| Because of the high melt viscosity after plasticizing and the large temperature difference between the die and melt,the filling of microstructure will be incomplete,which will lead to the low precision of microstructure replication in the process of injection molding of microstructural products with traditional polymer materials.In this paper,we proposed an innovative method of microstructure molding,UV curing injection molding.The liquid UV curing material with adjustable viscosity at room temperature is used in the molding process,without plasticizing under high temperature and high pressure conditions.It has the characteristics of energy saving,high efficiency and precision,which explore a new way for high precision,high efficiency and scale forming of micro parts.In this paper,we investigated the process and reaction degree of UV curing injection molding,the typical defects of microfluidic chip,effect of the process conditions,and material formula on the replication accuracy.We also study on the bonding strength of the microfluidic chip systematically,according to the requirement of the microfluidic chip's application,we put forward the method of improving the hydrophilicity of the UV curing material chip.The main work include the following aspects,1.We explored the relationship between the molding material and the UV reaction rate and UV reaction degree from the angle of reaction kinetics,when the monomer mass fraction is the same,the reaction rate and reaction degree of the formulation containing low functional group monomer or oligomer is higher than that of multifunctional monomer or oligomer.When the content of photo-initiator in the formula is 3wt%-5wt%,the reaction rate and degree of the UV reaction are basically the same,we also studied on the microfluidic chip molding time of linear UV LED under different formulations and technological conditions.2.We investigated the mechanism and main influencing factors of cracks and yellowing defects in UV curing injection molding.Under the influence of the principle of UV curing molding,the improper selection of process conditions and material formulations will lead to cracks and yellowing of the products.The experimental results show that reducing the content of TMPTA monomer in the formula,reducing the irradiation intensity of linear UV LED,decreasing the scanning rate of linear light source and increasing the pressure holding pressure can solve the crack defect of the product to some extent.In order to improve the forming time of the products,we got the reasonable technological parameters of three kinds of monomers,which do not produce cracks in the experiment.The effects of material formula,UV intensity and irradiation time on the products yellowing were expound.We got the experimental formula and treatment method to improve the yellowing phenomenon of the products.3.We study on the replication accuracy of the microstructure products of UV curing injection molding,study on the main influence parameters of the bonding strength of UV-cured microfluidic chip at the same time.The micro structure on the microfluidic chip mode by UV curing material have the same precision,the results showed that the scanning rate of the liner UV LED light have a great influence on the copying accuracy of the product.4.We characterized the hydrophilicity of the UV-cured microfluidic chip by the contact angle,and described the principle of measuring the contact angle by the measurement angle method.It found that the material composition is the main factor affecting the hydrophilicity of microfluidic chips.UV irradiation intensity and irradiation time have little effect on the hydrophilicity of the chip.The water contact angle of the chip was reduced from about 60 degrees to about 17 degrees by optimizing the material formula,which improved the hydrophilicity of microfluidic chip remarkably. |
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