3.5. Fourier transform infrared spectroscopy (FTIR)
In order to estimate the true K S content in the active packaging
(as against the percentage added to PCRPTE) a calibration curve was constructed using powdered PCRPET mixed with different known
concentrations of K S from 1.0 to 5.0 wt.%. Based on this calibrating
equation and on the analysis of 5 samples it was established that
the addition of KS at a level of 2.5 wt.% to the extruder infl ow, g av e a
concentration of 1.82 0.65 wt.% on the active packaging, while the
addition at 4.0 wt.% gave 5.01 1.71 wt.% on the packaging. In this
latter case a higher concentration was found to exist in the finished
packaging material than what was originally added to the extruder,
which can be attributed to the agglomeration of KS and a non ho-mogenous distribution of the agglomerate in the PCRPET matrix,
mentioned earlier. This result indicates that the industrial process
of extrusion used in this work should be improved to produce a
more homogeneous material and/or that the KS addition of 4.0 wt.%
by extrusion is high to produce a good quality PCRPET active fi lm.