Structure-property relationships of LCP blended materials

Injection-molded articles tend to exhibit skin-core and multi-layer morphologies in which the LCP domain aspect ratio varies considerably with location within the part. The hierarchy of structures found within LCP/TP blends was elucidated by Silverstein et al. who said the microdomains form domains, the domains form microlayers, the microlayers form sublayers, and the sublayers form a layered structure . The structural hierarchy in PET/CLP blends was characterized by Narh who found good agreement of fibril length observed in sublayers with a numerical prediction. 

The transition between low-aspect ratio and high-aspect ratio domains can be quite abrupt, as shown in reference 13. In those portions of the part where the flow is favorable to the formation of high-aspect ratio domains, the forest of LCP needles emerging from the surface can be quite spectacular, especially considering that the domains did not exist prior to the formation of the part, but were formed in situ. 

Of course the adhesion between the LCP domains and the matrix must be poor for the elongated domains to pull out and appear needle-like, rather 

7 SEM micrographs of LCP fibrils, both skin (a) and core (b) regions. 

In other cases the adhesion between matrix and LCP reinforcement is good. The next SEM micrograph. Fig. 5.8, shows a rather similar forest of tapered needles, but in this case the tapering was due to drawdown during break (as opposed to brittle fracture) and not to puU out of poorly adhering domains, since the adhesion is seen to be excellent. 

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