| Polylactic acid is a synthetic polymer material derived from natural sources.It has the advantages of high mechanical strength,good degradability,and good sustainability.Products made from polylactic acid can replace some petroleum-based materials in many fields.potential.Rosin is a natural product derived from pine trees.China’s rosin resources are very rich,accounting for about 60% of the world’s rosin resources.Polymerized rosin is a polymer mixture made of rosin and has many excellent properties,such as With strong durability,strong oxidation resistance,low acid value,high softening point,etc.,it has a wide range of applications in food,medicine,paper,electronics and many other fields.Many scholars are committed to the research and development of polylactic acid products,but it is rarely reported that polylactic acid can obtain a new structure by mixing polymerized rosin and polylactic acid.Adding polymerized rosin as a raw material to the preparation of polylactic acid products can increase the added value of polymerized rosin,expand the application range of polymerized rosin,and provide a new process method for the preparation of polylactic acid products.The thesis first proposed a method of polymerizing rosin as the dispersed phase,without using organic solvents,and using only the catalyst stannous octoate to make the ring-opening polymerization of lactide directly form polylactic acid nanospheres.The morphology and particle size dispersion index of the prepared polylactic acid nanospheres were characterized at different cooling temperatures.After comparison,the cooling temperature was the most important factor affecting the particle size of the polylactic acid nanospheres.The low cooling temperature can make the particle size of the polylactic acid nanospheres more uniform.When the external cooling temperature is-80℃,the particle size of the polylactic acid nanospheres is170 nm.When the temperature is 20℃,the particle size of the polylactic acid nanospheres is210 nm.There are two different The difference in particle size of the polylactic acid nanospheres at the cooling temperature is about 14%;the effect on the crystallinity is that the lower the cooling temperature,the lower the crystallinity of the polylactic acid nanospheres,the higher the cooling temperature,and the higher the crystallinity;and The external cooling temperature has no effect on the thermal properties and chemical structure of the polylactic acid nanospheres.The thesis successfully used polymerized rosin as a porogen,and prepared a polylactic acid porous film using the results of a non-solvent phase separation method,and carried out different proportions of polymerized rosin as a porogen to form the porous structure,ultraviolet light transmission rate,and surface Characterization of water repellency,crystallinity and thermodynamic properties.The results show that polymerized rosin can be used as a porogen to prepare polylactic acid porous membranes.When the proportion of polymerized rosin is between 0 and 80%,the porous structure on the surface of the polylactic acid porous membrane increases significantly,the number increases by about 87%,and the pore size increases by about11 %;The change of the porous structure also improves the hydrophobicity of the polylactic acid porous film.Compared with the ordinary polylactic acid film,the water contact angle of the polylactic acid porous film can be increased by 26.1°;the polymerized rosin gives the polylactic acid porous film a special interface The anti-ultraviolet transmission ability of the polylactic acid porous film prepared after adding polymerized rosin is improved,and the difference in the highest transmittance in the same wavelength range can reach 73%;in terms of crystallinity and thermodynamic properties,the polymerized rosin is prepared during the preparation process.The addition of polylactic acid can significantly increase the crystallinity and glass transition temperature of the polylactic acid porous film,and the glass transition temperature can be increased by 34°C.In addition,polylactic acid spinning is also a hot research direction today.For the first time in this paper,polymerized rosin and polylactic acid are mixed for melt spinning,which can simply prepare polylactic acid nanofibers.The prepared composite fiber with complex structure can split into smaller fibers by itself under a certain external force.The diameter of the fine fiber is between 100nm～200nm.Combining the characteristics of the fiber,it is named as the polylactic acid split nanofiber..During the preparation process,it was found that the ratio of melting temperature to polymerized rosin was the main factor affecting the formation of polylactic acid lobed nanofibers.The optimal preparation plan for polylactic acid lobed nanofibers was researched and established as follows: 180°C melting temperature,30% PR mass ratio;shear viscosity affects the fiber forming performance during melt spinning.After rotating rheological tests on samples with different polymerized rosin content,it is found that the shear viscosity of polylactic acid and polymerized rosin in the molten state is consistent with spinning Require.The viscosity of all samples showed a decreasing trend with the increase of shear rate.The temperature was negatively correlated with the shear viscosity of the sample.The higher the temperature,the lower the shear viscosity.At the same time,the dynamic thermodynamic analysis of polymerized rosin and polylactic acid Compatibility analysis shows that the compatibility order is: PLLA>30%PR>40%PR>20%PR>10%PR.This paper focuses on the structural effects of adding polymerized rosin on the preparation of polylactic acid products,and proposes a new idea and method for preparing polylactic acid products based on polymerized rosin,and verifies the feasibility of the method,in order to broaden the application and preparation of polymerized rosin.Lactic acid special structure products provide reference and reference. |
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