The thioacetamide derivative(TD)-composite preservation system(TDCPS)exhibits superior preservation effects on natural rubber latex(NRL)and significantly enhances its vulcanization efficiency and mechanical properties...The thioacetamide derivative(TD)-composite preservation system(TDCPS)exhibits superior preservation effects on natural rubber latex(NRL)and significantly enhances its vulcanization efficiency and mechanical properties.This study primarily investigated the principal chemical groups and mechanism of action of TDCPS in promoting NRL vulcanization through a comparative analysis.The results indicated that the key functional groups(thioamide and pyridine)in TDCPS synergistically accelerated crosslinking,reducing the vulcanization time by 41.18%compared to the high-ammonia(HA)preservation system.At an optimal TDCPS dosage of 5 mmol·L^(−1),vulcanized films achieved a tensile strength of 34.18 MPa,with a sulfur content of 1.5 phr further improving the strength by 42.26%.TD outperformed the conventional accelerators 2-imidazolidinethione(ETU)and 3-hydroxypyridine(3-Hp)in promoting the crosslinking density and mechanical performance while eliminating ammonia-related environmental risks.This eco-friendly system demonstrates the industrial potential for sustainable rubber production.展开更多
This study delves into the pivotal role of sulfur vulcanization in defining the mechanical characteristics of natural rubber(NR)latex-dipped products.Utilizing sulfur vulcanization,known for its operational simplicity...This study delves into the pivotal role of sulfur vulcanization in defining the mechanical characteristics of natural rubber(NR)latex-dipped products.Utilizing sulfur vulcanization,known for its operational simplicity and cost-effectiveness,we examine its ability to enhance product elasticity and mechanical strength through various sulfidic bond formations such as mono-,di-,and polysulfidic bonds.Different vulcanization systems and sulfur contents were evaluated for their influence on the mechanical attributes of latex films,employing three types of NR latex,namely concentrated NR(CNR),deproteinized NR(DPNR),and small rubber particle NR(SRP),each representing distinct non-rubber components(NRCs).The study utilized advanced atomic force microscopy(AFM)equipped with PeakForce Quantitative Nanomechanical Mapping(QNM)to visualize and measure Young’s modulus distribution across the film of pre-vulcanized latex.Our findings reveal that films by CNR processed using the conventional vulcanization(CV)system exhibited enhanced tensile strength and elongation at break.It even showed a lower crosslink density than those processed using the efficient vulcanization(EV)system.Interestingly,DPNR films showed a more uniform distribution of Young’s modulus,correlating well with their superior mechanical strength.In contrast,SRP films showed excessive network structure formation in the particles due to accelerated vulcanization rates,hampering subsequent post-vulcanization interparticle crosslinking in film formation and remaining more rigid.The overall results Illustrate clearly that the ultimate mechanical properties of the latex films are strongly dependent on the type of sulfidic bonds formed.This research reveals further the very intricate relationship between the vulcanization methods,sulfur content,and latex type in optimizing the mechanical performance of NR latex products.It provides valuable insights for industry practices aimed at improving the quality and performance of latex-dipped goods.展开更多
In order to reduce the temperature difference caused by condensed water in vulcanized tire capsules,the flow field and temperature field inside vulcanized tire capsules were numerically simulated by setting three diff...In order to reduce the temperature difference caused by condensed water in vulcanized tire capsules,the flow field and temperature field inside vulcanized tire capsules were numerically simulated by setting three different intake angles based onvolume of fluid(VOF)multiphase flow model.When the intake air is blown to the upper and lower tire sides of the vulcanized capsule at 18°from the horizontal direction,the distribution of condensed water at the bottom of the capsule changes obviously due to the effect of vorticity flow,and the distribution along the wall is more uniform.When the inlet air is blown down the tire side,the condensate is most evenly distributed along the wall,and the maximum temperature difference drops to 9.5℃.The results show that changing the distribution of condensed water by adjusting the proper intake angle can effectively reduce the temperature difference of condensed water in vulcanized capsules.展开更多
The fabrication of magnetorheological （MR） elastomers was studied by two vulcanization methods, including heat vulcanization （HV） and radiation vulcanization （RV）, were employed to fabricate MRE samples. The dyn...The fabrication of magnetorheological （MR） elastomers was studied by two vulcanization methods, including heat vulcanization （HV） and radiation vulcanization （RV）, were employed to fabricate MRE samples. The dynamical mechanical properties were characterized by using a dynamic mechanic analyzer. In particular, both the MR effect and its durability were investigated. The experimental results showed that RV samples have large magnetoinduced modulus, large zero-field modulus, and good durability property of MR effect. To explain these results, cubic deformation and plasticizer migration were analyzed. Large magneto-induced modulus of RV sample results from cubic deformation during vulcanization process. And the plasticizer migration results in better durability of MR effect.展开更多
Kinetics of natural rubber （NR） vulcanization by lanthanum O, O＇-diisopropyldithiophosphate [ La（DiPDP）3 ] was studied. La（DiPDP）3 had remarkable accelerating effect on the vulcanization of NR. The rate constan...Kinetics of natural rubber （NR） vulcanization by lanthanum O, O＇-diisopropyldithiophosphate [ La（DiPDP）3 ] was studied. La（DiPDP）3 had remarkable accelerating effect on the vulcanization of NR. The rate constant k6 of the reaction that turned polysulphidic cross-links into the modified main chain was higher than that of desulfuration reaction of polysulfidic cross-links （k3 ）. The activation energies （Ea2, Ea3, and Ea6） of the formation, desulfuration, and decomposition of polysulfidic cross-links were 87.57,102.34, and 95.01 kJ · mol^-1, respectively. Activation energy （Eas） of the reaction that turned the cross-link precursors into the modified main chain was 82.67 kJ · mol^-1. It could be concluded that the proportion of polysulphidic cross-links was higher than mono- and di- sulphidic cross-links during induction and curing periods, mono- and di- sulphidic cross-links increased as curing temperature rose. In the temperature range of 140 - 160 ℃, the amounts of polysulphidic cross-links were similar. However, over 160℃, mono- and di- sulphidic cross-links increased rapidly. Moreover, cross-link density of the vulcanizates was determined from the equilibrium-swelling data. A chemical probe detected the concentration of polysulphidic cross-links of vulcanizates. The change trend of the results predicated from equation corresponded to that of the experimental results.展开更多
According to the vulcanization kinetic equation of natural rubber （NR） established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructe...According to the vulcanization kinetic equation of natural rubber （NR） established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructed by means of incremental method. The description of non-isothermal in-mold vulcanization process is carried out by the finite element method. The mold-opening time, the rubber and mold temperatures, the degree of rubber cure and its distribution characteristics are numerically analyzed, by changing the key formulas and parameters in the process including the temperature of curing medium, the concentration of 2-mercaptobenzothiazole, the heat transfer manner of mold side, and the convective heat transfer coefficient of heating boundary. The quantitative results will help engineers to design proper formulas and optimize processing conditions.展开更多
A novel TU derivative, N-phenyl-N＇-（γ-triethoxysilane）-propyl thiourea （STU）, is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time ...A novel TU derivative, N-phenyl-N＇-（γ-triethoxysilane）-propyl thiourea （STU）, is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl iso- thiocyanate fragment still remains in the NPUSTU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.展开更多
This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber （SBR） with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the c...This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber （SBR） with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.展开更多
Allyl terminated polyether was used to improve the hydrophilicity of addition-cured room temperature vulcanization silicone rubber. With the increasing of the polyether, both the hydrophilicity and water absorbed of t...Allyl terminated polyether was used to improve the hydrophilicity of addition-cured room temperature vulcanization silicone rubber. With the increasing of the polyether, both the hydrophilicity and water absorbed of the vulcanizates were increased. The mechanical properties were also improved by adding the polyether. The result showed that 1.5wt% of the polyether provided the silicone rubber with proper hydrophilicity.展开更多
Dithiocarbamate vulcanization accelerators (DVAs) are widely used in rubber manufacturing, yet their potential human exposure and associated health risks remain poorly understood. Previous studies have identified DVAs...Dithiocarbamate vulcanization accelerators (DVAs) are widely used in rubber manufacturing, yet their potential human exposure and associated health risks remain poorly understood. Previous studies have identified DVAs in various environmental matrices, such as dust and sediments, but their occurrence in human biological samples has not been investigated. This study aims to fill this critical research gap by conducting the first comprehensive biomonitoring assessment of DVAs in human urine, providing direct evidence of human exposure. A total of 263 urine samples were collected from Chinese adults and analyzed for eight DVAs. Seven out of eight target compounds were detected, with detection frequencies ranging from 14 % to 94 %. Zinc diethyldithiocarbamate (ZDEC) was the predominant compound, with a mean concentration of 1.6 ng/mL (range: <LOD–12 ng/mL). Notably, males exhibited significantly higher urinary levels of ZDEC (1.7 ± 0.28 ng/mL vs. 1.3 ± 0.33 ng/mL;p = 0.021) and zinc dibutyldithiocarbamate (ZDBC;0.78 ± 0.18 ng/mL vs. 0.50 ± 0.10 ng/mL;p = 0.017) compared to females, while urinary concentrations of ZDEC and zinc dibenzyldithiocarbamate (ZBEC) were inversely correlated with age. Daily exposure (DE) estimation revealed that ZDEC had the highest mean DE value at 48 ng/kg bw/day, followed by ZEPC (29 ng/kg bw/day) and ZDBC (21 ng/kg bw/day). These findings provide essential insights into human exposure patterns to DVAs, offering a scientific basis for future risk assessment and regulatory considerations. Given the widespread detection of these compounds and their potential toxicity, further research is warranted to elucidate their health implications and major exposure pathways.展开更多
An inverse vulcanized polymer,SZIM combining Zn2+-imidazole coordination bonds and polysulfide bonds was synthesized and incorporated into bio-based Eucommia ulmoides gum (EUG) to generate EUG-SZIM-xs.The residual cry...An inverse vulcanized polymer,SZIM combining Zn2+-imidazole coordination bonds and polysulfide bonds was synthesized and incorporated into bio-based Eucommia ulmoides gum (EUG) to generate EUG-SZIM-xs.The residual crystallinity of the EUG matrix synergistically interacted with the dual cross-linking networks to establish reversible deformation domains,providing EUG-SZIM-xs with quick shape memory capability at moderate temperatures.The damping properties were also investigated,and EUG-SZIM-xs displayed high tanδ values (>0.3) when the SZIM dosage was higher than 5.5 phr,which showed a positive correlation with SZIM concentration.Such good damping performance endowed the EUG-SZIM-xs with broadband low-frequency sound absorption.In addition,the dual cross-linking networks endowed the materials with reprocessability under different catalytic systems,and the 1,8-diazobicyclic[5.4.0]undeca-7-ene (DBU)-catalyzed samples exhibited better mechanical properties than EUG-SZIM-xs.展开更多
Inherent brittleness and low heat resistance are the two major obstacles that hinder the wide applications of poly（L-lactide）（PLLA）. In this study,we report a fully biobased,highly toughened and heat-resistant PLL...Inherent brittleness and low heat resistance are the two major obstacles that hinder the wide applications of poly（L-lactide）（PLLA）. In this study,we report a fully biobased,highly toughened and heat-resistant PLLA ternary blend,which was prepared by dynamic vulcanization of PLLA with poly（D-lactide）（PDLA） and an unsaturated bioelastomer（UBE）. The results indicated that during dynamic vulcanization PDLA cocrystallized with PLLA to form stereocomplex（SC） crystallites,which not only enhanced the molecular entanglement but also accelerated the crystallization rate of PLLA matrix. With increase in the content of PDLA,the matrix molecular entanglement increased while phase-separation was enhanced,which enabled the impact strength to increase first and then decrease. The ternary blends containing 10 wt.% PDLA showed the highest impact strength. The presence of SC crystallites makes it possible to achieve a fully sustainable PLLA/VUB/PDLA ternary blend with highly crystalline matrix under conventional injection molding,due to the high nucleation efficiency of SC towards crystallization of PLLA. The highly crystalline ternary blend showed excellent heat resistance and better impact toughness than high impact polystyrene.展开更多
This paper proposes a push-pull airflow combined with a top draft hood to conduct local exhaust in a rubber workshop.Field measurements are carried out to investigate the characteristics of the emission source,while n...This paper proposes a push-pull airflow combined with a top draft hood to conduct local exhaust in a rubber workshop.Field measurements are carried out to investigate the characteristics of the emission source,while numerical simulation is performed based on the measurement to test the capture efficiency and to further optimize various parameters including push velocity,hood height and exhaust air rate.Compared with the high-hanging hood,the low-hanging hood can effectively capture the pollutant generated by tyre with lower exhaust air rate.The capture efficiency of the low-hanging hood reaches 98.18%with exhaust air rate of 6000 m^(3)/h and push air velocity of 5m/s.The results indicates that the new ventilation appliance can effectively collect the pollutant at a relatively low exhaust rate.展开更多
Rubbers or elastomers play an important role in hi-tech technology and civilian daily life because of their unique and strategical properties.Generally,the rubber additives are essential components for rubbers’practi...Rubbers or elastomers play an important role in hi-tech technology and civilian daily life because of their unique and strategical properties.Generally,the rubber additives are essential components for rubbers’practical application.Nowadays,developing novel multifunctional additives has attracted increasing research attention.In this work,low-cost crude carbon dots(CCDs)were used as multifunctional additives for natural rubber/silica system(without any additional modification)through industrial compatible melt-mixing method.The results revealed that the CCDs could disperse well in the NR/silica system,and they could not only endow the rubber compound with excellent anti-aging capability due to CCDs’radical scavenging activity because of their plenty of nitrogen-containing species,but also improve the curing rate and mechanical performance of the rubber composite.Also,the CCDs could reduce the rolling resistance of the rubber composites(tanδvalue at 7%strain of the rubber composite could be decreased by 34%),which is promising for the application of energy-saving tire industry.Lastly,the addition of CCDs could effectively reduce the ZnO dosage by at least 40%in the rubber composite without deteriorating its performance.Overall,this work provides valuable guidance to develop novel cheap yet effective additives for the elastomer.展开更多
Inverse vulcanized polymers(IVPs) that generated from elemental sulfur and smaller amounts of alkenes have found broad promising applications such as cathode materials for Li-S batteries, dynamic and repairable materi...Inverse vulcanized polymers(IVPs) that generated from elemental sulfur and smaller amounts of alkenes have found broad promising applications such as cathode materials for Li-S batteries, dynamic and repairable materials, optics applications, and metal sorption. However, their exploration in organic synthesis is still unprecedented. Here we first report the application of inverse vulcanized polymers in catalysis for organic transformations. A biomass-derived inverse vulcanized polymer(IVP-EAE) is found to be capable of catalyzing cross-coupling reactions in a transition-metal-free fashion under visible light.This method allows the direct C–H functionalization of pyrroles and N-arylacrylamides with(hetero)aryl halides, respectively, leading to the formation of two sets of structurally important scaffolds including pyrrole-containing biaryls and 3,3-disubstituted oxindoles with high selectivity. We anticipate this study will not only unveil the new potential of IVPs, but also offer a distinct type of catalysts for organic transformations.展开更多
Reducing the amount of zinc oxide(ZnO)is a continuous pursuit of the rubber industry because of the high cost and environmental pollution of Zn.However,reducing the amount of ZnO will inevitably lead to a decrease in ...Reducing the amount of zinc oxide(ZnO)is a continuous pursuit of the rubber industry because of the high cost and environmental pollution of Zn.However,reducing the amount of ZnO will inevitably lead to a decrease in the crosslinking density and the loss of mechanical properties of rubber;thus,this remains a huge challenge.Herein,we prepared Zn single-atoms supported on graphene oxide(Zn SAs@GO)as controlled-release catalysts for effective rubber vulcanization,which can improve the crosslinking density and mechanical properties of rubber by reducing Zn dosage compared to commercial ZnO by 82.5%.X-ray absorption spectroscopy(XAS)analysis reveals that Zn±O bond is 2.03 A in Zn SAs@GO,which possesses moderate Zn±O binding energy.Thus Zn^(2+)ions can be controlled-release and participate in the vulcanization reaction with higher activity.Moreover,due to the homogeneous dispersion of Zn atoms in Zn SAs@GO,zinc catalysts were fully utilized during the vulcanization process,resulting in a 6.6%increase in crosslinking density of the prepared vulcanized rubber compared to that of commercial ZnO.This work contributes to the development of large-scale preparation for SACs and potentially pave the way for their applications in industrial rubber manufacture.展开更多
基金the Ministry of Agriculture and Rural Affairs of Chinathe Department of Science and Technology of the Hainan Province for their support+2 种基金financially supported by the National Key R&D Program of China(No. 2022YFD2301201)Hainan Province Science and Technology Special Fund (No. ZDYF2024XDNY284)Earmarked Fund for China Agriculture Research System (No.CARS-33-JG1)
文摘The thioacetamide derivative(TD)-composite preservation system(TDCPS)exhibits superior preservation effects on natural rubber latex(NRL)and significantly enhances its vulcanization efficiency and mechanical properties.This study primarily investigated the principal chemical groups and mechanism of action of TDCPS in promoting NRL vulcanization through a comparative analysis.The results indicated that the key functional groups(thioamide and pyridine)in TDCPS synergistically accelerated crosslinking,reducing the vulcanization time by 41.18%compared to the high-ammonia(HA)preservation system.At an optimal TDCPS dosage of 5 mmol·L^(−1),vulcanized films achieved a tensile strength of 34.18 MPa,with a sulfur content of 1.5 phr further improving the strength by 42.26%.TD outperformed the conventional accelerators 2-imidazolidinethione(ETU)and 3-hydroxypyridine(3-Hp)in promoting the crosslinking density and mechanical performance while eliminating ammonia-related environmental risks.This eco-friendly system demonstrates the industrial potential for sustainable rubber production.
基金supported by Mahidol University(Fundamental Fund:fiscal year 2024 by the National Science Research and Innovation Fund(NSRF),FF-078/2567)Academy of Tropical Agricultural Sciences for Science and Technology Innovation Team of National Tropical Agricultural Science Center(No.CATASCXTD202401)the National Research Council of Thailand(NRCT)via the Royal Golden Jubilee Ph.D.Program(No.PHD/0150/2560)。
文摘This study delves into the pivotal role of sulfur vulcanization in defining the mechanical characteristics of natural rubber(NR)latex-dipped products.Utilizing sulfur vulcanization,known for its operational simplicity and cost-effectiveness,we examine its ability to enhance product elasticity and mechanical strength through various sulfidic bond formations such as mono-,di-,and polysulfidic bonds.Different vulcanization systems and sulfur contents were evaluated for their influence on the mechanical attributes of latex films,employing three types of NR latex,namely concentrated NR(CNR),deproteinized NR(DPNR),and small rubber particle NR(SRP),each representing distinct non-rubber components(NRCs).The study utilized advanced atomic force microscopy(AFM)equipped with PeakForce Quantitative Nanomechanical Mapping(QNM)to visualize and measure Young’s modulus distribution across the film of pre-vulcanized latex.Our findings reveal that films by CNR processed using the conventional vulcanization(CV)system exhibited enhanced tensile strength and elongation at break.It even showed a lower crosslink density than those processed using the efficient vulcanization(EV)system.Interestingly,DPNR films showed a more uniform distribution of Young’s modulus,correlating well with their superior mechanical strength.In contrast,SRP films showed excessive network structure formation in the particles due to accelerated vulcanization rates,hampering subsequent post-vulcanization interparticle crosslinking in film formation and remaining more rigid.The overall results Illustrate clearly that the ultimate mechanical properties of the latex films are strongly dependent on the type of sulfidic bonds formed.This research reveals further the very intricate relationship between the vulcanization methods,sulfur content,and latex type in optimizing the mechanical performance of NR latex products.It provides valuable insights for industry practices aimed at improving the quality and performance of latex-dipped goods.
基金supported in part by the National Natural Science Foundation of China(No.52176040)Shandong Natural Science Foundation(No.ZR2021ME161)the Science and Technology SMES Innovation Ability Improvement of Shandong Province(No.2023TSGC0290)。
文摘In order to reduce the temperature difference caused by condensed water in vulcanized tire capsules,the flow field and temperature field inside vulcanized tire capsules were numerically simulated by setting three different intake angles based onvolume of fluid(VOF)multiphase flow model.When the intake air is blown to the upper and lower tire sides of the vulcanized capsule at 18°from the horizontal direction,the distribution of condensed water at the bottom of the capsule changes obviously due to the effect of vorticity flow,and the distribution along the wall is more uniform.When the inlet air is blown down the tire side,the condensate is most evenly distributed along the wall,and the maximum temperature difference drops to 9.5℃.The results show that changing the distribution of condensed water by adjusting the proper intake angle can effectively reduce the temperature difference of condensed water in vulcanized capsules.
基金The work was supported by the National Natural Science Foundation of China （No.10672154）.
文摘The fabrication of magnetorheological （MR） elastomers was studied by two vulcanization methods, including heat vulcanization （HV） and radiation vulcanization （RV）, were employed to fabricate MRE samples. The dynamical mechanical properties were characterized by using a dynamic mechanic analyzer. In particular, both the MR effect and its durability were investigated. The experimental results showed that RV samples have large magnetoinduced modulus, large zero-field modulus, and good durability property of MR effect. To explain these results, cubic deformation and plasticizer migration were analyzed. Large magneto-induced modulus of RV sample results from cubic deformation during vulcanization process. And the plasticizer migration results in better durability of MR effect.
基金Project supported by the Guangdong Natural Science Foundation (05006563)
文摘Kinetics of natural rubber （NR） vulcanization by lanthanum O, O＇-diisopropyldithiophosphate [ La（DiPDP）3 ] was studied. La（DiPDP）3 had remarkable accelerating effect on the vulcanization of NR. The rate constant k6 of the reaction that turned polysulphidic cross-links into the modified main chain was higher than that of desulfuration reaction of polysulfidic cross-links （k3 ）. The activation energies （Ea2, Ea3, and Ea6） of the formation, desulfuration, and decomposition of polysulfidic cross-links were 87.57,102.34, and 95.01 kJ · mol^-1, respectively. Activation energy （Eas） of the reaction that turned the cross-link precursors into the modified main chain was 82.67 kJ · mol^-1. It could be concluded that the proportion of polysulphidic cross-links was higher than mono- and di- sulphidic cross-links during induction and curing periods, mono- and di- sulphidic cross-links increased as curing temperature rose. In the temperature range of 140 - 160 ℃, the amounts of polysulphidic cross-links were similar. However, over 160℃, mono- and di- sulphidic cross-links increased rapidly. Moreover, cross-link density of the vulcanizates was determined from the equilibrium-swelling data. A chemical probe detected the concentration of polysulphidic cross-links of vulcanizates. The change trend of the results predicated from equation corresponded to that of the experimental results.
基金financially supported by the National Key Basic Research Program of China(2012CB821505)the Natural Science Foundation of Shandong Province(No.JQ201016)
文摘According to the vulcanization kinetic equation of natural rubber （NR） established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructed by means of incremental method. The description of non-isothermal in-mold vulcanization process is carried out by the finite element method. The mold-opening time, the rubber and mold temperatures, the degree of rubber cure and its distribution characteristics are numerically analyzed, by changing the key formulas and parameters in the process including the temperature of curing medium, the concentration of 2-mercaptobenzothiazole, the heat transfer manner of mold side, and the convective heat transfer coefficient of heating boundary. The quantitative results will help engineers to design proper formulas and optimize processing conditions.
基金financially supported by the National Natural Science Foundation of China(Nos.51003031 and 51303026)Science Foundation for Universities and Institutions of Dongguan City(No.2012108102008)the Research Fund for the Doctoral Program of Dongguan University of Technology(No.ZJ121002)
文摘A novel TU derivative, N-phenyl-N＇-（γ-triethoxysilane）-propyl thiourea （STU）, is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl iso- thiocyanate fragment still remains in the NPUSTU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.
基金financially supported by the National Natural Science Foundation of China(No.51203096)the Ph.D.Programs Foundation of Ministry of Education of China(No.20100181120020)Sichuan University
文摘This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber （SBR） with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.
文摘Allyl terminated polyether was used to improve the hydrophilicity of addition-cured room temperature vulcanization silicone rubber. With the increasing of the polyether, both the hydrophilicity and water absorbed of the vulcanizates were increased. The mechanical properties were also improved by adding the polyether. The result showed that 1.5wt% of the polyether provided the silicone rubber with proper hydrophilicity.
基金supported by Natural Science Foundation of Zhejiang Province(LR23D030001,LBY23H200003,and LY21B070006)National Natural Science Foundation of China(42477453).
文摘Dithiocarbamate vulcanization accelerators (DVAs) are widely used in rubber manufacturing, yet their potential human exposure and associated health risks remain poorly understood. Previous studies have identified DVAs in various environmental matrices, such as dust and sediments, but their occurrence in human biological samples has not been investigated. This study aims to fill this critical research gap by conducting the first comprehensive biomonitoring assessment of DVAs in human urine, providing direct evidence of human exposure. A total of 263 urine samples were collected from Chinese adults and analyzed for eight DVAs. Seven out of eight target compounds were detected, with detection frequencies ranging from 14 % to 94 %. Zinc diethyldithiocarbamate (ZDEC) was the predominant compound, with a mean concentration of 1.6 ng/mL (range: <LOD–12 ng/mL). Notably, males exhibited significantly higher urinary levels of ZDEC (1.7 ± 0.28 ng/mL vs. 1.3 ± 0.33 ng/mL;p = 0.021) and zinc dibutyldithiocarbamate (ZDBC;0.78 ± 0.18 ng/mL vs. 0.50 ± 0.10 ng/mL;p = 0.017) compared to females, while urinary concentrations of ZDEC and zinc dibenzyldithiocarbamate (ZBEC) were inversely correlated with age. Daily exposure (DE) estimation revealed that ZDEC had the highest mean DE value at 48 ng/kg bw/day, followed by ZEPC (29 ng/kg bw/day) and ZDBC (21 ng/kg bw/day). These findings provide essential insights into human exposure patterns to DVAs, offering a scientific basis for future risk assessment and regulatory considerations. Given the widespread detection of these compounds and their potential toxicity, further research is warranted to elucidate their health implications and major exposure pathways.
基金supported by the Natural Science Foundation of Hunan Province(No.2024JJ7392)the National Natural Science Foundation of China(No.52463002)+1 种基金Educational Commission of Hunan Province(No.22A0383)Special Funds for Construction of Innovative Provinces in Hunan Province(No.2020SK2028).
文摘An inverse vulcanized polymer,SZIM combining Zn2+-imidazole coordination bonds and polysulfide bonds was synthesized and incorporated into bio-based Eucommia ulmoides gum (EUG) to generate EUG-SZIM-xs.The residual crystallinity of the EUG matrix synergistically interacted with the dual cross-linking networks to establish reversible deformation domains,providing EUG-SZIM-xs with quick shape memory capability at moderate temperatures.The damping properties were also investigated,and EUG-SZIM-xs displayed high tanδ values (>0.3) when the SZIM dosage was higher than 5.5 phr,which showed a positive correlation with SZIM concentration.Such good damping performance endowed the EUG-SZIM-xs with broadband low-frequency sound absorption.In addition,the dual cross-linking networks endowed the materials with reprocessability under different catalytic systems,and the 1,8-diazobicyclic[5.4.0]undeca-7-ene (DBU)-catalyzed samples exhibited better mechanical properties than EUG-SZIM-xs.
基金supported by the National Science Foundation of China (51673158)the Opening Project of Key Laboratory of Polymer Processing Engineering (South China University of Technology),Ministry of Education (KFKT02)the Fundamental Research Funds for the Central Universities (XDJK2017A016 and XDJK2017C022)
文摘Inherent brittleness and low heat resistance are the two major obstacles that hinder the wide applications of poly（L-lactide）（PLLA）. In this study,we report a fully biobased,highly toughened and heat-resistant PLLA ternary blend,which was prepared by dynamic vulcanization of PLLA with poly（D-lactide）（PDLA） and an unsaturated bioelastomer（UBE）. The results indicated that during dynamic vulcanization PDLA cocrystallized with PLLA to form stereocomplex（SC） crystallites,which not only enhanced the molecular entanglement but also accelerated the crystallization rate of PLLA matrix. With increase in the content of PDLA,the matrix molecular entanglement increased while phase-separation was enhanced,which enabled the impact strength to increase first and then decrease. The ternary blends containing 10 wt.% PDLA showed the highest impact strength. The presence of SC crystallites makes it possible to achieve a fully sustainable PLLA/VUB/PDLA ternary blend with highly crystalline matrix under conventional injection molding,due to the high nucleation efficiency of SC towards crystallization of PLLA. The highly crystalline ternary blend showed excellent heat resistance and better impact toughness than high impact polystyrene.
文摘This paper proposes a push-pull airflow combined with a top draft hood to conduct local exhaust in a rubber workshop.Field measurements are carried out to investigate the characteristics of the emission source,while numerical simulation is performed based on the measurement to test the capture efficiency and to further optimize various parameters including push velocity,hood height and exhaust air rate.Compared with the high-hanging hood,the low-hanging hood can effectively capture the pollutant generated by tyre with lower exhaust air rate.The capture efficiency of the low-hanging hood reaches 98.18%with exhaust air rate of 6000 m^(3)/h and push air velocity of 5m/s.The results indicates that the new ventilation appliance can effectively collect the pollutant at a relatively low exhaust rate.
基金supported by the National Natural Science Foundation of China(Nos.52103065,51988102 and 52273003)the scientific research fund of Wuhan Institute of Technology(No.K2021044).
文摘Rubbers or elastomers play an important role in hi-tech technology and civilian daily life because of their unique and strategical properties.Generally,the rubber additives are essential components for rubbers’practical application.Nowadays,developing novel multifunctional additives has attracted increasing research attention.In this work,low-cost crude carbon dots(CCDs)were used as multifunctional additives for natural rubber/silica system(without any additional modification)through industrial compatible melt-mixing method.The results revealed that the CCDs could disperse well in the NR/silica system,and they could not only endow the rubber compound with excellent anti-aging capability due to CCDs’radical scavenging activity because of their plenty of nitrogen-containing species,but also improve the curing rate and mechanical performance of the rubber composite.Also,the CCDs could reduce the rolling resistance of the rubber composites(tanδvalue at 7%strain of the rubber composite could be decreased by 34%),which is promising for the application of energy-saving tire industry.Lastly,the addition of CCDs could effectively reduce the ZnO dosage by at least 40%in the rubber composite without deteriorating its performance.Overall,this work provides valuable guidance to develop novel cheap yet effective additives for the elastomer.
基金the National Natural Science Foundation of China (NSFC, Nos. 22071024, 22271047)the Natural Science Foundation of Fujian Province (Nos.2021J06020, 2022J011121)the Top-Notch Young Talents Program of China, and the Science and Technology Project of Minjiang University (No.MJY21027) for generous financial support。
文摘Inverse vulcanized polymers(IVPs) that generated from elemental sulfur and smaller amounts of alkenes have found broad promising applications such as cathode materials for Li-S batteries, dynamic and repairable materials, optics applications, and metal sorption. However, their exploration in organic synthesis is still unprecedented. Here we first report the application of inverse vulcanized polymers in catalysis for organic transformations. A biomass-derived inverse vulcanized polymer(IVP-EAE) is found to be capable of catalyzing cross-coupling reactions in a transition-metal-free fashion under visible light.This method allows the direct C–H functionalization of pyrroles and N-arylacrylamides with(hetero)aryl halides, respectively, leading to the formation of two sets of structurally important scaffolds including pyrrole-containing biaryls and 3,3-disubstituted oxindoles with high selectivity. We anticipate this study will not only unveil the new potential of IVPs, but also offer a distinct type of catalysts for organic transformations.
基金supported by the Ministry of Science and Technology of China (2020YFA0710203)the Major Frontier Research Project of the University of Science and Technology of China (LS2060000002)+5 种基金the Joint Funds of the National Natural Science Foundation of China (U23A2081)the National Natural Science Foundation of China (22221003)the Anhui Provincial Key Research and Development Project (2023z04020010)the Anhui Provincial Natural Science Foundation (2108085UD06, 2208085UD04)the USTC Research Funds of the Double First-Class Initiative (YD2060006005)the Experimental Center of Engineering and Material Science in the University of Science and Technology of China for the support。
文摘Reducing the amount of zinc oxide(ZnO)is a continuous pursuit of the rubber industry because of the high cost and environmental pollution of Zn.However,reducing the amount of ZnO will inevitably lead to a decrease in the crosslinking density and the loss of mechanical properties of rubber;thus,this remains a huge challenge.Herein,we prepared Zn single-atoms supported on graphene oxide(Zn SAs@GO)as controlled-release catalysts for effective rubber vulcanization,which can improve the crosslinking density and mechanical properties of rubber by reducing Zn dosage compared to commercial ZnO by 82.5%.X-ray absorption spectroscopy(XAS)analysis reveals that Zn±O bond is 2.03 A in Zn SAs@GO,which possesses moderate Zn±O binding energy.Thus Zn^(2+)ions can be controlled-release and participate in the vulcanization reaction with higher activity.Moreover,due to the homogeneous dispersion of Zn atoms in Zn SAs@GO,zinc catalysts were fully utilized during the vulcanization process,resulting in a 6.6%increase in crosslinking density of the prepared vulcanized rubber compared to that of commercial ZnO.This work contributes to the development of large-scale preparation for SACs and potentially pave the way for their applications in industrial rubber manufacture.
