Preparation,Application And Mechanism Of Low-precipiated Bis-uracil Derivates Stabilizer For Poly(Vinyl Chloride)

Poly(vinyl chloride)(PVC)has been applicated in many field because of its fire resistance,abrasive resistance,corrosion resistance and outstanding mechanical property,being one of the five general-purpose plastics in the world.As PVC is going to thermal degradation under processing temperature,thermal stabilizer is obbligato.With the enhancement of people's awareness of environmental protection,more attention has been payed to non-poisonous and environmental organic stabilizers with no “zinc burning”.However,most organic stabilizers are micromolecule and easy to migrate,resulting to the decline of beauty and thermal stability of PVC.Therefore,this paper developed a low-precipiated organic stabilizers system.The following three works have been done:(1)6-amino-1,3-dimethyluracil with good stabilizing effect was selected as stabilizing group.Then,bis-uracil derivates with different length of aliphatic chain were synthesized by the reaction between octanal,undecanal and DAU.The effect of compatibility between thermal stabilizer and PVC on thermal stability and precipitation performance of thermal stabilizer was investigated Due to longer aliphatic chain,USU showed better compatibility with PVC than OSU.The ratio of precipitated USU was 1.5 %,which was about half of OSU.At the same time,though having less stabilizing groups,USU showed better stabilizing effect than OSU because of better compatibility with PVC.The initial color of PVC samples can maintain 50 min in discolor test.(2)UESU was prepared by the reaction between DAU and 10-Undecenal.Then Oligomer P-UESU was synthesized through cationic polymerization.Though P-UESU formed microcell as P-UESU could not be effectively diffused into PVC because of the incompatibility of P-UESU and PVC,resulting in the high initial haze of PVC and low light transmittance,P-UESU tended to gather rather than separated out because of its large molecular weight.The ratio of precipitated P-UESU was less than 0.2 % and didn't rised with time.On the other hand,although the initial color of PVC with P-UESU got worse,the discoloration test time and dynamic thermal stability time of PVC were 110 min and 30 min,respectively.And P-UESU can be used as low-precipitated,non-transparent stabilizer.(3)For better stabilizing effect,ESBO and TPP were chosen as the auxiliary thermal stabilizers and used with USU and P-UESU,preparing low-precipated and high stabilizing efficient bis-uracil derivates stabilizer system.PVC with USU/ESBO/TPP showed remarkable stability and transparency.PVC samples just showed yellow after heating 160 min at 180? and the transmittance of it was about 90 %.But ESBO and TPP promoted the precipitation of USU.The ratio of precipitated and haze of USU reached 2.3 % and 25 %,respectively.So the auxiliary stabilizer of USU need to be further selected and optimized.As for P-UESU,P-UESU trended to gather in PVC.So,the ratio of precipitated P-UESU maintain low level when used with ESBO and TPP.The ratio of precipitated of P-UESU was still less than 0.25 %.Besides,PVC with P-UESU/ESBO/TPP showed good thermal stability and its dynamic thermal stability time reached 41 mins,which meet the requirement of commercial stabilizers.