Effect Of Organotin And Calcium Stearate,Magnesium Stearate And Zinc Stearate On Thermal Stability Of PVC

The thermal stability of polyvinyl chloride?PVC?stabilized by methyltin mercaptide?DX-181?compounded with calcium stearate?CaSt₂?,magnesium stearate?MgSt₂?or zinc stearate?ZnSt₂?and dipentaerythritol?Di-PE?was investigated by static aging experiment and Thermogravimetry differential scanning calorimetry?TG-DTG-DSC?.The thermal degradation kinetic parameters and mechanism model of PVC with the better stabilizer formulations were obtained by non-isothermal kinetic calculation and generalized kinetic analysis at different heating rates.And the thermogravimetric-infrared spectrometer?TG-FTIR?,scanning electron microscope and energy dispersive x-ray microanalysis?SEM-EDS?and dynamic mechanical analysis?DMA?were used to study the effects of stabilizers on thermal degradation process and dynamic mechanical property of PVC.The main conclusions can be summarized into the following four aspects:0.5 portion of CaSt₂ or MgSt₂ can replace 0.5 portion of DX-181,and it is equivalent to 1.0 portion of DX-181.However,0.5 portion of ZnSt₂ or Di-PE can not replace 0.5 portion of DX-181.It can significantly enhance the thermal stability of PVC when the appropriate amount of Di-PE is combined with DX-181 and CaSt₂?or MgSt₂ or ZnSt₂?.The thermal degradation process of PVC with composite stabilizers DX-181,CaSt₂?or MgSt₂ or ZnSt₂?and Di-PE added at a ratio of 0.5:0.5:1.0 can be divided into two stages.Among them,when CaSt₂,MgSt₂ and ZnSt₂ were compounded,the first-stage activation energies were 129.6kJ/mol,112.6kJ/mol and 127.5kJ/mol,respectively,and the second-stage activation energies were 257.4kJ/mol,271.0kJ/mol and 261.7kJ/mol,respectively.These mean that when ternary compounding,CaSt₂ and ZnSt₂ have better first-stage stability,while MgSt₂ has better second-stage stability.The thermal degradation mechanisms of the three preferred PVC systems are basically consistent with the kinetic model of F3 chemical reaction in the decomposition rates of0.5-0.7.The organotin and metal soap composite thermal stabilizers studied have played a certain role in reducing the evolution of aromatic hydrocarbons and esters and delaying the large-scale release of HCl gas during the thermal degradation of PVC.However,there are also some differences.The complexation of ZnSt₂ reduces the amount of CO₂produced,the complexation of CaSt₂ effectively inhibits the precipitation of CO₂ in the second stage,while the complexation of MgSt₂ both reduces the release of CO₂ and increases the detachment temperature of HCl.Micropores of different sizes and amounts appear on the surface of the sample due to the precipitation of gaseous products during the PVC aging process.The key to the effect of stabilizers on the thermal stability of PVC is the inhibition of gas evolution such as HCl.The compatibility of the PVC system after modification is good.DX-181 and MgSt₂ have the effect of lowering the glass transition temperature?T_g?and increasing the storage modulus and loss factor of PVC products.After compounding Di-PE,the interaction among the three can improve the T_g while causing a slight decrease in the storage modulus and loss factor.Figure[38]table[22]reference[81]...