Home  About us  Contact
 

Essential Work (essential + work)

Distribution by Scientific Domains
Polymers and Materials Science87%

Selected Abstracts

Polyolefin nanocomposites: Essential work of fracture analysis

POLYMER ENGINEERING & SCIENCE, Issue 6 2004
M. N. Bureau
The tensile properties and the fracture toughness, based on the essential work of fracture (EWF) method, of melt-compounded polymer nanocomposites based on polypropylene (PP) with organo-modified clays (montmorillonite) and maleic anhydride (MA),grafted PP coupling agents were studied. Depending on the compounding sequence and on whether a coupling agent was used, some improvements in tensile properties were observed. These improvements were related to the level of dispersion of clay particles. The highest tensile properties were obtained for the PP/clay compound showing the highest surface density of uniform sub-micron particles. The mechanical improvements of the PP/clay compounds were those of a microcomposite in which the fiber reinforcement has an average aspect ratio of 17,35. The PP/clay compounds with coupling agents and with highest surface density of uniform sub-micron particles showed very good fracture toughness, with EWF values slightly higher than those of unfilled PP. Fractographic observations showed that clay particles acted as void nucleation sites, which then grew and coalesced, promoting fibrillation of the remaining material between the voids. The EWF results indicated that the void nucleation density determined the fracture toughness. The EWF results also indicated that the plastic work dissipation related to the stability of the fibrillation, which was promoted by the use of a coupling agent. Polym. Eng. Sci. 44:1142,1151, 2004. © 2004 Society of Plastics Engineers. [source]

Essential work of fracture (EWF) analysis for compression molded alternating poly(propylene carbonate)

POLYMER ENGINEERING & SCIENCE, Issue 3 2004
K. L. Fung
In this investigation, the main objective was to study the mechanical properties of alternating poly(propylene carbonate) copolymer (PPC). The PPC used in this study was derived from propylene oxide and carbon dioxide using zinc glutarate as catalyst. The molecular weight of the PPC copolymer used in this study has M,n,33,000. The synthesized PPC was compression molded into sheets of thickness ,1mm. The fracture toughness of the PPC films was determined using the essential work of fracture (EWF) technique, at a laboratory temperature of 20°C, and a loading rate of 1 mm/min. During the EWF measurement, a significant amount of plastic deformation has taken place around the initial ligament region. The measured specific total fracture work (wf) was observed to vary in a linear fashion with the specimen ligament (l), and hence satisfied the basic requirement for EWF analysis. The specific essential fracture work (we) for the PPC film was measured to be 11.0 kJ/m2. The PPC showed a prominent recovery behavior. The severely deformed region surrounding the fracture ligament was observed to recover completely 8 days after fracture testing. Polym. Eng. Sci. 44:580,587, 2004. © 2004 Society of Plastics Engineers. [source]

Effect of cavitation on the plastic deformation and failure of isotactic polypropylene

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007
Bing Na
Abstract To clarify the effect of cavitation, which is mostly induced by crystalline phase, on the plastic deformation and failure of isotactic polypropylene, solid-state annealing at 160°C for 1.5 h is adopted to change the crystalline phase only while the amorphous phase keeps nearly intact. With aid of a special video setup, the relation of true stress and strain as well as the evolution of volume strain with axial strain has been derived. Enhancing crystalline phase due to annealing increases the yield stress and volume strain simultaneously. Moreover, the strain corresponding to steep increasing of volume strain is comparable with that related to yield, indicating that cavitation at early stage is accompanied with process of yield. With knowledge of toughness derived from impact tensile stretching and essential work of fracture (EWF), respectively, the relationship between cavitation and toughness has been correlated to some degree. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

Polyolefin nanocomposites: Essential work of fracture analysis

POLYMER ENGINEERING & SCIENCE, Issue 6 2004
M. N. Bureau
The tensile properties and the fracture toughness, based on the essential work of fracture (EWF) method, of melt-compounded polymer nanocomposites based on polypropylene (PP) with organo-modified clays (montmorillonite) and maleic anhydride (MA),grafted PP coupling agents were studied. Depending on the compounding sequence and on whether a coupling agent was used, some improvements in tensile properties were observed. These improvements were related to the level of dispersion of clay particles. The highest tensile properties were obtained for the PP/clay compound showing the highest surface density of uniform sub-micron particles. The mechanical improvements of the PP/clay compounds were those of a microcomposite in which the fiber reinforcement has an average aspect ratio of 17,35. The PP/clay compounds with coupling agents and with highest surface density of uniform sub-micron particles showed very good fracture toughness, with EWF values slightly higher than those of unfilled PP. Fractographic observations showed that clay particles acted as void nucleation sites, which then grew and coalesced, promoting fibrillation of the remaining material between the voids. The EWF results indicated that the void nucleation density determined the fracture toughness. The EWF results also indicated that the plastic work dissipation related to the stability of the fibrillation, which was promoted by the use of a coupling agent. Polym. Eng. Sci. 44:1142,1151, 2004. © 2004 Society of Plastics Engineers. [source]

Essential work of fracture (EWF) analysis for compression molded alternating poly(propylene carbonate)

POLYMER ENGINEERING & SCIENCE, Issue 3 2004
K. L. Fung
In this investigation, the main objective was to study the mechanical properties of alternating poly(propylene carbonate) copolymer (PPC). The PPC used in this study was derived from propylene oxide and carbon dioxide using zinc glutarate as catalyst. The molecular weight of the PPC copolymer used in this study has M,n,33,000. The synthesized PPC was compression molded into sheets of thickness ,1mm. The fracture toughness of the PPC films was determined using the essential work of fracture (EWF) technique, at a laboratory temperature of 20°C, and a loading rate of 1 mm/min. During the EWF measurement, a significant amount of plastic deformation has taken place around the initial ligament region. The measured specific total fracture work (wf) was observed to vary in a linear fashion with the specimen ligament (l), and hence satisfied the basic requirement for EWF analysis. The specific essential fracture work (we) for the PPC film was measured to be 11.0 kJ/m2. The PPC showed a prominent recovery behavior. The severely deformed region surrounding the fracture ligament was observed to recover completely 8 days after fracture testing. Polym. Eng. Sci. 44:580,587, 2004. © 2004 Society of Plastics Engineers. [source]

Combined effect of temperature and thickness on work of fracture parameters of unplasticized PVC film

POLYMER ENGINEERING & SCIENCE, Issue 3 2002
A. Arkhireyeva
The combined effect of temperature and thickness on the essential work of fracture (EWF) parameters for an unplasticized poly(vinyl chloride) (uPVC) film was investigated using double edge notched tension specimens. It was found that for the range of temperatures (23°C to 60°C) and thicknesses (0.15 mm to 0.40 mm) studied here, specific essential work of fracture (we) was independent of temperature at each thickness but increased with thickness at each temperature. It was found that at each temperature, we and its yielding (we,y) and necking/tearing components (we,nt), all increased linearly with increasing thickness. However, whilet we showed no significant variation with respect to temperature, its yielding component (we,y) decreased and its necking/tearing component increased (we,nt) with increasing temperature. It was found that estimated values of we and its components we,y and we,nt via crack opening displacement values were by and large unsatisfactory, being either much higher or lower than the directly measured values. [source]

Mechanism of light-induced translocation of arrestin and transducin in photoreceptors: Interaction-restricted diffusion

IUBMB LIFE, Issue 1 2008
Vladlen Z. Slepak
Abstract Many signaling proteins change their location within cells in response to external stimuli. In photoreceptors, this phenomenon is remarkably robust. The G protein of rod photoreceptors and rod transducin concentrates in the outer segments (OS) of these neurons in darkness. Within ,30 minutes after illumination, rod transducin redistributes throughout all of the outer and inner compartments of the cell. Visual arrestin concurrently relocalises from the inner compartments to become sequestered primarily within the OS. In the past several years, the question of whether these proteins are actively moved by molecular motors or whether they are redistributed by simple diffusion has been extensively debated. This review focuses on the most essential works in the area and concludes that the basic principle driving this protein movement is diffusion. The directionality and light dependence of this movement is achieved by the interactions of arrestin and transducin with their spatially restricted binding partners. © 2007 IUBMB IUBMB Life, 60(1): 2,9, 2008 [source]