The Microstructure And Mechanical Properties Of Multiphase Rubber-plastic Materials Were Studied Using Nanomechanical Systems

Polymer composites are widely used in various fields because of their advantages in physical and chemical properties such as high specific strength,large specific modulus,fatigue resistance,corrosion resistance,versatility,easy structure design and easy processing.In order to meet the increasingly high performance and structure requirements of materials,it is important to design and characterize the structure and performance of materials from a microcosmic level.Nanoindentation technology is a method for testing the micro-scale mechanical properties of materials.It can obtain the local mechanical properties of the material and character the microstructure of the composite by recording the the load and the depth in the indentation process.In recent years,although the nanoindentation technology has been significantly improved in the experimental method,experimental principle and instrument resolution,there are still many problems for polymer materials especially viscoelastic material to test the micro-scale mechanical properties by using the nanoindentation technology.This paper focus on the application of nanoindentation technology in rubber and plastics materials.The mechanical properties of the composites are closely related to the mechanical properties of each phase and interface.In this article,the nanoindentation technique was used to characterize the micromechanical properties of the nanoparticals reinforced plastic,the partical reinforced rubber composites and rubber blends in ench phase and their interfaces.Besides,the relationship between the microstructure and the macroscopic properties of the composites was established by plotting the three-dimensional topography corresponding to the mechanical properties.In addition,viscoelasticity affects the results of nanoindentation,so the viscoelasticity of the material was studied from the micro-scale by changing the conditions in the indentation experiment.The specific research work is as follows:(1)The surface mechanical properties of hydroxyapatite/polylactic acid(HA/PLA)composites at microscale were studied by quasi-static and dynamic indentation techniques.The effect of viscoelasticity on the quasi-static mechanical properties of the samples was discussed by changing the loading time and the unloading time.The dynamic mechanical properties of the materials were also investigated in dynamic mode.The dimensional stability of the composites was studied by creep behavior and scratches.The results show that the loading condition affectes the test results of modulus and hardness only when the creep is insufficient in the quasi-static mode.The dynamic modulus and the hardness decrease with the increase of the pressing depth.The hardness curve of HA/PLA composites in microdomain showed that the plastic deformation of local indentation is smaller under the same load,which indicates that HA improves the mechanical properties of PLA.(2)The microstructural of CCTO/PDMS composites was characterized by nanoindentation technique.The main work focuses on the use of ultra-low load indentation conditions to draw the three-dimensional map corresponding to the mechanical properties,which reflects the relationship between microstructure and macroscopic properties and reveal the reasons why CCTOs with different particle sizes have different effects on matrix enhancement.By comparing the modulus images obtained under different loads,5?N was used as the optimal load.By comparing the microdomain modulus curve around the micro particles,it is found that the interface transition zone become large with the decrease of the particle size when the CCTO's particle size is less than 1?m.But when the particle size is reduced to 300nm,the micro-modulus is no longer increased,indicating that the particle sizes effect the enhancement of particle.(3)The quasi-static and dynamic nanoindentation experiments were carried out by using nanoindentation technique.The effect of time rate on quasi-static mechanical properties was studied by changing the loading,holding and unloading time in quasi-static experiment.The influence of test frequency and dynamic load on dynamic mechanical properties was investigated in dynamic mode.Taking into account the experimental results,we found the ideal test conditions of quasi-stic mode are loading holding time5s and holding time 20s.The results of dynamic indentation show that the storage modulus depends on the frequency and the stronger dependency of frequency is found when the powder content is increased.The loss factor increased first and then decreased with the increase of the frequency.The loss angle increased when the dynamic load increased.It was found the powder inside the material become dense with the increase content of the powder by testing the microdomain mechanical property of the rubber blends.Thus the interface with the crosslinking gradient formed by the vulcanization was increased.As a result,the tensile strength decreased monotonically with the increase of the powder content.