Study On Polyester Plasticizers With Low Molecular Weight By Diacid And Diol

Plasticizers are a kind of important fine chemicals. They are used in plastics industriesas necessary additives. With the fast development of PVC matetials and their wide use infields, the demond of plasticizers is increasing. To date, phthalate esters are the commonplasticizers used in flexible PVC applications. However, they raise enormous concernsabout ecosystems and human health. In this work, a series of polyester plasticizers withexcellent performance were prepared and expected to be developed to the environmentalfriendly additives substituting for phthalate plasticizers.The nadic-anhydride polyester plasticizers (P-MPO-NA, P-BDO-NA and P-DEG-NA),hexahydrophthalic-anhydride polyester plasticizers(P-MPO-HHPA and P-BDO-HHPA) andtrimellitic-anhydride polyester plasticizers (P-Gl-TMA) were respectively synthesized bynadic-anhydride, hexahydrophthalic-anhydride, trimellitic-anhydride,2-methyl-1,3-propanediol,1,4-butanediol, diethylene glycol and glycerine via esterificationreaction with tetra-n-butyl titanate as catalyst and2-ethyl-hexanol as chain terminationreagent. The optimized reaction conditions were determined after the investigation for thestuff ration, the amount of catalyst and chain-end reagent and the reaction time. The averagemolecular weight (M_n) of the polyester plasticizers were determinated by GPC. The formingof ester group in polyester plasticizers was verified by ATR-FTIR and1H-NMR. Theirplasticizing performance, compatibility, thermostablility, migration were investigated andcompared with those of DOP. The results showed that P-MPO-NA, P-MPO-HHPA andP-Gl-TMA possessed excellent performance.The optimized synthesis conditions of P-MPO-NA are as follows:n(MPO):n(NA)=1.20, n(2-ethyl-hexanol):n(NA)=0.60, reaction time=7h,m(catalyst)=0.15%of total mass, esterification yield=99.6%, M_n=9842. The results ofapplication performance are as follows: a. The surfaces and cross-section ofPVC/P-MPO-NA film are found to be more smooth and neat than that of PVC/DOP.Moreover, the χ (Flory-Huggins parameters) of P-MPO-NA(-1.08) is lower than that ofDOP(-0.01), also indicating that the former has better compatibility with PVC than DOP; b.The Tgof PVC/P-MPO-NA film was reduced to-16.38℃and its EΔ(%) and EΔTs(%)were107%and114%, which reveal that P-MPO-NA has good plasticizing performance asDOP; c. The weight losses of PVC/P-MPO-NA film were only respectively1.29%and12.18%during the volatility and extractability tests which were far below that of DOP. Theoptimized proportion of best resistance migration is as follows: m(P-MPO-NA):(PVC)=1.1, where the PVC film shows lower Tg, better toughness and malleability, excellentwithstanding migration.The optimized synthesis conditions of P-MPO-HHPA are as follows:n(MPO):n(HHPA)=1.35, n(2-ethyl-hexanol):n(HHPA)=0.70, reaction time=7.5h,m(catalyst)=0.30%of total mass, esterification yield=99.7%, M_n=9839. The elongation atbreak and tensile strength of PVC/P-MPO-HHPA film were447.82%and17.88MPa. Theweight losses of PVC/P-MPO-HHPA film were4.22%and23.53%during the volabilityand extractability tests, respectively. The decomposition temperature ofPVC/P-MPO-HHPA film was raised to311.54℃and the weight losses was significantlydecreased.P-Gl-TMA (M_n=10612) was successfully synthesized by trimellitic anhydride andglycerol. The energy of reaction intermediates was calculated by Gaussian03[“6-31G(d,p)”]. Constitutional unit B was proposed to have possiblly competitive advantage based onits minimum energy (-669137.6213kcal/mol). P-Gl-TMA was characterized and itsplasticized performance was tested in detail. Structure B was comfirned as the mainconstitutional unit. The tensile strength of PVC/P-Gl-TMA film(17.05MPa) was higher thatof DOP(16.02MPa), implying that P-Gl-TMA obviously increased the toughness of PVCfilm. The weight losses of PVC/P-Gl-TMA (2.19%and14.78%) were lower thanPVC/DOP(9.69%and36.3%) in volatility and extraction test, which illustrated P-Gl-TMAenhanced the withstanding migration performance. The decomposition temperature ofPVC/P-Gl-TMA film were308.54℃and473.13℃. They were higher than that ofPVC/DOP in the two degradation stages, which illustrating that P-Gl-TMA effectivelyimproved the thermostability of the PVC film.