JP6075246B2 - Rubber seal material life evaluation method - Google Patents
Rubber seal material life evaluation method Download PDFInfo
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- JP6075246B2 JP6075246B2 JP2013175809A JP2013175809A JP6075246B2 JP 6075246 B2 JP6075246 B2 JP 6075246B2 JP 2013175809 A JP2013175809 A JP 2013175809A JP 2013175809 A JP2013175809 A JP 2013175809A JP 6075246 B2 JP6075246 B2 JP 6075246B2
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- 229920001971 elastomer Polymers 0.000 title claims description 76
- 239000005060 rubber Substances 0.000 title claims description 76
- 239000000463 material Substances 0.000 title claims description 47
- 238000011156 evaluation Methods 0.000 title description 16
- 230000006835 compression Effects 0.000 claims description 61
- 238000007906 compression Methods 0.000 claims description 61
- 238000012360 testing method Methods 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 34
- 230000001133 acceleration Effects 0.000 claims description 16
- 239000003566 sealing material Substances 0.000 claims description 14
- 238000007789 sealing Methods 0.000 claims description 11
- 238000013213 extrapolation Methods 0.000 claims description 8
- 238000006073 displacement reaction Methods 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- 230000006698 induction Effects 0.000 claims description 3
- 238000005481 NMR spectroscopy Methods 0.000 description 20
- 238000005259 measurement Methods 0.000 description 20
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 18
- 230000008961 swelling Effects 0.000 description 12
- 230000007423 decrease Effects 0.000 description 10
- 238000004132 cross linking Methods 0.000 description 8
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 6
- 230000000875 corresponding effect Effects 0.000 description 5
- 230000006866 deterioration Effects 0.000 description 5
- 229920000459 Nitrile rubber Polymers 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- 230000007774 longterm Effects 0.000 description 3
- 239000004014 plasticizer Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000036962 time dependent Effects 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229920002943 EPDM rubber Polymers 0.000 description 2
- 229920000181 Ethylene propylene rubber Polymers 0.000 description 2
- 229920005601 base polymer Polymers 0.000 description 2
- 229920005549 butyl rubber Polymers 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229920006168 hydrated nitrile rubber Polymers 0.000 description 2
- 150000002825 nitriles Chemical class 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 229920001084 poly(chloroprene) Polymers 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 238000000944 Soxhlet extraction Methods 0.000 description 1
- 229920006311 Urethane elastomer Polymers 0.000 description 1
- 238000003811 acetone extraction Methods 0.000 description 1
- 229920000800 acrylic rubber Polymers 0.000 description 1
- 125000002015 acyclic group Chemical group 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229920005560 fluorosilicone rubber Polymers 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000004899 motility Effects 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000000611 regression analysis Methods 0.000 description 1
- 239000012779 reinforcing material Substances 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Description
本発明はゴムシール材の寿命評価方法に係り、特にパルス法NMR(核磁気共鳴)を用いたゴムシール材の寿命評価方法に関する。 The present invention relates to a rubber seal material life evaluation method, and more particularly to a rubber seal material life evaluation method using pulsed NMR (nuclear magnetic resonance).
熱劣化が主となる環境下で使用されるゴムシール材の寿命評価にあたっては、複数温度環境下で定圧縮変位を負荷する温度加速試験が一般的に行われる。評価指標にはシール性能の経時変化と密接に関連する圧縮永久ひずみ(compression set)が多く用いられる。圧縮永久ひずみを評価指標とした場合には、圧縮永久ひずみが各加速温度において限界値に達する時間を推定し、更にそのアレニウスプロットの直線外挿により使用環境温度において限界値に達する時間を寿命として推定する。しかしながら、対象部材が小さい場合や、長期の温度加速による部材の変形が生じる場合など、寸法測定誤差が増大した際には、圧縮永久ひずみの評価指標としての適用性が低下する。 In evaluating the life of a rubber seal material used in an environment where thermal degradation is mainly used, a temperature acceleration test in which a constant compression displacement is applied under a multi-temperature environment is generally performed. As an evaluation index, a compression set that is closely related to a change in seal performance with time is often used. When compression set is used as an evaluation index, the time for compression set to reach the limit value at each acceleration temperature is estimated, and the time to reach the limit value at the operating environment temperature by linear extrapolation of the Arrhenius plot is used as the lifetime. presume. However, when the dimension measurement error increases, such as when the target member is small or the member is deformed due to long-term temperature acceleration, the applicability as an evaluation index of compression set is reduced.
また、予め機器に装着されたOリングやゴムシートにおいては、初期圧縮率が不明である場合も多い。この場合は初期に圧縮されていた寸法に対するひずみ量である圧縮永久ひずみは求められないため、同じように圧縮永久ひずみの評価指標としての適用性が低下する。 Further, in many cases, the initial compression rate is unknown for an O-ring or a rubber sheet that is mounted on a device in advance. In this case, since the compression set which is the amount of strain with respect to the dimension compressed in the initial stage is not obtained, the applicability as an evaluation index of the compression set similarly decreases.
硬度や伸びなどの機械特性をゴムシール材の寿命の評価指標とすることもあるが、計測精度や、シール性能の低下との相関性の観点から、適切な評価指標とならないことが多い。同じく、ゴム構造の状態を示す架橋密度を評価指標とすることも可能であるが、ゴム材料は、油分、灰分、カーボンなどの複合材料となっているため、ゴム構造の把握だけではシール性能の劣化を把握できない場合がある。 Although mechanical properties such as hardness and elongation may be used as an evaluation index for the life of the rubber seal material, it is often not an appropriate evaluation index from the viewpoint of measurement accuracy and correlation with a decrease in seal performance. Similarly, the crosslink density indicating the state of the rubber structure can be used as an evaluation index, but since the rubber material is a composite material such as oil, ash, and carbon, the sealing performance can be improved only by grasping the rubber structure. Deterioration may not be grasped.
ゴムの架橋状態を測定・評価する技術として、パルス法NMRでゴムのスピン−スピン緩和時間T2を測定し、得られたスピン−スピン緩和時間T2をもとに、平均緩和時間MT2を算出してゴムの架橋度を評価する方法(特許文献1:特開2002−71595号公報)や、パルス法NMRにより測定された平均緩和時間MT2と、ゴムベルトの走行試験結果から得られた耐久寿命との関係からゴムベルトの耐久寿命を推定する方法(特許文献2:特開2001−249091号公報)が提案されている。 As a technique for measuring and evaluating the crosslinked state of rubber, the spin-spin relaxation time T 2 of the rubber is measured by pulse NMR, and the average relaxation time MT 2 is calculated based on the obtained spin-spin relaxation time T 2. Method of calculating and evaluating the degree of crosslinking of rubber (Patent Document 1: Japanese Patent Application Laid-Open No. 2002-71595), average relaxation time MT 2 measured by pulse method NMR, and durability obtained from a running test result of a rubber belt A method for estimating the durable life of a rubber belt from the relationship with the life (Patent Document 2: Japanese Patent Laid-Open No. 2001-249091) has been proposed.
パルス法NMR装置によりゴムの架橋構造、主にゴムの分子同士の架橋点やカーボンなどの補強材によって拘束されている(硬い)部分の状態を観測する場合、その観測結果は必ずしもゴムの架橋構造全体の状態を精度よく反映したものとはならない。 When observing the rubber cross-linking structure, mainly the cross-linking points between rubber molecules and the (hard) part constrained by a reinforcing material such as carbon using a pulse NMR apparatus, the observation result is not necessarily the rubber cross-linking structure. It does not accurately reflect the overall condition.
特許文献3(特開2011−38945)には、シーケンスとしてCarr−Purcell−Meiboom−Gill(CPMG)法を用いたパルス法NMR測定により得られるT2緩和曲線を緩和時間の異なる2成分に分離し、各々の緩和時間及び成分比率を重回帰分析してゴム物性を解析する手法が記載されている。 In Patent Document 3 (Japanese Patent Laid-Open No. 2011-38945), a T 2 relaxation curve obtained by pulsed NMR measurement using the Carr-Purcell-Meiboom-Gill (CPMG) method as a sequence is separated into two components having different relaxation times. A method for analyzing the physical properties of rubber by multiple regression analysis of each relaxation time and component ratio is described.
特許文献4(特開2012−173093)には、パルス法NMR装置を用いるゴム材料の検査方法であって、Carr−Purcell−Meiboom−Gill(CPMG)法によりゴムのスピン−スピン緩和時間T2を測定し、得られたT2緩和曲線(自由誘導減衰曲線)を、緩和時間の短いT2 S成分と、緩和時間の長いT2 L成分とに分割し、上記T2 L成分の緩和時間から破断伸びEbを予測するゴム材料の検査方法が記載されている。 Patent Document 4 (Japanese Patent Application Laid-Open No. 2012-173093) discloses a rubber material inspection method using a pulsed NMR apparatus, which uses a Carr-Purcell-Meiboom-Gill (CPMG) method to determine the spin-spin relaxation time T 2 of rubber. measured, resulting the T 2 relaxation curve (free induction decay curve), and short T 2 S component of the relaxation time is divided into a long T 2 L component of the relaxation time, the relaxation time of the T 2 L component A method for inspecting a rubber material for predicting the breaking elongation Eb is described.
上記特許文献1〜4には、ゴムシール材の圧縮永久ひずみに代る寿命を評価する指標としての適用性について記載されていない。すなわち、特許文献1〜4によるパルス法NMRで測定されるT2緩和時間によるゴム材料の劣化評価は、架橋密度や硬度といった特定の計測項目と相関する物性値としての活用方法を提案したものであり、シール性の低下を捉える指標としての活用方法については記載されていない。架橋密度や硬度は、シール性の低下と相関する場合も多いが、架橋密度の経時変化がないにもかかわらずシール性が低下する場合も存在するため、シール性の評価に必要な物性変化を把握できない可能性がある。 The above Patent Documents 1 to 4 do not describe applicability as an index for evaluating the life of the rubber seal material in place of compression set. That is, the deterioration evaluating the rubber compositions according to the T 2 relaxation time measured by pulse method NMR by Patent Document 1 to 4, which was proposed a method utilizing a physical property value correlated with specific measurement items such crosslinking density and hardness Yes, it does not describe how to use it as an index to capture the decrease in sealing performance. The crosslink density and hardness often correlate with a decrease in sealability, but there are also cases where the sealability decreases even though there is no change in the crosslink density over time. It may not be possible to grasp.
また、従来のパルス法NMRを用いた劣化評価においては、パルス法NMRを用いて測定されたT2緩和曲線を波形分離において2成分に近似した際の運動性の高い成分と運動性の短い成分を共に用いる。この場合、運動性の異なる3つ以上の成分に分けられる材料については適用性が低くなる。また、2成分に近似できる場合でも、運動性によって緩和時間が大幅に異なる場合は、いずれかの成分についてT2緩和時間を測定する方法の適用性が低下し、これに伴って値の信頼性が低下する。 Further, in the degradation evaluation using the conventional pulse method NMR, a high mobility component and a short mobility component when the T 2 relaxation curve measured using the pulse method NMR is approximated to two components in waveform separation. Are used together. In this case, the applicability of the material divided into three or more components having different motility is lowered. In addition, even when the two components can be approximated, if the relaxation time varies greatly depending on the mobility, the applicability of the method of measuring the T 2 relaxation time for any component is reduced, and the reliability of the value is accordingly reduced. Decreases.
本発明は、パルス法NMRにより、ゴムシール材の寿命を高精度に評価することができるゴムシール材の寿命評価方法を提供することを目的とする。 An object of the present invention is to provide a method for evaluating the life of a rubber sealing material, which can evaluate the life of the rubber sealing material with high accuracy by pulsed NMR.
本発明のゴムシール材の寿命評価方法は、パルス法NMRでゴムシール材のスピン−スピン緩和時間T2を測定し、得られたT2緩和曲線(自由誘導減衰曲線)を緩和時間の短いT2 S成分と、緩和時間の長いT2 L成分とに分割し、このT2 Sに基づいてゴムシール材の寿命を評価することを特徴とするものである。 In the rubber seal material life evaluation method of the present invention, the spin-spin relaxation time T 2 of the rubber seal material is measured by pulse NMR, and the obtained T 2 relaxation curve (free induction decay curve) is converted to T 2 S having a short relaxation time. The component is divided into a component and a T 2 L component having a long relaxation time, and the life of the rubber seal material is evaluated based on the T 2 S.
本発明では、熱劣化が支配的であると考えられる場合には、測定対象となるゴムシール材と同一組成の未使用ゴム材料の試験片に定圧縮変位を与えて加速温度条件下に置き、その後各試験片のT2緩和時間を測定して分子運動性の低い成分の緩和時間であるT2 Sを求める。また、複数の試験片について圧縮永久ひずみを測定し、T2 Sと圧縮永久ひずみの検量関係を求める。この検量関係に基づいてあらかじめ定められた圧縮永久ひずみの上限値に対応する評価対象のT2 Sの限界値(下限値)を定める。そして、測定対象ゴムシール材について測定したT2 Sが限界値に達する時間を求め、更にそのアレニウスプロットの直線外挿により使用環境温度(例えば常温)において限界値に達する時間を寿命として推定することが好ましい。 In the present invention, when thermal degradation is considered to be dominant, a constant compression displacement is applied to a test piece of an unused rubber material having the same composition as the rubber seal material to be measured, and the test piece is placed under an accelerated temperature condition. measured the T 2 relaxation time of each specimen Request T 2 S is a relaxation time of less molecular mobility component. Further, the compression set was measured for a plurality of test strips to determine the calibration relationship compression set and T 2 S. Based on the calibration relationship, a limit value (lower limit value) of T 2 S to be evaluated corresponding to a predetermined upper limit value of compression set is determined. Then, the time for T 2 S measured for the measurement target rubber seal material to reach the limit value is obtained, and the time to reach the limit value at the use environment temperature (for example, normal temperature) is further estimated as the lifetime by linear extrapolation of the Arrhenius plot. preferable.
本発明では、シール部分を有する機器類を供試体として評価することもできる。この場合は、シール材を装着した供試体を加速温度条件下に置き、その後、供試体に装着されたゴムシール材の圧縮永久ひずみとT2 Sとを測定して同様の方法により寿命を推定することが可能である。 In the present invention, devices having a seal portion can be evaluated as a specimen. In this case, the specimen mounted with the sealing material is placed under an accelerated temperature condition, and then the compression set and T 2 S of the rubber sealing material mounted on the specimen are measured to estimate the lifetime by the same method. It is possible.
その際、初期圧縮率が不明の場合には、加速後の各供試体の気密試験を行ってシール性能を判定すると共に、各供試体に装着されたゴムシール材のT2緩和時間を測定してT2 Sを求め、シール性能を維持できるT2 Sの限界値(下限値)を定め、測定したT2 Sがこの限界値に達する時間を推定し、更にそのアレニウスプロットの直線外挿により使用環境温度において限界値に達する時間を機器類のシール材の寿命として推定することが好ましい。 At that time, when the initial compression ratio is unknown, the sealing performance is determined by performing an airtight test of each specimen after acceleration, and the T 2 relaxation time of the rubber seal material attached to each specimen is measured. seeking T 2 S, defined limit T 2 S to maintain the sealing performance (the lower limit), the measured T 2 S estimates the time to reach this limit, further use by linear extrapolation of the Arrhenius plot It is preferable to estimate the time to reach the limit value at the environmental temperature as the lifetime of the sealing material of the equipment.
前述のようにしてT2 Sを求めた後に、圧縮永久ひずみとの検量関係やそれに基づく限界値の確定、シール性能が維持できる限界値の確定、限界値に到達する時間の推定、アレニウスプロットの直線外挿に基づく寿命推定等を行うに当たっては、T2 Sそのものの値を用いるのではなく、各加速品と未加速品のT2 Sの差を用いることも可能である。この場合、各加速品と未加速品のT2 Sの差の限界値は下限値ではなく、上限値となる。 After obtaining T 2 S as described above, calibration relation with compression set and determination of limit value based on it, determination of limit value capable of maintaining seal performance, estimation of time to reach limit value, Arrhenius plot In performing life estimation based on linear extrapolation, the value of T 2 S itself can be used instead of the value of T 2 S between each accelerated product and unaccelerated product. In this case, the limit value of the difference between T 2 S between the accelerated product and the non-accelerated product is not the lower limit value but the upper limit value.
本発明は、ゴムシール材の劣化促進後に計測していた圧縮永久ひずみに代えて、パルス法NMR装置を用いてT2緩和時間を測定し、その経時変化データによって耐久性を評価するようにしたものである。本発明は、シール性と相関性の高い圧縮永久ひずみの代替としての機能をもつように開発した手法であり、シール性の経時変化に基づいて寿命を精度よく推定することができると共に、初期圧縮率が不明であるため圧縮永久ひずみが測定できない場合でもシール材の寿命評価を行うことが可能である。 In the present invention, the T 2 relaxation time is measured using a pulsed NMR apparatus instead of the compression set measured after promoting the deterioration of the rubber seal material, and the durability is evaluated based on the time-dependent change data. It is. The present invention is a method developed to have a function as an alternative to compression set having a high correlation with sealability, and can accurately estimate the life based on the change in sealability with time, and can also be used for initial compression. Since the rate is unknown, it is possible to evaluate the life of the sealing material even when the compression set cannot be measured.
本発明では、T2緩和時間の運動性の短い成分のみを対象とすることができ、材料に応じて最適なパルス印加方法を選択することにより、ゴムシール材の寿命を精度よく評価することができる。なお、パルス法NMRによる測定はサンプル形状による制約がないため、サンプルの形状、破損状態によらず測定が可能である。 In the present invention, only a component having a short mobility of T 2 relaxation time can be targeted, and the life of the rubber seal material can be accurately evaluated by selecting an optimum pulse application method according to the material. . Note that measurement by pulsed NMR is not limited by the shape of the sample, and can be measured regardless of the shape of the sample and the state of breakage.
本発明のゴムシール材の寿命評価方法では、パルス法NMRによってゴムシール材のT2 Sを求める。ゴムシール材のゴム材料としては、アクリロニトリルブタジエンゴム(NBR)、水素化アクリロニトリルブタジエンゴム(HNBR)、フッ素ゴム(FKM)、ウレタンゴム(U)、シリコーンゴム(VMQ,FVMQ)、エチレンプロピレンジエンゴム(EPDM)、エチレンプロピレンゴム(EPM),クロロプレンゴム(CR)、アクリルゴム(ACM)、ブチルゴム(IIR)、スチレンブタジエンゴム(SBR)などが挙げられる。ゴムシール材は、環状(円環状、楕円環状、三角環状、四角環状、五角以上の多角環状等)であってもよく、非環形のシート状などいずれの形状のものであってもよい。 In the method for evaluating the lifetime of the rubber seal material of the present invention, T 2 S of the rubber seal material is determined by pulse method NMR. Rubber materials for the rubber seal material include acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), fluorine rubber (FKM), urethane rubber (U), silicone rubber (VMQ, FVMQ), ethylene propylene diene rubber (EPDM). ), Ethylene propylene rubber (EPM), chloroprene rubber (CR), acrylic rubber (ACM), butyl rubber (IIR), styrene butadiene rubber (SBR), and the like. The rubber seal material may be annular (annular, elliptical, triangular, quadrilateral, pentagonal or more polygonal) or any other shape such as an acyclic sheet.
本発明者による実験の結果、T2 Sは、各種ゴムシール材の圧縮永久ひずみと良好な相関関係を有していることが認められた。圧縮永久ひずみはゴムシール材の寿命評価に有効な指標であり、圧縮永久ひずみが各加速温度において上限値に達する時間を推定し、更にそのアレニウスプロットの直線外挿により使用環境温度において上限値に達する時間を寿命として精度よく推定することができる。 As a result of experiments by the present inventor, it was confirmed that T 2 S has a good correlation with compression set of various rubber seal materials. Compression set is an effective index for evaluating the life of rubber seals. Estimate the time for compression set to reach the upper limit at each acceleration temperature, and reach the upper limit at the ambient temperature by linear extrapolation of the Arrhenius plot. The time can be accurately estimated as the lifetime.
ところが、ゴムシール材のサイズが小さい場合や、長期の温度加速による部材の変形が生じる場合など、寸法測定誤差が増大した際には、圧縮永久ひずみの評価指標としての適用性が低下する。 However, when the size measurement error increases, such as when the size of the rubber seal material is small or when the member is deformed due to long-term temperature acceleration, the applicability as an evaluation index of compression set decreases.
また、予め機器に装着されたOリングやゴムシートにおいては、初期圧縮率が不明である場合も多い。この場合も同じように圧縮永久ひずみの評価指標としての適用性が低下する課題があった。 Further, in many cases, the initial compression rate is unknown for an O-ring or a rubber sheet that is mounted on a device in advance. In this case as well, there is a problem that applicability as an evaluation index of compression set similarly decreases.
本発明では、圧縮永久ひずみと良好な相関関係を有するT2 Sを評価指標とするため、ゴムシール材のサイズが小さい場合や、長期の温度加速による部材の変形が生じる場合などであっても、ゴムシール材の寿命を精度よく評価することができる。また、初期圧縮率が不明であっても、ゴムシール材の寿命を評価することができる。 In the present invention, since T 2 S having a good correlation with compression set is used as an evaluation index, even when the size of the rubber seal material is small, or when deformation of the member due to long-term temperature acceleration occurs, The life of the rubber seal material can be accurately evaluated. Even if the initial compression rate is unknown, the life of the rubber seal material can be evaluated.
本発明において、パルス法NMRによるスピン−スピン緩和時間T2の測定は、ソリッドエコー(Solid Ecoh)法で行うのが好ましい。 In the present invention, the measurement of the spin-spin relaxation time T 2 by pulsed NMR is preferably performed by the solid echo method.
パルス法NMRにより得られたT2緩和曲線からT2 Sを求めるには、緩和曲線を下記式(1)にカーブフィッティングし、
F(t)=A2Sexp(−t/T2 S)m + A2Lexp(−t/T2 L)m …(1)
T2 Sを求める。なお、(1)式中A2Sは緩和時間の短い成分のt=0時の強度、A2Lは緩和時間の長い成分のt=0時の強度、tは観測時間である。また、mは対象によって異なるが、ゴムの場合は1となることが多い。
In order to obtain T 2 S from the T 2 relaxation curve obtained by the pulse method NMR, the relaxation curve is curve-fitted into the following formula (1),
F (t) = A 2S exp (-t / T 2 S) m + A 2L exp (-t / T 2 L) m ... (1)
T 2 S is obtained. In the formula (1), A 2S is the intensity at t = 0 of the component having a short relaxation time, A 2L is the intensity at t = 0 of the component having a long relaxation time, and t is the observation time. In addition, m varies depending on the object, but is often 1 in the case of rubber.
熱劣化が支配的である環境下で使用されるゴムシール材の寿命を評価するには、評価対象となるゴムシール材と同一ゴム組成を有する未使用の複数のゴム試験片ついて所定の圧縮率の定圧縮変位を与え、これを加速温度(3段階以上、例えば60,80,100℃)に所定時間(複数段階)静置する。そして、所定の経過時間毎に各サンプルについてT2緩和時間を測定し、T2 Sを求める。加えて、複数の異なる経過時間の試験片について圧縮永久ひずみを測定する。この結果に基づいて、圧縮永久ひずみとT2 Sとの検量関係(例えば、図2(a)に示されるグラフ)を求める。さらに、この検量関係に基づいて、予め定められた圧縮永久ひずみの上限値に対応するT2 Sの限界値を求める。 In order to evaluate the life of a rubber seal material used in an environment where thermal degradation is dominant, a predetermined compression ratio is determined for a plurality of unused rubber test pieces having the same rubber composition as the rubber seal material to be evaluated. A compressive displacement is given, and this is left still for a predetermined time (multiple steps) at acceleration temperature (3 steps or more, for example, 60, 80, 100 ° C.). Then, the the T 2 relaxation time were measured for each sample at every predetermined elapsed time, obtaining the T 2 S. In addition, compression set is measured for a plurality of specimens with different elapsed times. Based on this result, a calibration relationship between the compression set and T 2 S (for example, the graph shown in FIG. 2A) is obtained. Further, based on this calibration relationship, a limit value of T 2 S corresponding to a predetermined upper limit value of compression set is obtained.
シール材を有する機器類を供試体として評価する場合は、供試体を加速温度条件下に置き、その後、供試体に装着されたゴムシール材のT2緩和時間を測定してT2 Sを求め、複数の異なる経過時間の試験片について測定した圧縮永久ひずみとT2 Sの検量関係(例えば、図2(a)に示されるグラフ)を求め、さらにこの検量関係に基づいて予め定められた圧縮永久ひずみの上限値に対応するT2 Sの限界値を求める。 When evaluating equipment having a sealing material as a specimen, place the specimen under accelerated temperature conditions, and then measure T 2 relaxation time of the rubber sealing material attached to the specimen to obtain T 2 S. A calibration relationship (for example, the graph shown in FIG. 2A) between compression set and T 2 S measured for a plurality of test pieces having different elapsed times is obtained, and compression permanent determined in advance based on the calibration relationship. A limit value of T 2 S corresponding to the upper limit value of the strain is obtained.
その際、初期圧縮率が不明の場合には、温度加速後の各供試体の気密試験を行ってシール性能を判定すると共に、各供試体についてT2緩和時間を測定してT2 Sを求め、シール性能を維持できるT2 Sの限界値(下限値)を定める。 At that time, when the initial compression ratio is unknown, the sealing performance is determined by performing an airtight test of each specimen after temperature acceleration, and T 2 relaxation time is measured for each specimen to obtain T 2 S. The limit value (lower limit value) of T 2 S that can maintain the sealing performance is determined.
T2 Sを求めた後に、圧縮永久ひずみとの検量関係やそれに基づく限界値の確定、シール性能が維持できる限界値の確定を行うに当たっては、T2 Sそのものの値を用いるのではなく、各加速品と未加速品のT2 Sの差を用いることも可能である。この場合、各加速品と未加速品のT2 Sの差の限界値は下限値ではなく、上限値となる。 After obtaining T 2 S , when determining the calibration relationship with compression set, the limit value based on it, and the limit value that can maintain the sealing performance, the value of T 2 S itself is not used. It is also possible to use the difference in T 2 S between accelerated and unaccelerated products. In this case, the limit value of the difference between T 2 S between the accelerated product and the non-accelerated product is not the lower limit value but the upper limit value.
評価対象とするゴムシール材についてパルス法NMRによってT2緩和時間を測定し、T2 Sを求める。この求めたT2 Sあるいは各加速品(加速温度条件下においた試験片)と未加速品(加速温度条件下におかなかった試験片)のT2 Sの差が限界値に達する時間を求め、更にそのアレニウスプロットの直線外挿により使用環境温度において限界値に達する時間を機器類のゴムシール材の寿命として推定し、ゴムシール材の寿命を評価する。 T 2 relaxation time is measured by pulse method NMR for the rubber seal material to be evaluated, and T 2 S is obtained. The difference obtained T 2 S or T 2 S of each accelerating articles (accelerated temperature conditions in at specimens) and non-accelerated articles (not placed accelerated temperature conditions specimen) seek time to reach the limit value Further, the time to reach the limit value at the operating environment temperature is estimated as the life of the rubber seal material of the equipment by linear extrapolation of the Arrhenius plot, and the life of the rubber seal material is evaluated.
[実施例1]
高ニトリルNBRをベースポリマーとした外径199.5mmの未使用のリングパッキンから切り出した39mm×19mm×厚さ6.5mmの平板試験片について、パルス法NMRを用いてT2 S及びT2 L(JMN−MU25、Solid Echo法、90°pulse2.0μsec、繰り返し時間4sec、積算回数8回)を測定した。また、この平板試験片について、膨潤量(トルエン、37℃)、アセトン可溶分(ソックスレー抽出、8時間)を測定した。
[Example 1]
A flat test piece of 39 mm × 19 mm × 6.5 mm thickness cut out from an unused ring packing having an outer diameter of 199.5 mm using high nitrile NBR as a base polymer was subjected to T 2 S and T 2 L using pulsed NMR. (JMN-MU25, Solid Echo method, 90 ° pulse 2.0 μsec,
[実施例2]
実施例1と同一の平板試験片に、圧縮率が10%となるようなスペーサーを用いて定圧縮変位を与え、これを加速温度(60,80,100℃)に設定した空気恒温槽に各試験時間(約1000〜12800時間)が経過するまで静置した。
[Example 2]
A constant compression displacement was applied to the same flat plate test piece as in Example 1 using a spacer with a compression ratio of 10%, and this was applied to an air thermostat set at an acceleration temperature (60, 80, 100 ° C.). It left still until test time (about 1000-12800 hours) passed.
この加速温度処理後の試験片について圧縮永久ひずみを測定すると共に、実施例1と同一の測定を行った。 The compression set was measured for the test piece after the accelerated temperature treatment, and the same measurement as in Example 1 was performed.
[結果・考察]
図1に加速温度処理に供した試験片の圧縮永久ひずみの経時変化を示す。60,80,100℃のいずれの加速温度の場合も、経時に伴い圧縮永久ひずみが増大していることが認められる。
[Results and Discussion]
FIG. 1 shows a change with time of the compression set of a test piece subjected to accelerated temperature treatment. It can be seen that the compression set increases with time at any acceleration temperature of 60, 80, and 100 ° C.
同試験片について、パルス法NMRを用いて20℃において測定したT2緩和曲線を波形分離にて2成分に近似した。 For the test pieces, it approximates the 2 components the T 2 relaxation curve measured at 20 ° C. using the pulsed NMR technique in waveform separation.
図2(a)にT2 Sと圧縮永久ひずみとの関係を示し、図2(b)にT2 Lと圧縮永久ひずみとの関係を示す。図2(a),(b)の通り、圧縮永久ひずみの増大とともにT2 S、T2 Lが小さくなる良い相関が見られる。 FIG. 2A shows the relationship between T 2 S and compression set, and FIG. 2B shows the relationship between T 2 L and compression set. As shown in FIGS. 2 (a) and 2 (b), there is a good correlation that T 2 S and T 2 L become smaller as the compression set increases.
図3(a),(b)にアセトン可溶分とT2 S、T2 Lとの関係を示す。図3(a),(b)の通り、アセトン可溶分の減少とともにT2 S、T2 Lが小さくなる相関が見られる。 3A and 3B show the relationship between acetone-soluble matter and T 2 S and T 2 L. As shown in FIGS. 3A and 3B, there is a correlation in which T 2 S and T 2 L become smaller as the acetone-soluble content decreases.
図4(a),(b)に実施例2において加速温度処理に供した試験片の20℃測定におけるT2 S、T2 Lと、同一条件で加速温度処理した試験片について測定したトルエン膨潤量の関係を示す。20℃測定におけるT2 S、T2 Lとトルエン膨潤量との間には相関は見られない。 4 (a) and 4 (b), toluene swelling measured for the test pieces subjected to accelerated temperature treatment under the same conditions as T 2 S and T 2 L in 20 ° C. measurement of the test piece subjected to accelerated temperature treatment in Example 2 in FIGS. The relationship of quantity is shown. There is no correlation between T 2 S and T 2 L measured at 20 ° C. and the toluene swelling amount.
T2 S、T2 Lと膨潤量に相関が見られないのに対し、T2 S、T2 Lとアセトン可溶分については一定の相関が認められる理由については、膨潤量は架橋密度に関連することから、本試験片においては架橋密度の経時変化が小さかったためにT2 S、T2 Lと膨潤量に相関が見られなかったものと考えられる。これに対し、アセトン可溶分の変化は可塑剤残存量の変化に関連することから、本試験片においては、主として可塑剤の揮発により分子鎖の運動性、すなわちT2 S、T2 Lが減少したものと推察される。 There is no correlation between T 2 S and T 2 L and the amount of swelling, whereas the reason why there is a certain correlation between T 2 S and T 2 L and acetone-soluble components is that the amount of swelling depends on the crosslinking density. Since it is related, in this test piece, since the time-dependent change of the crosslinking density was small, it is thought that there was no correlation between T 2 S , T 2 L and the swelling amount. On the other hand, since the change in acetone-soluble content is related to the change in the residual amount of plasticizer, in this test piece, the mobility of molecular chains, that is, T 2 S and T 2 L are mainly caused by volatilization of the plasticizer. Presumed to have been reduced.
図5に、実施例1において未加速の試験片について、アセトン抽出およびトルエンによる膨潤を行っていない状態の試料を測定した結果のパルス法NMRの測定温度とT2 S及びT2 Lの成分比の関係を示す。温度上昇に伴ってT2 Sの成分比が減少し70℃でほぼ消滅することが確認できる。 FIG. 5 shows the measurement temperature of pulse method NMR and the component ratio of T 2 S and T 2 L as a result of measuring a sample in an unaccelerated test piece in Example 1 that was not subjected to acetone extraction and swelling with toluene. The relationship is shown. It can be confirmed that the component ratio of T 2 S decreases with increasing temperature and almost disappears at 70 ° C.
また、図5に、同試験片についてアセトン可溶分の抽出およびトルエンによる膨潤を行った後に20℃において測定したT2 SとT2 Lの成分比を合わせて示した。図5の通り、トルエン膨潤後にT2 Sはほぼ消滅している。 FIG. 5 also shows the component ratio of T 2 S and T 2 L measured at 20 ° C. after the acetone-soluble component was extracted and swollen with toluene. As shown in FIG. 5, T 2 S almost disappears after toluene swelling.
以上より、T2 Sは分子鎖における絡み合い点や架橋点近傍の分子運動性が低い部分の緩和時間、T2 Lは絡み合い等の影響が小さい部分の緩和時間を捉えたものと推定でき、実施例1,2の試験片において、20℃のT2 Sは、絡み合い点近傍における分子鎖の運動性を主に捉えているものと考えられる。
From the above, it can be estimated that T 2 S captures the relaxation time of the portion where molecular mobility is low in the molecular chain and near the crosslinking point, and T 2 L captures the relaxation time of the portion where influence of entanglement is small. In the test pieces of Examples 1 and 2,
[実施例3,4]
前記リングパッキンから切り出した平板試験片の代わりに、高ニトリルNBRゴムをベースポリマーとしたOリング付きダイヤフラムを装着した圧力調整器の該Oリングについて、該圧力調整器に装着したままの状態で実施例1,2と同様の測定を行い、結果を図6〜8に示した。図6〜8の(a)図はT2 Sと圧縮永久ひずみ、アセトン可溶分及び膨潤量の関係を示し、図6〜8の(b)図はT2 Lと圧縮永久ひずみ、アセトン可溶分及び膨潤量の関係を示す。
[Examples 3 and 4]
The O-ring of the pressure regulator equipped with a diaphragm with an O-ring made of high nitrile NBR rubber as the base polymer instead of the flat plate test piece cut out from the ring packing was mounted on the pressure regulator. Measurements similar to those of Examples 1 and 2 were performed, and the results are shown in FIGS. FIGS. 6 to 8 (a) show the relationship between T 2 S and compression set, acetone solubles and swelling, and FIGS. 6 to 8 (b) show T 2 L , compression set and acetone acceptable. The relationship between a soluble content and the amount of swelling is shown.
図6〜8の通り、T2 Sは圧縮永久ひずみ、アセトン可溶分及び膨潤量と良好な相関を示す。本試験片については、架橋密度と可塑剤残存量共に経時変化があったため、双方とも一定の相関が認められたものと推察される。これに対し、このサンプルの場合、T2 Lと圧縮永久ひずみ、アセトン可溶分及び膨潤量との相関は低い。 As shown in FIGS. 6 to 8, T 2 S shows a good correlation with compression set, acetone-soluble component, and swelling amount. With respect to this test piece, both the crosslink density and the residual amount of plasticizer changed with time, and it is assumed that a certain correlation was observed in both. On the other hand, in the case of this sample, the correlation between T 2 L , compression set, acetone-soluble content, and swelling amount is low.
これらの結果より、熱劣化が支配的である環境下に置かれるゴムシール材のT2 Sの経時変化は材料の形状、配合や、劣化メカニズムによらず、圧縮永久ひずみと良好な相関を示し、寿命評価指標として信頼性が高いことが認められた。また、本試験で対象としたシール材において、20℃にて測定されたT2 Sと圧縮永久ひずみの相関が確認された。 From these results, the time-dependent change in T 2 S of the rubber seal material placed in an environment where thermal deterioration is dominant shows a good correlation with compression set regardless of the shape, composition, and deterioration mechanism of the material, It was confirmed that the life evaluation index is highly reliable. In addition, in the sealing material targeted in this test, a correlation between T 2 S measured at 20 ° C. and compression set was confirmed.
[実施例5]
実施例1で用いたものと同一の未使用の複数個の平板ゴム試験片について実施例2と同じくスペーサーを用いて圧縮率10%の定圧縮変位を与え、これを加速温度60℃、80℃、又は100℃に設定した空気恒温槽内に静置した。そして、1000hr、1500hr、3000hr、5000hr、7000hr(100℃のみ)、又は12800hr(60、80℃)経過毎に各試験片について実施例2と同様にしてT2緩和時間を測定し、T2 Sを求めると共に、圧縮永久ひずみを測定した。この結果に基づいて、加速温度毎の処理時間とT2 Sとの関係を図9に示した。また、圧縮永久ひずみとT2 Sとの検量関係を求めた。この検量関係は、前述の図2(a)の通りである。
[Example 5]
A plurality of unused flat rubber test pieces identical to those used in Example 1 were subjected to constant compression displacement with a compression rate of 10% using spacers as in Example 2, and this was applied to acceleration temperatures of 60 ° C. and 80 ° C. Or in an air thermostat set to 100 ° C. Then, the T 2 relaxation time was measured for each test piece in the same manner as in Example 2 every 1000 hours, 1500 hours, 3000 hours, 5000 hours, 7000 hours (only at 100 ° C.), or 12800 hours (60, 80 ° C.), and T 2 S And the compression set was measured. Based on this result, the relationship between the processing time for each acceleration temperature and T 2 S is shown in FIG. Further, a calibration relationship between compression set and T 2 S was obtained. This calibration relationship is as shown in FIG.
この検量関係に基づいて,予め定められた圧縮永久ひずみの上限値(この実施例では80%)に対応するT2 Sを求めたところ、81μsecであった。そこで、この81μsecをT2 Sの限界値とすることとした。 Based on this calibration relationship, T 2 S corresponding to a predetermined upper limit value of compression set (80% in this example) was obtained and found to be 81 μsec. Therefore, this 81 μsec is set as the limit value of T 2 S.
各加速温度に保持された試験片がこのT2 S限界値(81μsec)に達するまでの経過時間を図9より読み取ったところ、
100℃の場合2820hr
80℃の場合8329hr
60℃の場合28431hr
であった。この処理温度と経過時間をアレニウスプロットし、図10に示すアレニウス線図を得た。図10の縦軸は経過時間hの逆数の自然対数値1n(1/h)である。横軸は処理温度(絶対温度)Kの逆数の1000倍値1000/Kである。
When the elapsed time until the test piece held at each acceleration temperature reaches the T 2 S limit value (81 μsec) is read from FIG. 9,
2820hr at 100 ° C
8329 hr at 80 ° C
28431hr at 60 ° C
Met. This processing temperature and elapsed time were Arrhenius plotted to obtain the Arrhenius diagram shown in FIG. The vertical axis in FIG. 10 is the natural logarithm value 1n (1 / h) which is the reciprocal of the elapsed time h. The horizontal axis is 1000 / K, which is 1000 times the reciprocal of the processing temperature (absolute temperature) K.
図10において、得られた直線に対し使用環境温度20℃(その絶対温度の逆数1000/Kは、1000/(273+20)=3.41)保持下での限界値に達するまでの経過時間を求めたところ、次の通り537663hr(約61年)であった。 In FIG. 10, the elapsed time until reaching the limit value with the use environment temperature of 20 ° C. (the reciprocal of the absolute temperature is 1000 / K is 1000 / (273 + 20) = 3.41) is obtained for the obtained straight line. As a result, it was 537663 hr (about 61 years) as follows.
すなわち、図10において3.41の横軸値に対応する縦軸値は−13.195である。
e−13.195=1/h
より、h=1/e−13.195
=1/1.8599×10−6
=537663hr
従って、このOリングの20℃保持下での寿命は約61年であると評価された。
That is, the vertical axis value corresponding to the horizontal axis value of 3.41 in FIG. 10 is −13.195.
e -13.195 = 1 / h
From h = 1 / e -13.195
= 1 / 1.8599 × 10 −6
= 537663 hr
Therefore, it was evaluated that the lifetime of this O-ring when held at 20 ° C. was about 61 years.
Claims (7)
得られたT2緩和曲線(自由誘導減衰曲線)を緩和時間の短いT2 S成分と、緩和時間の長いT2 L成分とに分割し、
このT2 Sに基づいてゴムシール材の寿命を評価することを特徴とするゴムシール材の寿命評価方法。 Spin rubber seal member in pulse method NMR - measuring the spin relaxation time T 2,
The obtained T 2 relaxation curve (free induction decay curve) is divided into a T 2 S component having a short relaxation time and a T 2 L component having a long relaxation time,
A method for evaluating the life of a rubber seal material, wherein the life of the rubber seal material is evaluated based on the T 2 S.
評価対象となるゴムシール材と同一組成の未使用試験片に定圧縮変位を与えて加速温度条件下に置き、その後複数の試験片の圧縮永久ひずみを測定する工程と、
前記各試験片のT2 Sを測定してT2 Sと圧縮永久ひずみの検量関係を求める工程と、
この検量関係に基づいてあらかじめ定められた圧縮永久ひずみの上限値に対応する評価対象のT2 Sの限界値を求める工程と、
評価対象ゴムシール材について測定したT2 Sとこの限界値に基づいて評価対象ゴムシール材の寿命を評価する工程と
を有することを特徴とするゴムシール材の寿命評価方法。 In claim 1,
A step of applying a constant compression displacement to an unused test piece having the same composition as the rubber seal material to be evaluated and placing it under accelerated temperature conditions, and then measuring the compression set of a plurality of test pieces,
Measuring T 2 S of each test piece to obtain a calibration relationship between T 2 S and compression set;
Obtaining a limit value of T 2 S to be evaluated corresponding to a predetermined upper limit value of compression set based on the calibration relationship;
A method for evaluating the life of a rubber seal material, comprising: T 2 S measured for the rubber seal material to be evaluated and a step of evaluating the life of the rubber seal material to be evaluated based on the limit value.
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