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.
Highlights
Poly(vinyl chloride) (PVC) is the third largest plastic after polyethylene (PE) and polypropylene (PP) [1,2]
Thermal stabilizers can be generally divided into lead salts, soap salts, organotin, rare earth and organic auxiliary thermal stabilizers
The elemental analysis results are shown in Table 1; it was confirmed that the mass ratio of
Summary
Poly(vinyl chloride) (PVC) is the third largest plastic after polyethylene (PE) and polypropylene (PP) [1,2]. It can be widely used in industry, architecture, agriculture, medicine and other fields because of its outstanding physical and chemical properties, including fire resistance, wear resistance, best comprehensive mechanical properties, transparency, electrical insulation, chemical resistance, heat resistance, sound insulation and other advantages [3,4]. Lead salts and organotin stabilizers have a strong stabilizing effect on PVC, their application is limited due to their toxicity and cost limitations [8,9]
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