Development and Investigation of Lanthanum Sulfadiazine with Calcium Stearate and Epoxidised Soyabean Oil as Complex Thermal Stabilizers for Stabilizing Poly(vinyl chloride)

Abstract

Lanthanum sulfadiazine (LaSD) was synthesized from sulfadiazine and lanthanum nitrate using water as solvent under alkaline conditions, and was used as a novel rare earth thermal stabilizer to stabilize poly(vinyl chloride) (PVC). The structure of LaSD was characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR) and thermo- gravimetric analysis (TGA). The influence of lanthanum sulfadiazine with calcium stearate (CaSt2) and epoxidized soybean oil (ESBO) on stabilizing PVC was studied by using the Congo red test, oven discoloration test, UV-vis spectroscopy and thermal decomposition kinetics. The results showed that the addition of LaSD as a thermal stabilizer can significantly improve the initial whiteness and long-term stability of PVC. In addition, the synergies between LaSD, ESBO, and CaSt2 can provide outstanding improvement in the long-term thermal stability of PVC. When the ratio of LaSD/ESBO/CaSt2 is 1.8/0.6/0.6, its thermal stability time is 2193 s which is the best state for stabilizing PVC. Furthermore, comparing the reaction energy (Ea) and the variations in the conjugate double bond concentration in PVC samples, the order of thermal stability of PVC was PVC/LaSD/ESBO/CaSt2 > PVC/LaSD/ESBO > PVC/LaSD. The thermal stability mechanism of LaSD on PVC was studied by the AgCl precipitation method and FTIR spectrum. The results showed that the action of LaSD on PVC was achieved through replacing unstable chlorine atoms and absorbing hydrogen chloride.

Effects of Organic Based Heat Stabilizer on Properties of Polyvinyl Chloride for Pipe Applications: A Comparative Study with Pb and CaZn Systems

“…The first stage is mainly attributed to dehydrochlorination by the removal of hydrogen chloride from the PVC main chain, thus forming a conjugated polyene structure. The second stage is mainly attributed to the fracture of conjugated polyene structures to form small molecular weight linear or cyclic hydrocarbons, and finally tar formation [ 25 , 26 ]. In addition, it was observed that there is a substage in the first stage of the PVC, indicating the existence of different events in this stage, suggesting a complex dehydrochlorination mechanism.…”

Thermal stabilization of polyvinyl chloride by calcium and zinc carboxylates derived from byproduct of palm oil refining

“…This is because the tested formula uses high Ca/Zn ratios. As reported in the literature (Balköse et al, 2001;Ye et al, 2019), a high Ca/Zn ratio has advantages in long stability times but is lacking in initial color. The recommended Ca/Zn ratio in a mixed metal formulation is 0.25 to 4.00 with the lower and higher ratios being prioritized for initial color and long-term stability, respectively (Balköse et al, 2001).…”

“…The disadvantage of organic thermal stabilizers are their poor stability ( Guangbao et al., 2020 ). The second group, which has been industrialized and well applied in PVC production, includes salts or carboxylates of lead, tin, or mixed metals ( Ye et al., 2019 ). Lead salts are known as the oldest thermal stabilizer ( Schiller, 2015 ).…”

“…Organic tin groups are known to be effective, but they are expensive ( Song et al., 2022 ). Mixed metal thermal stabilizers are popularly used due to their advantages of being non-toxic and low price ( Ye et al., 2019 ). The commonly used metal combinations are alkaline earth and transition IIB metals, especially the Ca/Zn pair ( El-Ghaffar et al., 2019 ).…”

Enhancing the Initial Whiteness and Long-Term Thermal Stability of Polyvinyl Chloride by Utilizing Layered Double Hydroxides with Low Surface Basicity

“…However, the traditional thermal stabilizers, such as lead/cadmium salts and organotin, pose health and environmental hazards, leading to regulations such as EU 76/769/EEC, WEEE, and RoHS that require the use of non-toxic, environmentally friendly, and efficient thermal stabilizers [ 8 ]. Thermal stabilizers of β-diketone compounds, zinc stearate, and LDHs show great potential as practical alternatives [ 4 , 9 , 10 , 11 , 12 , 13 , 14 ].…”