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Differential Scanning Calorimeter

Non-isothermal crystallisation and melting behaviour of the fibres are studied using a Perkin-Elmer Pyris-1 differential scanning calorimeter (DSC), as shown in Fig. 3.4. DSC is a thermoanalytical technique in which melting and crystallisation behaviour of the fibres can be measured with the increase and decrease of temperature, respectively. About 3 mg of PP fibre was weighed accurately and encapsulated in an aluminium pan. Samples were heated from 30 to 220 °C at the heating rate of 10 K/min to study the melting behaviour of the fibres. The crystallinity and crystalline structure of the PP fibres could be calculated through this heating. The samples were then kept at 220 °C for 5 min to eliminate their thermal history. Subsequently, the samples were cooled to 30 °C at the rate of 10 K/min to study their crystallisation behaviour with temperature; and reheated to 220 °C at the heating rate of 10 K/min to

Test apparatus for the DSC test

Fig. 3.4 Test apparatus for the DSC test

study their melting behaviour with temperature. All measurements were carried out under the nitrogen atmosphere to avoid thermal-oxidative degradation. In both crystallisation and melting experiments the peak temperatures were obtained for crystallisation temperature (Tc) and melting temperature (Tm), respectively. Crystallinity refers to the degree of crystallisation of the PP fibres. The crystallinity has a significant influence on hardness, density and transparency. The crystallinity of the PPs is calculated using Eq. (3.2) (Cerqueira et al. 2006)

where, AHf is the heat of fusion of PP fibres and AH0 is the heat of fusion of a

f f

totally crystalline PP taken as 207 J/g (Yeo et al. 2003).

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