Polymer matrix composites defined

Throughout this summary we have neglected the effect of dispersion on the overall transport of mass and heat. This is due to the fact that if dispersion is included, dispersion tensors must be determined before the equation can be solved. This can be done by solving the appropriate transport equation within a unit cell. Because a unit cell cannot be defined in most reinforcements used in polymer matrix composites, however, dispersion tensors cannot be accurately determined, so we have left dispersion effects out of our equations. In general, we anticipate dispersion to play a minor role in the IP, AP, and RTM processes. This assumption can be checked, however, by evaluating the dispersion terms using an approach similar to [16] where experiments and correlations are used to determine the importance of dispersion. 

Before developing the necessary equations to predict the temperature within a composite part, it is enlightening to consider the thermal diffusion problem in polymer matrix composites. Thermal diffusivity is defined as... 

CMCs are significantly different from monolithic ceramics, or even from fairly well understood polymer matrix composites (PMCs). The combination of limited duetility of the eeramic matrices and the highly aggressive environments in which they are intended to operate present notable challenges to defining eonstituent requirements. 

A composite material can be defined as a material in which two or more distinct structurally complementary substances are combined to produce structural or functional properties which are different from the individual components. Composites may be either synthetic or natural. Polymer matrix composites are much easier to produce than other composites, because of their low cost, low density and ease of processing. Composites have two phases, a continuous matrix phase and a dispersed phase or reinforcement phase. Polymer composites can be classified according to the nature of the dispersed phase as micro-or nanocomposites. ... 

With the advent of PNCs, further increases in composite properties have been made possible. PNCs represent a new class of polymer matrix composites, which consist of a conventional polymer matrix in which nanoparticles have been dispersed to provide the desired increase in performance. Nanoparticles are defined as particles having at least one characteristic dimension, that is, length, width, or... 

Melting and glass transition temperatures are important parameters relative to in-service applications of polymers. They define, respectively, the upper and lower temperatnre limits for numerous applications, especially for semicrystalline polymers. The glass transition temperature may also define the upper use temperature for glassy amorphous materials. Furthermore, T and Tg also influence the fabrication and processing procednres for polymers and polymer-matrix composites. These issnes are discnssed in sncceeding sections of this chapter. 

Micro-composites are formed when the polymer chain is unable to intercalate into the silicate layer and therefore phase separated polymer/clay composites are formed. Their properties remain the same as the conventional micro-composites as shown in Figure 2(a). Intercalated nano-composite is obtained when the polymer chain is inserted between clay layers such that the interlayer spacing is expanded, but the layers still bear a well-defined spatial relationship to each other as shown in Figure 2(b). Exfoliated nano-composites are formed when the layers of the day have been completely separated and the individual layers are distributed throughout the organic matrix as shown in Figure 2(c). 

The substrate/silane interphase and the silane/matrix interphase are equally important in considering the mechanism of reinforcement by silane coupling agents in composites. The mineral oxide/silane interphase is more well defined than a metal/silane or a silane/matrix interphase. For example, in the case of a metal substrate, surface oxides may dissolve into the silane layer or form a complex. In the case of the silane/matrix interphase, a diffuse boundary layer may exist due to dispersion of physisorbed silanes in the matrix phase or penetration of the matrix resin into chemisorbed silane layers. Many features of the interaction of a silane coupling agent with a polymer matrix are specific to the system, and thus the chemistry of the silane/matrix interphase must be characterized and defined for each system. 

Plastics are defined as processable materials based on polymers. These materials can be transformed into finished products, such as bottles, containers, films, hoses, coatings, lacquers, etc. As a result of today s multitude of plastic applications there is a corresponding enormous variety of plastic materials. The polymer matrix as well as the incorporated plastic additives can be made to differ in such a variety of ways with respect to their chemical composition and structure that one finds or can develop a tailor made product for every application. 

Polymer composite systems usually exist in a metastable (unstable) state of mechanical equilibrium. This is because a mixture of mutually insoluble components separates extremely slowly due to the very low diffusion coefficients of the polymer matrix of the ingredients. This state of polymer systems is sometimes defined as kinetic compatibility [28]. 

Basic rheological parameters of polymer blends determined by the properties of the polymer matrix, so the properties of melts are generally defined by PHB. Lower viscosity of the melt blend composition (due to the formation of a continuous matrix PHB) in this case will significantly simplify the processing of the investigated materials. Also, the data in Figure 2.6 are consistent with the position that the greater the difference in viscosity of mixed polymers, the earlier the formation of a continuous matrix less viscous component. 

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