Particulate polymers

Figure 5.22 Problem domain in the micro-mechanical analysis of the particulate polymer composite...

Sorption Studies Using Particulate Polymer Enmeshed in PTFE... 

Errede, L.A. Stoesz, J.D. Sirvio, L.M. Swelling of particulate polymers enmeshed in poly(tetra-fluoroethylene). J. Appl. Polym. Sci. 1986, 31 (8), 2721-2737. 

Alternative methods of determining exist. In one method (86) particulate polymer Is stirred In a closed container which contains a dilute A-B solution. The change In free solution solute concentration monitored over a period of time Indicates the magnitude of the solute-polymer Interaction and yields a value of... 

Particulate polymer composites with fibers are a very active area of development, particularly carbon nanotubes and nanofiber composites, and the new graphite and polymer composites [35]. This fact, combined with the continued interest in nancomoposites based in nanometric clays [36], suggests that improvements in mechanical properties of particulate and short-fiber polymer composite materials will continue to be reported. 

Fu, S.Y., Feng, X.Q., Lauke, B., Mai, Y.W., 2008. Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate-polymer composites. Compos. Eart B Eng. 39, 933-961. 

Jaj Jajam, K. C., Tippur, H. V. Quasi-static and dynamic fi-acture behavior of particulate polymer composites A study of nano- vs. micro-size filler and loading-rate effects. Compos. Part B -... 

The MIP can be produced in whatever format is desired, though most MlAs reported are still based on conventional acrylate/vinyl based particulate polymers. A reference polymer, which may be a nonimprinted polymer or NIP made similarly to the MIP but without template or a control polymer or CIP imprinted with a very different template but otherwise similar to the MIP, is also required for assay optimization. It... 

Once the SMPF skeleton was prepared within the mold, the particulate polymer matrix was prepared. The thermoplastic particles (CAPA 6506) were first added to the EPON 828 resin while stirring by a mechanical mixer. The volume fraction of the thermoplastie partieles was... 

Particulate-polymer nanocomposites can be prepared by any one of the following general approaches ... 

Rigid inorganic nanoparticles with a smaller aspect ratio are also promising reinforcing and/or toughening materials for polymers [2]. Several comprehensive reviews have been already pubHshed in the literature regarding the effect of particle size, interfacial adhesion, and particle content of particulate-polymer composites [5,6]. 

It is known that the essential characteristics of composites (such as energy absorption) depend on key parameters like shape and dimension of particles, mechanical properties of the filler and the host matrix, filler-matrix interfacial strength, as well as volume fraction and particle dispersion in the matrix [9]. More specifically, the fracture behavior of particulate polymer composites depends on the following factors ... 

In this section, the effects of the above factors on the facture behavior of particulate polymer composites are discussed. 

In addition to the discussed factors, the type of loading (quasi-static or dynamic) affects the mechanical response and fractme behavior of particulate polymer composites. 

In spite of the several investigations carried out on the mechanical properties and fracture behavior of particulate polymer composites at room temperature, there are limited attempts on micro-fracture mechanisms under high temperatures. The dependence of creep deformation on stress, time, loading speed, and temperature is well known [51]. 

The traditional measuring devices such as strain gauge and extensometer are capable of providing a single point strain and average strain in a specific direction, respectively. It is well known that the damage processes are microstructure dependent and macromechanical behavior of particulate polymer composites mainly depend on their... 

Therefore, characterizing the macromechanical properties of particulate polymer composites without studying the microstructural damage mechanisms and their effects on macromechanical properties is not possible. 

In this chapter, the fracture of WPCs as particle-filled polymer composites was elaborated. The characterization of particulate polymer composites fracture behavior and the influencing factors such as particle size as well as orientation, temperature, and loading were discussed. The fracture observation using special setup was described and the diverse numerical methods to analyze the fracture of such composites were reviewed. Finally the finite element simulation of the fracture for WPG specimen with real geometrical model was conducted and the agreement of results compared to the experimental ones was demonstrated. 

K. C. Jajam, Fracture Behavior of Particulate Polymer Composites (PPCs) andlnterpen-etrating Polymer Networks (IPNs) Study of Filler Size, Filler Stiffness and Loading Rate Effects, PhD Thesis, Auburn University (2013). 

Finally, in this section it is perhaps worth pointing out that emphasis has been placed on particulate polymer supports. It must be remembered, however, that other formats are possible and may eventually lead to industrial application. Some indication of the direction in which research is moving is given in the following section. 

Most thermoplastic materials are moulded by the process of injection moulding. In this process, the polymer is heated in a cylindrical chamber to a temperature at which it will flow and then it is forced in to a relatively cold, closed mould cavity by means of hydrolytically applied high pressure through a plunger or ram, but recently by means of a reciprocating screw that serves the dual purpose of providing the molten polymer mass and forcing it into the mould. The particulate polymer is picked up by the rotation of the screw, compressed and melted, the melt is mixed, and delivered to the entrance of the mould. The screw then moves forward to force a fixed volume of the molten polymer... 

Theoretical description of devolatilization of particulate polymer can generally be achieved with a relatively high degree of accuracy. In most cases, the process will be diffusion controlled. The diffusion coefficients in solid polymers are very low, ranging from about 10" mys to 10 mys. The temperature in the polymeric particle can usually be taken as constant since the thermal diffusivity (a 10" mys) is many orders of magnitude higher than the diffusion coefficient. 

Measurement of the external coefficient of friction of particulate polymers is very difficult because of the very large number of variables that influence the coefficient of friction. Many investigators have made elaborate measurements on the external coefficient of friction [24-32]. The result of this work is that many variables have been identified that affect the frictional behavior however, most measurement techniques do not yield accurate and reproducible results that can be used in the analysis of the extrusion process. The most elaborate measurements and the most meaningful results have probably been obtained at the DKl in Darmstadt, Germany [95]. It is possible to obtain reproducible results by very careful experimental techniques and special surface preparation of the metal wall. However, the frictional coefficients determined in this fashion are hardly representative of the frictional process conditions occurring in an extruder. 

If the transport of particulate polymer occurs by plug flow, then the only frictional coefficient of importance is the external coefficient of friction. This condition is usu-... 

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