Self-reinforcement

The macroscopic orientation of their extended-chain crystals depends on the orientation imparted by flow during mol ding. Because of the fibrous nature of the extended-chain crystals, these materials behave as self-reinforcing composites, with excellent mechanical properties. 

The liquid crystal polymers consist of rod-like molecules which, during shear, tend to orient in the direction of shear. Because of the molecular order the molecules flow past each other with comparative ease and the melts have a low viscosity. When the melt is cooled the molecules retain their orientation, giving self-reinforcing materials that are extremely strong in the direction of orientation. 

In Chapter 3 it was pointed out that certain rod-like polymers showed many of the attributes of liquid crystals in the melt. In particular, these molecules were oriented in shear to such an extent that interchain entanglement was small and the melts had a low viscosity. On cooling of the melt these rod-like molecules remained oriented, effectively self-reinforcing the polymer in the direction of flow. The essential differences in the properties of liquid crystal polymers... 

The two-piece hood with outer panel and inner support panel may give way in the future to a one-piece, self-reinforced molded hood. 

Deck lids can take the same parts consolidation path as hoods. The deck lid, inner, with spoiler and the deck lid, outer, could be combined into a one-piece self-reinforced deck lid. 

Head-group analysis by H1 NMR demonstrated the presence of one Si-H group per PIB molecule. These data are self-reinforcing and prove that HSi-PIB can be prepared by the use of the HSi(CH3)2CH2CH29CH2Cl/Me3Al initiating system. 

Thermoplastic resins, self-reinforced, 26 Thermoplastics, preparation of, 257-258 Thermoplastic step-growth polymers, 3 Thermosetting polyester resins, 29-31 Thermosetting resins, 3-4, 19 Thermotropic compounds, 49 THF. See Tetrahydrofuran (THF) Thiobisphenol S (TBPS), 364 Thionyl chloride, 80 activation of, 111 3,3 -linked polymers, 480 Tin-amine coordination complex, 234 Tin compounds, 86, 232-233... 

C) Synergistic H2 coordination. When the metal has both donor and acceptor orbitals, interaction with the cthh and ohh orbitals of H2 can act synergistically (cooperatively) in the Dewar-Chatt-Duncanson mode. Such self-reinforcing charge flow enables a significantly stronger interaction than does simple dative coordination of H2. 

This article is an overview of the novel technology of self-reinforced LCPs with polyesters, poly(ethylene terephthalate) (PET) and poly(ethylene naphtha-late) (PEN) [10-13, 21, 23], LCP/polyester blends in a polyester matrix form in situ fibrils which improve the mechanical properties. LCPs have an inherently low melt viscosity, and provide LCP/polyester blends that effectively lower the melt viscosity during melt spinning [24], and fast injection-molding cycles. The miscibility between the LCP and polyesters can be controlled by the degree of transesterification [25] in the reactive extrusion step, and fibril formation in LCP-reinforced polyester fibers has been studied. 

Recycling more effective solutions are sought. The development of the mono-material concept is favourable to thermoplastics and self-reinforcing thermoplastic composites such as self-reinforced polypropylene (Curv from BP). 

Underbody parts in self-reinforced polypropylene (Curv) for the Audi A4. 

Elongations at break are low, while moduli and hardnesses are in a high or very high range due to the self-reinforcement of the polymer crystals. Notched impact strengths are also in a good range. 

Advanced all-polymer prepregs or self-reinforced polymers... 

Table 6.27 compares some self-reinforced polypropylene properties with those of other general-purpose solutions. 

The (property/density) ratios show that the self-reinforced polypropylene is comparable to the general-purpose GMTs with a much higher impact resistance ratio. 

Other self-reinforced polymers are being developed. For example, PURE is based on highly oriented co-extruded tapes of polypropylene and a consolidation binder. Properties vary according to the form (see Table 6.27) - sheets, tapes or fabrics. 

Table 6.27 Examples of self-reinforced polypropylene properties compared to other general-pnrpose solutions...

Examples of properties of self-reinforced polypropylene tapes and sheets ... 

As in blood coagulation (see p. 290), the early components in the complement system are serine proteinoses, which mutually activate each other through limited proteolysis. They create a self-reinforcing enzyme cascade. Factor C3, the products of which are involved in several functions, is central to the complement system. 

For the fixed circumference of a wire loop, only some wavelengths are self-reinforcing, (a) The loop affixed to the post of a mechanical vibrator at rest. Waves are sent through the wire when the post vibrates, (b) Waves created by vibration at particular rates are self-reinforcing, (c) Waves created by vibration at other rates are not self-reinforcing. 

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