通过高斯加权的~1H CPMG弛豫曲线测定橡胶交联密度
|
摘要
CPMG(Carr-Purcell-Meiboom-Gill)回波法是测量橡胶交联密度[常用交联点之间的分子量(Mc)表示]的一种常用核磁共振(NMR)技术,但实验发现通过该技术获得的Mc对于CPMG序列中脉冲间隔时间具有较强的依赖性,导致交联密度NMR测量值与橡胶材料硬度的相关性低.为了克服这一缺点,本文对不同脉冲间隔时间下CPMG实验测得的质子横向驰豫曲线进行高斯加权.通过对高斯加权求和后的质子横向驰豫曲线进行处理分析,实现了对橡胶交联密度更加准确地测量,大幅提升了天然橡胶交联密度NMR测量值与材料硬度的相关性.本文方案测量能获得与~1H DQ NMR方法相当,或比之更佳的交联密度-硬度相关性.同时,本文方案比~1H DQ NMR方法更为高效,整体测量时间缩短为~1H DQ NMR实验时间的1/10.
CPMG sequence is widely used to measure crosslink density of rubber. However, the crosslink density obtained by this technique has a strong dependence on the interval times between the pulses in CPMG sequence, and the results measured have only a weak correlation with rubber hardness. To overcome this shortcoming, we proposed in this work to construct a ~1H T2 relaxation curve by summing Gaussian-weighted CPMG relaxation curves acquired at by varying the interval time between the pulses in CPMG sequence. Using the multi-echo Gaussian-weighted relaxation curve to calculate the crosslink density gave results that had greatly improved correlation with the rubber hardness. The new method was also fast and efficient, as it took only one-tenth of the experimental time required for the conventional ~1H double quantum NMR(~1H DQ NMR) experiment.
CPMG sequence is widely used to measure crosslink density of rubber. However, the crosslink density obtained by this technique has a strong dependence on the interval times between the pulses in CPMG sequence, and the results measured have only a weak correlation with rubber hardness. To overcome this shortcoming, we proposed in this work to construct a ~1H T2 relaxation curve by summing Gaussian-weighted CPMG relaxation curves acquired at by varying the interval time between the pulses in CPMG sequence. Using the multi-echo Gaussian-weighted relaxation curve to calculate the crosslink density gave results that had greatly improved correlation with the rubber hardness. The new method was also fast and efficient, as it took only one-tenth of the experimental time required for the conventional ~1H double quantum NMR(~1H DQ NMR) experiment.
引文
[1]WANG Z L.Crosslinking density of rubbers and the method of determination[J].World Rubber Industry,1998,25(4):41-46.王作龄.橡胶的交联密度与测定方法[J].世界橡胶工业,1998,25(4):41-46.
[2]ZHU R P,ZHOU B,YANG J,et al.Effect of crosslinking density on dynamic performance of natural rubber[J].Special Purpose Rubber Products,2009,30(1):43-45.朱闰平,邹波,杨军,等.交联密度对天然橡胶动态性能的影响[J].特种橡胶制品,2009,30(1):43-45.
[3]STUDEBAKER M L.Lithium aluminum hydride analysis of sulfur-cured vulcanizates[J].Rubb Chem Tech,1970(43):624-643.
[4]SCHLOGL S,TRUTSCHEL M L,CHASSéW,et al.Entanglement effects in elastomers:macroscopic vs microscopic properties[J].Macromolecules,2014,47(9):2759-2773.
[5]MULLINS L.Determination of degree of crosslinking in natural rubber vulcanization.Part I[J].J Polym Sci,1956,19(92):225-236.
[6]LITVINOV V M,Dias A A.Analysis of network structure of UV-cured acrylates by 1H NMR relaxation,13CNMR spectroscopy and dynamic mechanical experiments[J].Macromolecules,2001,34(12):4051-4059.
[7]GENNES P G D.Reptation of a polymer chain in the presence of fixed obstacles[J].J Chem Phys,1971,55(2):572-579.
[8]KUHN W,PEREGI E,FEI Z,et al.Network dynamics of crosslinked polymers-crosslinking,filler and aging characterized by NMR parameters[J].Mater Res Soc Symp Proc,1991,33(1):217-223.
[9]KUHN W,BARTH P,HAFNER S,et al.Material properties imaging of cross-linked polymers by NMR[J].Macromolecules,1994,27(20):5773-5779.
[10]FEDOTOV V D,Schneider H.Structures and dynamics of bulk polymers by NMR-methods[M].Springer-Verlag,1989.
[11]ZHAO S Y,WANG Y Y,ZHANG R C,et al.Low-field NMR studies on the structure and dynamics of nanocompositehydrogels[J].Chinese J Magn Reson,2014,31(2):172-184.赵守远,王媛媛,张荣纯,等.低场固体NMR研究纳米复合凝胶结构与动力学[J].波谱学杂志,2014,31(2):172-184.
[12]GAO Y,ZHANG R C,LV W F,et al.Critical effect of segmental dynamics in polybutadiene/clay nanocomposites characterized by solid state 1H NMR spectroscopy[J].J Phys Chem C,2014,118(10):5606-5614.
[13]SAALW?CHTER K.Proton multiple-quantum NMR for the study of chain dynamics and structural constraints in polymeric soft materials[J].Prog Nucl Mag Res Sp,2007,51(1):1-35.
[14]HAHN E L,Spin Echoes[J].Phys Rev,1950,80:580-594.
[15]CARR H Y,PURCELL E M.Effect of diffusion on free precession in nuclear magnetic resonance experiments[J].Phys Rev,1954,94(3):630-638.
[16]MEIBOOM S,GILL D.Modified spin-echo method for measuring nuclear relaxation times[J].Rev Sci Instrum,2004,29(8):688-691.
[17]BAUM J,PINES A.NMR studies of clustering in solids[J].J Am Chem Soc,1986,108(24):7447-7454.
[18]SAALW?CHTER K,KLüPPEL M,LUO H,et al.Chain order in filled SBR elastomers:a proton multiple-quantum NMR study[J].Appl Magn Reson,2004,27(3,4):401-417.
[19]SAALW?CHTER K,ZIEGLER P,SPYCKERELLE O,et al.1H multiple-quantum nuclear magnetic resonance investigations of molecular order distributions in poly(dimethyl siloxane)networks:Evidence for a linear mixing law in bimodal systems[J].J Chem Phys,2003,119(6):3468-3482.
[20]SAALW?CHTER K.1H multiple-quantum nuclear magnetic resonance investigations of molecular order in polymer networks.II.Intensitydecay and restricted slow dynamics[J].J Chem Phys,2004,120(1):454-64.
[21]SAALW?CHTER K,AND B H,LóPEZMANCHADO M A.Chain order and cross-link density of elastomers as investigated by proton multiple-quantum NMR[J].Macromolecules,2005,38(38):9650-9660.
[22]HEUERT U,KN?RGEN M,MENGE H,et al.New aspects of transversal 1H NMR relaxation in natural rubber vulcanization[J].Polym Bull,1996,37(4):489-496.
[23]SIMON G,BIRNSTIEL A,SCHIMMEL K H.Network characterization of end-linked poly(dimethyl siloxane)by 1H NMR spin-spin relaxation[J].Polym Bull,1989,21(2):235-241.
[24]FRY C G,LIND A C.Determination of crosslink density in thermoset polymers by use of solid-state proton NMR techniques[J].Macromolecules,1988,601(2):921-929.
[25]WHITTAKER A K,BREMNER T,ZELAYA F O.The effect of field inhomogeneous and molecular diffusion on the NMR transverse relaxation behavior of polymer melts[J].Polymer,1995,36(11):2159-2164.
[26]HILL L W.Calculation of crosslink density in short chain networks[J].Prog Org Coat,1997,31(3):235-243.
[27]GOTLIB Y Y,LIFSHITZ M I,SHEVELEV V A,et al.The influence of the chemical crosslinking network on the spin-spin relaxation of crosslinked and swelling polymer systems[J].Polymer Science U.s.s.r,1976,18(10):2630-2636.
[28]KLUPPEL M,MENGE H,SCHMIDT H,et al.Influence of preparation conditions on network parameters of sulfur-cured natural rubber[J].Macromolecules,2001,34(23):8107-8116.
[29]LIU T Q,FANG Q H,HU Z L,et al.Study on relationship between cross-linking density and crystallization characteristic of gutta-percha rubber[J].China Rubber Industry,2013,60(10):593-597.刘天琦,方庆红,胡之朗,等.杜仲橡胶硫化胶交联密度与结晶性能关系研究[J].橡胶工业,2013,60(10):593-597.
[30]BREMNER T,RUDIN A.The effect of degassing on the measurement of transverse relaxation times in molten polymers[J].J Polym Sci B,1996,34(11):1893-1902.
[31]MITROBOLSKY.Gaussian Distribution[M].Beijing:Science Press,1959.
[2]ZHU R P,ZHOU B,YANG J,et al.Effect of crosslinking density on dynamic performance of natural rubber[J].Special Purpose Rubber Products,2009,30(1):43-45.朱闰平,邹波,杨军,等.交联密度对天然橡胶动态性能的影响[J].特种橡胶制品,2009,30(1):43-45.
[3]STUDEBAKER M L.Lithium aluminum hydride analysis of sulfur-cured vulcanizates[J].Rubb Chem Tech,1970(43):624-643.
[4]SCHLOGL S,TRUTSCHEL M L,CHASSéW,et al.Entanglement effects in elastomers:macroscopic vs microscopic properties[J].Macromolecules,2014,47(9):2759-2773.
[5]MULLINS L.Determination of degree of crosslinking in natural rubber vulcanization.Part I[J].J Polym Sci,1956,19(92):225-236.
[6]LITVINOV V M,Dias A A.Analysis of network structure of UV-cured acrylates by 1H NMR relaxation,13CNMR spectroscopy and dynamic mechanical experiments[J].Macromolecules,2001,34(12):4051-4059.
[7]GENNES P G D.Reptation of a polymer chain in the presence of fixed obstacles[J].J Chem Phys,1971,55(2):572-579.
[8]KUHN W,PEREGI E,FEI Z,et al.Network dynamics of crosslinked polymers-crosslinking,filler and aging characterized by NMR parameters[J].Mater Res Soc Symp Proc,1991,33(1):217-223.
[9]KUHN W,BARTH P,HAFNER S,et al.Material properties imaging of cross-linked polymers by NMR[J].Macromolecules,1994,27(20):5773-5779.
[10]FEDOTOV V D,Schneider H.Structures and dynamics of bulk polymers by NMR-methods[M].Springer-Verlag,1989.
[11]ZHAO S Y,WANG Y Y,ZHANG R C,et al.Low-field NMR studies on the structure and dynamics of nanocompositehydrogels[J].Chinese J Magn Reson,2014,31(2):172-184.赵守远,王媛媛,张荣纯,等.低场固体NMR研究纳米复合凝胶结构与动力学[J].波谱学杂志,2014,31(2):172-184.
[12]GAO Y,ZHANG R C,LV W F,et al.Critical effect of segmental dynamics in polybutadiene/clay nanocomposites characterized by solid state 1H NMR spectroscopy[J].J Phys Chem C,2014,118(10):5606-5614.
[13]SAALW?CHTER K.Proton multiple-quantum NMR for the study of chain dynamics and structural constraints in polymeric soft materials[J].Prog Nucl Mag Res Sp,2007,51(1):1-35.
[14]HAHN E L,Spin Echoes[J].Phys Rev,1950,80:580-594.
[15]CARR H Y,PURCELL E M.Effect of diffusion on free precession in nuclear magnetic resonance experiments[J].Phys Rev,1954,94(3):630-638.
[16]MEIBOOM S,GILL D.Modified spin-echo method for measuring nuclear relaxation times[J].Rev Sci Instrum,2004,29(8):688-691.
[17]BAUM J,PINES A.NMR studies of clustering in solids[J].J Am Chem Soc,1986,108(24):7447-7454.
[18]SAALW?CHTER K,KLüPPEL M,LUO H,et al.Chain order in filled SBR elastomers:a proton multiple-quantum NMR study[J].Appl Magn Reson,2004,27(3,4):401-417.
[19]SAALW?CHTER K,ZIEGLER P,SPYCKERELLE O,et al.1H multiple-quantum nuclear magnetic resonance investigations of molecular order distributions in poly(dimethyl siloxane)networks:Evidence for a linear mixing law in bimodal systems[J].J Chem Phys,2003,119(6):3468-3482.
[20]SAALW?CHTER K.1H multiple-quantum nuclear magnetic resonance investigations of molecular order in polymer networks.II.Intensitydecay and restricted slow dynamics[J].J Chem Phys,2004,120(1):454-64.
[21]SAALW?CHTER K,AND B H,LóPEZMANCHADO M A.Chain order and cross-link density of elastomers as investigated by proton multiple-quantum NMR[J].Macromolecules,2005,38(38):9650-9660.
[22]HEUERT U,KN?RGEN M,MENGE H,et al.New aspects of transversal 1H NMR relaxation in natural rubber vulcanization[J].Polym Bull,1996,37(4):489-496.
[23]SIMON G,BIRNSTIEL A,SCHIMMEL K H.Network characterization of end-linked poly(dimethyl siloxane)by 1H NMR spin-spin relaxation[J].Polym Bull,1989,21(2):235-241.
[24]FRY C G,LIND A C.Determination of crosslink density in thermoset polymers by use of solid-state proton NMR techniques[J].Macromolecules,1988,601(2):921-929.
[25]WHITTAKER A K,BREMNER T,ZELAYA F O.The effect of field inhomogeneous and molecular diffusion on the NMR transverse relaxation behavior of polymer melts[J].Polymer,1995,36(11):2159-2164.
[26]HILL L W.Calculation of crosslink density in short chain networks[J].Prog Org Coat,1997,31(3):235-243.
[27]GOTLIB Y Y,LIFSHITZ M I,SHEVELEV V A,et al.The influence of the chemical crosslinking network on the spin-spin relaxation of crosslinked and swelling polymer systems[J].Polymer Science U.s.s.r,1976,18(10):2630-2636.
[28]KLUPPEL M,MENGE H,SCHMIDT H,et al.Influence of preparation conditions on network parameters of sulfur-cured natural rubber[J].Macromolecules,2001,34(23):8107-8116.
[29]LIU T Q,FANG Q H,HU Z L,et al.Study on relationship between cross-linking density and crystallization characteristic of gutta-percha rubber[J].China Rubber Industry,2013,60(10):593-597.刘天琦,方庆红,胡之朗,等.杜仲橡胶硫化胶交联密度与结晶性能关系研究[J].橡胶工业,2013,60(10):593-597.
[30]BREMNER T,RUDIN A.The effect of degassing on the measurement of transverse relaxation times in molten polymers[J].J Polym Sci B,1996,34(11):1893-1902.
[31]MITROBOLSKY.Gaussian Distribution[M].Beijing:Science Press,1959.