Epoxy Resin

by:SANDAO     2020-12-18

One possible cause is that the free formaldehyde content material increased with a decrease of the curing response of extent. Furthermore, the free formaldehyde content material of PUF1resin, PUF2resin, and PUF3resin had been decreased by 18%, 14% and 25%, respectively. In addition, with the delay of addition stage of adipic acid dihydrazide, the free formaldehyde content of resins decreased steadily. The free formaldehyde content material of resin with adipic acid dihydrazide added within the second alkaline stage was 0.34%. In phrases of the formaldehyde content, the PUF3resin had the best property.


The mass loss in this stage contains the decomposition of the methylene bond within the adhesive, releasing the free formaldehyde. The mass lack of UF, MUF1, PUF1, AUF3, and CUF resins in this stage have been 8.81%, 11.73%, 9.seventy three%, 9.seventy five%, and 8.three%, respectively.


However, other physicochemical properties of resins, such as curing time, strong content material and viscosity, also play essential roles in figuring out the resin applicability. As proven in Table 5, the addition of adipic acid dihydrazide caused a rise of solids content material of the resins and a lower of preliminary viscosity of the resins.


The AUF6% resin had the most important stable content of fifty four.3%, while the opposite three AUF resins had the identical solids content material of 53.2%. Moreover, with a symmetrical bifunctional construction, the increase of adipic acid dihydrazide content material did not affect the viscosity of AUF resins (Xuet al. 2016). Thus, the addition of various amounts of melamine, PVOH, or adipic acid dihydrazide had completely different results on the physicochemical properties of the resins relating to curing time, viscosity, or strong content material.


The percent of mass loss at second weight loss stage was 69.14%, 62.26%, seventy one.03%, 70.26%, and fifty three.54% for UF, MUF1, PUF1, AUF3,and CUF, respectively. In the primary two phases, the burden loss price of CUF resin was the smallest among the many five resins, which means that the great modifier improved the thermal stability of the adhesive. The third weight reduction stage occurred in the range of 350 to 600 °C.


The position of attribute absorption peaks of the resins didn't change after mixing modifiers to the resins. In addition, there was no new adsorption band in the infrared spectrum, which could possibly be because of the comparable curing reactions of the 5 resins. Figure four reveals that the free formaldehyde contents in UF resin, MUF1resin, PUF1resin, AUF3resin and CUF resin have been zero.44%, 0.34%, zero.36%, zero.34%, and zero.24%, respectively. Furthermore, CUF resin meets the technical necessities of the UF resin normal, as the free formaldehyde in adhesive utilized in the wooden manufacturing must be decrease than 0.30%. Compared with the UF resin, the free formaldehyde content of MUF1resin, MUF2resin, and MUF3resin was decreased by 23%, 16%, and sixteen%, respectively.


Table four reveals that there was no apparent relationship between the curing time and the PVOH content. This result's attributed to the truth that the surplus PVOH just isn't capable of participate within the polycondensation reaction with the resin as a result of its giant viscosity (Zhanget al.2005; Huanget al.2006). The solids content material of the resin was determined based mostly on an oven-drying method. Approximately 1 g of resin was placed into a continuing temperature oven for 2 h at one hundred twenty °C.

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