Terahertz-time domain spectroscopy (THz-TDS) has the ability to probe the crystallinity of several materials, mainly due to the interaction of THz radiation with optical phonons in crystal lattices. Crystallinity of polymers is a particularly important parameter, as it affects many properties of the material, such as yield stress, modulus elasticity, among others. In this work, THz-TDS has been applied to investigate the crystallinity of polytetrafluoroethylene (PTFE) samples. PTFE samples with variable crystallinities were prepared by means of ball-milling in a planetary ball mill. THz spectra of PTFE pellets (thickness = 1.72 mm) were acquired using a THz-TDS spectrometer operating with the asynchronous optical sampling (ASOPS) principle. The acquisition time for each spectrum was around 4 minutes. The THz spectra of PTFE showed an absorption peak at 3.73 THz which could be directly correlated with the crystallinity, as shown in Figure 1. As the milling time increases, it is clear that the 3.73 THz peak becomes less intense. Preliminary differential scanning calorimetry (DSC) measurements showed that the heat of fusion correlates well with the 3.73 THz peak intensity (R<sup>2</sup> = 0.90), indicating that THz spectroscopy can be a useful tool to probe the crystallinity of PTFE in a shorter time.

Investigating the crystallinity of polytetrafluoroethylene (PTFE) by using terahertz time-domain spectroscopy (THz-TDS)

249th National Meeting (2015)

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