Glass fiber reinforced LCP

Figure 3.469. SEM-micrographs of polished surfaces of glass-fiber reinforced LCP. The layered structure across plate thickness is obvious in micrograph (a). The degree of fiber alignment parallel to the MFD is visible in micrograph (b) for LCP-30 GF and in (c) for LCP-50 GF. The high orientation in the latter one is obvious. (B-C = 25) [1255],...

Fig. 5.99 A glass fiber reinforced LCP composite is shown to have interesting morphology. A polished thin section is shown in polarized light (A) (color section) to exhibit a fine domain texture with some orientation of the polymer on the glass surfaces. SEM fracture views (B-D) show the tenacious adhesion of the LCP to the fibers. Fibrillar structures are oriented parallel to the fiber surface and submicrometer sized domains are observed (D).

Fig. 5.99A A glass fiber reinforced LCP composite is shown to have interesting morphology. A polished thin section is shown in polarized light to exhibit a fine domain texture with some orientation of the polymer on the glass surfaces.

Figure 6.75 Flexural stress amplitude versus cycles to failure at 23°C of Celanese Zenite 6130 BK010—30% glass fiber-reinforced LCP [18]. 

Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties. 

Figure 4.108 Stress vs. strain at various temperatures for Celanese Vectra A130—30% glass fiber reinforced, standard grade LCP.

Figure 4.114 Stress vs. strain at 23°C for several Celanese Vectra L130—30% glass fiber reinforced, high flow LCPs.

It should be noted that there is not simply an addition of thermotropic LCPs into fiber-reinforced plastics to get in situ hybrid composites. Bafna et al. used glass fibers to decrease the anisotropy of LCP fibril-reinforced polyetherimide [136]. He et al. improved the processability and mechanical performances of glass fiber-reinforced polypropylene by the addition of LCPs [159]. However, these two works did not actively and purposely generate a reinforced composite with the reinforcements having their diameters at two orders of magnitude. The key point for in situ hybrid composites is the formation of LCP fibrils in the material system. As a combination of in situ composite and hybrid fiber reinforcing, the fabrication of in situ hybrid composites utilizes fabrication... 

In summary, then, a suitable processing history that includes extensional flow can yield a reinforcing, microfibrillar morphology of the dispersed LCP phase. Modulus values that are similar to those of short glass fiber-reinforced plastics can... 

Figure 14.4 Capillary rheology of 30% glass fiber-reinforced SPS versus 30% glass fiber-reinforced liquid crystalline polymer (LCP),poly(l,4cyclohexamethylene tere-phthalate) (PCI), and polybutylene terephthalate (PBT). All resins were tested 50°C above their melting point.

A liquid crystalline polymer contains rigid rod like structure as discussed earlier which forms the hquid crystal phases. This rod like molecular conformations and chain stiffness give LCPs their most important self-reinforcing properties that are close to that of glass fiber reinforced composites. 

During fabrication, the LCP forms fine fibrils that reinforce the thermoplastic polymer matrix. The mechanism of reinforcement resemble those of glass fibers. However, when light weight is a key issue, in situ composites are superior in comparison to glass fibers. ... 

In addition, LCPs display viscosities that are considerably lower than other polymers. For this reason, the processability of LCP reinforced composites is better. Of course the price of LCP is much higher than the price of glass fibers. 

From the viewpoint of composite mechanics, the better performances of composites come from the effective reinforcing effect of the reinforcements and effective stress transferring from the mafiix to the reinforcements. The reinforcing LCP fibrils in in situ composites are generated during the melt processing of LCP blends, which is different fi om conventional glass or carbon fiber-reinforced composites. So the formation of LCP fibrils becomes one of the most important aspects in the preparation of in situ composites, except the common interfacial interaction in fiber-reinforced plastics. 

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