10% elastomer), the estimated extension ratio of the yielding zone of the fractured surface is 2 for the ductile failure and 5 for the brittle crack. A criterion for shifting from brittle to ductile failure based on precrack critical plastic-zone volume is proposed.
Fracture toughness of PC/ABS blend under different stain rates by various J-integral methods
(1995)
LU, ML
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
FRACTURE-TOUGHNESS OF A POLYCARBONATE/ACRYLONITRILE-BUTADIENE-STYRENE BLEND BY THE ASTM E813 AND HYSTERESIS ENERGY J-INTEGRAL METHODS - EFFECT OF SPECIMEN THICKNESS AND SIDE GROOVE
(1995-06-01)
LU, ML
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
A previously developed non-conventional J integral based on hysteresis energy and the ASTM E813 methods have been employed to test the fracture toughness of a polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend. A systematic study of the effect of the specimen thickness (from B=4 to 15 mm) and the presence of a V-shaped side groove on the resultant J(1c) has been carried out. The results show that the J(1c) values obtained from the hysteresis energy method and the E813-81 method are comparable, but are similar to 60-90% lower than those obtained from the E813-87 method. When the specimen thickness is relatively thin, the J(1c) values obtained from the V-shaped-side-grooved specimens are slightly higher than those from samples without the side groove, but this difference gradually decreases with an increase in the specimen thickness. The J(1c) values obtained from the ungrooved specimens are almost independent of the specimen thickness (from B=4 to 15 mm) for all of these methods. The critical initiation displacements in terms of the onset of crack initiation, determined from the plots of hysteresis energy vel sus displacement, hysteresis ratio versus displacement, and crack growth length versus displacement, are fairly close in value. This means that the critical crack initiation and the corresponding J(1c) obtained from this hysteresis energy method indeed represent the actual physical event of the onset of crack initiation.
FRACTURE-TOUGHNESS OF ACRYLONITRILE-BUTADIENE-STYRENE BY J-INTEGRAL METHODS
(1995-09-01)
LU, ML
;
LEE, CB
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
The fracture toughness of acrylonitrile-butadiene-styrene (ABS) was determined by three J-integral methods, ASTM E813-81, E813-87, and by hysteresis. The critical J values (J(1c)) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813-81 and hysteresis methods result in comparable J(1c) values, whereas the ASTM E813-87 was similar to 40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the corresponding J(1c) represents a physical event of crack initiation. The elastic storage energy, the input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to the J(1c) obtained from the E813-81 or the hysteresis method.
FRACTURE-TOUGHNESS OF HIGH-IMPACT POLYSTYRENE BASED ON 3 J-INTEGRAL METHODS
(1993-03-10)
LEE, CB
;
LU, ML
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
Three J-integral methods and their modified versions have been used to characterize the fracture toughness of high-impact polystyrene (HIPS) with different thicknesses. The Jc values obtained were highest from the E813-87 method, followed by the E813-81 method, then by the hysteresis method. The hysteresis method based on the steep rising of hysteresis energy under constant displacement-controlled loading in Jc determination has many advantages over the ASTM E813-81 or the E813-87 method. The requirement of crack growth length measurements is no longer necessary and the controversial issue on the crack blunting line can also be avoided. The E813-87 method-resulted in significantly higher Jc values for polymers' but the modified version of E813-87, by moving the offset line from the original 0.2 to 0.1 mm, resulted in comparable Jc values. Since crazes as the main failure mechanism for HIPS, well-defined crack blunting does not expect to occur and the Jc obtained by the original E813-81 based on the theoretically predicted blunting line is indeed slightly higher. The modified version of E813-81 by neglecting the blunting line in Jc determination is believed to be more reasonable for HIPS. The nature of polymers will determine whether the crack tip will be blunted, partially blunted, or not blunted. ASTM E813-81 is appropriate for those polymers with a well-defined blunted crack tip (such as elastomer-modified poly-carbonate), whereas the modified version of ASTM E813-81 seems better for those polymers with craze as the main failure mechanism (such as HIPS). Experimental results indicated that this hysteresis method is able to inherently adjust the crack blunting effect and therefore can be applied to any type of ductile polymer.
FRACTURE-TOUGHNESS OF PC/PBT BLEND-BASED ON J-INTEGRAL METHODS
(1995-05-31)
LU, ML
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
The fracture toughness of a polycarbonate/poly(butylene terephthalate) (PC/PBT) blend was determined using three different J-integral methods, ASTM E813-81, E813-87, and hysteresis energy. The critical J values (J(1c)) obtained are largely independent of the cross-head speed (range from 0.5 to 50 mm/min). ASTM E813-81 and hysteresis energy methods result in comparable J(1c) values, while the E813-87 method estimates J(1c) to be 60-80% higher. The critical displacement determined from the plots of hysteresis (energy and ratio) and the true crack growth length vs. displacement is very close. This indicates that the critical displacement determined by the hysteresis energy method is indeed the displacement at the onset of crack initiation and the corresponding J(1c) represents a physical event of crack initiation. (C) 1995 John Wiley and Sons, Inc.
HPLC ANALYSIS OF POLYCARBONATE OLIGOMERS AND ITS PROCESS APPLICATIONS IN THE INTERFACIAL PHOSGENATION REACTION
(1990-08-05)
GU, JT
;
HUANG, SL
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
IN-SITU COMPATIBILIZATION OF PBT/ABS BLENDS THROUGH REACTIVE COPOLYMERS
(1994)
LEE, PC
;
KUO, WF
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
Styrene-acrylonitrile-glycidyl methacrylate (SAG) copolymer with ethyltriphenyl phosphonium bromide (ETPB) catalyst has been used successfully as in situ compatibilizer to compatibilize the immiscible and incompatible blends of poly(butylene terephthalate) (PBT) and acrylonitrile-butadiene-styrene (ABS). This SAG copolymer contains reactive glycidyl groups that are able to react with PET end groups (-COOH or -OH) under melt conditions to form SAG-g-PET copolymer. However, the rate of the grafting reaction is slow without the presence of catalyst. The ETPB catalyst is highly efficient: even at a concentration as low as 50 ppm, it is able to promote the grafting reaction to obtain the maximum achievable properties. The compatibilized PBT/ABS blend has smaller phase domain, higher viscosity, and significantly improved mechanical properties compared to the corresponding non-compatibilized blend.
IN-SITU COMPATIBILIZATION OF PET/PS BLENDS THROUGH REACTIVE COPOLYMERS
(1993-08-05)
MAA, CT
;
CHANG, FC
;
應用化學系
;
Department of Applied Chemistry
Polymer blends of poly (ethylene terephthalate) (PET) and polystyrene (PS) are immiscible and incompatible, which has been well recognized. Styrene-glycidyl methacrylate (SG) copolymer has been synthesized by suspension polymerization and employed in this study as an in situ compatibilizer for the polyblends of PET and PS. This copolymer contains reactive epoxy functional groups that are able to react with PET end groups (-OH and -COOH) under melt conditions to form SG-graft-PET copolymer. The presence of a small amount of phosphonium catalyst (200 ppm) accelerates the graft reaction and results in a better compatibilized blend. The compatibilized PET/PS blend has a smaller phase domain and higher viscosity than does the corresponding noncompatibilized blend. Mechanical properties of the compatibilized blends have also been improved significantly over the corresponding noncompatibilized blends. (C) 1993 John Wiley & Sons, Inc.