Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 02, 2019 - November 04, 2019
One method of manufacturing MEMS is the strereolithography which uses UV photopolymer. Microelements, however, fabricated by stereolithography have poorer strength than metal components usually used to machine. So that reason, it is applied in limited fields. Mechanical properties of micromaterials are different from those of bulk materials and characterization of mechanical properties for micro specimens is needed to design reliable micromachines and MEMS.
In this study, we tried to improve the mechanical properties by adding cellulose nanofibers (CNF) in one of the reinforcement to UV photopolymer. Moreover we created micro specimens by stereolithography, and evaluated the mechanical properties by tensile test.
Since CNF has Hydrophilic Groups, it is difficult to disperse by adding CNF to general hydrophobic photopolymer. In previous studies, When composites were made using freeze-dried CNF and water-dispersed CNF, we were able to make test specimens with addition rate of 1.5 mass% and increase the Young's modulus of the specimen. However, as the addition rate increased, CNF aggregated in the resin to form clusters due to decrease in dispersibility. The tensile strength and the elongation also decreased greatly. For these reasons, we needed to improve dispersibility of CNF in UV photopolymer.
Therefore, we examined the effect of improving dispersibility of CNF in the photopolymer by using a method of Replacing water of CNF slurry in acetone by using centrifugation and a method of chemically aminating a hydrophilic group of CNF. As a result of compositing with acetone-dispersed CNF and aminated CNF, dispersibility was improved. With an addition rate of acetone-dispersed CNF 4.0 mass% and aminated CNF of 5.0 mass% , we could create test spesimens. As compared with the composite of water-dispersed CNF, the Young's modulus and the tensile strength increased, and the decrease in strain was suppressed.
