# Study of Mechanical Properties of Micron Polystyrene-Tughened Epoxy Resin
## 4 Conclusions  
In this work, a new micron-material-modified epoxy resin adhesive was prepared by toughening epoxy resin with micron polystyrene (PS) microspheres as micron filler, and three different mechanical properties of the modified adhesive in tensile, bending and impact were investigated, and the following conclusions were drawn.  
1. The mechanical properties of the epoxy resin were significantly improved by adding the appropriate amount of micron polystyrene (PS). The tensile strength, the tensile modulus of elasticity, flexural strength, flexural modulus and impact strength of the adhesives showed a trend of increasing and then decreasing with the increase in PS incorporation; 2.5 wt% of PS resulted in the optimum mechanical properties, which were improved by 77%, 147.7%, 71%, 35% and 22%, respectively, compared with the pure epoxy resin.
2. The influence of PS admixture on the elongation at break and bending deflection of the adhesive was significant; the elongation at break and bending deflection of the adhesive were maximum when the PS admixture was 0. With the increase in PS mass fraction, the elongation at break and flexural deflection of the adhesive increased, but still less than the pure resin.
3. Correlations between the microscopic morphology and the mechanical properties of the adhesive were obtained using SEM techniques. The PS particles produce large deformation to absorb energy when the matrix fractures, and crack expansion needs to bypass or shear the PS particles, thus inhibiting the crack expansion and achieving  
Figure 14: Micromorphology of the tensile section of epoxy resin colloid: (**a**) tensile section of epoxy resin with PS mass fraction of 0 wt%; (**b**) tensile section of epoxy resin with PS mass fraction of 1.25 wt%; (**c**) tensile section of epoxy resin with PS mass fraction of 2.5 wt%; (**d**) tensile section of epoxy resin with PS mass fraction of 3.75 wt%; (**e**) tensile section of epoxy resin with PS mass fraction of 5 wt%.  
toughening. When the PS weight fraction increases to 5%, PS particles in the resin appear to adhere to the agglomeration phenomenon, resulting in a decrease in the mechanical properties of the adhesive.  
Conceptualization, C.L. and Y.L.; methodology, C.L.; validation, C.L. and Z.C.; formal analysis, C.L.; investigation, Z.C.; resources, Z.C.; data curation, C.L. and Y.L.; writing--original draft preparation, C.L., Y.L. and Z.C.; writing--review and editing, Y.L.; visualization, C.L.; supervision, C.L. and Z.C.; project administration, C.L.; funding acquisition, Z.C. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China through Grant Nos. 51708047, 51778069 and 51978081, the Natural Science Foundation of Hunan Province through Grant No. 2019J50670, and the Excellent Youth Project of the Hunan Provincial Department of Education through Grant No. 19B013.  
Not applicable.  
The data used to support this study are available from the corresponding author upon request.  
We would like to thank the reviewers for their valuable suggestions.  
The authors declare that they have no conflict of interest.