Filled polymer

Particulate Composites. These composites encompass a wide range of materials. As the word particulate suggests, the reinforcing phase is often spherical or at least has dimensions of similar order ia all directions. Examples are concrete, filled polymers (18), soHd rocket propellants, and metal and ceramic particles ia metal matrices (1). 

This article addresses the synthesis, properties, and appHcations of redox dopable electronically conducting polymers and presents an overview of the field, drawing on specific examples to illustrate general concepts. There have been a number of excellent review articles (1—13). Metal particle-filled polymers, where electrical conductivity is the result of percolation of conducting filler particles in an insulating matrix (14) and ionically conducting polymers, where charge-transport is the result of the motion of ions and is thus a problem of mass transport (15), are not discussed. 

Slides Microstructures of GFRP, glass-filled polymer, cermet, wood sectioned piece of cord-reinforced automobile tyre. 

ABS, polycarbonate and polysulphone) but large effects on crystalline polymers. It is particularly interesting, as well as being technically important, that for many crystalline polymers the unfilled polymer has a heat deflection temperature (at 1.82MPa stress) similar to the Tg, whereas the filled polymers have values close to the T (Table 9.2). 

Glass-reinforced grades of SAN exhibit a modulus several times that of the unfilled polymer and, as with other glass-filled polymers, a reduced coefficient of thermal expansion and lower moulding shrinkage. The materials are thus of interest on account of their high stiffness and dimensional stability. 

The glass-fibre nylons have a resistance to creep at least three times as great as unfilled polymers. In the case of impact strength the situation is complex since unfilled nylons tend to break showing tough fracture whereas the filled polymers break with a brittle fracture. On the other hand the glass-filled polymers are less notch sensitive and in some tests and service conditions the glass-filled nylons may prove the more satisfactory. 

In the case of glass-filled polymers, moulding shrinkage is somewhat lower (0.003-0.005 cm/cm). 

The layers in the plate-like structure of talc are Joined by very weak van der Waals forces, and therefore delamination at low shear stress is produced. The plate-like structure provides high resistivity, and low gas permeability to talc-filled polymers. Furthermore, talc has several other structure-related unique properties low abrasiveness, lubricating effect, and hydrophobic character. Hydrophobicity can be increased by surface coating with zinc stearate. 

It should be noted once more that filled polymers may be treated as three-phase systems only nominally, since thermodynamically the interphase cannot be regarded as a phase in its own right. 

An alternative reason why particle size can affect the polymer melt or solution viscosity consists of the agglomeration of the filler. The higher the dispersity of the filler the higher is its tendency to agglomeration [138-140,161]. Agglomeration, as will be shown below, affects the properties of filled polymers. 

Nielsen proposed a formula [216] for estimating the elasticity modulus of a filled polymer ... 

---