Mingshi SONG
,
Guixian HU
,
Zhihong YANG
,
Qiang XU
,
Sizhu WU
,
null
,
null
,
null
,
null
材料科学技术（英文）
The structural model of the multiple-transient networks and the mechanism of the multiple-reptation entangled chains due to the dynamic reorganization in the entangled sites were extensively applied on the die swell of polymeric liquids in the steady simple shear flow. The total (recoverable and unrecoverable) viscoelastic free energy of deformation and flow, the constitutire equation and the expression of the simple shear (tanψ) were deduced from the conformational probability distribution function of the entangled polymer chains. It found that: (1) the magnitudes of simple shear (tanψ) depended not only on the free recoil (or recoverable strain) but also on the viscous heating (or unrecoverable strain); (2) the total recoil may be resolved into the instantaneous and delayed recoil. Based on these facts, the functions of the partition and two experiential fractions of the recoverable ( ) and the unrecoverable ( ) conformations for the recoil and viscous heating of polymeric liquids were defined correspondingly. Then the correlation of the instantaneously and ultimately (or total) recoverable strains to the (N1/τ12)W and the fraction of trans-form conformation was obtained. After introducing the condition of uniform two-dimensional extension (αx=αy=α, αz=α-2) and the swell ratio (B=α), two sets of equations on the instantaneous and ultimate swelling ratios (BE, BEVT) were obtained, and a method to determine the fraction of the recoverable transform conformation were proposed. The equations of BE and BE5 were verified by the experimental data of HDPE (high denisity polyethylene) at two different high temperatures. It shows that the molecular theory of die swell can be used to predict the correlation of the swelling to the (N1/τ12)W and the fraction of trans-form conformation.
关键词:
Die swell
,
null
,
null
Mingshi SONG
,
Qiang XU
,
Guixian HU
,
Sizhu WU
,
null
材料科学技术（英文）
A general expression for the correlation of the simple shear (tan ) to the molecular parameters and the shear rate ( ) was deduced. It shows that the simple shear (tan ) may be resolved into free recoil (recoverable strain) and viscous heating (unrecoverable strain). The magnitudes of the simple shears for recoil (tan E) and (tan V) for viscous heating not only depended on the molecular parameters and the operational variables, but also on the exponential fractions of the recoverable (1- ) and unrecoverable ( ) conformations for recoil and viscous heating. Therefore the magnitudes of the simple shears (tan E) for recoil and (tan V) for viscous heating are, respectively, expressed as the partition function to the (1- )th power and the partition function to the ( )th power. Thus correlations of the total recoil and the ultimately recoverable strains to the molecular parameters [ , a, η0, GN0 and (1- )] and the operational variables ( ), (L=D) and tr) were deduced respectively, which show that at very different shear rates ( ) the polymeric liquids may exhibit a very different viscoelastic behaviors. After introducing the uniform two-dimensional extension, the definition of swelling ratio and the ratio of L to D [De=(L/D)], two expressions for the ultimate die swelling effect and the ultimate extrudate swelling ratio BEVT5 to the molecular parameters [ , a, η0, GN0 and (1- )] and the operational variables ( , (L/D) and tr) were obtained. The two correlation expressions were verified by the experimental data of high-density polyethylene (HDPE) which shows that the two correlation expressions can be used to predict the correlations of the ultimate extrudate swelling behaviors of polymeric liquids to the molecular parameters and the operational variables.
关键词:
Die swell
,
null
,
null
Mingshi SONG
,
Wen ZHOU
,
Guixian HU
,
Lijiang HU
材料科学技术（英文）
A double-network model is established, which consists of the segments, E and A-constituent chains, the polymeric chains entangled with other ones by multi-entanglement and polymeric chains connected to a great number of destructible particles by multi-adsorption, based on which the E and A-constituent chains can be recreated and released dynamically. The distribution function of the end-to-end vector, the statistical distribution function of conformation for two kinds of chains in the multi-entanglement and multi-adsorption states and their number of polymeric chains are calculated by the combination of statistical mechanics and kinetics. Then the viscoelastic free energies of deformation for two kinds of the networks and suspensions are calculated by Boltzmann's statistical theory. Also, elastic modulus and memory function for two kinds of the network and suspensions are derived. Consequently, a new molecular theory of the non-linear viscoelasticity for polymeric suspensions is proposed, and the constitutive equation and material function with yielding and thinning for the polymeric suspensions in different flow fields are derived from this theory.
关键词:
Mingshi SONG
,
Wen ZHOU
,
Guixian HU
,
Lijiang HU
材料科学技术（英文）
The memory function and elastic modulus were introduced into the O-W-F type of constitutive equations with the Cauchy-Green and Finger tensors for simple fluid, and then the concrete constitutive equation and material function for polymeric suspensions in the different flow fields were formulated: 1) Viscosity and first normal-stress difference coefficient in the shear flow field; 2) Tensile viscosity at the uni-axial elongation flow field; and 3) Dynamic viscosity and modulus in the dynamic field. Then the dependence of the material function on the deformation rate and weight fraction of fillers was discussed, and the shear flow curves with four characteristic regions ( I-low shear rate plateau region, II-apparent yielding region, III-intermediate rate plateau region, and IV-shear thinning region.) were explained theoretically. Finally, it was verified by a number of experimental values for the rheological suspensions and the viscoelastic and mechanical behaviors can be predicted by the molecular theory of non-linear viscoelasticity for polymeric suspensions.
关键词:
Mingshi SONG
,
Chen ZHANG
,
Guixian HU
材料科学技术（英文）
Based on the molecular theory of non-linear viscoelasticity with constrained entanglements in polymer melts, the material functions in simple shear flow were formulated, the theoretical relations between. eta((gamma) over dot), psi (10)((gamma) over dot) and shear rate ((gamma) over dot), and topologically constrained dimension number n ' and a were derived. Linear viscoelastic parameters (eta (0) and G(N)(0)) and topologically constrained dimension number (n ' a and <()over bar>) as a function of the primary molecular weight (M-n), molecular weight between entanglements (M-C) and the entanglement sites sequence distribution in polymer chain were determined. A new method for determination of viscoelastic parameters (eta (0), psi (10), G(N)(0) and J(e)(0)), topologically constrained dimension number (n ', a and v) and molecular weight (M-n, M-c and M-e) from the shear flow measurements was proposed. It was used to determine those parameters and structures of HDPE, making a good agreement between these values and those obtained by other methods. The agreement affords a quantitative verification for the molecular theory of nonlinear viscoelasticity with constrained entanglement in polymer melts.
关键词:
