CN104076136A - Method for analyzing aging mechanism of silicone rubber by utilizing variable activation energy - Google Patents

Abstract

The invention provides a method for analyzing an aging mechanism of silicone rubber by utilizing variable activation energy, which belongs to the technical field of the method for analyzing the aging mechanism of the silicone rubber. The method provided by the invention comprises the following four steps: carrying out a hot oxygen aging experiment of the silicone rubber, performing an X-ray diffraction photoelectron spectroscopy test and a nuclear magnetic resonance test on an aging specimen, analyzing XPS and NMR test results and analyzing activation energy in an aging process by utilizing compression permanent deformation. According to the method for analyzing the aging mechanism of the silicone rubber by utilizing the variable activation energy, the aging mechanism is preliminarily analyzed by virtue of a chemical test, a changing curve of the activation energy is calculated and derived by utilizing the compression permanent deformation of changes of physical properties, and both are combined by virtue of the activation energy to analyze the aging mechanism, so that the aging mechanism of the silicone rubber can be accurately speculated. The method is a simple and practical method for analyzing the mechanism of the silicone rubber and has great significance on further researching the aging mechanism of the silicone rubber.

Description

A kind of method that becomes energy of activation analysis silicon rubber agine mechaism of utilizing

Technical field

The present invention relates to a kind of method that becomes energy of activation analysis silicon rubber agine mechaism of utilizing, belong to the silicon rubber agine mechaism method and technology field of analyzing.

Background technology

Rubber is the high resiliency polymeric material with reversible deformation, is widely used in and manufactures in tire, sebific duct, adhesive tape, cable and other rubbers.

Silicon rubber in rubber synthetic material is typical half inorganics half organic polymer, both there is the thermotolerance of inorganic polymer thing, there is again organic macromolecule compliance, thereby be widely used in the sophisticated industry such as space flight, aviation as Nai Gaore and low temperature resistant rubber packing material.But rubber parts is subject to the impact of internal and external factor in its military service process, and mechanical property etc. can decline gradually and then lose use value.Even in the relatively short military service process of rubber parts, the aging and degradation problem of rubber parts is still the key factor that affects its storage reliability.And the immediate cause that after ageing of rubber, physical property declines is exactly that chemical reaction has occurred elastomeric material, there is variation in strand and functional group, and the agine mechaism of therefore studying after ageing of rubber is the basic of performance change after research ageing of rubber.The reason that can also fundamentally understand ageing of rubber by the agine mechaism after research ageing of rubber, for the research of the ageing-resistant aspect of elastomeric material provides foundation, is playing an important role aspect follow-up study ageing of rubber.

In the process of research ageing of rubber mechanism, can symbolize the variation of ageing of rubber mechanism by the change of research ageing process energy of activation.The agine mechaism of rubber under a certain condition is comprising many different reaction equations, but along with the change of reaction conditions, the proportion of these reaction equations changes gradually, and the proportion that may exist some reaction increases, and the proportion of some reaction reduces.And in ageing process, in the time that the proportion of reaction changes, the energy of activation of whole aging reaction can change, and just the variation by energy of activation is mapped with the variation of reacting proportion like this in research process, further studies the agine mechaism in whole ageing process.

Summary of the invention

The object of the invention is the problem existing in order to solve above-mentioned prior art, in order to make rubber product be applied to better reality, understand and grasp its aging rule.And then provide a kind of method that becomes energy of activation and analyze silicon rubber agine mechaism of utilizing.

The object of the invention is to be achieved through the following technical solutions:

Utilize a method that becomes energy of activation analysis silicon rubber agine mechaism,

The thermo-oxidative ageing experiment of step 1, silicon rubber

First silicone rubber test pieces is carried out to hot oxygen accelerated aging test.The fixture of experiment use is the compression clamp that machining manufacturing plant of Harbin Institute of Technology manufactures, and it is of a size of 240x30x18mm.The hot-air exchange test case that the thermo-oxidative ageing case of experiment use provides for Wuxi Ke Laimu environmental science and technology company limited, its operating room is of a size of 450x450x500mm, temperature fluctuation≤± 0.5K.

Carry out silicon rubber baking oven accelerated aging test with reference to GB GB/T 3512; Before sample is put into ageing oven, according to GB/T2941-2006 " preparation of rubber physical test method sample and adjusting universal program ", all samples are carried out to pre-service; With reference to GB GB/T 1683, sample is put among fixture, in each fixture, put 4 samples, between each sample, distance is greater than 5mm, compressibility 25%.According to the regulation in ISO:11346-2004 " assessment of sulfuration or thermoplastic rubber-serviceable life and maximum operation (service) temperature ", the time that the highest test temperature should make material property reach critical value is not less than 100h; The time that minimum test temperature should make material property reach critical value is at least 1000h.The selection of test temperature need meet GB/T 2941-2006.According to " preparation of rubber physical test method sample and adjusting universal program ", selected 250 DEG C, 180 DEG C, 165 DEG C, 150 DEG C, 135 DEG C, 120 DEG C as silicon rubber accelerated test temperature spot.

Step 2, aging test specimen is carried out to X diffraction light electronic energy spectrum test and nuclear magnetic resonance test

Aging test specimen after hot oxygen accelerated deterioration under different condition is carried out respectively to the test of X diffraction light electronic energy spectrum and nuclear magnetic resonance test.The experiment condition of XPS is: the Al Ka source of X source monochromatization, energy: 1486.6eV, 10mA × 15KV, bundle spot size: 700 × 300 μ m; Scan pattern: CAE; Full spectrum scanning: logical can be 160eV.

Nuclear magnetic resonance apparatus is Bruker AVANCE III 400 WB.Nuclear magnetic spectrum instrument has been equipped with the gauge orifice of 4 millimeters, and the X passage of its probe is 79.50 megahertzes, and other passages are adjusted to 400 megahertzes.Dry fine-powdered sample is contained in the titanium rotor of sealing, is rotated with the frequency of 5kHZ.Each sample is carried out to 10000 scanning record altogether.

Obtain the element spectrogram of the silicon rubber under different aging conditions by the test of XPS and nuclear magnetic resonance.

Step 3, XPS and NMR test result are analyzed

Learn from the result of XPS, along with the increase of aging temperature and digestion time, in silastic material, C constituent content reduces gradually, and O constituent content increases gradually, this is the increase that causes oxygen element due to dioxygen oxidation silicon rubber side group, formation hydrocarbon is lost in air and causes carbon to reduce, and element silicon is carried out to swarming processing, and Si element has following three kinds of chemical environment SiO in siloxane ₂c ₂, SiO ₃c, SiO ₄corresponding chemical bond energy position is 101.9,102.8,103.6 respectively.Peak to these three chemical bond energy positions carries out the calculating of peak area, draws the relative scale of these three kinds of environment under different aging conditions.Learn and be all under aging 57h, along with aging temperature is increased to 150 DEG C again to 180 DEG C, SiO by 120 DEG C ₂c ₂relative content from 51% to 27% again to 23%, reduce gradually and SiO ₃the relative content of C from 43% to 48% is to 63% the trend that raises gradually again.See the increase facing to aging temperature and digestion time from the result of nuclear magnetic resonance.The relative content of silicon hydroxyl reduces, and SiO ₃c and SiO ₄relative content increase.The variation of the relative content by silicon hydroxyl is learnt thus, and silicon rubber main side group that occurs in ageing process is aging and forms silicon hydroxyl, but along with aging carrying out, silicon hydroxyl radical attacks siloxane main chain forms cross-linked structure and ring texture.By the test of above chemical detection can analyze silicon rubber ageing process comprise side group be oxidized by oxygen crosslinked, react with moisture in air and form silicon hydroxyl, silicon hydroxyl and react with main chain and form three main reactions of cross-linked structure.

Step 4, utilize compression set to the analysis of ageing process energy of activation

1, the energy of activation analytical approach of silicon rubber ageing process

Research silicon rubber ageing properties y and time t funtcional relationship, determine that its expression formula is as follows:

$y={\mathrm{Be}}^{{-\mathrm{K\τ}}^{\mathrm{\α}}}---\left(1\right)$

In formula: B---constant;

K---velocity constant, d ^-1;

α---empirical constant;

τ---digestion time, d;

Y---represent ageing properties index, if select compression set ε as aging characteristics index, y=1-ε;

Between velocity constant K and aging temperature T, in certain temperature range, obey Arrhenius formula:

K＝Ae ^-E/RT (2)

In formula: E---apparent activation energy, J/mol ^-1;

R---gas law constant (equals 8.314Jmol ^-1k ^-1);

T---absolute temperature, K;

Definite method of undetermined parameter α is successive approximation method, and its criterion is to be accurate to after radix point the undetermined parameter α of 2 to make the I value in formula (3) minimum.

$I=\underset{i=1}{\overset{p}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(y_{\mathrm{ij}}-{\hat{y}}_{\mathrm{ij}})}^2---\left(3\right)$

In formula: y _ij---when i temperature, the trial value of the compression set rate of its j testing site;

---when i temperature, the predicted value of the compression set rate of its j testing site.

In order to calculate the value of empirical constant α, first formula (1) is obtained to its form of straight lines after log-transformation, as follows:

Y＝a+bX (4)

In formula:

Y＝lgy；a＝lgB； X＝τ ^α

Adopt least square method estimated parameter a and b:

$b_i=\frac{\mathrm{\ΣXY}-\frac{\mathrm{\ΣX}\·\mathrm{\ΣY}}{n}}{\mathrm{\Σ}{X}^2-\frac{{\left(\mathrm{\ΣX}\right)}^2}{n}}---\left(5\right)$

$a_i=\frac{\mathrm{\ΣY}}{n}-b\·\frac{\mathrm{\ΣX}}{n}---\left(6\right)$

Can try to achieve thus p the velocity constant K under test temperature _i=-2.303b _iwith the test constant B trying to achieve like this in formula (1) is:

$\hat{B}=\frac{\mathrm{\Σ}{B}_i}{p}---\left(7\right)$

Then formula (2) is carried out to log-transformation, obtains:

W＝C+DZ (8)

In formula:

W＝lgK；C＝lgA； Z＝T ^-1

Adopt least square method estimated parameter C and D:

$D=\frac{\mathrm{\ΣWZ}-\frac{\mathrm{\ΣW}\·\mathrm{\ΣZ}}{p}}{\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}}---\left(9\right)$

$C=\frac{\mathrm{\ΣW}}{p}-D\·\frac{\mathrm{\ΣZ}}{p}---\left(10\right)$

The estimated value that can try to achieve thus p the velocity constant K under test temperature is:

${\hat{K}}_i={10}^{(C+{\mathrm{DZ}}_i)}---\left(11\right)$

Will with value bring formula (1) into, obtain so formula (3) becomes:

$I==\underset{i=1}{\overset{p}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(y_{\mathrm{ij}}-\hat{B}{e}^{-{\hat{K}}_i{{\mathrm{\τ}}^{\mathrm{\α}}}_{\mathrm{ij}}})}^2---\left(12\right)$

From above formula, find out that I is the function about empirical constant α.Convert different α values and attempt, constantly dwindle and attempt interval and trial interval.When empirical constant α is a number that is accurate to 2 significant digits, and make I value hour, this number is exactly its solution.

Verify the linear dependence of W=C+DZ equation with r method of inspection, the calculating formula of correlation coefficient r is as follows:

$r=\frac{\mathrm{\ΣWZ}-\frac{\mathrm{\ΣW}\·\mathrm{\ΣZ}}{p}}{\sqrt{[\mathrm{\Σ}{W}^2-\frac{{\left(\mathrm{\ΣW}\right)}^2}{p}][\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}]}}---\left(13\right)$

The standard deviation calculation method of W is as follows:

$S_W=S\sqrt{1+\frac{1}{p}+\frac{{(Z_0-\stackrel{\‾}{Z})}^2}{[\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}]}}---\left(14\right)$

In formula:

$S=\sqrt{\frac{(1-r^2)[\mathrm{\Σ}{W}^2-\frac{{\left(\mathrm{\ΣW}\right)}^2}{p}]}{p-2}}$

The upper limit of the fiducial limit of W is:

W＝C+DZ+tS _W (15)

T value in can finding formula in the numerical tabular that is df=p-2 in degree of freedom, its level of significance is 0.05.If the calculated value of correlation coefficient r is greater than tabular value, W and Z linear dependence, equation is set up; Otherwise W is uncorrelated with Z linearity, and equation is untenable.

2, utilize energy of activation to change to analyze the variation of agine mechaism

Utilize the computing method of energy of activation above, application Matlab programming calculates the parameter in method.By calculating in the time that empirical constant α value is 0.38, I value minimum is 0.05799.By the value of α bring formula (5) into, (6) obtain a _iand b _i, and then try to achieve test constant B and aging speed constant K at each temperature.1000/T is mapped with lgK, each section of slope of a curve represents energy of activation, can find out that the slope of three sections is significantly different, and in a course of reaction, in the time that the ratio of a certain reaction wherein changes, energy of activation can change.Along with the rising of temperature of reaction, energy of activation reduces gradually, analyze thus silicon rubber in ageing process, along with the rising of temperature of reaction, three reaction velocitys that occur are all accelerated, and silicon hydroxyl radical attacks main chain forms the fastest that this reaction rate of crosslink bond increases, and therefore the proportion of this reaction increases, and the energy of activation of this reaction is lower with respect to the energy of activation of other reactions, therefore overall energy of activation declines.

Change energy of activation of the present invention is analyzed the method for silicon rubber agine mechaism, by test chemical, agine mechaism is carried out to preliminary analysis, and utilize this calculation of parameter of physical property variation compression set to derive the change curve of energy of activation, by energy of activation, both are combined to analysis agine mechaism, just can infer more accurately the mechanism of silicon rubber in ageing process, be a kind of simple and practical silicon rubber mechanism based method analysis, there is to very large meaning later research silicon rubber agine mechaism aspect.

Brief description of the drawings

Fig. 1 is that silicon rubber becomes energy of activation Arrhenius figure.

Embodiment

The present invention is described in further detail below: the present embodiment is implemented under taking technical solution of the present invention as prerequisite, provided detailed embodiment, but protection scope of the present invention is not limited to following embodiment.

A kind of method that becomes energy of activation analysis silicon rubber agine mechaism of utilizing that the present embodiment is related, concrete operation step is as follows:

The thermo-oxidative ageing experiment of step 1, silicon rubber

First silicone rubber test pieces is carried out to hot oxygen accelerated aging test.The fixture of experiment use is the compression clamp that machining manufacturing plant of Harbin Institute of Technology manufactures, and it is of a size of 240x30x18mm.The hot-air exchange test case that the thermo-oxidative ageing case of experiment use provides for Wuxi Ke Laimu environmental science and technology company limited, its operating room is of a size of 450x450x500mm, temperature fluctuation≤± 0.5K.

Carry out silicon rubber baking oven accelerated aging test with reference to GB GB/T 3512; Before sample is put into ageing oven, according to GB/T2941-2006 " preparation of rubber physical test method sample and adjusting universal program ", all samples are carried out to pre-service; With reference to GB GB/T 1683, sample is put among fixture, in each fixture, put 4 samples, between each sample, distance is greater than 5mm, compressibility 25%.According to the regulation in ISO:11346-2004 " assessment of sulfuration or thermoplastic rubber-serviceable life and maximum operation (service) temperature ", the time that the highest test temperature should make material property reach critical value is not less than 100h; The time that minimum test temperature should make material property reach critical value is at least 1000h.The selection of test temperature need meet GB/T 2941-2006.According to " preparation of rubber physical test method sample and adjusting universal program ", selected 250 DEG C, 180 DEG C, 165 DEG C, 150 DEG C, 135 DEG C, 120 DEG C as silicon rubber accelerated test temperature spot.

Step 2, aging test specimen is carried out to X diffraction light electronic energy spectrum test and nuclear magnetic resonance test

Aging test specimen after hot oxygen accelerated deterioration under different condition is carried out respectively to the test of X diffraction light electronic energy spectrum and nuclear magnetic resonance test.The experiment condition of XPS is: the Al Ka source of X source monochromatization, energy: 1486.6eV, 10mA × 15KV, bundle spot size: 700 × 300 μ m; Scan pattern: CAE; Full spectrum scanning: logical can be 160eV.

Nuclear magnetic resonance apparatus is Bruker AVANCE III 400 WB.Nuclear magnetic spectrum instrument has been equipped with the gauge orifice of 4 millimeters, and the X passage of its probe is 79.50 megahertzes, and other passages are adjusted to 400 megahertzes.Dry fine-powdered sample is contained in the titanium rotor of sealing, is rotated with the frequency of 5kHZ.Each sample is carried out to 10000 scanning record altogether.

Obtain the element spectrogram of the silicon rubber under different aging conditions by the test of XPS and nuclear magnetic resonance.

Step 3, XPS and NMR test result are analyzed

Learn from the result of XPS, along with the increase of aging temperature and digestion time, in silastic material, C constituent content reduces gradually, and O constituent content increases gradually, this is the increase that causes oxygen element due to dioxygen oxidation silicon rubber side group, formation hydrocarbon is lost in air and causes carbon to reduce, and element silicon is carried out to swarming processing, and Si element has following three kinds of chemical environment SiO in siloxane ₂c ₂, SiO ₃c, SiO ₄corresponding chemical bond energy position is 101.9,102.8,103.6 respectively.Peak to these three chemical bond energy positions carries out the calculating of peak area, draws the relative scale of these three kinds of environment under different aging conditions.Learn and be all under aging 57h, along with aging temperature is increased to 150 DEG C again to 180 DEG C, SiO by 120 DEG C ₂c ₂relative content from 51% to 27% again to 23%, reduce gradually and SiO ₃the relative content of C from 43% to 48% is to 63% the trend that raises gradually again.See the increase facing to aging temperature and digestion time from the result of nuclear magnetic resonance.The relative content of silicon hydroxyl reduces, and SiO ₃c and SiO ₄relative content increase.The variation of the relative content by silicon hydroxyl is learnt thus, and silicon rubber main side group that occurs in ageing process is aging and forms silicon hydroxyl, but along with aging carrying out, silicon hydroxyl radical attacks siloxane main chain forms cross-linked structure and ring texture.By the test of above chemical detection can analyze silicon rubber ageing process comprise side group be oxidized by oxygen crosslinked, react with moisture in air and form silicon hydroxyl, silicon hydroxyl and react with main chain and form three main reactions of cross-linked structure.

Step 4, utilize compression set to the analysis of ageing process energy of activation

1, the energy of activation analytical approach of silicon rubber ageing process

Research silicon rubber ageing properties y and time t funtcional relationship, determine that its expression formula is as follows:

$y={\mathrm{Be}}^{{-\mathrm{K\τ}}^{\mathrm{\α}}}---\left(1\right)$

In formula: B---constant;

K---velocity constant, d ^-1;

α---empirical constant;

τ---digestion time, d;

Y---represent ageing properties index, if select compression set ε as aging characteristics index, y=1-ε;

Between velocity constant K and aging temperature T, in certain temperature range, obey Arrhenius formula:

K＝Ae ^-E/RT (2)

In formula: E---apparent activation energy, J/mol ^-1;

R---gas law constant (equals 8.314Jmol ^-1k ^-1);

T---absolute temperature, K;

Definite method of undetermined parameter α is successive approximation method, and its criterion is to be accurate to after radix point the undetermined parameter α of 2 to make the I value in formula (3) minimum.

$I=\underset{i=1}{\overset{p}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(y_{\mathrm{ij}}-{\hat{y}}_{\mathrm{ij}})}^2---\left(3\right)$

In formula: y _ij---when i temperature, the trial value of the compression set rate of its j testing site;

---when i temperature, the predicted value of the compression set rate of its j testing site.

In order to calculate the value of empirical constant α, first formula (1) is obtained to its form of straight lines after log-transformation, as follows:

Y＝a+bX (4)

In formula:

Y＝lgy；a＝lgB； X＝τ ^α

Adopt least square method estimated parameter a and b:

$b_i=\frac{\mathrm{\ΣXY}-\frac{\mathrm{\ΣX}\·\mathrm{\ΣY}}{n}}{\mathrm{\Σ}{X}^2-\frac{{\left(\mathrm{\ΣX}\right)}^2}{n}}---\left(5\right)$

$a_i=\frac{\mathrm{\ΣY}}{n}-b\·\frac{\mathrm{\ΣX}}{n}---\left(6\right)$

Can try to achieve thus p the velocity constant K under test temperature _i=-2.303b _iwith the test constant B trying to achieve like this in formula (1) is:

$\hat{B}=\frac{\mathrm{\Σ}{B}_i}{p}---\left(7\right)$

Then formula (2) is carried out to log-transformation, obtains:

W＝C+DZ (8)

In formula:

W＝lgK；C＝lgA； Z＝T ^-1

Adopt least square method estimated parameter C and D:

$D=\frac{\mathrm{\ΣWZ}-\frac{\mathrm{\ΣW}\·\mathrm{\ΣZ}}{p}}{\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}}---\left(9\right)$

$C=\frac{\mathrm{\ΣW}}{p}-D\·\frac{\mathrm{\ΣZ}}{p}---\left(10\right)$

The estimated value that can try to achieve thus p the velocity constant K under test temperature is:

${\hat{K}}_i={10}^{(C+{\mathrm{DZ}}_i)}---\left(11\right)$

Will with value bring formula (1) into, obtain so formula (3) becomes:

$I==\underset{i=1}{\overset{p}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(y_{\mathrm{ij}}-\hat{B}{e}^{-{\hat{K}}_i{{\mathrm{\τ}}^{\mathrm{\α}}}_{\mathrm{ij}}})}^2---\left(12\right)$

From above formula, find out that I is the function about empirical constant α.Convert different α values and attempt, constantly dwindle and attempt interval and trial interval.When empirical constant α is a number that is accurate to 2 significant digits, and make I value hour, this number is exactly its solution.

Verify the linear dependence of W=C+DZ equation with r method of inspection, the calculating formula of correlation coefficient r is as follows:

$r=\frac{\mathrm{\ΣWZ}-\frac{\mathrm{\ΣW}\·\mathrm{\ΣZ}}{p}}{\sqrt{[\mathrm{\Σ}{W}^2-\frac{{\left(\mathrm{\ΣW}\right)}^2}{p}][\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}]}}---\left(13\right)$

The standard deviation calculation method of W is as follows:

$S_W=S\sqrt{1+\frac{1}{p}+\frac{{(Z_0-\stackrel{\‾}{Z})}^2}{[\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}]}}---\left(14\right)$

In formula:

$S=\sqrt{\frac{(1-r^2)[\mathrm{\Σ}{W}^2-\frac{{\left(\mathrm{\ΣW}\right)}^2}{p}]}{p-2}}$

The upper limit of the fiducial limit of W is:

W＝C+DZ+tS _W (15)

T value in can finding formula in the numerical tabular that is df=p-2 in degree of freedom, its level of significance is 0.05.If the calculated value of correlation coefficient r is greater than tabular value, W and Z linear dependence, equation is set up; Otherwise W is uncorrelated with Z linearity, and equation is untenable.

2, utilize energy of activation to change to analyze the variation of agine mechaism

Utilize the computing method of energy of activation above, application Matlab programming calculates the parameter in method.By calculating in the time that empirical constant α value is 0.38, I value minimum is 0.05799.By the value of α bring formula (5) into, (6) obtain a _iand b _i, and then try to achieve test constant B and aging speed constant K at each temperature.1000/T is mapped with lgK, as shown in Figure 1, each section of slope of a curve represents energy of activation, can find out that the slope of three sections is significantly different, and in a course of reaction, in the time that the ratio of a certain reaction wherein changes, energy of activation can change.Along with the rising of temperature of reaction, energy of activation reduces gradually, analyze thus silicon rubber in ageing process, along with the rising of temperature of reaction, three reaction velocitys that occur are all accelerated, and silicon hydroxyl radical attacks main chain forms the fastest that this reaction rate of crosslink bond increases, and therefore the proportion of this reaction increases, and the energy of activation of this reaction is lower with respect to the energy of activation of other reactions, therefore overall energy of activation declines.

The above; it is only preferably embodiment of the present invention; these embodiments are all the different implementations based under general idea of the present invention; and protection scope of the present invention is not limited to this; every be familiar with those skilled in the art the present invention disclose technical scope in; the variation that can expect easily or replacement, within all should being encompassed in protection scope of the present invention.Therefore, protection scope of the present invention is as the criterion with the protection domain of claims.

Claims (1)

1. utilize a method that becomes energy of activation analysis silicon rubber agine mechaism, it is characterized in that,

The thermo-oxidative ageing experiment of step 1, silicon rubber

First silicone rubber test pieces is carried out to hot oxygen accelerated aging test, the fixture of experiment use is the compression clamp that machining manufacturing plant of Harbin Institute of Technology manufactures, it is of a size of 240x30x18mm, the hot-air exchange test case that the thermo-oxidative ageing case of experiment use provides for Wuxi Ke Laimu environmental science and technology company limited, its operating room is of a size of 450x450x500mm, temperature fluctuation≤± 0.5K;

Carry out silicon rubber baking oven accelerated aging test with reference to GB GB/T 3512; Before sample is put into ageing oven, according to GB/T2941-2006 " preparation of rubber physical test method sample and adjusting universal program ", all samples are carried out to pre-service; With reference to GB GB/T 1683, sample is put among fixture, in each fixture, put 4 samples, between each sample, distance is greater than 5mm, compressibility 25%; According to the regulation in ISO:11346-2004 " assessment of sulfuration or thermoplastic rubber-serviceable life and maximum operation (service) temperature ", the time that the highest test temperature should make material property reach critical value is not less than 100h; The time that minimum test temperature should make material property reach critical value is at least 1000h; The selection of test temperature need meet GB/T 2941-2006; According to " rubber physical test method sample preparation and regulate universal program ", selected 250 DEG C, 180 DEG C, 165 DEG C, 150 DEG C, 135 DEG C and 120 DEG C are as silicon rubber accelerated test temperature spot;

Step 2, aging test specimen is carried out to X diffraction light electronic energy spectrum test and nuclear magnetic resonance test

Aging test specimen after hot oxygen accelerated deterioration under different condition is carried out respectively to the test of X diffraction light electronic energy spectrum and nuclear magnetic resonance test; The experiment condition of XPS is: the Al Ka source of X source monochromatization, energy: 1486.6eV, 10mA × 15KV, bundle spot size: 700 × 300 μ m; Scan pattern: CAE; Full spectrum scanning: logical can be 160eV;

Nuclear magnetic resonance apparatus is Bruker AVANCE III 400 WB; Nuclear magnetic spectrum instrument has been equipped with the gauge orifice of 4 millimeters, and the X passage of its probe is 79.50 megahertzes, and other passages are adjusted to 400 megahertzes; Dry fine-powdered sample is contained in the titanium rotor of sealing, is rotated with the frequency of 5kHZ, and each sample is carried out to 10000 scanning record altogether;

Obtain the element spectrogram of the silicon rubber under different aging conditions by the test of XPS and nuclear magnetic resonance;

Step 3, XPS and NMR test result are analyzed

Learn from the result of XPS, along with the increase of aging temperature and digestion time, in silastic material, C constituent content reduces gradually, and O constituent content increases gradually, this is the increase that causes oxygen element due to dioxygen oxidation silicon rubber side group, formation hydrocarbon is lost in air and causes carbon to reduce, and element silicon is carried out to swarming processing, and Si element has following three kinds of chemical environment SiO in siloxane ₂c ₂, SiO ₃c, SiO ₄corresponding chemical bond energy position is 101.9,102.8,103.6 respectively; Peak to these three chemical bond energy positions carries out the calculating of peak area, draws the relative scale of these three kinds of environment under different aging conditions; Learn and be all under aging 57h, along with aging temperature is increased to 150 DEG C again to 180 DEG C, SiO by 120 DEG C ₂c ₂relative content from 51% to 27% again to 23%, reduce gradually and SiO ₃the relative content of C from 43% to 48% is to 63% the trend that raises gradually again; See that from the result of nuclear magnetic resonance the relative content of silicon hydroxyl reduces facing to the increase of aging temperature and digestion time, and SiO ₃c and SiO ₄relative content increase, the variation of the relative content by silicon hydroxyl is learnt thus, silicon rubber main side group that occurs in ageing process is aging formation silicon hydroxyl, but along with aging carrying out, silicon hydroxyl radical attacks siloxane main chain forms cross-linked structure and ring texture, by above chemical detection test can analyze silicon rubber ageing process comprise side group be oxidized by oxygen crosslinked, react with moisture in air and form silicon hydroxyl, silicon hydroxyl and react with main chain and form three main reactions of cross-linked structure;

Step 4, utilize compression set to the analysis of ageing process energy of activation

1, the energy of activation analytical approach of silicon rubber ageing process

Research silicon rubber ageing properties y and time t funtcional relationship, determine that its expression formula is as follows:

$y={\mathrm{Be}}^{{-\mathrm{K\τ}}^{\mathrm{\α}}}---\left(1\right)$

In formula: B---constant;

K---velocity constant, d ^-1;

α---empirical constant;

τ---digestion time, d;

Y---represent ageing properties index, if select compression set ε as aging characteristics index, y=1-ε;

Between velocity constant K and aging temperature T, in certain temperature range, obey Arrhenius formula:

K＝Ae ^-E/RT (2)

In formula: E---apparent activation energy, J/mol ^-1;

R---gas law constant (equals 8.314Jmol ^-1k ^-1);

T---absolute temperature, K;

Definite method of undetermined parameter α is successive approximation method, and its criterion is to be accurate to after radix point the undetermined parameter α of 2 to make the I value in formula (3) minimum;

$I=\underset{i=1}{\overset{p}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(y_{\mathrm{ij}}-{\hat{y}}_{\mathrm{ij}})}^2---\left(3\right)$

In formula: y _ij---when i temperature, the trial value of the compression set rate of its j testing site;

---when i temperature, the predicted value of the compression set rate of its j testing site;

In order to calculate the value of empirical constant α, first formula (1) is obtained to its form of straight lines after log-transformation, as follows:

Y＝a+bX (4)

In formula:

Y＝lgy；a＝lgB； X＝τ ^α

Adopt least square method estimated parameter a and b:

$b_i=\frac{\mathrm{\ΣXY}-\frac{\mathrm{\ΣX}\·\mathrm{\ΣY}}{n}}{\mathrm{\Σ}{X}^2-\frac{{\left(\mathrm{\ΣX}\right)}^2}{n}}---\left(5\right)$

$a_i=\frac{\mathrm{\ΣY}}{n}-b\·\frac{\mathrm{\ΣX}}{n}---\left(6\right)$

Can try to achieve thus p the velocity constant K under test temperature _i=-2.303b _iwith the test constant B trying to achieve like this in formula (1) is:

$\hat{B}=\frac{\mathrm{\Σ}{B}_i}{p}---\left(7\right)$

Then formula (2) is carried out to log-transformation, obtains:

W＝C+DZ (8)

In formula:

W＝lgK；C＝lgA； Z＝T ^-1

Adopt least square method estimated parameter C and D:

$D=\frac{\mathrm{\ΣWZ}-\frac{\mathrm{\ΣW}\·\mathrm{\ΣZ}}{p}}{\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}}---\left(9\right)$

$C=\frac{\mathrm{\ΣW}}{p}-D\·\frac{\mathrm{\ΣZ}}{p}---\left(10\right)$

The estimated value that can try to achieve thus p the velocity constant K under test temperature is:

${\hat{K}}_i={10}^{(C+{\mathrm{DZ}}_i)}---\left(11\right)$

Will with value bring formula (1) into, obtain so formula (3) becomes:

$I==\underset{i=1}{\overset{p}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(y_{\mathrm{ij}}-\hat{B}{e}^{-{\hat{K}}_i{{\mathrm{\τ}}^{\mathrm{\α}}}_{\mathrm{ij}}})}^2---\left(12\right)$

From above formula, find out that I is the function about empirical constant α, convert different α values and attempt, constantly dwindle and attempt interval and trial interval.When empirical constant α is a number that is accurate to 2 significant digits, and make I value hour, this number is exactly its solution;

Verify the linear dependence of W=C+DZ equation with r method of inspection, the calculating formula of correlation coefficient r is as follows:

$r=\frac{\mathrm{\ΣWZ}-\frac{\mathrm{\ΣW}\·\mathrm{\ΣZ}}{p}}{\sqrt{[\mathrm{\Σ}{W}^2-\frac{{\left(\mathrm{\ΣW}\right)}^2}{p}][\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}]}}---\left(13\right)$

The standard deviation calculation method of W is as follows:

$S_W=S\sqrt{1+\frac{1}{p}+\frac{{(Z_0-\stackrel{\‾}{Z})}^2}{[\mathrm{\Σ}{Z}^2-\frac{{\left(\mathrm{\ΣZ}\right)}^2}{p}]}}---\left(14\right)$

In formula:

$S=\sqrt{\frac{(1-r^2)[\mathrm{\Σ}{W}^2-\frac{{\left(\mathrm{\ΣW}\right)}^2}{p}]}{p-2}}$

The upper limit of the fiducial limit of W is:

W＝C+DZ+tS _W (15)

T value in can finding formula in the numerical tabular that is df=p-2 in degree of freedom, its level of significance is 0.05, if the calculated value of correlation coefficient r is greater than tabular value, W and Z linear dependence, equation is set up; Otherwise W is uncorrelated with Z linearity, and equation is untenable;

2, utilize energy of activation to change to analyze the variation of agine mechaism

Utilize the computing method of energy of activation above, application Matlab programming calculates the parameter in method, and by calculating in the time that empirical constant α value is 0.38, I value minimum is 0.05799, by the value of α bring formula (5) into, (6) obtain a _iand b _i, and then try to achieve test constant B and aging speed constant K at each temperature, 1000/T is mapped with lgK, each section of slope of a curve represents energy of activation, the slope that can find out three sections is significantly different, and in a course of reaction, in the time that the ratio of a certain reaction wherein changes, energy of activation can change, along with the rising of temperature of reaction, energy of activation reduces gradually, analyze thus silicon rubber in ageing process, along with the rising of temperature of reaction, three reaction velocitys that occur are all accelerated, and silicon hydroxyl radical attacks main chain forms the fastest that this reaction rate of crosslink bond increases, therefore the proportion of this reaction increases, and the energy of activation of this reaction is lower with respect to the energy of activation of other reactions, therefore overall energy of activation declines.