DIFFERENTIAL SCANNING CALORIMETRY (DSC)

DSC is widely used to characterize the thermal properties of WPCs. DSC can mea­sure important thermoplastic properties, including the melting temperature (Tm), heat of melting, degree of crystallinity x(%), crystallization, and presence of recy- clates, nucleating agents, plasticizers, and polymer blends (the presence, composi­tion, and compatibility). Thermal analysis of the WPC samples was carried out on a differential scanning calorimeter (Perkin Elmer Instruments, Pyris Diamond DSC,

Shelton, Connecticut) with the temperature calibrated with indium. All DSC mea­surements were performed with samples of about (9.5 ± 0.1) mg under a nitrogen atmosphere with a flow rate of 20 mL/min. Three replicates were run for each speci­men. All samples were subjected to the same thermal history with the following thermal protocol, which was slightly modified from the one reported by Valentini et al.45.

1. First, the samples were heated from 40 to 180 °C at a heating rate of 20 °C/ min to remove any previous thermal history.

2. Second, the samples were cooled from 180 to 40.00 °C at a cooling rate of 10 °C/min to detect the crystallization temperature (Tc).

3.

Подпись: following equation: Xcor(%) Подпись: ДНт ДН Q. Xr Подпись: (1)

Finally, the samples were heated from 40 to 180 °C at a heating rate of 10 °C/min to determine Tm. Tm and the heat of fusion (днт) were calcu­lated from the thermograms obtained during the second heating. The heats of fusion were normalized on the basis of the weight fraction of PP present in the sample. The values of днт were used to estimate X, which was adjusted for each sample in XcOr (%) based on the percentage of polypro­pylene in the composite. Crystallinity (Xcor) was estimated according to the

ДНm and ДН0 are, respectively heats (J/g) of melting of composite and 100% crystalline PP, taken as 207.1 J/g,46 and Xpp is the PP fraction in the composite.

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