Rheology and processing

Chapters 5 and 6 consider the rheology of rubbers in some detail. The theoretical development and characterization techniques outUned in those chapters apply equally well to TPEs. However, there are fundamental differences in the response to stress between a conventional rubber and a TPE. Of course the biggest dissimilarity is that a TPE wiU flow at higher temperatures while a crosslinked rubber will not. Some of the similarities and differences between 

FIGURE 17 Schematic model for a polyurethane with monodisperse hard segment lengths showing spherulitic structure of hard domains and the orientation of chain segments within the 

More specifically, the dynamic mechanical properties are significantly different in TPEs vs. conventional elastomers. The WLF equation (see Chapter 5) does not generally apply to TPEs since two phases make the material 

FIGURE 18 Storage modulus (E ) and tan delta (EVE ) vs. temperature for MDI-ED-PTMO 

Rheological measurements can also supply a measure of the ODT temperature independent of scattering measurements. In this method, the storage and loss moduli are measured as a function of frequency at different temperatures above and below the MST. One strain level should be used for these experiments since it has been shown that below the ODT, the dynamical mechanical properties are highly strain dependent. The WLF equation is then 

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Rheological and processability behaviors were studied in a Monsanto processability tester (MPT), which is an automatic high-pressure capillary viscometer. The entire barrel and capillary are electrically heated with a microprocessor-based temperature controller [14], The... 

Polymer Rheology and Processing Universite Pierre et Marie Curie Vitry-sur-Seine, France... 

The molecular weight distribution is an important parameter for controlling the rheological and processing properties of rubber ... 

Han, C.D. 2006. Rheology and Processing of Polymeric Materials, vols I and II. Oxford University Press, New York. 

To start with, there is a brief discussion on the morphology, rheology, and processing characteristics of TPVs to aid better understanding of the subject. 

T. Boronat, V. Segui, M. Peydro, and M. Reig, Influence of temperature and shear rate on the rheology and processability of reprocessed ABS in injection molding process,. Mater. Process. Technol., 209(5) 2735-2745, March 2009. 

ClieieitbsiuoU, N P Introduction to Polymer Rheology and Processing, CRC Press, LLC. Boca Raton, FL, 1999. 

The type of chosen polymer and additives most strongly influences the rheological and processing properties of plastisols. Plastisols are normally prepared from emulsion and suspension PVC which differ by their molecular masses (by the Fickentcher constant), dimensions and porosity of particles. Dimensions and shape of particles are important not only due to the well-known properties of dispersed systems (given by the formulas of Einstein, Mooney, Kronecker, etc.), but also due to the fact that these factors (in view of the small viscosity of plasticizer as a composite matrix ) influence strongly the sedimental stability of the system. The joint solution of the equations of sedimentation (precipitation) of particles by the action of gravity and of thermal motion according to Einstein and Smoluchowski leads 37,39) to the expression for the radius of the particles, r, which can not be precipitated in the dispersed system of an ideal plastisol. This expression has the form ... 

Compatibility of PVC with plasticizer (PI) also strongly influences the rheological and processing properties of plastisols 48>. The effects of the diverse plasticizers on PVC varies since some plasticizers (even well compatible with polymer), e.g. dibutylphthalate (DBP), may readily escape from the obtained materials and articles 17,23,43. Plasticizers which are poorly compatible with PVC (the so-called secondary PI ) may be used for the purpose-oriented change of viscosity properties of a system (fluidity increase) and saving the base PI component. 

Thermoplastic Melt Rheology and Processing, A. V. Shenoy and D. R. Saini... 

J. L. White, Elastomer Rheology and Processing, Rubber Chem. Technol., 42, 256-338 (1969). 

Effects of Additives and Modifiers on the Rheology and Processing of Compounded Systems... 

In addition to the opportunities for new materials synthesis and characterization along these lines, transport properties, rheology, and processing techniques for liquid crystal polymers are essentially unexplored. Experiences with synthesis of polymer structure based on these liquid crystal templates may open up other creative avenues for template synthesis, for example, inside other crystalline structures, chlathrates, or zeolites, or on surfaces [4], Composites, alloys, or mixtures of liquid crystalline and flexible polymers may produce new materials. 

Acierno D and Collyer AA (Eds), "Rheology and Processing of Liquid Crystal Polymers", Chapmann and Hall, London, 1996. 

Rheological measurements must be tailored to the particular process and problem of interest. This is the key to successful solution of rheological and processing problems. Relevant rheological experiments are best made at the same temperatures, flow rates, and deformation modes that prevail in the process of interest. 

The selection of results provided in the present book is unique in the sense that it allows one to grasp the key issues in polymer rheology and processing at once, through a series of detailed state of the art contributions. Generally these issues can only be found in different books. Each paper was reviewed by experts and by the book editors and some coordination was established in order to achieve a readable and easy access style. 

This chapter provides an overview of current researches on liquid crystalline polymers (LCPs). Topics include syntheses of main-chain and side-chain LCFs, structured characterization of LCFs and LCP networks and rheology and processing. Applications of LCP/polymer blends as self-reinforced polymers and electro-optical meterials are also discussed. 

Utracki, L.A. Rheology and Processing of Multiphase Systems In Current Topics in Polymer Science Vol. II Ottenbrite, R.M. Utracki, L.A. Inoue, S. Eds. Hanser Publ., Munchen/Wien/New York, 1987... 

Crystallization can also be induced by the chain extension which occurs in an orientational flow. This is of obvious importance in rheology and processing, and it has been... 

In the rheology and processing of polymers the kinetic aspects of the glass transition are of particular interest since the achievement of thermodynamic equilibrium in the amorphous, high-molar-mass polymer is beyond the time frame of the dynamic environment of processing. One way of viewing the glass transition (Stachurski, 1987) is to consider the... 

The starting point in the kinetic analysis of the oxidation of polypropylene is the measurement of the extent of oxidation of the polymer as a function of time. In rheological and processing studies it is difficult to obtain real-time chemical information, and many of the chemical changes are elucidated after processing by analysis of the polymer product... 

Halley, P. (1993) The Effect of Surfaces and Struemres on the Rheology and Processing of LLDPE, Thesis, Brisbane, University of Queensland. 

Kalyon, D. Yilmazer, U. (1990) Rheological behaviour of highly fiUed suspensions which exhibit wall slip, in CoUyer, A., Utracki, L.A. (Eds.) Polymer Rheology and Processing, London Elsevier. 

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