Antiozonants and antioxidants are additives commonly used in the rubber industry to enhance the durability and performance of rubber products. Ozone, present in the atmosphere, can cause rubber to degrade over time th...Antiozonants and antioxidants are additives commonly used in the rubber industry to enhance the durability and performance of rubber products. Ozone, present in the atmosphere, can cause rubber to degrade over time through a process known as ozone cracking. These rubber additives are added to rubber compounds to protect against this degradation. They work by reacting with ozone, preventing it from attacking and breaking the molecular chains in the rubber, helping to maintain the structural integrity of the rubber product. It is now well known that 6PPD contributes to the extension of the service life of rubber products. However, recent studies have shown that 6PPD can be harmful to the environment, especially when end-of-life tyres (ELTs) are contaminated with the water. With the effect of ozone, 6PPD is converted to 6PPD quinone, which is toxic enough to kill some sensitive fish species such as Coho Salmon (Oncorhynchus kisutch). This study drew attention to new chemical compounds and natural products that can be used as antiozonants and antioxidants in the rubber industry instead of 6PPD. Although the scientific studies are promising, the fact that 6PPD is still used in production shows that more scientific studies and social awareness need to be developed in this area.展开更多
The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in nu...The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in numerical calculations owing to their simple mathematical forms.This study developed a PPD model for rocks(rock masses)based on the Alejanoe-Alonso(A-A)dilatancy model.The developed model comprehensively reflects the influences of confining pressure(σ_(3))and plastic shear strain(γ^(p)),with the advantages of a simple mathematical form,while requiring fewer parameters and demonstrating a clear physical significance.The overall fitting accuracy of the PPD model for 11 different rocks was found to be higher than that of the A-A model,particularly for Witwatersrand quartzite and jointed granite.The applicability and reliability of the PPD model to jointed granites and different scaled Moura coals were also investigated,and the model was found to be more suitable for the soft and large-scale rocks,e.g.deep rock mass.The PPD model was also successfully applied in studying the mechanical response of a circular tunnel excavated in strain-softening rock mass,and the developed semi-analytical solution was compared and verified with existing analytical solutions.The sensitivities of the rock dilatancy to γ^(p) and σ_(3) showed significant spatial variabilities along the radial direction of the surrounding rock,and the dilation angle did not exhibit a monotonical increasing or decreasing law from the elasticeplastic boundary to the tunnel wall,thereby presenting the σ3-or γ^(p)-dominated differential effects of rock dilatancy.Tunnel deformation parabolically or exponentially increased with increasing in situ stress(buried depth).The developed PPD model is promising to conduct refined numerical and analytical analyses for deep tunneling,which produces extensive plastic deformation and exhibits significant nonlinear post-peak behavior.展开更多
文摘Antiozonants and antioxidants are additives commonly used in the rubber industry to enhance the durability and performance of rubber products. Ozone, present in the atmosphere, can cause rubber to degrade over time through a process known as ozone cracking. These rubber additives are added to rubber compounds to protect against this degradation. They work by reacting with ozone, preventing it from attacking and breaking the molecular chains in the rubber, helping to maintain the structural integrity of the rubber product. It is now well known that 6PPD contributes to the extension of the service life of rubber products. However, recent studies have shown that 6PPD can be harmful to the environment, especially when end-of-life tyres (ELTs) are contaminated with the water. With the effect of ozone, 6PPD is converted to 6PPD quinone, which is toxic enough to kill some sensitive fish species such as Coho Salmon (Oncorhynchus kisutch). This study drew attention to new chemical compounds and natural products that can be used as antiozonants and antioxidants in the rubber industry instead of 6PPD. Although the scientific studies are promising, the fact that 6PPD is still used in production shows that more scientific studies and social awareness need to be developed in this area.
基金funded by a Special Fund for Basic Research on Scientific Instruments of the National Natural Science Foundation of China(Grant No.41827807)the Study on Intelligent Technology for Tunnels Construction of Sichuan-Tibet Railway(Grant No.19-21-1).
文摘The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in numerical calculations owing to their simple mathematical forms.This study developed a PPD model for rocks(rock masses)based on the Alejanoe-Alonso(A-A)dilatancy model.The developed model comprehensively reflects the influences of confining pressure(σ_(3))and plastic shear strain(γ^(p)),with the advantages of a simple mathematical form,while requiring fewer parameters and demonstrating a clear physical significance.The overall fitting accuracy of the PPD model for 11 different rocks was found to be higher than that of the A-A model,particularly for Witwatersrand quartzite and jointed granite.The applicability and reliability of the PPD model to jointed granites and different scaled Moura coals were also investigated,and the model was found to be more suitable for the soft and large-scale rocks,e.g.deep rock mass.The PPD model was also successfully applied in studying the mechanical response of a circular tunnel excavated in strain-softening rock mass,and the developed semi-analytical solution was compared and verified with existing analytical solutions.The sensitivities of the rock dilatancy to γ^(p) and σ_(3) showed significant spatial variabilities along the radial direction of the surrounding rock,and the dilation angle did not exhibit a monotonical increasing or decreasing law from the elasticeplastic boundary to the tunnel wall,thereby presenting the σ3-or γ^(p)-dominated differential effects of rock dilatancy.Tunnel deformation parabolically or exponentially increased with increasing in situ stress(buried depth).The developed PPD model is promising to conduct refined numerical and analytical analyses for deep tunneling,which produces extensive plastic deformation and exhibits significant nonlinear post-peak behavior.
