Polymers 2020 , 12 , 173
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This behavior is observed in Figure 6 where the addition of Disprosol 17 ® to the coating decreases the T g values slightly by increasing the softening of the chemical duple which was evidenced on the brittle property of the polymer under this temperature, generating a high adhesion coating that can be easily coupled to yankee dryers working at lower temperatures [33]. 3.6. Relative Adhesion of Polycoat 38 ® The relative adhesion of the coating was measured by the peel adhesive method [2,5] and although the peel produced is not similar to that of a crepe blade, it is possible to measure the force required to release the paper without breaking it [2]. In the procedure, the metallic surface of the yankee is simulated at 105 ◦ C by a metal panel at the same temperature covered with coating and attached to a low grammage tissue paper in order to compare the Polycoat 38 ® with other commercial coatings [2,5,15]. Table 1 shows the results of relative adhesion of di ff erent coatings together with Polycoat 38 ® .
Table1. Relative adhesion of di ff erent coatings commercially available.
Coating
Relative Adhesion (gF / 3in)
PAE Dispro620 ® Discrepel HRC ®
2823 1595 1179 1078
Glyoxilated Polydadmac
Polycoat 38 ®
Polycoat 38:Disprosol 17 ® (1:1,4)
966
CR180 ®
N / A
N / A: No adhesion. As observed in Table 1, the adhesion of the Polycoat 38 ® is lower than a PAE such as Dispro620 ® [12], a high adhesion can lead to paper tearing during production because the tensile force required to tear paper of grammage 15 g / m 2 in general, is close to 600–1000 gF / 3in, which is a value far below than the given by the PAE. Likewise, other polymer-based coatings such ® as Polydadmac or Discrepel HRC ® can be highly cationic, which generate a strong adhesion of the paper to the yankee so that during their addition, a large amount of release would have to be added and thus decrease the adhesion but increase costs [10,11]. Adding for example, Disprosol 17 ® to the Polycoat 38 ® , we observed a decrease of 10% in the adhesion of the coating, which apparently resembles more the dry strength of low grammage paper. Thus, it was possible to balance the adhesiveness of the coating on the yankee as reflected during the application and production of the paper [7,8]. 3.7. Durability Test of the Polycoat 38 ® The swelling erosion test of Polycoat 38 ® showed a polymer degradation of 95.9% after 24 h when comparing the initial swollen weight and the dry weight at 37 ◦ C using Equation (1) [5]. To evaluate the rewetting of the polymer, the time that takes for the yankee to rotate 360 ◦ was used since it is the time in which another layer of coating is sprayed again [3]. This time value was equivalent to 0.26 s and was obtained from the data provided in Section 2.4. Using the result of the erosion of the polymer in 24 h and the yankee rotation time, a value of 0.0003% loss of durability during one yankee rotation was obtained. This result is practically negligible and means that there would not be degradation caused by humidity during the Polycoat 38 ® uses [4,5]. 3.8. Quality Parameters of the Polycoat 38 Resin and Disprosol 17 Release Agent Physicochemical properties of the coating and the release agents were determined according to the quality requirements of both products and are presented in Table 2.
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