In December 2003, the European Commission’s Joint Research Centre (JRC) was entrusted by DG Enterprise
to verify the validity and applicability of the testing methods, proposed by DuPont, for the identification,
characterisation and quantification of their new fibre (elastomultiester). This is an elastic bicomponent fibre
made by a combination of two different polyesters (side-by-side structure). The elastic properties are due to
crimps that are formed, after heat treatment, and due to the different shrinkage of the two components. The
crimp is not mechanically induced and the yarn can be used directly, as no texturing or covering before weaving
is needed.
Experimental results confirmed that microscopy and differential scanning calorimetry (DSC) can identify both the
multicomponent nature of the new fibre and its chemical composition, whereas Fourier Transform Infrared
Spectroscopy (FT-IR) can confirm only its chemical composition.
The normal pre-treatment, described in Directive 96/73/EC, was proved to be applicable to the new
bicomponent fibre and the agreed allowance value of 1.50 % was adopted for the new fibre, in agreement with
the European Network of National Experts on Textile Labelling (ENNETL). The solubility properties of
elastomultiester were evaluated. In particular, the chemical methods 1, 2, 4, 6 – 9, 13 and 14 of Directive
96/73/EC were tested and considered suitable for the quantification of elastomultiester in binary mixtures with
other fibres. With the exception of method 14, the novel fibre was insoluble in all the mentioned methods and
showed correction factors d equal to the ones of polyester (1.00 for methods 1, 2, 4, 7, 9, 13 and 1.01 for
methods 6 and 8, respectively). In addition, also the manual separation method described in Directive 96/73/EC
was proved to be suitable for the quantification of elastomultiester in binary mixtures with other fibres.
A new quantitative method based on DSC was developed and successfully applied to the quantification of
binary mixtures of elastomultiester with polyester and cotton and to ternary mixtures with polyester/cotton,
polyester/viscose and modal/viscose. The method is also applicable to mixtures of elastomultiester with nylon. It
led to a good repeatability and results were generally as good as the ones obtained with chemical methods. The
comparison with quantification based on the manual separation method showed differences usually lower than 1
%. The method shows two important advantages, the first being the rapidity of the analysis and the second
being the possibility to avoid manual separation in the quantification of mixtures polyester/elastomultiester.
The JRC developed a test method to measure the recoverable stretch and the permanent deformation of yarns
and single filaments based on elongation. Experiments performed on single filaments of elastomultiester
showed that, at 50 % elongation, the novel fibre is intrinsically elastic and proved that the elasticity is not due to
the construction of yarns and to the fact that they contain several single filaments; on the contrary single
filaments are as elastic as yarns. In fact, in these conditions the per cent permanent deformations were usually
lower than or equal to 10 %.
Based on experimental results, discussions during the 2nd, 3rd, and 4th ENNETL meetings, the name and
definition agreed and proposed for the new fibre were “elastomultiester: fibre formed by interaction of two or
more chemically distinct linear macromolecules in two or more distinct phases (of which none exceeds 85 % by
mass) which contains ester groups as dominant functional unit (at least 85 %) and which, after suitable
treatment, when stretched to one and half times its original length and released, recovers rapidly and
substantially to its original length”.JRC.I.2-Chemical assessment and testin
