Polymers 2020 , 12 , 173
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3.4. Thermogravimetric Analysis (TGA) of the Polycoat 38 ® Resin Figure 5 shows the weight loss of the polymer in function of the temperature. The first loss is due to the amount of water retained in the interstices of the polymer which tend to evaporate between 45 and100 ◦ C [29]. The second loss is observed between 351 and 378 ◦ C, corresponding to the rupture of the main chains in the polymer, leading to its degradation [25]. The given temperature is higher than the working temperature of the surface of the yankee [5], which indicates that there will be no problems due to the deterioration and subsequent breakage of the main chains of the polymer and the opening of the azetidine rings [5], needed to adhere the paper through OH cellulose groups on the yankee’s surface [30].This indicates that a loss of durability of the coating will not be present since the yankee surface temperature is lesser than the coating degradation temperature [5], meaning that the coating performance will not be a ff ected, so loss of bulk in the finished paper rolls and cross machine direction profile issues of uniformity in the produced paper roll will not be observed [7].
Figure5. Thermogravimetric analysis of the polyamine ( Polycoat 38 ® ) resin synthesized.
3.5. Di ff erential Scanning Calorimetry (DSC) of the PAE Resin The di ff erential scanning calorimetry analysis is of utmost importance because it shows the vitreous transition temperatures ( T g ) of the resin [31]. The value of T g on the central axis is between the range in which the behavior of the polymer is between glassy and rubbery [31]. The T g needs to be greater than the yankee working temperature, otherwise the coating will not be soft enough to prevent blade chattering [5,7], wearing it out and producing a direct contact with the yankee by loss of thickness of the coating layer and a “smooth” crepe with more space between the crepe pockets [5]. In this case, the temperature of the yankee where the product was proven exceeded 100 ◦ Cand it can be seen in Figure 6 that the T g of the coating alone and emulsified with release in a proportion similar to that used in the yankee were 85.7 and 77.7 ◦ C, in which the polymer behaves like a thermoplastic rubber and is soft enough to produce high quality paper [31]. This DSC behavior was similar to other polyamide-based resins as reported by Huang K. et al. [32].
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