The Synthesis Of Hyperbranched Poly Caprolactone And Its Toughening Effects Research

Hyperbranched polyester(HPE)owns highly branched structure which give its some properties such as low viscosity,good solubility and high chemical reactivity.HPE is widely used in biomedical materials and polymer modification fileds.At present,the synthesis methods of HPE are complex,or monomer synthesis complex,or need more reaction steps to complete,all these makes its high cost and limit the application.Hyperbranched poly caprolactone(HPCL)as hot spot of HPE research received widely attention,but its complex synthesis process makes HPCL’s applications are only biological and pharmaceutical materials.In this paper,hyperbranched poly caprolactone were synthesized by one step through ring-opening condensation method and the HPCL were used into amorphous EP and semi-crystalline PLA substrate to study the effect on material properties of hyperbranched products.In the first part,HPCL was synthesis by ring-opening poly-condensation method from hydroxy-propionic acid and ε-caprolactone.The HPCL with different branched degree(DB)was obtained by optimizing the reaction conductions.Their structure and properties were characterized by FTIR、NMR、GPC、DSC et al.Quaternary carbon atom splitting which caused by different molecular configuration of BPA can be found in 13C-NMR of HPCL,confirming that the product has indeed the hyperbranched structure.In the second part,HPCL(DB:0.60)were added pure EP composite and flam retardant composite as toughening agent to study the effect on their properties.Pure EP had low toughness of which the elongation was less than 8% and the impact strength was less than 16 kJ·m-2.The toughness of EP can be significantly improved after adding a small amount of HPCL.When the addition of HPCL was 3%,the impact strength reach 21.99 kJ·m-2 which improved 102.0% compared with pure EP.After put HPCL into pure EP,the tensile properties,the bending performance,and the stiffness of EP all improved.All these indicate that HPCL does plays a good role in toughing EP.After adding HPCL into flame retardant EP composite with zinc hydroxyl stannate(ZHS),the experiment results show that the mechanical properties of flame retardant EP had also improved.When the addition of HPCL was 3%,the sample had best toughness.Compared with EP/ZHS system,the elongation and impact strength improved 46.6% and 73.4% respectively.HPCL had little effect on flame retardant properties and thermal properties,and the cone calorimetry data showed that HPCL had inhibitory effect on burning behaviour of EP system.In the third part,HPCL(DB:0.47)was put into pure Polylactic acid(PLA)substrate and flame retardant PLA composite.The experiment data showed that HPCL can significantly improved the elongation at break and tensile strength of pure PLA.Compared with pure PLA,when the addition of HPCL was 15%,the elongation and impact strength were the maximum which improved 60.6% and 35% respecyively.DSC and DMA data showed that Tg of PLA composite were decreased when adding HPCL into the PLA composite.This indicated that HPCL had better plasticizing effect for PLA.After adding the mmonium polyphosphate(APP)and pentaerythritol(PER)as flame retardant system into PLA,the flame retardance of PLA improved but the mechanical properties of PLA decreased.When HPCL replaced PER for PLA/APP-PER composite,the results showed that with the increase of HPCL,elongation at break and tensile strength of the PLA composite increased.When PER was totally replace,the elongation at break and tensile strength comes to 16.15% and 52.09 MPa which improved 112.0% and 13.9% respectively compared with the original system.At the same time,the limiting oxygen index(LOI)drops after PER was replaced by HPCL,but the vertical flame grade had not changed.