Mechanical, thermal and colorimetric properties of LLDPE coloured with a blue nanopigment and conventional blue pigments

Purpose – This research deals with a new kind of nanopigment, obtained from the combination of organic dyes and layered nanoclays, that the authors call nanoclay-colorant pigment (NCP). Whilst they have already been employed in inks and coatings, to date these nanopigments have not been used as pigments for polymers. The existing lack of knowledge surrounding them must be redressed in order to bridge the gap between current academic studies and commercial exploitation. Therefore, the main purpose of this paper is to examine the hitherto unknown aspects of the NCP, which relate specifically to their applicability as a new type of colorant for polymers. Design/methodology/approach – A blue NCP has been prepared at the laboratory according to the patented method of synthesis (patent WO0104216), using methylene blue and montmorillonite nanoclay. It has then been applied to a thermoplastic polymer (linear low-density polyethylene – LLDPE) to obtain a coloured sample. Furthermore, samples with the same polymer but using conventional blue colorants have been prepared under the same processing conditions. The mechanical, thermal and colorimetric properties of these materials have been compared. Findings – The thermal stability of the sample coloured with NCP is reduced to some extent, while the mechanical strength is slightly increased. Moreover, this sample has better colour performance than the conventionally pigmented samples. Originality/value – In this paper, a blue NCP has been synthesised and successfully employed with polyethylene and the obtained sample shows better colour performance than polyethylene with conventional pigments.

This research was supported by the Spanish Ministry for Education and Science by means of the grant number DPI2005-08999-C02-02, and, the Spanish Ministry of Science and Innovation by the grant number DPI2008-06455-C02-02. Verónica Marchante Rodríguez would like to thank the “Conselleria d'Empresa, Universitat i Ciència” for the PhD grant that she has received.