Nanocomposites and nanomaterials

Polymeric nanofilled composites with adjustable microfibrillary structure
Rezanova N.M., Budash Yu.O., Plavan V.P., Kucherenko Ye.V.
Kyiv National University of Technology and Design 
Nemirovich-Danchenko, 2, Kyiv-01011, Ukraine. 
E-mail: Ku4erenko_Elizaveta@i.ua

The priority direction for the modification of polymeric materials is the development of a new class of nanofilled composites in which the in situ component of the dispersed phase forms microfibrils (microfiber) in a dispersion medium (MFC). 
The aim of the work is to establish the relationship between the morphology and the properties of microfibrillar composites and multifilament yarns obtained by processing nanofilled thermodynamically incompatible polymer blends. Studies were carried out on polypropylene/copolyamide mixtures (PP/CPA) with an ingredient ratio of 30/70, which contained (0.1÷3.0) wt% pyrogenic aluminum oxide (Al2O3).Analysis of micrographs of cross-sections of extrudates and PP samples after extraction of the CPA from them suggests that the introduction of Al2O3 nanoparticles into the melt of the PP/CPA mixture allows adjusting its microstructure. In nanofilled compositions, the degree of dispersion of droplets of the component of the dispersed phase increases, and the proportion of particles with De<2 μm increases ~ 4 times (from 4 to 17%). The shape of the PP particles in the initial composition is generally close to round (SF>0.98 for 64% of the particles). The introduction of nano-additives into the mixture leads to a shift in the distribution curve in terms of the SF index towards smaller values. The most perfect morphology is formed when the content of aluminum oxide is 1.0 wt. % The diameter of the PP microfibers is reduced to 2.2 μm, their mass fraction increases to 94.9%. As one would expect, the mechanical characteristics of mono- and complex yarns are determined by the structure of the composition. The maximum reinforcement effect is achieved for monofilaments molded from a mixture in which microfibers are the predominant type of structure and their diameters are minimal. Breaking strength (P) and initial modulus (E) increase ~ by 40% and 20%, respectively. An important practical result of the work is that the threads from nanofilled PP microfibrils, obtained from a modified thermodynamically incompatible PP/CPA system, have mechanical characteristics at the level of textile yarns.