Nano-/microfibrillar polymer–polymer and single polymer composites: The converting instead of adding concept

The article describes the concept of converting instead of adding used for preparation of the two new polymer materials, namely, the nano/microfibrillar polymer–polymer composites (PPCs) and the true nanofibrillar single polymer composites (SPCs). The reasons for the failure of the common polymer nanocomposites, i.e. those prepared via adding of nano-sized fillers to the polymer matrix are mentioned, followed by description of the definitions, nomenclature, advantages and disadvantages of the nanofibrillar polymer–polymer composites and SPCs. After discussing the basic problems in polymer science and technology as the environmental impact, the interfacial adhesion quality in polymer composites, and the aspect ratio of the reinforcing component, the currently most important technique for converting the polymers into nano-sized materials, the electrospinning, is critically analyzed and compared with the concept of nanofibrillar composites (NFCs). According to NFC after extrusion and cold drawing of a polymer blend, followed by selective dissolution of the major component, neat nanofibrils (with diameters of 50–250 nm) can be separated. The latter can be used for SPCs manufacturing characterized by superior mechanical properties (improvement of tensile modulus and strength up to 400%). This method for converting of any bulk polymer into nano-sized material was recently made environmental-friendly by using water only as a solvent. Its further development was the control of the final nanomorphology: (i) if H-bonding between the blend partners is missing, the observed morphology is of individual not interconnected nanofibrils and (ii) in case H-bonds are present the nanomorphology represents a nanofibrillar nanoporous 3-D network. In this way the method allows the manufacturing of nanofibrillar PPCs and SPCs avoiding the dispersion problem (for PPCs) as well as the problem of interface adhesion quality (for SPCs).