The Preparation Of N-containing Organic Compound Thermal Stabilizers And Its Application In Poly(Vinyl Chloride)

As is known to all,poly?vinyl chloride??PVC?is one of the five general-purpose plastics with wide application and huge output.The structural factors and structural defects of PVC make its thermal stability very poor,and it is often needs to add thermal stabilizer to inhibit its degradation during the process of molding.With the enhancement of people's awareness of environmental protection and the implementation of relevant laws and regulations,the research and application of thermal stabilizers are developing in the direction of non-toxicity and environmental protection.And organic stabilizers have attracted great attention because of their non-toxic and environmentally friendly characteristics.In this paper,the effect of the synthesis process conditions on the yield of6-amino-1,3-dimethyluracil is studied.The optimum synthesis process conditions of6-amino-1,3-dimethyluracil were determined by controlling the reaction temperature,the ratio of raw materials,catalyst dosage and other factors.And the product was analyzed and characterized by measuring melting point,Fourier infrared spectroscopy,X-ray diffraction spectroscopy.As a thermal stabilizer for PVC,the effect of 6-amino-1,3-dimethyluracil on the static thermal stability and dynamic thermal stability of PVC was evaluated by the Congo red test,thermal aging experiment,thermogravimetric analysis method,torque rheometer method.The results show that the addition of 6-amino-1,3-dimethyluracil helps to improve the discoloration of PVC products and prolong the hea t stability time.And the thermal stability is more excellent when 6-amino-1,3-dimethyluracil combined with zinc stearate?Zn St₂?and calcium stearate?Ca St₂?.On this basis,the thermal stability of 6-amino-1,3-dimethyluracil to PVC was analyzed by TG-IR analysis technology in the calcium-zinc composite stabilizer.Experimental data shows that6-amino-1,3-dimethyluracil has the ability to replace the active chlorine atoms in the PVC molecular chain,which can prevent the formation of conjugated double bond s.In macro presentation,it improves the initial coloration of PVC and show the characteristics of an initial heat stabilizer.In addition,there is a good synergistic thermal stabilization effect between 6-amino-1,3-dimethyluracil and Zn St₂,which can effectively delay the autocatalytic phenomenon,which is due to the heterocyclic structure of6-amino-1,3-dimethyluracil can complex Zn Cl₂,a by-product of Zn St₂.It can also make up for the shortcomings separately with Ca St₂,the long-term heat stabilizer,while improving the initial thermal stability and it also extends the time of long-term thermal stability.The non-isothermal degradation process of 6-amino-1,3-dimethyluracil/Ca-Zn co-stabilizer for PVC was studied by TG-DTG thermal analysis.And the thermal degradation reaction mechanism of PVC after adding 6-amino-1,3-dimethyluracil is obtained by establish kinetic functions.The results show that there are two degradation stages in PVC.The first degradation stage can be subdivided into two steps due to two dechlorination reactions.The second degradation stage is difficult to describe with a mathematical model because the reaction is too complicated.The activation energy of thermal degradation mechanism is random nucleation and subsequent growth.The the thermal degradation mechanism is three-dimensional diffusion.Different amounts of 6-amino-1,3-dimethyluracil are added to the Ca-Zn co-stabilizer for PVC,and the processing performance,tensile performance and transparency performance of PVC products were measured by torque rheometer,universal testing machine and transparency test.The results show that the more6-amino-1,3-dimethyluracil was added,the worse the processing properties,tensile properties and transparency of PVC.The effect of 6-amino-1,3-dimethyluracil in Ca-Zn thermal stabilizer for PVC was analyzed by Congo red test and thermal aging experiment.The results show that when the ratio of Ca/Zn is 4:1,the composite stabilizer has the best thermal stability,and the thermal stability increases with the increase in the amount of6-amino-1,3-dimethyluracil.According to the analysis,the appropriate dosage of6-amino-1,3-dimethyluracil in the Ca-Zn co-stabilizer for PVC should from 1 to 3 phr.Aiming at the shortcoming of 6-amino-1,3-dimethyluracil's deficient long-term stability,the addition of tetramethylol glycoluril as an auxiliary stabilizer can effectively extend the thermal stability time of PVC products.