Tris(hydroxymethyl)aminomethane (TRIS) is a commonly used biological buffer and common bulk drug ligand material. It has a white crystalline powder with a chemical registration number of 77-86-1. This material can also be used as a PVC thermal The organic matter of the stabilizer has a structure similar to that of polyhydroxy compounds and alkanolamines. In this experiment, TRIS, PER (pentaerythritol) and DEA (diethanolamine) were compounded with DMAU, and their synergistic effects were compared, and the mechanism was discussed; the optimal synergistic heat stabilizer and calcium-zinc heat stabilizer and The auxiliary heat stabilizer β-diketone was compounded, and its synergistic heat stabilization effect was studied.

The synergistic thermal stability of DMAU and TRIS

TRIS is an organic thermal stabilizer that has the stabilizing effect of absorbing HCl and nucleophilic substitution of unstable chlorine atoms. It has the characteristics of both polyol and alkanolamine in structure. Therefore, use it in conjunction with DMAU to observe whether it can achieve a better synergistic effect than polyols and alkanolamines. Table 1 is the experimental formula of DMAU and TRIS synergistic thermal stability.

The samples 1 to 6 in Table 1 were subjected to static thermal aging experiments, and the results found that when the total amount of thermal stabilizers added is the same, the long-term thermal stability of the samples using TRIS and DMAU at the same time is better than using one of them alone. Heat stabilizers. This shows that TRIS and DMAU, which are pure organic heat stabilizers, have a synergistic stabilizing effect. When the dosage ratio of TRIS and DMAU is 2:1, the long-term thermal stability of the sample is the best (sample No. 3). From the perspective of initial whiteness, the samples containing DMAU are better, indicating that DMAU has a more obvious effect of stabilizing PVC at the initial stage in the synergistic system. The initial whiteness of samples 1 to 2 is poor, indicating that the effect of not using synergistic heat stabilizers is poor, and the use of TRIS alone cannot effectively inhibit the initial coloring.

Table 3 is the induction time and stabilization time of samples 1 to 6, and Figure 1 is the HCl removal curve of samples 1 to 6. It can be seen from Table 3 and Figure 1 that the rate of PVC removal of HCl (the faster the conductivity changes, the greater the relative rate of removal of HCl from the PVC sample) is mainly related to the amount of TRIS, that is, TRIS is more important in the synergistic system The role is to absorb HCl. It is worth noting that although the amount of TRIS in sample No. 3 is lower than that in sample No. 2, its induction time and stabilization time are slightly better than those of sample No. 2 containing only TRIS, which is consistent with the conclusion of the static aging experiment. Therefore, the static aging and HCl removal experiments prove that when TRIS:DMAU is 2:1, the sample has good initial thermal stability and long-term thermal stability.

Experiment summary

Using static thermal aging, dehydrochlorination, and dynamic thermal stability experiments to study tris (TRIS) and 1,3-dimethyl-6-semiuracil (DMAU) as polyvinyl chloride (PVC) heat stabilizers Synergy. The results show that compared with TRIS or DMAU alone, when TRIS and DMAU are mixed at 2:1, the sample can obtain good plasticization and better dynamic thermal stability, and is better than pentaerythritol and DMAU, diethanolamine and DMAU The effect of synergy.