| Natural rubber latex(NRL)is a kind of renewable polymer material with excellent properties.It has been widely used in the manufacturing of tires,hoses,industrial products and medical products.The rubber hydrocarbon component of NRL is polyisoprene,which has high molecular chain unsaturation and is prone to aging,and hence the limited application.Improving the aging resistance of NRL is of great significance to industrial production and social construction.The main purpose of this paper is to improve the thermal aging resistance of natural latex.The aging resistance of natural latex was improved by two aspects,including optimization of the preparation process and filling and modification of different forms of inorganic nanofillers.The main research content andconclusions are as follows:1.Ultrasound pretreatment for vulcanizing agent dispersions prepared by planetary ball milling was carried out.The dispersions were slowly added to the latex,and then the pretreated vulcanized natural latex film(YS-NRL)was prepared.The results showed that the dispersions were uniformly dispersed in the natural latex after ultrasonic pretreatment,and there were no obvious particles in the tensile failure cross section.The contact angle difference between upper and lower surfaces of latex was reduced to 13.64°.At the same time,the crosslinking density of YS-NRL was increased,and the swelling degree was decreased by 9.5%.The mechanical properties of YS-NRL were enhanced significantly.The tensile strength retention rate reached 89.41%after aging at 70? for 240 h.2.The surface modification of nano-calcium carbonate(Nano-CaCO3)and nano-silica(Nano-SiO2)was carried out by using silane coupling agent DDES.Granular inorganic nanoparticles/natural latex nanocomposites with different filling forms were prepared by latex blending method.The infrared analysis showed that the siloxane groups of DDES reacted with hydroxyl groups on the surface of nanoparticles and formed DDES graft modified layer on the surface of M-CaC03 and M-Si02.When the DDES content was 15%,the modification effect was best.The contact angles with M-CaCO3 and M-SiO2 increased to 130.910 and 123.43°,respectively,and the grafting percentages were 25.13%and 44.07%,respectively.The properties of CaCO3/SiO2/NRL samples prepared by M-CaCO3 and M-SiO2 co-filled NRL were still good.In this case,the granular fillers uniformly dispersed within the NRL matrix and formed the granular filler-rubber network together with NRL,which performed good nano-synergistic enhancement effect.It led to the increase of the energy storage modulus(G')?the reduction of the loss modulus(G“),the increase of the thermal conductivity by 7.8%,and the decrease of the swelling degree by 13.75%.Meanwhile,the co-filled latex samples performed uniform failure cross-section and fewer exposed particles.The tensile strength and tear strength retention rates were 81.45%and 38.54%,respectively,after aging at 70? for 480h.3.Fewer layered M-ISIC was prepared through DDES surface modification and high energy nanoimpact milling using nano-ISIC.Then,layered inorganic nanoparticles/natural latex nanocomposites(M-ISIC/NRL)with different fill contents were prepared by latex blending.The infrared analysis showed that the siloxane groups of DDES successfully reacted with the hydroxyl groups on the Nano-ISIC surface to form a graft modified layer.High-energy nano-impact milling can effectively improve the surface reaction active points of nano-ISIC.After 4 hours of impact milling,the grafting percentage of the modified nano-ISIC surface was up to 53.08%,and the surface contact angle was increased to 141.36°.In the M-ISIC/NRL samples filled with 1 phr M-ISIC content,layered inorganic nanoparticles were stably embedded in the latex matrix and evenly dispersed,which effectively promoted the vulcanization cross-linking reaction of the latex.A stable layered filler-rubber network was established.The results of RPA analysis showed that the G' of samples increased significantly and the G" decreased.The tensile strength and tear strength retention of the samples reached 86.75%and 66.75%,respectively,after aging at 70? for 240 h.The thermal conductivity and swelling parameters of natural latex decreased by 18.22%and 19.43%,respectively,due to the barrier effect of the laminar structure of M-ISIC.Both granular and layered inorganic nano-particles can effectively improve the thermal aging resistance of natural latex,and their strengthening mechanisms are different.The binding force between the granular filler and natural latex is better than that of the layered filler,and the prepared granular inorganic nanoparticle/natural latex nanocomposite has strong resistance to thermal aging for a long time.The excellent barrier properties of the layered filler provide the substrate superior heat and solvent resistance,and the layered inorganic nanoparticles/natural latex nanocomposite has high performance retention under hot oxygen conditions in a short time.Figure[50]Table[12]References[171]. |
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