Synergistic Modification of PVC with Nitrogen-Containing Heterocycle and Tung-Oil Based Derivative for Enhanced Heat Stabilization and Plasticization Behavior

The additives present in polyvinyl chloride(PVC)materials are the major source of organic by-products during PVC degradation.The thermal stabilizer and plasticizer are the main additives that endow PVC with the required properties during its processing.However,these two additives easily migrate when samples are obtained by physical mixing of the additives with PVC.This causes the reduction of PVC sample efficacy and the increase in the formation of organic by-products in the radiolysis process.In this work,two kinds of grafted PVC samples(tungoil derivative grafted PVC and Atz grafted PVC,abbreviated as P-GT4 and P-AZ3)were synthesized by chemical grafting of 3-amino-1,2,4-triazole(Atz)and tung-oil derivative on PVC,respectively.These two PVC samples were then blended at different mass ratios to obtain hybrid PVC materials with excellent plasticization,thermal stability and migration resistance ability.Differential scanning calorimetry(DSC),discoloration,Congo red test and thermogravimetric analysis(TGA)showed that when the mass ratio of P-GT4 to P-AZ3 in the mixed PVC resin was 1:3,the resulting P1:3-GT4-AZ3(P4)presented the best plasticization and thermal stability.The kinetics of thermal decomposition showed that the activation energy of P4 was much higher than that of the reference material[PVC/DOTP/CaSt2/ZnSt2,PVC/CZ41 for short]at mass lossα=20%and 80%.In addition,the leaching test showed that P4 material possessed excellent migration resistance ability.

The Promoting Effect of Multifunctional Groups on the Thermal and Mechanical Properties of PVC Materials

The development of PVC materials grafted with mannich base originated from myrcene(P-MAM-g,where the mannich base derived from myrcene is abbreviated as MAM)via green and effective synthetic methods is a good strategy to avoid unacceptable discoloration and deterioration of thermal and mechanical properties caused by autocatalytic dehydrochlorination(DHC)during PVC processing.In this study,MAM with double bonds,amino groups,ester groups,and phospholipid groups was introduced into the chains of PVC to improve the thermal stability of PVC.The experimental results showed that the covalent attachment of MAM to PVC enhanced both the initial and the long-term stability of PVC.The enhanced performance of P-MAM-g compared with unmodified PVC is attributed to the simultaneous introduction of double bonds and amino groups into the PVC structure.The double bonds trapped the unstable chlorine atoms originated from the degradation of the PVC chain and reacted with the labile macromolecular radicals originated from PVC,thus inhibiting the radical degradation of the PVC chain.Furthermore,the amino groups absorbed the HCl produced in the degradation of PVC,inhibiting the adverse effects of HCl.P-MAM-g displayed better intrinsic flexibility and anti-migration ability of organic functional components compared with the control PVC materials.A possible stabilizing mechanism of the P-MAM-g was also presented.