Synthesis Poly (Butylene Succinate) Ionomer And Its Foaming Mechanism

Poly(butylene succinate)(PBS)is one of fully biodegradable polymer which derived from biomass.It is synthesized by succinate and 1,4-butanidol.Compared with other alphatic polyester,PBS has excellent mechanical properties and good processability.However,due to the linear structure and the low entanglement between molecular chains,PBS has the low melt strength.So the application of PBS for foaming materials is limited.Therefore,it is significantly essential and practical to improve the melt strength of PBS in order to broaden its use.In order to improve the melt strength of PBS,PBSUIs were synthesized.Differential scanning calorimetry(DSC),X-ray diffraction(XRD)and dynamic rheology measurements were used to study the crystallization and rheological properties.Then we investigated the influence of saturation temperature,saturation pressure,foaming temperature and ionic group content on cell morphology of PBSUIs foam.The study showed that the crystal structure was not obviously changed with different content of diethanolamine hydrochloride or after it had been foamed.With the increased of ionic group,the crystallinity of PBSUIs decreased,and the distance between the crystals was reduced.Based on the plasticizing effect of Sc-CO2 in foaming process,the mobility of the molecular chain had been improved,so the degree of crystallinity PBSUI was increased.Results also showed that shear thinning behaviour could be found.In the low frequency area,complex viscosity of PBSUIs was higher than PBSU,and increased with the increase of the ion content.PBSU and PBSUIs could be microcellular foaming materials after foamed.As the saturation temperature and the saturation pressure rise,the cell size of foaming PBSUIs decreased first and then increased,the cell density increased first and then decreased,and the average wall thickness decreased first and then increased,the opening rate increased.As the foaming temperature rised,the cell size of foaming PBSUIs decreased first and then increased,the cell density increased first and then decreased,and the average wall thickness and the opening rate decreased first and then increased.The cell morphology of PBSUI was quadrilateral and the pentagon,and the cell exhibited were stretched.The cell size decreased,the cell density increased,the mean cell wall thickness decreased,the opening rate decreased with the ionic group content increased.Under the optimal foaming conditions,the cell diameter of PBSUI-3 was only 2.05?m and the cell density reached 1.73 × 1010.A series of phosphorus-containing PBS ionomers(PBSI-K)were successfully synthesized by melt polycondensation.The crystallinity of PBSI-K decreased with the increase of ionic monomer content,and its crystal structure was the same as pure PBS.The ionomer and pure PBS exhibited shear thinning behavior within the test frequency range.In the low frequency region,the complex viscosity of PBSIs-K was higher than that of pure PBS at the same shear rate,the complex viscosity of PBSIs-K was further enhanced with the increase of ion concentration.But when the ion content reached to 10%,the complex viscosity,storage modulus and loss of modulus decreased.The addition of DHPPO-K enhanced the stability of PBSIs-K under an air atmosphere,but reduces its stability under a nitrogen atmosphere.Under the nitrogen and air atmosphere,the amount of carbon residue of the PBSI10-K was 12.6% and 6.90% respectively.The tensile strength of PBSIs-K decreased with the increase of the content of ionic groups in the molecular chain,and the elongation at break increased first and then decreased with the increase of the ionic group,and the ionic group content reached to 7.5 mol% was the largest.PBS and PBSIs-K were foamed by Sc-CO2.The cell structure of PBS and PBSIs-K foaming material was studied in detail,and the foaming mechanism of PBS ionomer was proposed.The cell size and wall thickness of pure PBS was large,but the cell size of the PBSIsK foam was reduced,the cell wall was thinned,the quality of the cells was improved,and the "tufted" structure appeared in PBSI3-K and PBSI5-K foaming materials.PBSIs-K cells also showed a marked orientation,tensile state.In addition,the ionic clusters are aggregated to form a physical cross-linking,so the melt viscosity of the material increased.Sc-CO2 in the pure PBS homogeneous nucleation,nucleation efficiency was low,and because of the low melt viscosity of pure PBS,and ultimately lead to pure PBS foam material cell density was low,low foaming ratio,cell diameter,Thick wall.In the PBS ionomer,due to the presence of ion clusters,the polymer matrix can dissolve more CO2,and the ion cluster aggregation makes it more obvious heterogeneous nucleation,nucleation point increased,eventually leading to PBS ionomer Foam material cell density,high expansion ratio,cell diameter,wall thickness.The "tufted" structure with an elongated cell at the edge appeared and making the cell diameter decreased and wall thickness thiner in the final material.