Effect of temperature on polymer migration

In this study, we investigated the temperature gradient effect on the polymer dynamics in a flow field. To simplify our analysis, we adopted a two-bead harmonic dumbbell model, and found that there were significant effects on the polymer migration not only due to the nonhomogeneity of the flow field, but also due to the temperature difference.     

Effect of temperature gradient on polymer migration

Polymer migration in a flow field is a well-known phenomenon, and it has been verified that the sources of such phenomena are nonhomogeneity of the flow field, concentration effects, and hydrodynamic interactions between the polymer molecules and walls. In this study, we investigate the temperature gradient effect on polymer dynamics due to an imposed flow field. The diffusion equation and concentration profile of the polymer molecules induced by a temperature gradient using a two-bead dumbbell model are obtained from the Fokker-Planck equation. From the concentration equation constructed for a dilute solution in a general flow geometry, we find that there are significant effects on the polymer migration not only due to the nonhomogeneity of the flow field, but also due to temperature gradients.     

Effect of die temperature on the flow of polymer melts. Part II: Extrudate swell

The effect of die wall temperature on the extrudate swell of polymer melts flowing through dies with single and dual circular channels was studied. Extrudate swell was measured at constant flow rates using an Instron capillary rheometer with a modified die section. It was found that under isothermal conditions, extrudate swell plotted against the average wall shear stress gave rise to a temperature independent correlation for polystyrene. Under non-isothermal conditions, such a correlation did not exist, which might be due to the change of wall shear stress in the axial direction. The extrudate swell in the non-isothermal cases can be better correlated with the wall shear stress at die exit. For the two-hole die, changes of die wall temperature varied both the flow rate ratio and the extru date swell ratio. The latter is, however, much less sensitive to the die wall temperature than the former.     

Concentration dependence of zero-shear viscosity for polymer solutions: A test of the lyons-tobolsky equation

The empirical equation proposed by Lyons and Tobolsky (1) to describe the concentration dependence of zero-shear viscosity in polymer solutions was tested on a variety of data taken from the literature, covering different polymer-solvent systems, molecular weight, temperature, and the whole concentration range. This equation was fitted to each set of experimental viscosity-concentration data by a least squares method. The validity of this equation is verified. The dependence of the optimal values obtained for the three parameters intrinsic viscosity, [η], Huggins constant, k, and new empirical constant, b, on molecular weight, temperature, and solvent is also discussed.     

The temperature dependence of the doolittle equation parameter for polymer liquids

The Doolittle equation parameter for polymer liquids is a function of temperature. Its dependence on temperature can be expressed by a quadratic equation. The constants in the equation are determined for four vinyl-type polymer liquids: polystyrene (PS), poly(vinyl acetate) (PVAc), polydimethylsiloxane (PDMS), and polyisobutylene (PIB). It was found that the Doolittle parameter decreases with increasing temperature. Equations are presented for the pressure and temperature coefficients of viscosity, isoviscous temperature coefficient of volume, and the constant K_m in the Miller equation. Comparisons of the predictions of the equations, with those in the literature, are favorable. © 1993 John Wiley & Sons, Inc.     

Effect of interface on bulk polymer: control of glass transition temperature of rubber

In current paper, we demonstrated that molecular dynamics and glass transition of rubber can be controlled by constructing attractive interface between rubber matrix and fillers. Based on a combination of experiments and molecular simulations, it was revealed that interfacial segmental mobility was reduced and glass transition temperatures (T_gs) of epoxidized natural rubber (ENR) were significantly improved due to in situ polymerization of zinc dimethacrylate (ZDMA). During curing, ZDMA polymerizes in rubber matrix, resulting in the appearance of nanodispersion phases of poly-ZDMA (PZDMA). It was demonstrated that coordination interaction exists between epoxy groups and PZDMA in interfacial regions. Furthermore, using dynamic Monte Carlo simulations, it was observed that the interfacial regions that have highest content of epoxy groups exhibit lowest segmental mobility. Then, the increase of ZDMA content leads to the rise of the fraction of absorbed interfacial segments, and thus the T_gs of filled rubbers are improved.     

Effect of temperature gradient on capillary migration slag components in refractories

Conclusions On the assumption of capillary migration of particles due to the overflow of a sufficiently thin external contact layer, an equation is obtained for the velocity of droplets in immiscible liquids. In the temperature gradient field, the rate of separation of the segregating phases and the formation of the zones in the refractory is proportional to the temperature coefficient of the interphase tension, and is retarded with increase in the slag's viscosity. In contrast to previously known equations, we postulate an inverse relationship for the rate of displacement and the size of the separating droplet of segregating iron-manganese oxide melt.Translated from Ogneupory, No.5, pp. 15–19, May, 1992.     

Effect of hybrid nanoparticles on glass transition temperature of polymer nanocomposites

Changes in the glass transition temperatures of composites based on polystyrene and nanosized macromolecular nanostructures (molecular silicasols, dendrimers) are reported. Silicasols are nanosized particles consisting of a silica core and an ethyl phenyl shell; dendrimers are formed using a carbosilane core with ethyl phenyl end groups. It has been observed that the glass transition temperatures of the composites (T_gc) may be either above or below the glass transition temperature of polystyrene, depending on the size of the filler particles. A theoretical model based on the relation between the glass transition temperature and the configurational entropy of the composite, which satisfactorily describes the experimental dependence, was developed. It is found that the effect of the size of the hybrid nanoparticles on T_gc was determined using two factors. First, the presence of an organic layer on the surface of nanoparticles increases the number of degrees of freedom and the entropy of the system, thereby reducing T_gc. Second, the particles present in the polymer reduce the number of configuration states of macromolecules, which reduces the disorientation entropy. This effect leads to an increase T_gc. The competition between these two main factors determines the sign of the glass transition temperature deviation. The size of the particles and their organic surface layer play the key roles in the thermodynamic properties of the composites. POLYM. COMPOS., 37:1978–1990, 2016. © 2015 Society of Plastics Engineers     

Studies on polymer latex films: II. Effect of surfactants on the water vapour permeability of polymer latex films

Poly(butyl methacrylate) films have been prepared from surfactant-free latices which had post-added commonly used latex stabilisers. Water vapour transmission rates were used to study film permeability in relation to morphology, which was also studied by freeze fracture replication transmission electron microscopy. The extent of latex coalescence depended upon the chemical nature of the stabiliser employed and at monolayer coverage was not necessarily deleterious to the barrier properties of the films.     

Concentration,temperature and deformation effects in concentrated polymer solutions with volatile solvents

A novel high pressure polymer solution viscometer has been experimentally evaluated using the polystyrene/ethylbenzene system. The polymer solutions range in concentration from 60 weight percent polystyrene to the pure melt. The overall temperature range is 132°C to 240°C. The shear rates range from roughly 5 s^?1 to 2000 s^?1. It has been concluded that the present method is useful in determining the shear dependent behavior of these volatile solutions, The shear dependent nature of this system is consistent with accepted non-Newtonian viscosity theory.     

Starch‐filled ternary polymer composites. II: Room temperature tensile properties

The room temperature tensile properties of granular starch‐filled low‐density polyethylene (PE) and starch‐filled blends of PE and poly(hydroxy ester ether) (PHEE) are presented. At low filler contents (?_f), the filled PE:PHEE blend has a higher yield stress and tensile strength than either the starch/PE composites or the unfilled matrix. The increase in the yield stress indicates that matrix yielding occurs before debonding. At high filler contents, the tensile strength of the filled blend is again greater than the strength of the starch/PE composites. This increase in strength is the result of higher debonding stresses in the ternary composite. In both materials there is a change in the deformation process at a critical filler content, ?_cr. Below ?_cr, deformation involves the growth of debonded regions; above ?_cr, deformation is confined to narrow damaged zones. There is a reduction in the strain at failure when this change in the deformation process occurs. Although the PHEE surface coating affects the debonding stress and the tensile strength, it does not affect the strain at failure or the tensile modulus. For both composite materials, the increase in modulus with ?_f can be adequately described using a simplified form of the Kerner equation. Polym. Eng. Sci. 44:1839–1847, 2004. © 2004 Society of Plastics Engineers.     

养护温度对粉煤灰基矿物聚合物强度影响的研究

研究了不同养护温度下粉煤灰基矿物聚合物的抗压强度，以及经过1d高温养护后常温条件下强度的发展特点。结果表明：提高养护温度可以提高粉煤灰基矿物聚合物的抗压强度，缩短养护时间。同时，其强度提高程度因激发剂溶液种类不同而不同，5MK2SiO3溶液的提高程度最高；其它3种激发剂的提高幅度较小，高温养护7d时的强度与常温28d时的强度接近。     

Effect of polymer latexes with varied glass transition temperature on cement hydration

Influence of styrene‐acrylate latexes with varied glass transition temperature (T_g) on cement hydration was studied and the mechanism was analyzed. Results show that polymer latexes with varied T_g retard cement hydration to different extents. Specifically, low T_g polymer shows stronger retardation effect than the high T_g polymer. Despite similar surface charges, colloidal particles with lower T_g exhibit higher affinity to surface of cement grains than the high T_g polymer, indicated by the higher adsorption amount and denser covering layer. The low T_g polymer experiences particle packing, deforming, and film forming processes along with the consumption of water during cement hydration, which eventually produces a covering layer of polymer surrounding cement grains. However, for the high T_g polymer, film forming process is absent. Consequently, the higher adsorption amount and the film‐formation process along with cement hydration are the two reasons for the stronger retardation effect of the low T_g polymer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45264.     

Interfacial tension in polymer melts. Part II: Effects of temperature and molecular weight on interfacial tension

Interfacial tension is one of the most important parameters that govern the morphology of polymer blends and the quality of adhesion between polymers. However, few data are available on interfacial tension due to experimental difficulties. A pendant drop apparatus was used for the determination of the interfacial tension for the polymer pair polypropylene/polystyrene (PP/PS). The effects of temperature and molecular weight were evaluated. The range of temperatures used was from 178° to 250°C, and the range of molecular weights used was from 1590 to 400,000. The interfacial tension decreased linearly with increasing temperature. With only one exception, higher molecular weight systems showed weaker dependence of interfacial tension on temperature than lower molecular weight systems. Also, polydisperse systems showed a stronger dependency on temperature than the monodisperse systems. The value of the interfacial tension, which increases with molecular weight, appears to level off at molecular weights above the entanglement chain length. For the polymer pair PP/PS, the dependency of the interfacial tension on the number average molecular weight appears to follow the well-known semi-empirical (?2/3) power rule over most of the range of molecular weights. Comparable correlations were obtained with values of the power between ?1/2 and ?1.0.     

Effect of filler treatment on temperature dependence of resistivity of carbon-black-filled polymer blends

Polyblends prove to be able to provide more possibilities for tailoring conductive polymer composites in comparison with individual polymer systems. Accordingly, ethylene–vinyl acetate—low-density polyethylene (EVA–LDPE) filled with carbon black (CB) was prepared in this study as a candidate for positive temperature coefficient (PTC) material. In consideration of the fact that CB distribution plays the leading role in controlling a composite's conduction behavior, chemical treatment of CB was applied to reveal its influence on percolation and the PTC effect. It was found that titanate coupling agent treatment facilitated sufficient distribution of CB in LDPE phase, leading to lower resistivity and a squarer PTC curve. Composites filled with nitric-acid-treated CB exhibited specific temperature dependence of resistivity as a result of the heterogeneous dispersion of CB at the interface of EVA–LDPE, which might provide the materials with a new function. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 489–494, 1999     

Effect of a moving flame on the temperature of polymer coatings and substrates

A computational model is developed to predict the temperature profile over an organic coating on a metal surface as a result of the action of a moving flame. The deflection of the flame as it impinges on the surface is simulated and its consequent heat transfer to the polymer is determined. The scanning action of the flame across the substrate is quantified and the temperature profiles within the polymer are calculated. The results show a substantial build up of temperature at the surface and large temperature gradients throughout the thickness, which are due to the low thermal conductivity of polymers. This can be particularly detrimental for polymers owing to their low softening and decomposition temperatures. The model can be applied to flame impingement on a bulk polymer or on an organic coating on a metal substrate. The research shows the risks of a moving flame overheating a polymer surface and indicates remedial measures.     

Study of Aromatic Compounds Derived from Sugarcane Bagasse: II. Effect of Concentration

The results of a set of experiments that were designed to integrate current knowledge on the major constituents of sugarcane bagasse lignin, specifically p‐coumaric, ferulic, syringic acids, and vanillin are presented. These aromatic compounds have well‐known antioxidant power and they are very important for the food, pharmaceutical, and nutraceutical industries. Following a study on the effect of pH upon the spectra of these monomers and the determination of their pK_a values, their self‐association properties in ethanol as a solvent, particularly at concentrations < 10^–4 M were investigated using UV spectrophotometry and their K_ass values were determined. The results collected allowed to better understand the chemistry of sugarcane lignin and provide a contribution to the possible exploitation of this abundant straw material for the recovery of fine chemicals.     

Study on morphology of ternary polymer blends. II. Effect of composition

The composition effect on morphology of polypropylene/ethylene–propylene–diene terpolymer/polyethylene (PP/EPDM/PE) and polypropylene/ethylene–propylene–diene terpolymer/polystyrene (PP/EPDM/PS) ternary blends has been investigated. In all of the blends, polypropylene as the major phase was blended with two minor phases, that is, EPDM and PE or PS. From morphological studies using the SEM technique a core–shell morphology for PP/EPDM/PE and separated dispersed morphology for PP/EPDM/PS were observed. These results were found to be in agreement with the theoretical predictions. The composition of components affected only the size of dispersed phases and had no appreciable effect on the type of morphology. The size of each dispersed phase, whether it forms core or shell or disperses separately in matrix, can be related directly to its composition in the blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1138–1146, 2001     

Effect of viscous dissipation on the temperature of the polymer during injection molding filling

During injection molding, viscous dissipation changes the temperature distribution by playing the role of an energy source, which affects heat transfer rates. Understanding the effect of the viscous dissipation assists the designing of the cooling system in injection molding process. In this article, the effect of the viscous dissipation on the temperature distribution throughout a rectangular channel for different polymers at different inlet velocities and temperatures is studied. A cross type rheological model depending on the temperature and pressure is assumed for polymer materials polystyrene (PS) and polypropylene (PP). The evolution of the flow velocity inside the channel is presented. The quantity of heat added due to viscous dissipation to the polymer is also calculated up to different positions through the channel. A numerical finite volume code for the simulation of polymer melt flow in a channel is used and a validation of this numerical code is presented. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.