Preparation Of Acetylarea Derivatives And Their Applications For PVC Thermal Stabilizer

As one of the general-purpose plastics,polyvinyl chloride(PVC)exhibits thermal instability due to its own structural defects,so it is necessary to add thermal stabilizers in the processing and molding.At present,the researches and applications of thermal stabilizers focus on non-toxic,high efficiency and environmental protection.Among them,some organic stabilizers have been extensively concerned because of their non-toxic and environmentally friendly properties.In this paper,cyanoacetic acid,urea,1,3-dimethylurea,glycidyl methacrylate were used as raw materials to synthesize5,6-diamino-1,3-dimethyluracil,cyanoacetylurea and cyanoacetyl urea derivative as thermal stabilizers that contain acetylurea structure.The application of these compounds as thermal stabilizers of PVC were investigated.This work helped to develop environmentally friendly and efficient organic thermal stabilizers,and provide data support for related researches.1 ? Using 1,3-dimethyl-6-aminouracil as a raw material,5,6-diamino-1,3-dimethyluracil(DDU)was synthesized.The structure of DDU was characterized by fourier transform infrared,nuclear magnetic resonance spectroscopy and mass spectrometry.Congo red method,thermal aging method,thermogravimetric analysis and torque rheometer were used to evaluate the influence of DDU on the static and dynamic thermal stability of PVC,followed by the study of the stabilization mechanism.The results of the Congo red method showed that its thermal stabilizing effect is much higher than that of calcium stearate,zinc stearate and calcium-zinc composite stabilizers.It is an excellent PVC thermal stabilizer.When DDU was used in combination with calcium and zinc,it showed a good synergistic stabilizing effect,and the "zinc burn" phenomenon was significantly alleviated,which was better than the conventional calcium and zinc composite stabilizer.When the ratio of calcium stearate/zinc stearate/DDU is 1.8:1.2:2,the stabilizing effect of the composite thermal stabilizer reached the best.The possible mechanism showed that it not only absorbed HCl,but also replaced the unstable chlorine atoms on the PVC chain,effectively delaying the degradation of PVC.2? To some extent,the synthesis and post process of DDU was laborious.Therefore,cyanoacetyl urea was synthesized using acetic anhydride as dehydrant and urea and cyanoacetic acid as reactants.The preparation and purification were facile.It was characterized by infrared,nuclear magnetic,and melting point tests,and its thermal stabilizing effect on PVC as a thermal stabilizer was evaluated.Thermogravimetric analysis showed that it was stable at the processing temperature of PVC.Congo red method showed that cyanoacetyl urea increased the static thermal stability time of PVC,and the improvement was greater than the calcium stearate,zinc stearate and calcium zinc composite thermal stabilizers under the experimental conditions.The synergistic effect of cyanoacetyl urea,calcium stearate,zinc stearate,and calcium-zinc compound thermal stabilizers was studied by the Congo red method and the thermal aging method.It was found that they had obvious synergistic effects,and the "zinc burning" phenomenon was also significantly delayed.It showed that cyanoacetyl urea is a good auxiliary thermal stabilizer for calcium stearate or zinc stearate.The possible mechanism showed that these cyanoacetyl ureas could effectively absorb HCl,thereby slowing down the degradation of PVC.3? Cyanoacetylurea showed good stabilization effect.However,as low molecular weight molecule,it might be imcompatible with PVC.Cyanoacetylurea was modified with glycidyl methacrylate to obtain N-((2-hydroxy-3-methacryloxy)propyl)cyanoacetylurea(NCy).The thermal aging test and thermal weight loss analysis were used to evaluate the effect of this compound on the thermal stability of PVC and was compared with cyanoacetyl urea.The results showed that the thermal stabilization effect of the compound is slightly lower than that of cyanoacetyl urea,because the content of cyanoacetyl urea was reduced.Thermal aging test and thermal weight loss analysis were used to analyze the synergistic effect of the compound with calcium stearate,zinc stearate,and calcium/zinc composite thermal stabilizers.The results also showed that the synergy of the compound,calcium stearate,zinc stearate,and calcium/zinc composite thermal stabilizers was somewhat lower than that of the corresponding cyanoacetyl urea and calcium-zinc thermal stabilizers.From a standpoint,it was still better than calcium stearate,zinc stearate,and calcium-zinc composite thermal stabilizers.