Structural polymers thermoset-matrix materials

Polymer features that lead to miscibility with polysulfone should be further quantihed to be able to optimize the membrane separation characteristics of polymer mixtures. On the other hand, in the case of immiscible polysulfone blends, it is desirable to better define the features of the blend components that lead to a particular morphology. Some of those features are perhaps going to be different in the case of thermoplastic and thermoset matrix materials, but viscosity is certainly going to be relevant in both cases. However, in order to best utilize the polysulfone blends that have been discussed in this chapter, more work is required to better comprehend their structure-property-processing relationships. 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

In most of the above composites, as polymer matrices, thermoset polymers have gained major industrial importance as matrix materials. The use of thermoplastic matrices for aramid FRPs is being increasingly studied recently. There are also a vast number of applications where aramid fibers are the sole constituent, e.g., in protective apparel, armor systems, ropes, etc. During the last decade the aramid containing FRP composites have developed into economically and structurally viable construction materials for buildings and bridges [4]. 

Multiphase or multicomponent polymers can clearly be more complex structurally than single phase materials, for there is the distribution of the various phases to describe as well as their internal structure. Most polymer blends, block and graft copolymers and interpenetrating networks are multiphase systems. A major commercial set of multiphase polymer systems are the toughened, high impact or impact modified polymers. These are combinations of polymers with dispersed elastomer (rubber) particles in a continuous matrix. Most commonly the matrix is a glassy amorphous thermoplastic, but it can also be crystalline or a thermoset. The impact modified materials may be blends, block or graft copolymers or even all of these at once. 

The other general application of polysulfone blends is in the area of impact-modified materials. The general approach adopted here has proven to be useful when the polysulfone is blended with both thermoplastic and thermoset matrix polymers. In this case, immiscibility of the two polymers is the desired phase structure, but control of the phase separation process is needed to be able to optimize the enhancement in fracture and impact properties of the matrix polymer. In other words, there is more to the observed... 

The chemical structure of the epoxy matrix constituent as well as processing are reported to strongly influence 11 -I3> the thermoset network and hence the properties and durability of the crosslinked polymer 11 ,4-16). The cure of a reactive prepolymer involves the transformation of low-molecular-weight reactive substances from liquid to rubber and solid states as a result of the formation of a polymeric network by chemical reaction of some groups in the system. Gelation and vitrification are the two macroscopic phenomena encountered during this process which strongly alter the viscoelastic behavior of the material. 

The described biopolymers are embedded in a biopolymer matrix whose task is to guarantee the stability of the structure, to protect the mechanically high-quality fibres from radiation and aggressive infiuences, and to transmit shear forces. The polymers are usually subdivided into thermosets and thermoplastics which are equally suitable as matrices for the structural material. 

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