The online spinning process of commingled yarns is investigated in terms of distribution homogeneity and thermal shrinkage. In comparison with previous hybrid yarns intermingled by air jet texturing technology, the online spinning process could avoid fibre damage and improved the yarn distribution homogeneity. Our experiments show that both hybrid yarn tensile strengths and mechanical properties of unidirectional composites were improved based on an optimized sizing for glass fibres consisting of aminosilane and maleic anhydride grafted polypropylene film former. We found that the online commingled yarns do not tend to thermal shrinkage, whereas air jet textured yarns show shrinkage depending on the molecular orientation during processing of hybrid yarns or textile fabrics made thereof. Nanostructured interfaces introduced by smallest amounts of carbon nanotubes in sizings enable to achieve multifunctional effects such as improved tensile strength of glass fibres, modified morphology of interphases, and new fracture mechanisms.