Preparation Of Super-hydrophobic Multi-walled Carbon Nanotubes And Their Modified Study Of Natural Rubber

The unique structure of carbon nanotubes brings it excellent physical properties such as electrical conductivity,thermal conductivity and mechanical properties,making it a reinforcing filler for many polymer matrices.However,it has strong van der Waals force and high surface energy,which is easy to cause agglomeration,resulting in poor dispersion of carbon nanotubes and main difficulty applied in polymer matrix.At present,there are many methods for surface modification of carbon nanotubes,and there are still many problems in some work on their use in weakly polar natural rubber.Either directly add unmodified carbon nanotubes,which agglomerate seriously in the rubber matrix,resulting in low cost performance,or use small molecule modification,which cannot build a good inorganic-organic interface structure in the rubber matrix,which hinders its large-scale application in high-performance rubber composites.In this paper,super-hydrophobic multi-walled carbon nanotubes SH-MWCNTs which has been prepared by surface-grafted polyurethane in a one-step process,and use them as functional fillers or additives for modifying natural rubber(NR).It is mainly divided into two parts.One is to prepare super-hydrophobic multi-walled carbon nanotubes SH-MWCNTs in a one-step process,and to characterize their structure and properties by using thermogravimetric,infrared spectroscopy,scanning electron microscopy,contact angle and Raman spectroscopy.Second,the prepared SH-MWCNTs black powder was used as an additive to modify natural rubber,and the microstructure and properties of the NR/SH-MWCNTs rubber composites were characterized by using transmission electron microscopy,mechanics,dynamic mechanics and thermal conductivity,revealing its interface characteristics and performance relationships.The results of the study are as follows:(1)The hydrophobic multi-walled carbon nanotubes SH-MWCNTs-3prepared by one-step method has the best comprehensive performance.The surface of SH-MWCNTs-3 can be grafted with polyurethane with a weight ratio of 6.5%;the contact angle with water is 171.25°,showing a super-hydrophobicity property.(2)Frozen ultrathin sections of the vulcanized samples of natural rubbercomposites modified by SH-MWCNTs-3 were performed.High-resolution transmission electron microscopy results showed that the carbon nanotubes had no visible agglomeration observed in the rubber matrix,and with the increase of the number of carbon nanotubes,they showed a certain continuous network structure in the natural rubber matrix,and the carbon nanotubes basically exist in the form of a single root.(3)The mechanical properties of NR/SH-MWCNTs rubber compositeswere then comprehensively analyzed.When 5 phr super-hydrophobic multi-walled carbon nanotubes SH-MWCNTs were added,the Akron abrasion value was 0.9 cm³/1.61km,which was much larger than that of the unmodified natural rubber.The abrasive resistance of NR/MWCNTs modified with multi-walled carbon nanotubes can maximize the rigidity of MWCNTs and reduce the peak value of tan?of natural rubber.At the same time,the thermal conductivity of the rubber increased to 0.2553W·m^-1K^-1,which was about 40.3%higher than that of adding unmodified MWCNTs.Through the research of this paper,the one-step preparation of super-hydrophobic multi-walled carbon nanotubes SH-MWCNTs is expected to be applied to various high-end rubber seals,tires,mine conveyor belts and other rubber products that require high abrasive resistance.