Fillers fibrous

In certain applications it is necessary to impart the strength required to a plastic part by the use of a fibrous fillers. The following types are among those used  

It is usually obvious whether a plastic contains a fibrous filler from either a visual inspection or the use of a relatively low powered optical microscope. 

TGA will enable the amount of carbon fibres in a composite to be quantified. The oxidation temperature of around 700 °C (instead of the 500-600 °C experienced with carbon blacks) will also provide a confirmation of their presence. 

As mentioned above, synthetic polymeric fibres can be identified by the IR microscope once sufficiently isolated or, by use of their melting point, by the hot stage microscope or DSC. In the case of DSC, some quantification data can be obtained from the size of the melting endotherm providing standards are available. 

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Fibrous fillers are often embedded in a laminar form. The fibres used have higher moduli than the resins in which they are embedded so that when the composite of resin plus fibre is strained in the plane of the fibrous layer the bulk of the stress is taken up by the fibre. This results in an enhancement of both strength and modulus when compared with the unfilled resin. 

Soon after World War II the hard thermoplastic floor tile was developed. These tiles use coumarone resins as a binder for the other ingredients, which may contain fibrous fillers such as asbestos, inert fillers such as china clay and softeners such as paraffin wax. 

Excellent mechanical properties with very high values for tensile strength, flexural strength and modulus in the flow direction. This applies to unfilled materials and may be further enhanced by incorporation of fibrous fillers. Quoted data for these properties are in the following ranges ... 

Of the fibrous fillers which greatly reduce the brittleness, blue asbestos fibre is normally used for battery boxes, the principal outlet. Other materials that may be used include cotton fibres, ground wood, slag wool and ground cork. 

Fibrous fillers are now gaining more importance over particulate fillers due to the high performance in mechanical properties. The influence of fiber diameter on the tensile behavior of short glass fiber on polyimide was reported [95], At higher concentrations thick fibers seem to be more advantageous probably because of the... 

The data given in Table 2 show that fibrous fillers have the optimum shape in terms of the maximum reinforcing effect, as could be expected. 

From the results of fiber testing for different cramped lengths one determines A and B (cf. [147]). The composite containing this particular fibrous filler is then tested under tension or bending to determine t. Then the attained strength is compared with the limiting one calculated by Eq. (18) and the coefficient k is found then one can predict k for any t value. 

For scaly fillers the increase of relative viscosity with filler concentration is not as pronounced as in case of fibrous fillers [177,178]. Owing to filler orientation, the flow curves for systems with different concentrations of a fibrous and a scaly filler may merge together at high shear rates [181]. In composites with a dispersed filler the decrease of the effective viscosity of the melt with increasing strain rate is much weaker. 

Fibrous fillers have often been reported to increase considerably 1 in comparison with unfilled systems [171,176, 189, 197, 198]. In this case, however, the inlet loss is due not to the highly elastic properties of the melt but to other reasons, such as pushing of the binder through the package (plug) of filler in the inlet zone. Pushing of the filler package forth into the channel, etc. 

The first difference of normal stresses (tr, t) may serve as an indirect index of the highly elastic properties of polymeric systems [199]. C. D. Han [200] related (ru with the residual pressure at outlet Pt)dt. Han, who observed its reduction in polypropylene filled with calcium carbonate [201], concluded that filling decreases the normal stresses. Note that addition of fibrous fillers, vice versa, somewhat increases Pexi, [180]. 

Fillers with particles nearly spherical in shape usually dimish <7n under a fixed shear stress [178,181, 182,202] in comparison with the pure polymer. In contrast, scales tend to step up the first difference of normal stresses [181]. Fibrous fillers have little effect on a, x value [181], except in a few cases where the tendency for... 

Based on this analysis it is evident that materials which are biaxially oriented will have good puncture resistance. Highly polar polymers would be resistant to puncture failure because of their tendency to increase in strength when stretched. The addition of randomly dispersed fibrous filler will also add resistance to puncture loads. From some examples such as oriented polyethylene glycol terephthalate (Mylar), vulcanized fiber, and oriented nylon, it is evident that these materials meet one or more of the conditions reviewed. Products and plastics that meet with puncture loading conditions in applications can be reinforced against this type of stress by use of a surface layer of plastic with good puncture resistance. Resistance of the surface layer to puncture will protect the product from puncture loads. An example of this type of application is the addition of an oriented PS layer to foam cups to improve their performance. 

Reinforcing agents (CB, talc, silica, and other organic and fibrous filler)... 

Particulate and fibrous fillers are added for a variety of effects, such as to improve the mechanical properties of the polymer to reduce shrinkage, as colourants, to reduce costs, and to improve flame retardancy. 

As with most nonpolar hydrocarbon-intense polymers, bitumens exhibit good resistance to attack by inorganic salts and weak acids. They are dark, generally brown to black, and their color is difficult to mask with pigments. They are thermoplastic materials with a narrow service temperature range unless modified with fibrous fillers and/or synthetic resins. They are abundant materials that are relatively inexpensive, thus their use in many bulk applications. 

Secondary ingredients in epoxy adhesives include reactive diluents to adjust viscosity mineral fillers to lower cost, adjust viscosity, or modify the coefficient of thermal expansion and fibrous fillers to improve thixotropy and cohesive strength. Epoxy resins are often modified with other resins to enhance certain properties that are necessary for the application. Often these modifications take the form of additions of elastomeric resins to improve toughness or peel strength. 

Particle size and shape will affect the degree of mixing required. Particles with large aspect ratios, such as fibrous fillers, and particles of large size are typically more difficult to disperse. In addition, high filler loading makes sufficient wetting of the filler more difficult because of the increased viscosities encountered. 

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