Essential work of fracture testing of PC-rich PET/PC blends with and without transesterification catalysts

0.7 mm sheets of blends of polycarbonate (PC) with polyethylene terephthalate (PET) rich in PC in the presence and absence of three different transesterification catalysts have been obtained using reactive extrusion-calendering processing method in order to evaluate the fracture toughness of these materials applying the essential work of fracture (EWF) approach which has not been previously reported in the literature. The morphology has been characterized by scanning electron microscopy (SEM). In addition, the tensile properties of these materials were determined. There is a decrease on the essential term (w _e) values of PC/PET blends without transesterification catalysts while blends with transesterification catalysts present an increment in comparison with neat PC which may related to the product of the transesterification that plays like an emulsifier/compatibilizing agent to reduce the interfacial tension between the components of the blend and reduce the interfacial tension between the two immiscible or incompatible component phases to get a better fracture behavior. This is confirmed by the tensile test results obtained which demonstrate higher values for E and σ _y in the case of blends with transesterification catalysts compared with neat PC. For non-essential term of fracture (βw _p), blends without catalysts exhibit an increase compared with neat PC by increasing the amount of PET which may due to the lowering of the yielding stress. In contrary, the presence of transesterification catalysts and especially Zn-based shows decrease as a consequence of the restriction that occurred on the movement of PC segments during the transesterification reactions or as a decohesion of the dispersed phase during the test.     

Synthesis,characteristic of a novel additive-type flame retardant containing silicon and its application in PC/ABS alloy

A novel flame retardant (DPA–SiN) containing phosphorus, nitrogen and silicon elements at the same time was synthesized. 9-(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-propanoic acid (DPA) synthesized through simple addition reaction of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acrylic acid (AA) was introduced into N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxysilane/dimethylsiloxane copolymer (SiN) to form a novel flame retardant (FR). The structure of DPA and DPA–SiN were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. After blend with PC/ABS, the flame-retardant properties of the PC/ABS/DPA–SiN blends are estimated by Limiting Oxygen Index (LOI) values and CONE Calorimeter, while thermal stabilities are investigated through Thermo Gravimetric Analysis (TGA). The morphological structures of the char formed after PC/ABS/DPA–SiN burnt in LOI test were investigated by Scanning Electron Microscopy (SEM).     

Fracture toughness and fracture mechanisms of PBT/PC/IM blends: Part V Effect of PBT-PC interfacial strength on the fracture and tensile properties of the PBT/PC blends

To investigate the effect of PBT-PC interfacial strength on the fracture toughness and toughening mechanisms of the PBT/PC system, a series of PBT/PC blends with different content of in situ formed PBT-PC copolymers were made by melt blending. The in situ copolymer was separately prepared via reactive blending of the PBT and PC in the presence of a transesterification catalyst in a twin-screw extruder for a few minutes. The reactive extrudate (RE) was studied using a DSC and the existence of the PBT-PC copolymer in the RE was confirmed. Microstructure characterizations of the PBT/PC/RE blends revealed that the domain sizes of the PBT and PC decrease and the PBT-PC interfacial strength increases with the RE content. Compared with the PBT/PC blend, all the PBT/PC/RE blends have higher yield strength, elongation at break as well as tensile modulus. The quasi-static fracture tests show that fracture toughness of the blends increases with the RE content. Since the highest toughness was obtained with the blend having the highest RE content (7.5%), it is not certain at this stage whether adding more than 7.5% RE will further improve the fracture toughness. The impact toughness of the PBT/PC/RE blends was found to decrease with the increase of the PBT-PC interfacial strength, which confirms the failure mechanisms proposed in the Part-4 of this series.     

PET／PC共混物的形态结构的研究

用偏光显微镜、X-ray衍射仪和示差扫描量热计(DSC)研究了聚对苯二甲酸乙二酯/聚碳酸酯(PET/PC)共混物的形态结构。结果表明:在PET/PC共混物中,当PC含量在50％以下时,PC的晶粒与PET的球晶分别分散在非晶区中;当PC含量在50％以上时,PET的晶柱与PC的晶粒分别分散在非晶区中。随着PC含量的增加,PET晶体的完整性被破坏,晶粒变小,结晶度下降,熔点降低。     

Effect of core–shell structured modifier ACR on ASA/SAN/ACR ternary blends

In this study, acrylonitrile–styrene–acrylic terpolymer/styrene–acrylonitrile copolymer/acrylic resin (ASA/SAN/ACR) ternary blends with different compositions were prepared by melting blending. Properties of the ternary blends were studied by differential scanning calorimetry, heat distortion temperature (HDT), Fourier transform infrared (FTIR) spectra, melt flow rate (MFR), mechanical properties, and scanning electron microscopy (SEM). The blends showed two T _gs at about −48 and 109 °C. FTIR analyses showed no strong interactions between the characteristic groups existed in the prepared blends. No obvious phase separation observed in SEM images indicated good compatibility in the blend system. With respect to mechanical properties and processability, the addition of ACR not only led to the improvement of impact strength and elongation at break, but also the decline of tensile strength, flexural properties, hardness, and MFR. Furthermore, heat resistance of ASA/SAN (70/30) binary blends decreased with the addition of ACR, but the HDT of ASA/SAN (30/70) almost remain unchanged.     

An unusual morphology and crystallization behavior in in situ formed polyphenylene oxide/polyamide 6 blends

Novel polyphenylene oxide/polyamide 6 (PPO/PA6) blends were synthesized via in situ polymerization of ε-caprolactam with PPO dissolved in it. The introduction of 10 wt% PPO into PPO/PA6 led to phase inversion of the blends, which was nearly completed by incorporating 15 wt% PPO into the blends. A single crystallization temperature (T _c) of PA6 was detected for PPO/PA6 with 1–4 wt% PPO, while double T _c existed in the blends with 6–15 wt% PPO. After eliminating previous thermal history, PPO/PA6 containing no more than 6 wt% PPO gave a single melting point (T _m), but the blends with 10–15 wt% PPO exhibited double T _m. Increasing PPO content in PA6 resulted in the transformation of its crystal form from α-crystal to γ-crystal, which might be attributed to hindrance of crystallization of PA6 particles in PPO-rich phase.     

Fracture mechanisms of poly(ethylene terephthalate) and blends with styrene-butadiene-styrene elastomers

Poly(ethylene terephthalate) (PET) was blended with 5 wt % of an elastomeric block copolymer. The hydrogenated styrene-butadiene-styrene (SEBS) elastomers were functionalized with 0–4.5 wt % maleic anhydride grafted on the midblock. Notched tensile tests in the temperature range − 40–55 °C differentiated among the blends in terms of their toughness. The least effective elastomer was the unfunctionalized SEBS; all the functionalized SEBS elastomers effectively increased the toughness of PET. Fractographic analysis indicated that PET and the blend with unfunctionalized SEBS fractured through a pre-existing craze. Although adhesion of the unfunctionalized SEBS to the matrix was poor, the elastomer strengthened the craze somewhat, as indicated by an increase in length of the pre-existing craze when final separation occurred. A functionalized SEBS caused the fracture mechanism to change from crazing to ductile yielding. Graft copolymer formed by reaction of PET hydroxyl end groups with the anhydride in situ was thought to act as an emulsifier to decrease particle size and improve adhesion. These factors promoted cavitation, which relieved the triaxiality at the notch root and permitted the matrix to shear yield. This revised version was published online in November 2006 with corrections to the Cover Date.     

PC／PET共混物的非等温结晶动力学

采用等速变温ＤＳＣ法对ＰＣ／ＰＥＴ共混体系的非等温结晶动力学进行了研究，结果表明，从玻璃态结晶时，随着ＰＣ含量的增加，ＰＥＴ组分的结晶速率先增加后降低。耐从熔体结晶时，体系的结晶速率随着ＰＣ含量的增加而增加，讨论了ＰＣ对ＰＥＴ组分结晶过程的影响。     

Processing conditions, morphology and properties of a polycarbonate + a thermotropic polymer liquid crystal blend

We have investigated phase structure – properties relationships of polycarbonate (PC) + a polymer liquid crystal (PLC) blends processed in a twin-screw extruder at several conditions. The PLC is PET/0.82 PHB – a copolyester of poly(ethylene terephtalate) and p -hydroxybenzoic acid. For comparison the blend was additionally extruded in a wide range of shear rates in a capillary rheometer at two different spinning rates and compression-molded. The blend processed in the rheometer exhibits lower values of modulus and tensile strength than the blend extruded due to destruction of the initial orientation and dispersion level gained during extrusion. The orientation of PLC-rich islands increases up to the shear rate of 50–100 s^–1, whereas deformation at higher shear rates exhibits a droplet–breakup phenomenon, confirmed by SEM micrographs. The rheological measurements (oscillation mode) evidence a high shear thinning of the PLC. By contrast, the influence of the deformation rate on the viscosity for PC and the blend is negligible, suggesting also a low interaction level in the interfacial area. This conclusion was confirmed by dynamic mechanical measurements. As expected, our experiments prove that structure and properties of the blend are affected by processing (shear and elongation) conditions. Increasing shear rate leads to elongation of dispersed domains but exceeding critical values can lead to droplet breakup and destruction of created structure. The unique morphology created during extrusion can be destroyed during additional processing (in rheometer). Formation of fibrils is also dependent on additional treatment – spinning speed. Optimized spinning speed can lead to 50% increase in stiffness of the blend. Electronic Publication     

Templated synthesis of mesoporous aluminas by <Emphasis Type="Italic">graft</Emphasis> copolymer and their CO<Subscript>2</Subscript> adsorption capacities

Mesoporous aluminas were synthesized via a sol–gel process by templating an amphiphilic graft copolymer, PVC–g–POEM, consisting of a poly(vinyl chloride) (PVC) backbone and poly(oxyethylene methacrylate) (POEM) side chains. The mesoporous structures of aluminas with large surface areas were confirmed by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption/desorption analysis. Aluminas synthesized with PVC–g–POEM graft copolymer exhibited higher CO₂ adsorption capacities (0.7 mol CO₂/kg sorbent) than aluminas synthesized without graft copolymer (0.6 mol CO₂/kg sorbent). The adsorption capacity of alumina strongly depends on its structure and calcination temperature; amorphous (400 °C) > γ phase (800 °C) > α phase (1000 °C).     

Kinetic and structural interpretations of post-yield crack resistance behavior of polyamide-6/polyolefin-g-maleic anhydride blends

Binary blends of polyamide-6 (PA-6)/polypropylene-grafted-maleic anhydride (PP-g-MA) and PA-6/low density polyethylene-grafted-maleic anhydride (LDPE-g-MA) were prepared with varied concentration (0–30 wt%) of maleic anhydride-grafted polyolefinic (PP) moiety as the impact modifier. The microstructural attributes and thermal properties of the blends were characterized by WAXD, FTIR, SEM, DSC, and TGA. The WAXD/DSC studies have revealed that the crystallinity of the blends decreased with the increase in the PP modifier whereas the onset of degradation temperature remained nearly unaffected. Comparative assessment of the crack toughness behavior of the blends has been carried out following the essential work of fracture (EWF) approach based on post-yield fracture mechanics (PYFM) concept. The kinetics of crack propagation of the blends has been discussed in the realms of structural and compositional parameters. An enhancement in the toughness (resistance to stable crack propagation) as indicated by a maximum in the non-EWF (βw _p) values have been observed at 10 and 20 wt% followed by a sharp and consistent drop in the composition regime of 10–20 and 20–30 wt% of PP-g-MA and LDPE-g-MA, respectively; conceptually implying possible ductile-to-semiductile transitions in the blend systems. The equivalence of PYFM–EPFM fracture parameters have been discussed following inequality criterion. Fractured surface morphology investigations revealed that the failure mode of the blends undergo a systematic transition from matrix-controlled homogeneous flow/deformation in the PP/polyamide phase to blend composition-dependent changes in the modes and extent of fibrillation via cavitation and shear-banding mechanisms.     

Thermomechanical properties of a polymer blend: Investigation of a third phase

This paper deals with immiscible blends of poly(ethylene terephthalate) with polycarbonate obtained by melt mixing. Miscibility of the polyester blends is influenced by transesterification reactions, that are catalyzed either by catalyst residues in the polyesters or by catalysts added on purpose in the blend. These reactions convert the initial homopolymers into block and even random copolymers and affect both the miscibility of the system and the adhesion between the phases. The effect of catalysts and stabilizers on the morphology of PET/PC 50/50 blends was investigated using dynamic mechanical thermal analysis, rheology, microscopy and tensile tests. PET/PC 50/50 containing 0.05 wt.% of lanthanide acetyl acetonate exhibit a irreversible transition occurring at temperature higher than the glass transitions of PET and PC. This transition induces a large increase of the shear modulus and it was attributed to the formation of a third phase in the blend.     

Structure formation and miscibility of sheets from PBT and LCP blends

Sheets from blends containing poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) were prepared using a twin-screw extruder. The LCP used is a copolymer composed of 20 mol % ethylene terephalate (PET) and 80 mol % p-hydroxybenzoic acid (PHB). Thermal behavior, viscoelastic properties, and structure of the sheets of various compositions were investigated by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), microwave orientation analysis (MOA), and wide angle x-ray diffraction (WAXD). X-ray diffractograms of extruded sheets from PBT, LCP, and their blends show a high degree of orientation along extrusion direction. The orientation is mainly due to the high crystallization rate of PBT, although crystallization and orientation of PBT in the PBT and LCP blends could also be induced by adding LCP. In the PBT and LCP blends, the thermal properties of the constituents are slightly changed indicating that PBT and LCP are partially miscible. DSC measurements show that as the amount of LCP added to the blend increased, the melting point T _m of PBT in the blends decreased. The single glass transition temperature T _g for the PBT and LCP was observed by DMA. Furthermore, no evidence of transesterification in PBT and LCP blends was observed by WAXD.     

Thermal stability,morphology, and X-ray diffraction studies of dynamically vulcanized natural rubber/chitosan blends

The thermal degradation behavior of cross-linked Natural Rubber/Chitosan (NR/CS) blends was studied by thermogravimetric analysis (TGA). Dicumyl peroxide (DCP) was selected as a cross-linking agent. Peroxide-cured NR/CS blends exhibit very good overall thermal properties. The activation energy of degradation was analyzed using the Horowitz–Metzger equation. Vulcanization of rubber phase in the blend increased the activation energy. From the activation energy values, it is found that among the series of the blend compositions, NR₈₅CS₁₅ blend vulcanized with 3 pphr DCP exhibits better thermal stability. Better adhesion between the two phases with the incorporation of DCP is achieved which results in an enhancement in the thermal stability. The DSC curve shows that, the T _g of chitosan in the blend increased to 242 °C by dynamic vulcanization. The morphology of the vulcanized blends was studied by scanning electron microscopy. More uniform distribution was exhibited by the vulcanization of NR phase in the blend. X-ray diffraction (XRD) study shows an enhancement in the crystallinity by vulcanization.     

具有高界面压应力的高分子共混物Ⅰ.制备和拉伸性能

考察了高界面压应力对不相容聚对苯二甲酸乙二醇酯(PET)/聚乙烯(PE)和聚碳酸酯(PC)/PE共混物拉伸性能的影响.高界面压应力是共混物低温成型(PE的成型温度)时,分散相与基体从加工温度冷却到室温过程中基体的收缩比分散相粒子大产生的.尽管PET/PE和PC/PE共混物极不相容,但拉伸强度和模量随着PET和PC含量增加而增加.PET与PC含量相同时,PC/PE的拉伸强度和模量高于PET/PE的.采用Takayanangi方程计算共混物的拉伸模量时,具有高界面压应力的PC/PE共混物的拉伸强度高于界面有良好粘结的共混物的理论值,表明在不添加增容剂时,可通过控制加工条件改善共混物界面相互作用,提高共混材料的性能.     

Poly(dimethylsiloxane)-polyimide blends in the formation of thick polyimide films

Thick polyimide layers can be formed by using some unique properties of poly(dimethylsiloxane)-polyimide (PDMS/PMDA–ODA) blends followed by surface modification and deposition of a second layer of polyimide precursor chemicals. The method is based on the micro-phase separation characteristics of these blends to yield surfaces that have PDMS-like character. Upon modification with UV/ozone treatment, a surface that is essentially SiO _x and hydrophilic in nature is produced. This surface is amenable to reaction and deposition of a second polyimide layer from polyimide precursors. The thicker polyimide layer has enhanced adhesion between the original layer of the blend and the new polyimide layer and this approach finds extensive applications for products that require thick polymer layers. Changes in surface energy for various blend compositions were monitored by measurement of advancing contact angle with de-ionized water. Contact angle for unmodified polyimide films was on the order of 70° and it increased to about 104° after blending with PDMS and curing. UV/ozone treatment reduced the contact angle of the doped polyimide to less than 5°. X-ray photoelectron spectroscopy (XPS) and angle resolved XPS (ARXPS) measurements were used to monitor the chemical compositions of the various surfaces. High-resolution XPS spectra in the Si2p region confirm the transformation of O–Si–C bonds in PDMS to SiO _x , where x is about 2. Scanning electron microscopy (SEM) of some selected samples shows that the blends contain phase separation of the polymers at the surfaces of the samples. Atomic force microscopy (AFM) of siloxane-free polyimide, and PDMS/PMDA–ODA blends both prior to and after UV/ozone exposure, show that the films are essentially flat at short treatment times (less than 60 min). AFM also reveals the separation of PDMS into micro-domains at the cured film surface and throughout the layer below the surface of the blended films. Adhesion of a subsequently deposited polyimide layer to the modified polyimide surface was found to be greatly improved when compared to the adhesion obtained for deposition onto a pristine polyimide surface.     

The study of tri-phasic interactions in nano-hydroxyapatite/konjac glucomannan/chitosan composite

The interactions among the three phases of nano-hydroxyapatite (n-HA), Konjac glucomannan (KGM) and Chitosan (CS) in n-HA/KGM/CS composite were investigated using TEM, IR, XRD, XPS and TGA methods. The crystalline structure of n-HA was studied by means of Rietveld method. A series of structure parameters, such as, cell lattice parameters (a or c), bonding lengths and a numerical index of distortion for PO₄ tetrahedron, were calculated by Newton–Raphson calculating method to characterize the crystalline structure of HA at atom level. The results showed that n-HA was mainly linked with KGM and CS by hydrogen bonding between OH⁻–PO₄³⁻ of n-HA and –C=O, –NH of KGM-CS copolymer, and there was a stable interface formed between the three phases in the composite. Besides, orientation of this hydrogen bonding resulted in the decrease of the relative crystallization degree of KGM-CS copolymer.     

Dielectric properties of polyarylate blends

Dielectric properties and molecular motion were studied by use ofdielectric spectroscopy and differential scanning calorimetry for twoblends, fully transesterificated polyarylate of bisphenol A withterephthalate/isophthalate (50/50) (PA)/polycarbonate of bisphenol A(PC) blends and PA/poly(ethylene terephthalate) (PET) blends. All thequenched PA/PC and PA/PET blends were amorphous and the glasstransition temperature (Tg) was varied with the blends ratioaccording to Gordon-Taylor equation. The PA/PET blends with more than60% of PET crystallized above the crystallization temperature. ThePA/PC and PA/PET blends showed two dielectric relaxations, above Tg and below Tg, which are related to a glasstransition and a local motion of short segment, respectively. The relaxation moved to lower temperatures as PC or PET contentincreases, reflecting the lowering Tg faithfully. In the PA/PETblends, the static (₀) and the limiting dielectricconstant (), and the increment () for the relaxation decreases with increasingtemperature and the decrease falled on one curve, independent of theblend ratio. Any ferro- and piezoelectricity were not observed fortwo blends.     

核壳结构改性剂对PBT/PC共混物的增韧作用

采用丙烯腈-丁二烯-苯乙烯（ABS）核壳结构改性剂增韧聚对苯二甲酸丁二醇酯（PBT）/聚碳酸酯（PC）共混物。动态力学测试（DMTA）结果表明,PBT与PC为热力学不相容体系,ABS的引入导致PBT、PC玻璃化转变温度相互靠近,相容性提高;差示扫描量热（DSC）研究结果表明,随着ABS的加入,PBT/PC体系中PBT的...     

Fracture toughness of multiphase polypropylene composites containing rubbery and particulate inclusions

The fracture toughness of binary and ternary phase polypropylene (PP) composites containing ethylene–propylene rubber (EPR) and glass beads, has been studied using the J-integral method at 23 and − 20 °C. For determining J _c, analysis of the stress-whitening zone was found to be more meaningful than the commonly used blunting line approach. Functionalized EPR was found to be more effective toughening additive for PP than EPR, in both binary and ternary phase compositions. Crack growth mechanisms were examined by scanning electron microscopy. In rubber-modified blends, cavitation and shear yielding were found to be the primary toughening mechanisms, while in ternary phase composites particle–matrix debonding played a major role. This revised version was published online in November 2006 with corrections to the Cover Date.