The Estimation of Mechanical Properties of Polymers from Molecular Structure ppt

... the theoreticians the approximate form to which their theories may be reduced. Linking the mechanical properties to the molec- ular properties of a material is the equation of state. Thermodynamic ... dependence of a polymer is strongly related to the entanglement molecular weight. Above 2Me, the viscosity of the melt in- creases as the 3.4 power of the molecular weight. In the glass, the mechanical ... calculated from only five basic molecular properties. They are the molecular weight, van der Waals volume, the length and number of rotational bonds in the repeat unit, as well as the Tg of the...

... gaps of Ge-core/Si-shell and Si-core/Ge-shell nanowires at the level of density functional theory, where the composition is definedas the ratio of the number of atoms of the core to the number of ... with each other,and thus the Young’s modulus of either core or shell is not the same as that of the isolated nanowire or the isolatednanotube. On the other hand, the Young’s modulus of acore–shell ... the existence of the region around the interface between the core and the shell of a core–shell nanowire.Basically, it is unreasonable for the core or the shell toinclude the volume of the whole...

... as the pressure of the left upper corner of the loop; the sig-nificance of this pressure will be discussed in detail below. Moving to the bottom of the loop, we can reason that the pressure of ... instantaneous atrial volume). The pressure of the point at the bottom right corner of the loop is the pressure in the ventricle at the end of the cardiac cycle and is called the end-diastolic pressure ... which specify the curvature of the line and are determined by the mechanical properties of the muscle as well as the structural features of the ventricle. This curve is called the "end-diastolic...

... to the sub-Tgsecondarytransitions). The strength and magnitude of these transitions depends on the de-gree of crystallinity and the size of the lamellae, and therefore is influenced by the thermal ... underlying molecular structure. The influence of other molecular parameters such as molecular weight (chain length) is mainlyrestricted to the rubber region, where it determines the width of the rubber ... and on the other, the molecular structure and processing history. The ability of a polymer material to deform is determined by the mobility of itsmolecules, characterized by specific molecular...

... effects on Tg.Theoreti-cally. the Tg value .should increase with pressure as a function of the ratio of the compressibility to the- thermal coefficient of expansion of the polymer. Other thermodynamic ... modulus, The maximum in the curve denotes the stress at yield avand the elongation at yield €v. The end of the curve denotes the failure of the material, which is characterized by the tensile ... value of the mixture by one or the other of the equations The glass transition of the polymer Is Tg. while that of the plasticizer is TgH\ the volume fraction of plasticizer is Fi(b), and its...

... effects on Tg.Theoreti-cally. the Tg value .should increase with pressure as a function of the ratio of the compressibility to the- thermal coefficient of expansion of the polymer. Other thermodynamic ... modulus, The maximum in the curve denotes the stress at yield avand the elongation at yield €v. The end of the curve denotes the failure of the material, which is characterized by the tensile ... value of the mixture by one or the other of the equations The glass transition of the polymer Is Tg. while that of the plasticizer is TgH\ the volume fraction of plasticizer is Fi(b), and its...

... Inc.ÆÀ1¼1=5boundaryisoneinwhich1in5ofthegrainboundaryatomsmatch,asshowninFig.2.8(c).Twinboundariesmayformwithincrystals.Suchboundarieslieacrossdeformationtwinplanes,asshowninFig.2.8(d).Notethattheatomsoneithersideofthetwinplanesaremirrorimages.Stackingfaultsmayalsobeformedwhentheperfectstackinginthecrystallinestackingsequenceisdisturbed,Figs2.8(e)and2.8(f).Thesemaybethoughtofastheabsenceofaplaneofatoms(intrinsicstackingfaults)ortheinsertionofrowsofatomsthatdisturbthearrangementofatoms(extrinsicstackingfaults).IntrinsicandextrinsicstackingfaultsareillustratedschematicallyinFigs2.8(e)and2.8(f),respectively.NotehowtheperfectABCABCstackingofatomsisdisturbedbytheinsertionorabsenceofrowsofatoms.2.3.4VolumeDefectsVolumedefectsareimperfectionssuchasvoids,bubble/gasentrapments,porosity,inclusions,precipitates,andcracks.Theymaybeintroducedintoasolidduringprocessingorfabricationprocesses.AnexampleofvolumedefectsispresentedinFig.2.9.ThisshowsMnSinclusionsinanA707steel.AnotherexampleofavolumedefectispresentedinFig.1.16(d).This ... Inc.whichisgivensimplybyÀðCAÀCBÞ=r0,thediffusionflux,J,maythenbeexpressedasJ¼D0expÀqkTdCdxð2:9ÞIfwescalethequantityqbytheAvogadronumber,thentheenergytermbecomesQ¼NAqandR¼kNA.Equation(2.9)maythusbeexpressedasJ¼ÀD0expÀQRTdCdxð2:10ÞIfwenowsubstituteD¼ÀD0expÀQRTintoEq.(2.10),weobtaintheusualexpressionforJ,i.e.,JisgivenbyJ¼ÀDdCdxð2:11ÞTheaboveexpressionisFick’sfirstlawofdiffusion.Itwasfirstpro-posedbyAdolfHicksin1855.Itisimportanttonoteherethatthediffusioncoefficientforself-diffusion,D,canhaveastrongeffectonthecreepproper-ties,i.e.,thetime-dependentflowofmaterialsattemperaturesgreaterthan$0.3–0.5ofthemeltingtemperatureindegreesKelvin.Also,theactivationenergy,Q,inEq.(2.10)isindicativeoftheactualmechanismofdiffusion,whichmayinvolvethemovementofinterstitialatoms[Fig.2.11(a)]andvacancies[Fig.2.11(b)].Diffusionmayalsooccuralongfastdiffusionpathssuchasdislocationpipesalongdislocationcores[Fig.2.12(a)]orgrainboundaries[Fig.2.12(b)].This ... the surface energy of the bubble/grain boundaries. We also assume that the rate of grain growth is inverselyproportional to the curvature of the grain boundaries, and that the curva-ture itself...

... enter into the problem. The engineermust appreciate the relevant aspects of mechanical behavior at the differentlength scales. Furthermore, the size scale of the structure can affect the mechanical ... that the origin of the unit cell is at the corner of the unit cell [Fig. 1.10(c)]. The sides of the unit parallelepiped alsocorrespond to the cartesian x, y, z axes, and the angles , ,  are the ... understanding of the mechanical properties of mate-rials. It is not intended to be a comprehensive review of all the differentaspects of mechanical properties; such a task would be beyond the capabil-ities...

... least not in the same way as the others. From Table 10, it can be seen that p53R2possesses a few mutants that behave differently from the rest of the promoters. Of these, amino acid residues 243and ... minimizing the sum of the individual prediction errorpercentage for the two classes.Structural modelling and energy calculations The three-dimensional structure of p53 was taken from the PDB entry ... algorithms have been developed recently [4–7]. The major drawback of these analyses is the lack of information regarding the activity or loss of activity of the target protein, as only a few variants...

... we have shownthat the antibacterial ⁄ fungicidal properties of trappin-2involve the cationic nature of the molecule, as assessed from the salt and heparin dependence of the antimicro-bial ... source of nitrogen [15], thereby competing with the antibacterialeffect of trappin-2. However, none of the bacteriatested destroyed trappin-2 in the incubation mixtures,suggesting that another, ... secretions,are believed to be part of the pulmonary innatedefense system, together with a vast array of defenseeffector molecules, including the defensin and cathelici-din families of antimicrobial peptides....