Investigation On Curing Kinetics And Mechanical Properties Of The System Of Epoxy Resin/Carboxyl-terminated Butadiene-acrylonitrile Rubber

The most common,effectively and used widely approach to modify the toughness of epoxy resin is blending reactive liquid rubber,which is capable of phase separation and has an considerable attraction that the system epoxy blend with reactive liquid rubber can reach a formation of a homogeneous solution at first stage as the solubility of reactive liquid rubber,such as CTBN,HTBN and ATBN.As we know,the mechanical properties of the cured epoxy resins is dominated by the dimension and distribution of the rubber as dispersed phase in the system,so how to control the curing kinetics of system to make the diameter of rubber particles to reach we need is valuable issue.The manuscript has explored the relationship among curing process,micromorphology and mechanical properties of cured system which use CTBN toughening epoxy resin.1.Differential scanning calorinmetry dynamic mode is carried out to determine the characteristic curing reaction temperature of IPDA and DGEBA,and which is influenced by the addition of CTBN or not.Besides,how the addition amount of CTBN affects the mechanical properties was explored by tensile and impact test.Based on the experiment results,it indicates that the addition of CTBN has not apparent effect on the characteristic curing temperature of IPDA and DGEBA.In the scope of 5~100phr of CTBN addition,there is approximately proportional relationship between the impact strength of the eventually cured product and the addition of CTBN.When the addition surpass 200 phr,the impact value of cured composite system come into reduce.Together with elastic modulus and elongation at break,we believe that 15~20phr is the optimal range of the addition of CTBN.2.In the part,we investigate the dynamic mechanics,micromorphology,mechanical properties of eventual system with various addition of CTBN in different pre-curing temperature to find that how the curing process affect the dimension and phase separation of rubber phase of CTBN.There a regularity is found in the process testing systems with different amount CTBN,which is the system pre-cure in the low temperature,the dimension of rubber dispersed phase will be larger,the shape of rubber particles will be more regular,which make the elongation at break be higher.In curing process,each temperature has a corresponding a curing degree and each degree of cure corresponds an extent of phase separation,so a curing process of gradient temperature curing is applied.The result indicates that the toughness of system has been further improved.3.In the section,composite cure agents consist of IPDA and 4,4-Aminophenyl sulfone(DDS)was employed for curing EP/CTBN to regulate the dimension of particles of rubber phase,which is of great importance for toughness of cured epoxy.The different initial reactive temperature of the hardeners was taken advantage to increase the diameter of the rubber particles.By non-isothermal and isothermal differential scanning(DSC),determining an appropriate stoichiometric proportion of the two hardeners to make the degree of cure lower than 0.6 at the low temperature,i.e.gelation should not occur when IPDA cured DGEBA,through which the grow-time of rubber particles could be artificial control.By transmission electron microscope(TEM),dynamic mechanical(DMA)and mechanical analysis,it is found that the dimension of rubber phase in epoxy matrix is larger than that cured by single IPDA and DDS.4.In this work,a new cure agent of liquid polyamide with low molecular weight is used to harden epoxy oligomer,which can make the molecular chains of cured product be flexible to “internally toughen” epoxy resin.The new firming agent work in coordination with CTBN to “internally and externally toughen” epoxy is a research content.The results show that the effect of polyamide “internal toughening” is better than that of CTBN “external toughening”;when they work together,“internally and externally toughen” epoxy resin,the toughening effect is as twice as CTBN “external toughening” on the elongation at break,which indicates that “internal and external toughening ” has great potential in modifying epoxy resins.