Preparation Of Crude Carbon Dots Multifunctional Auxiliary And Its Application In Rubber

As one of the most common polymer materials,rubber was used in various fields such as aviation,transportation,food,clothing,housing,and transportation.However,it was vulnerable to thermal/oxygen ageing.The most common solution to rubber ageing was to add antioxidants.However,many commercial antioxidants had problems such as uneven dispersion,migration out of the rubber matrix,pollution of the environment and waste of resources.In addition,zinc oxide（Zn O）,the most common active agent in the vulcanisation process of rubber,was found to be toxic to the aquatic organism,and in order to solve the problem of rubber ageing and improve product performances.In this thesis,crude carbon dots（CCDs）with good water solubility,low cytotoxicity,intriguing fluorescence properties and the ability to scavenge oxygen radicals were used as multifunctional additives for rubber matrix.In the first part of the thesis,we prepared unpurified crude carbon dots EDA-CCDs and U-CCDs by microwave method.The citric acid,ethylenediamine/urea,etc.,were used as precursors.TEM,FTIR,UV-vis,PL,Fenton and other tests were used to characterize the CCDs,TEM analysis showed that the EDA-CCDs and U-CCDs exhibited the spherical-like morphology,and the particle size was less than 10 nm;FTIR showed that there were groups such as-NH₂,-COOH and-OH on the surface.Fluorescence and oxygen radical scavenging experiments had shown that CCDs had good photoluminescence and oxygen radical scavenging capabilities.Next,we synthesized U-CCDs and EDA-CCDs prepared by microwave method and dispersed them into polar nitrile-butadiene rubber（NBR）or non-polar styrene-butadiene rubber（SBR）.U-CCDs and EDA-CCDs had a synergistic effect with butadiene rubber grafted maleic anhydride（BR-g-MAH）and silica（SiO₂）and promoted each other to well disperse in the matrix.The vulcanization properties,mechanical properties,and anti-aging properties for the as-prepared U-CCDs/NBR and EDA-CCDs/SBR composites were tested.The results showed that both U-CCDs and EDA-CCDs could completely replace zinc oxide to promote the vulcanization of NBR and SBR,and improved the anti-aging performance of the rubbers.With the increase of crude carbon dots content,the vulcanization rate and anti-aging properties were gradually improved.Among various rubber samples,the vulcanization rate for NBR with 5phr U-CCDs/0phr Zn O increased by 29%compared with the sample of NBR with 0phr U-CCDs/5phr Zn O,and the aging coefficient for the rubber increased by23.8%.Some rubber samples exhibited obvious fluorescence under UV light irradiation.Furthermore,we mixed EDA-CCDs with various inorganic fillers by a simple solid-phase blending method,so that the EDA-CCDs were loaded onto the inorganic fillers through non-covalent bonding.After drying the carrier,it was observed that each component of EDA-CCDs/inorganic filler exhibited different intensities of fluorescence under UV light irradiation;We prepared EDA-CCDs/SiO₂ silicone rubber,which exhibited uniform and strong blue fluorescence under UV light irradiation.We prepared EDA-CCDs/SiO₂/SBR by the open mill,and the as-prepared rubber composites were investigated.The SEM image of SBR with 4phr EDA-CCDs/40phr SiO₂ showed the uniform filler dispersion within the matrix.The T90 value of SBR with 2phr EDA-CCDs/40phr SiO₂ is 39.8%and 35.67%of the pure sample and the sample with 2phr antioxidant 4010,respectively,demonstrating the CCDs could significantly accelerated the vulcanization rate;the tensile strength of EDA-CCDs/SiO₂/SBR could reach 19.8Mpa,which is higher than that of pure sample,elongation at break increased from 309.7%（EDA-CCDs/SiO₂/SBR）to 401.3%（pure sample）;After thermal-oxidative aging at 100°C for 6 days,the tensile strength and elongation retention of EDA-CCDs/SiO₂/SBR were increased by 23.5%and 15.7%,compared with the rubber sample add with 2phr 4010,demonstrating that the EDA-CCDs/SiO₂/SBR had good thermal-oxidative aging resistance.In conclusion,the research in this paper showed that crude carbon dots can be used as a new,low-cost multifunctional（anti-aging,replacing zinc oxide,promoting vulcanization,fluorescence,etc.）rubber additives,and crude carbon dots had broad applications in the field of advanced rubber composites.