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
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
This paper outlines a mechanical transformation process for rubber recycling, demonstrating the development of a new material from used tires. With the crumbs obtained using a crusher-compactor, a novel material for t...This paper outlines a mechanical transformation process for rubber recycling, demonstrating the development of a new material from used tires. With the crumbs obtained using a crusher-compactor, a novel material for the manufacture of O-rings has been developed, with properties close to those found on the market. The process includes an experimental methodology of a sulfur vulcanization system choice and the quantification of ingredients, as well as the experimental determination of cure parameters. Mechanical tests on the samples completed the work by providing the mechanical characteristics of both unaged and aged (thermo-oxidative ageing) novel material. This process has a high potential for sustainable development and industrialization, making it a valuable contribution to the recycling of rubber in African developing countries.展开更多
By incorporating copper sulfate （CuSO4） particles into acrylonitrile butadiene rubber （NBR） followed by heat pressing, a novel vulcanization method is developed in rubber through the formation of coordination cros...By incorporating copper sulfate （CuSO4） particles into acrylonitrile butadiene rubber （NBR） followed by heat pressing, a novel vulcanization method is developed in rubber through the formation of coordination crosslinking. This method totally differs from traditional covalent or non-covalent vulcanization approaches of rubber. No other vulcanizing agent or additional additive is involved in this process. By analyzing the results of DMA, XPS and FT-IR, it is found that the crosslinking of CuSO4 particles filled NBR was induced by in situ coordination between nitrogen atoms of nitrile groups （-CN） and copper ions （Cu^2＋） from CuSO4. SEM and EDX results revealed the generation of a core （CuSO4 solid particle）- shell （adherent NBR） structure, which leads to a result that the crosslinked rubber has excellent mechanical properties. Moreover, poly（vinyl chloride） （PVC） and liquid acrylonitrile-butadiene rubber （LNBR） were used as mobilizer to improve the coordination crosslinking of CuSO4/NBR. The addition of PVC or LNBR could lead to higher crosslink density and better mechanical properties of coordination vulcanization. In addition, crystal water in CuSO4 played a positive role to coordination crosslinking of rubber because it decreased the metal point of CuSO4 and promoted the metal ionization.展开更多
Positron annihilation spectroscopy (PAS) was utilized to investigate the relationship between the free-volume hole properties and miscibility of dynamically vulcanized EPDM/PP blend. The results showed that the noncry...Positron annihilation spectroscopy (PAS) was utilized to investigate the relationship between the free-volume hole properties and miscibility of dynamically vulcanized EPDM/PP blend. The results showed that the noncrystalline region of PP and EPDM in the blend was partially miscible and the miscibility of the blend became worse when the weight percent of EPDM was <50%. This was also demonstrated by DMTA and mechanical properties of the blends with various compositions.展开更多
We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a ...We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a crosslinker on HCSR were studied. Thevulcanizates with fine mechanical properties could be obtained with suitable amounts ofTMDPDS. Sol fractions, and crosslinking density of vulcanizates and vulcanizationretardation effect of TMDPDS on hydrosilation curing silicone rubber were also discussed.展开更多
Casting is an important rubber manufacturing process for both production and material developments. A quick and flexible way of testing the constitutive materials properties of rubber products is very important for op...Casting is an important rubber manufacturing process for both production and material developments. A quick and flexible way of testing the constitutive materials properties of rubber products is very important for optimising the processing parameters and quality control. In many cases, standard tests such as tensile or compression tests are time consuming and require a large volume of materials. This work reports some recent work in using a combined numerical and experimental approach to characterise the properties of rubber materials during a casting process. Durometer shore hardness is used to test silicone rubbers (as a model material) with different compositions on different moulding planes and the linear elastic property is estimated from the hardnesses. The predicted properties are systematically compared with the experimental tests on hard and soft silicone rubber samples with different compositions. The work shows that shore hardness can be used as an effective way to monitor the materials properties during amoulding process for process optimisation and quality control.展开更多
Eight complexes of rare earth with 2 mercaptobenthiazole, RELCl 2·RE(OH) 3· x H 2O (L=2 mercaptobenthiazole, RE= La～Gd, Y, except for Pm, x =0, 2～4), were synthesized in unhydrous ethanol and char...Eight complexes of rare earth with 2 mercaptobenthiazole, RELCl 2·RE(OH) 3· x H 2O (L=2 mercaptobenthiazole, RE= La～Gd, Y, except for Pm, x =0, 2～4), were synthesized in unhydrous ethanol and characterized by elemental analyses, IR spectra and thermal analyses. The results show that the ligand is coordinated to the RE ion through both the exocyclic sulfur and the thiazole nitrogen. The vulcanizing properties of the La complex as accelerator were studied in the traditional tire rubber, which indicate that the cross linked rubber accelerated by the rare earth complex has good physical and dynamic mechanical properties by comparison.展开更多
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.
文摘This paper outlines a mechanical transformation process for rubber recycling, demonstrating the development of a new material from used tires. With the crumbs obtained using a crusher-compactor, a novel material for the manufacture of O-rings has been developed, with properties close to those found on the market. The process includes an experimental methodology of a sulfur vulcanization system choice and the quantification of ingredients, as well as the experimental determination of cure parameters. Mechanical tests on the samples completed the work by providing the mechanical characteristics of both unaged and aged (thermo-oxidative ageing) novel material. This process has a high potential for sustainable development and industrialization, making it a valuable contribution to the recycling of rubber in African developing countries.
基金This work was financially supported by the Program of National Natural Science Foundation of China(No.50473031).
文摘By incorporating copper sulfate （CuSO4） particles into acrylonitrile butadiene rubber （NBR） followed by heat pressing, a novel vulcanization method is developed in rubber through the formation of coordination crosslinking. This method totally differs from traditional covalent or non-covalent vulcanization approaches of rubber. No other vulcanizing agent or additional additive is involved in this process. By analyzing the results of DMA, XPS and FT-IR, it is found that the crosslinking of CuSO4 particles filled NBR was induced by in situ coordination between nitrogen atoms of nitrile groups （-CN） and copper ions （Cu^2＋） from CuSO4. SEM and EDX results revealed the generation of a core （CuSO4 solid particle）- shell （adherent NBR） structure, which leads to a result that the crosslinked rubber has excellent mechanical properties. Moreover, poly（vinyl chloride） （PVC） and liquid acrylonitrile-butadiene rubber （LNBR） were used as mobilizer to improve the coordination crosslinking of CuSO4/NBR. The addition of PVC or LNBR could lead to higher crosslink density and better mechanical properties of coordination vulcanization. In addition, crystal water in CuSO4 played a positive role to coordination crosslinking of rubber because it decreased the metal point of CuSO4 and promoted the metal ionization.
基金This work was financially supported by 863 Programme of China No.863-715-012-0160
文摘Positron annihilation spectroscopy (PAS) was utilized to investigate the relationship between the free-volume hole properties and miscibility of dynamically vulcanized EPDM/PP blend. The results showed that the noncrystalline region of PP and EPDM in the blend was partially miscible and the miscibility of the blend became worse when the weight percent of EPDM was <50%. This was also demonstrated by DMTA and mechanical properties of the blends with various compositions.
文摘We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a crosslinker on HCSR were studied. Thevulcanizates with fine mechanical properties could be obtained with suitable amounts ofTMDPDS. Sol fractions, and crosslinking density of vulcanizates and vulcanizationretardation effect of TMDPDS on hydrosilation curing silicone rubber were also discussed.
文摘Casting is an important rubber manufacturing process for both production and material developments. A quick and flexible way of testing the constitutive materials properties of rubber products is very important for optimising the processing parameters and quality control. In many cases, standard tests such as tensile or compression tests are time consuming and require a large volume of materials. This work reports some recent work in using a combined numerical and experimental approach to characterise the properties of rubber materials during a casting process. Durometer shore hardness is used to test silicone rubbers (as a model material) with different compositions on different moulding planes and the linear elastic property is estimated from the hardnesses. The predicted properties are systematically compared with the experimental tests on hard and soft silicone rubber samples with different compositions. The work shows that shore hardness can be used as an effective way to monitor the materials properties during amoulding process for process optimisation and quality control.
文摘Eight complexes of rare earth with 2 mercaptobenthiazole, RELCl 2·RE(OH) 3· x H 2O (L=2 mercaptobenthiazole, RE= La～Gd, Y, except for Pm, x =0, 2～4), were synthesized in unhydrous ethanol and characterized by elemental analyses, IR spectra and thermal analyses. The results show that the ligand is coordinated to the RE ion through both the exocyclic sulfur and the thiazole nitrogen. The vulcanizing properties of the La complex as accelerator were studied in the traditional tire rubber, which indicate that the cross linked rubber accelerated by the rare earth complex has good physical and dynamic mechanical properties by comparison.
