The Synthesis Of Branched Poly(butylene Adipate) And Its Plasticizing Effects Research

The migration of plasticizers in flexible polyvinyl chloride?PVC?products not only deteriorates the properties of the materials,but also causes some environmental problems.Therefore,the migration-resistant polyester plasticizers attract more attention in recent years.Due to their irregular branched structures,the branched polyesters have unique physical and chemical properties.The melt of the branched polyesters has a lower viscosity and better fluidity since the higher functionality and chain end density for their molecular chain.In this paper,three kinds of branched polybutylene adipates?BPBAs?were synthesized by melt polycondensation and added into PVC.The plasticizing effects of BPBAs with different branched structures for PVC were investigated,the effects of BPBAs on mechanical properties,thermal properties and other properties were also studied.In the first part,linear polybutylene adipate?LPBA?with low molecular weight was synthesized by melting polycondensation of adipic acid?AA?and 1,4-butanediol?BD?.The glycerol?GL?,trimethylolpropane?TMP?and trihydroxyphosphine oxide?THPO?as branching agents were introduced into the LPBA to prepare three kinds of BPBAs:BPBAG,BPBAT and BPBAP.Their structures and properties were characterized by intrinsic viscosity,fourier transform infrared spectroscopy?FTIR?,energy dispersive spectroscopy?EDS?,nuclear magnetic resonance spectroscopy(¹³C-NMR)and thermogravimetric analysis?TGA?.The experimental results showed that the product structures were as expected.In the second part,to study their plasticizing effects the BPBAG and BPBAT were applied into PVC.The experimental results showed that the plasticizing effects of both BPBAs with branched structures were better than LPBA and the BPBAT was superior to the BPBAG.The tensile strength of BPBAs plasticized PVC?PVC/BPBAs?was higher than that of LPBA plasticized PVC?PVC/LPBA?.The mechanical properties of BPBAT2?amount of1.0%TMP as branching agent?plasticized PVC were the best.The elongation at break of PVC/BPBAT2 reached 180.3%,which increased 49.6%than that of PVC/LPBA,and the low temperature toughness of PVC/BPBAT2 improved 20.3%than that of PVC/LPBA.Although the plasticizing effects of BPBAs for PVC were only 88%of dioctyl phthalate?DOP?,the thermal stability and migration resistance of PVC/BPBAs were significantly better than that of PVC/DOP.The scanning electron microscope?SEM?image and dynamic mechanical analysis?DMA?data showed the LPBA and BPBAs both have good compatibility with PVC.The DMA data confirmed that after BPBAs were added the stiffness of PVC samples reduced and the flexibility of PVC samples improved.In the third part,the plasticizing effects and flame retardant propertied of BPBAP applied in PVC were studied.The experimental results showed that the plasticizing effect of BPBAP with phosphorus branching structure for PVC was better than that of LPBA.PVC/BPBAP3?amount of 3.0%THPO as branching agent?has the best mechanical properties of plasticized PVC.The elongation at break of PVC/BPBAP3 reached 152%which was 30.7%higher than that of PVC/LPBA and the low temperature toughness of PVC/BPBAP3 was 26.9%higher than that of PVC/LPBA.For PVC the thermal stability and migration resistance of BPBAP were superior to DOP.The flame retardant properties of DOP,LPBA and BPBAP were compared.The results showed the limiting oxygen index?LOI?of PVC/LPBA was higher than that of PVC/DOP which increased to 31.8%from 28.1%.The introduction of phosphorous branching agent further improved the flame retardant properties.When the amount of THPO was 1.0%,3.0%and 5.0%,LOI of PVC/BPBAP increased to 32.9%,33.8%and 34.2%respectively.Cone calorimetric data showed that PVC/BPBAP5 has the highest fire performance index with the lowest heat release rate,smoke release rate,extinction area,mass loss rate,total heat release and total smoke release among the PVC samples.All the data indicated the BPBAP has good plasticizing effect and flame retardany for PVC.