Structural properties and impact fracture behavior of injection molded blends of liquid crystalline copolyester and modified poly(phenylene oxide)

Blends of a thermotropic liquid crystalline polymer (LCP) with modified poly (phenylene oxide) (PPO) were injection molded. The morphology, tensile properties and dynamic mechanical behavior of the blends have been studied as a function of LCP content. Furthermore, the impact performance of these blends has been investigated by the instrumented Izod and Charpy falling weight tests. The critical strain energy release rate (G_IC) of the blends were determined and the G_IC values were found to be dependent on the LCP content. The results are discussed and explained in terms of materials morphology.     

Tensile deformation mechanisms of polypropylene/elastomer blends reinforced with short glass fiber

Polypropylene hybrid composites reinforced with short glass fiber (SGF) and toughened with styrene–ethylene butylenes–styrene (SEBS) elastomer were prepared using extrusion and injection‐molding techniques. Moreover, hybrids compatibilized with SEBS‐grafted maleic anhydride (SEBS‐g‐MA) and hybrid compatibilized with PP grafted with maleic anhydride (PP‐g‐MA) were also fabricated. The matrix of the latter hybrid was designated as mPP and consisted of 95% PP and 5% PP‐g‐MA. Tensile dilatometry was carried out to characterize the fracture mechanisms of hybrid composites. Dilatometric responses showed that the elastic deformation was the dominant deformation mechanism for the SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrids. However, cavitation deformation prevailed over shearing deformation for both hybrids at the higher strain regime. The cavitation strain resulted from the debonding of glass fibers and from the crazing of the matrix in the SGF/SEBS/PP hybrid. In contrast, the cavitation was caused by the debonding of SEBS particles from the matrix of the SGF/SEBS‐g‐MA/PP hybrid. The use of PP‐g‐MA resulting in elastic deformation was the main mode of deformation in the low‐strain region for the SGF/SEBS/mPP and SEBS/SEBS‐g‐MA/mPP hybrids; thereafter, shearing appeared to dominate at the higher strain regime. This was attributed to the MA functional group improving the bonding between the SGF and PP. The correlation between fracture morphology and dilatometric responses also is presented in the article. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 441–451, 2003     

Fracture behavior of thermoplastic polyolefin/clay nanocomposites

A thermoplastic polyolefin (TPO) containing 70 wt % styrene–ethylene–butadiene‐styrene‐g‐maleic anhydride and 30 wt % polypropylene and its nanocomposites reinforced with 0.3–1.5 wt % organoclay were prepared by melt mixing followed by injection molding. The mechanical and fracture behaviors of the TPO/clay nanocomposites were investigated. The essential work of fracture (EWF) approach was used to evaluate the tensile fracture behavior of the nanocomposites toughened with elastomer. Tensile tests showed that the stiffness and tensile strength of TPO was enhanced by the addition of low loading levels of organically modified montmorillonite. EWF measurements revealed that the fracture toughness of the TPO/clay nanocomposites increased with increasing clay content. The organoclay toughened the TPO matrix of the nanocomposites effectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Implementation of a CMIP-based network management system

This paper discusses the experiences of the Provisioning And Monitoring (PAM) laboratory at NYNEX Science and Technology in incorporating the Common Management Information Protocol (CMIP) and the Telecommunications Management Network (TMN) concepts into a network management system developed to manage a network of broadband ATM switches supporting a CMIP interface, as well as a legacy switching platform supporting both a proprietary interface and the Simple Network Management Protocol (SNMP) interface. The primary focus of the discussion will be on the implementation issues pertaining to the CMIP interface and the TMN object model; in particular their complexities and the approaches used to manage that complexities while retaining their functionalities.     

Tensile deformation mechanism of polyamide 6,6/SEBS-g-MA blend and its hybrid composites reinforced with short glass fibers

Short glass fiber (SGF) reinforced polyamide 6,6 hybrid composites toughened with maleated styrene-ethylene butylenes-styrene (SEBS-g-MA) elastomer were prepared by compounding and subsequent injection molding. The hybrids were reinforced with 5, 10, 15, 20 and 30 wt% SGF. The matrix of the hybrids consisted of 80 wt% PA6,6 and 20 wt% SEBS-g-MA. Dilatometery was employed to characterize the deformation mechanisms of tough PA6,6/SEBS-g-MA 80/20 blend and its hybrid composites under uniaxial tension. Dilatometric responses showed that both cavitation and shear yielding occur in PA6,6/SEBS-g-MA 80/20 blend during deformation. And the cavitation deformation prevailed over shear yielding in this blend after the initial elastic deformation. Moreover, the volume strain was observed to increase considerably with increasing SGF content for the hybrids investigated. SEM examination revealed that microvoids originated from the debonding of glass fiber from the PA6,6 matrix were responsible for the cavitation strain in the hybrids. Consequently, cavitation deformation predominated over shear yielding in hybrids.     

Artificial neural network training utilizing the smooth variable structure filter estimation strategy

A multilayered neural network is a multi-input, multi-output nonlinear system in which network weights can be trained by using parameter estimation algorithms. In this paper, a novel training method is proposed. This method is based on the relatively new smooth variable structure filter (SVSF) and is formulated for feed-forward multilayer perceptron training. The SVSF is a state and parameter estimation that is based on the sliding mode concept and works in a predictor–corrector fashion. The SVSF training performance is tested on three benchmark pattern classification problems. Furthermore, a study is presented comparing the popular back-propagation method, the extended Kalman filter, and the SVSF.     

Mechanical behavior of CaCO3 particulate-filled β-crystalline phase polypropylene composites

β-crystalline phase polypropylene (PP) composites containing 5, 10, 20, 30, and 40% (by weight) of CaCO₃ filler were prepared by injection molding. The β-form PP was produced by adding a bicomponent β-nucleator consisting of equal amounts of pimelic acid and calcium stearate. The morphology, static tensile, and impact properties of these composites were investigated in this study. Scanning electron microscopy (SEM) observations revealed that the β-spherulites of the polymer matrix of the composites exhibit curved lamellae and sheaf-like structures. The fillers were observed to disperse within the inter-lamellar spacings of the β-PP composite containing 10% calcium carbonate addition. However, the filler particles tend to link together to form larger aggregates when the filler content reaches 20%. Static tensile measurements showed that the elastic modulus of the composites increases with increasing filler content but the yield strength decreases with increasing filler addition. The falling weight Charpy impact test indicated that the β-PP polymer exhibits the highest critical strain energy release rate (G_c) value. However, there was a drastic drop in G_c of the β-PP composites with increasing filler content. The results are discussed and explained in terms of materials morphology.     

Essential work of fracture (EWF) analysis for short glass fiber reinforced and rubber toughened nylon‐6

The effect of fiber content on the fracture toughness of short glass fiber reinforced and rubber toughened nylon‐6 has been investigated using the essential work of fracture (EWF) analysis under both quasi‐static and impact rates of loading. Under quasi‐static loading rate, matrix plastic deformation played a major role. Addition of 10 wt% of short glass fibers into a rubber toughened nylon‐6 matrix improved the fracture toughness substantially. This is due to the synergistic effect that comes from matrix yielding and fiber related energy absorption such as fiber debonding, fiber pull‐out and fiber fracture. With further increasing the glass fiber content, up to 20 and 30 wt%, even though plastic deformation could still take place on the fracture surfaces, the depth of the fracture process zones was much smaller when compared with the system with 10 wt% of glass fibers. The reduction in fracture process zone caused the reduction in fracture toughness. Under impact loading rate, the unreinforced blend still fractured in a ductile manner with gross yielding in the inner fracture process zone and the outer plastic zone. The unrein‐forced blend therefore possesseed higher fracture toughness. For the fiber reinforced blends, the matrix fractured in brittle manner and so fracture toughness of the reinforced blends decreased dramatically. The impact fracture toughness increased slightly after incorporation of a higher weight percentage of glass fibers.     

Facile synthesis and properties of semicrystalline copoly(arylene ether ketone) containing hydroquinone and phthalazinone

Two series of novel copoly(arylene ether ketone) were successfully synthesized from hydroquinone or bisphenol A, bis(4‐fluorophenyl)ketone and 4‐(4‐hydroxyphenyl)‐2,3‐phthalazin‐1‐one with anhydrous potassium carbonate as the catalyst. The synthesized polymers exhibited high glass‐transition temperatures together with excellent thermooxidative stability. The chain structure of these polymers was studied by means of ¹³C‐nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD) techniques. The experimental results showed that these “as‐made” copolyaryleneketones containing hydroquinone moieties exhibited a multiblock chain structure with long segments that mainly consisted mainly of hydroquinone and bis(4‐fluorophenyl)ketone at the middle of the molecular chain. These long segments exhibited crystallites in the produced polymers. The synthesized copolyaryleneketone containing 90 mol % hydroquinone possessed a glass‐transition temperature higher than that of commercial PEEK. The synthesized polymers also exhibited either fair processability or solubility. The glass‐transition temperatures, solubility, and tensile strengths of the two series of copolyaryleneketones tended to increase with increasing phthalazinone moiety content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2687–2695, 2001     

Quantification of pesticides in food crops using QuEChERS approaches and GC-MS/MS

The analysis of pesticides in food products requires accurate measurements for which standardised protocols have been developed. This paper reports the validation of QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based methods applied to three different food samples (brown rice, red pepper and mandarin orange) analysed using gas chromatography-tandem mass spectrometry (GC-MS/MS). The validation of the analytical methods used to measure 113 pesticides, including various insecticides, fungicides and herbicides, was conducted in three food matrices and at three spiking levels by three different laboratories. The set of validated results was interpreted, statistically analysed and visualised using principal component analysis (PCA). Notably, the matrix effects in GC-MS analysis for most of the tested pesticides from different matrices were lowered to practical values (less than 30%) appropriate for routine analysis. This allowed for the quantification of pesticides in the samples using standard and analyte protectants (APs) in the reagent method blank as a screening measure, providing an alternative to matrix-matched calibration. Alternatively, the use of only one standardised calibration (grape matrix) in combination with APs also allowed for the qualitative and semi-quantitative analysis of pesticides in different matrices. The inclusion of APs reduced the differences in the matrix-induced enhancement effects of various samples. The use of an internal standard (IS) to correct the matrix effects was also noted. The normalisation of the analyte peak with triphenyl phosphate (TPP) as an IS resulted in a slight improvement of validation values such as precision and linearity in only one laboratory, but it lowered the value of matrix effects in all three laboratories.