The Segregation Of Conductive Carbon Black In The Natural Rubber/Epoxidized Rubber Blending Materials And Its Effect On Electromagnetic Properties

Thermodynamic matrix-filer wetting behavior difference wasapplied to design co-continuous natural rubber (NR)/ epoxidized natural rubber (ENR) blends with preferential conductive carbon black (CCB) location by using two-roll mechanical mixing.The microstructure,electromagnetic properties and its relations were characterized by scanning electron microscope (SEM), dynamic-mechanical thermal analysis (DMA),four-probe low resistance meter, high resistance meter, vector network analyzer etc.Thermodynamic induced CCB preferential location in NR/ENR blend and its influence on the electromagnetic property were carefully analyzed. Moreover, compatibility and blend ratio of NR/ENR tailored microstructure-electromagnetic property were discussed. The workis aim to providing an efficient way todevelop NR-based microwave absorbing materials with light weight, broad effective bandwith and high microwave absorption (MA)capacity.(1) By theoretical analysis and experiment, the different matrix-filler wetting behaviors between NR (or and ENR) and CCB were investigated. Thermodynamicand morphological analysis indicated that co-continuous NR/ENR blend favored the formation of CCBnetwork, providing the composites with superior electromagnetic properties.Electromagnetic properties enhance with the increasing of CCB content. When CCB concentration is 3wt%,the minimum reflection loss (RLmin) of all composites is below-15dB. The RLmin and effective bandwith of CCB incorporated co-continuous NR/ENR composite are -15.64dB and 1.36 GHz, which are 27.6% and 54.5% higher than that of CCB/NR composite, respectively.(2) The influence of compatibility between NR and ENR on the microstructure and electromagnetic properties of CCB/NR/ENR composites were systematically studies by changing the epoxidation level of ENR. ENR with abundant epoxidegroups shows inferior wettability to CCB than NR, which is responsible for the preferential location ofCCB in the NR/ENR blend. Increasing the epoxidation degree of ENR promotes the preferential location ofCCB and creates stronger dielectric loss, thus enhancing the MA properties of CCB/NR/ENR composites.When the epoxidation degree increases to 40mol%, the MA capacity of the composite has beensignificantly enhanced by 42.8%. Meanwhile, the qualified frequency bandwidth (RL <-10 dB) ofcomposites with ENR is 88.9 % broader than that of CCB/NR composite.(3) Take the CCB filled NR and ENR with 40mol% epoxidegroups (ENR-40) for example,effects of blend ratios on the morphology and electromagneticproperties of CCB/NR/ENR composites was studied. The results show that the electrical conductivity,complex permittivity and loss factor of the composites increase first and then decrease with the increase of the ratio of ENR in the material. The composite has the best reflection loss of -23.15 dB in the Cband and the maximum effective bandwidth of 1.36 GHz when the blend ratio of NR:ENRwas 70:30 (wt/wt).