Liquid crystalline polymers microfibrils

Mechanical Properties. To reveal the reinforcing effect of liquid crystalline polymer microfibrils on the mechanical properties of the films both their dynamic torsional moduli and dynamic tensile moduli have been studied as a function of temperature using a Rheometrics Mechanical Spectrometer (RMS 800) and a Rheometrics Solids Analyzer (RSA II), respectively. For comparison purpose the modulus of neat matrix polymers and, in some cases, the modulus of carbon fiber and Kevelar fiber reinforced composites has also been measured. 

The objective of this work has been to generate films, tapes or ribbons which might serve as a prepreg from blends of either an Ultem or a PEEK or a high molecular weight PPS with various liquid crystalline polymers, to identify the parameters that control the formation of reinforcing microfibrils of LCP phase, and to study the mechanical properties of the composite films. 

Fig. 5.119 A new structure model is shown [435] that has more detail than in Fig. 5.111 published earlier [430]. The model suggests there is a hierarchy, at least on the scale from 500 nm to the 1 nm size scale, specific to the liquid crystalline polymers. The key element shown is the microfibril, the same microstmctural unit basic to melt spun and drawn flexible polymers. (From Sawyer et al [435] reproduced with permission.)...

Noishiki Y, Nishiyama Y, Wada M et al (2002) Mechanical properties of silk fibroin-microcrys-talline cellulose composite films. J Appl Polym Sci 86 3425-3429 O Sullivan AC (1997) Cellulose the structure slowly unravels. Cellulose 4 173-207 Oksman K, Mathew AP, Bondeson D et al (2006) Manufacturing process of cellulose whiskers/ polylactic acid nanocomposites. Compos Sci Technol 66 2776-2784 Orts WJ, Godbout L, Marchessault RH et al (1998) Enhanced ordering of liquid crystalline suspensions of cellulose microfibrils a small-angle neutron scattering study. Macromolecules 31 5717-5725... 

---