CN104634950A - Method for analyzing silicone rubber aging mechanism by utilizing variable activation energy - Google Patents

Abstract

The invention provides a method for analyzing a silicone rubber aging mechanism by utilizing variable activation energy, and belongs to the technical field of methods for analyzing the silicone rubber aging mechanism. The method disclosed by the invention comprises the following four steps: carrying out a thermo-oxidative aging experiment on silicone rubber, performing X-ray diffraction photoelectron spectroscopy testing and nuclear magnetic resonance testing on the aged test piece, analyzing the testing results of XPS and NMR, and analyzing the activation energy in the aging process by utilizing compression deformation. According to the method for analyzing the silicone rubber aging mechanism by utilizing the variable activation energy, the aging mechanism is preliminarily analyzed by virtue of a chemical test, the changing curve of the activation energy is calculated and deduced by utilizing parameters, namely physical property change and compression deformation, the physical property change and compression deformation are combined to analyze the aging mechanism by virtue of the activation energy, and the mechanism of the silicone rubber in the aging process can be accurately deduced. The method is a method for easily and practically analyzing a silicone rubber mechanism and has high significance on researching the silicone rubber aging mechanism in the future.

Description

A kind of utilization becomes the method that energy of activation analyzes silicon rubber agine mechaism

Technical field

The present invention relates to a kind of utilization and become the method that energy of activation analyzes silicon rubber agine mechaism, belong to and analyze silicon rubber agine mechaism method and technology field.

Background technology

Rubber is the strong flexible polymer 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, be thus 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 by 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 if in the relatively short military service process of rubber parts, the aging and degradation problem of rubber parts is still the key factor affecting its storage reliability.And the immediate cause that after ageing of rubber, physical property declines is exactly that elastomeric material there occurs chemical reaction, strand and functional group there occurs change, and the agine mechaism after therefore studying ageing of rubber is the basic of performance change after research ageing of rubber.Fundamentally can also be understood the reason of 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, play an important role in follow-up study ageing of rubber.

In the process of research ageing of rubber mechanism, the change of ageing of rubber mechanism can be symbolized by the change of research ageing process energy of activation.The agine mechaism of rubber under a certain condition contains 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 there is some reaction increases, and proportion of some reaction reduces.And in ageing process, when the proportion reacted changes, the energy of activation of whole aging reaction can change, and just the change by energy of activation is mapped with the change of reaction proportion like this in research process, the agine mechaism further in the whole ageing process of research.

Summary of the invention

The object of the invention is to solve above-mentioned prior art Problems existing, namely in order to make rubber product be applied to reality better, understanding and grasping its aging rule.And then provide a kind of utilization to become the method that energy of activation analyzes silicon rubber agine mechaism.

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

Utilize and become the method that energy of activation analyzes silicon rubber agine mechaism,

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

First hot oxygen accelerated aging test is carried out to silicone rubber test pieces.The fixture of experiment is the compression clamp that machining manufacturing plant of Harbin Institute of Technology manufactures, and it is of a size of 240 x 30 x 18mm.The hot-air exchange test case that the thermo-oxidative ageing case of testing provides for Wuxi Ke Laimu environmental science and technology company limited, its operating room is of a size of 450 x 450 x 500mm, temperature fluctuation≤± 0.5K.

Silicon rubber baking oven accelerated aging test is carried out 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 adjustment universal program ", pre-service is carried out to all samples; With reference to GB GB/T 1683, put into by sample among fixture, put 4 samples in each fixture, the spacing of each sample 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 adjustment 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 carried out to the test of X diffraction light electronic energy spectrum and nuclear magnetic resonance test

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

Nuclear magnetic resonance apparatus is Bruker AVANCE III 400 WB.Nuclear magnetic spectrometry is equipped with the gauge orifice of 4 millimeters, and the X passage of its probe is 79.50 megahertzes, and other passages carry out adjusting to 400 megahertzes.Dry fine-powdered sample is contained in closed titanium rotor, rotates with the frequency of 5kHZ.10000 scanning is carried out altogether and record to each sample.

The element spectrogram of the silicon rubber under different aging condition is obtained by the test of XPS and nuclear magnetic resonance.

Step 3, XPS and NMR test result to be analyzed

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

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:

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

In formula: B---constant;

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

α---empirical constant;

τ---digestion time, d;

Y---represent ageing properties index, if Selective Pressure compression permanent deformation ε is as aging characteristics index, then y=1-ε;

In certain temperature range, Arrhenius formula is obeyed between velocity constant K and aging temperature T:

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;

The defining method of undetermined parameter α is successive approximation method, and its criterion is that the undetermined parameter α of after being accurate to radix point 2 makes 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---during i-th temperature, the trial value of the compression set rate of its jth testing site;

---during i-th temperature, the predicted value of the compression set rate of its jth testing site.

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

Y＝a+bX (4)

In formula:

$Y=\mathrm{lgy};a=\mathrm{lgB};b=-\frac{K}{2.303};X={\mathrm{\τ}}^{\mathrm{\α}}$

Adopt Least Square Method parameter a and b:

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

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

The velocity constant under p test temperature can be tried to achieve thus the test constant B tried 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 log-transformation, obtains:

W＝C+DZ (8)

In formula:

$W=\mathrm{lgK};C=\mathrm{lgA};D=-\frac{E}{2.303R};Z=T^{-1}$

Adopt Least Square Method 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 can trying to achieve the velocity constant K under p test temperature is thus:

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

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 to attempt, constantly reduce and attempt interval and attempt interval.When empirical constant α is a number being accurate to 2 significant digits, and when making I value minimum, this number is exactly that it is separated.

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

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

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:

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

Then the upper limit of the fiducial limit of W is:

W＝C+DZ+tS _W(15)

Be can find t value in formula in the numerical tabular of 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, then W and Z linear correlation, equation is set up; Otherwise then W and Z is linearly uncorrelated, equation is untenable.

2, utilize energy of activation to change the change analyzing agine mechaism

Utilize the computing method of energy of activation above, application Matlab program calculation goes out the parameter in method.By calculating when empirical constant α value is 0.38, I value is minimum is 0.05799.The value of α is brought into formula (5), (6) obtain a _iand b _i, and then try to achieve test constant B and aging speed constant K at each temperature.Map to 1000/T 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, when 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 silicon rubber thus in ageing process, along with the rising of temperature of reaction, three reaction velocitys occurred all are accelerated, and silicone hydroxyl attack main chain forms the fastest of this reaction rate of crosslink bond increase, and proportion of therefore this reaction increases, and the energy of activation that the energy of activation of this reaction reacts relative to other is lower, therefore overall energy of activation declines.

Change energy of activation of the present invention analyzes the method for silicon rubber agine mechaism, by test chemical, preliminary analysis is carried out to agine mechaism, and utilize physical property to change this parameter of compression set and calculate the change curve deriving energy of activation, by energy of activation, both are combined analysis agine mechaism, just can infer the mechanism of silicon rubber in ageing process more accurately, be a kind of simple and silicon rubber mechanism based method analysis of practicality, have very large meaning to research silicon rubber agine mechaism aspect later.In addition, it is high that the present invention also has analysis silicon rubber agine mechaism accuracy rate, maneuverable feature.

Accompanying drawing explanation

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 premised on technical solution of the present invention, gives detailed embodiment, but protection scope of the present invention is not limited to following embodiment.

A kind of utilization involved by the present embodiment becomes the method that energy of activation analyzes silicon rubber agine mechaism, and concrete operation step is as follows:

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

First hot oxygen accelerated aging test is carried out to silicone rubber test pieces.The fixture of experiment is the compression clamp that machining manufacturing plant of Harbin Institute of Technology manufactures, and it is of a size of 240 x 30 x 18mm.The hot-air exchange test case that the thermo-oxidative ageing case of testing provides for Wuxi Ke Laimu environmental science and technology company limited, its operating room is of a size of 450 x 450 x 500mm, temperature fluctuation≤+ 0.5K.

Silicon rubber baking oven accelerated aging test is carried out 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 adjustment universal program ", pre-service is carried out to all samples; With reference to GB GB/T 1683, put into by sample among fixture, put 4 samples in each fixture, the spacing of each sample 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 adjustment 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 carried out to the test of X diffraction light electronic energy spectrum and nuclear magnetic resonance test

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

Nuclear magnetic resonance apparatus is Bruker AVANCE III 400 WB.Nuclear magnetic spectrometry is equipped with the gauge orifice of 4 millimeters, and the X passage of its probe is 79.50 megahertzes, and other passages carry out adjusting to 400 megahertzes.Dry fine-powdered sample is contained in closed titanium rotor, rotates with the frequency of 5kHZ.10000 scanning is carried out altogether and record to each sample.

The element spectrogram of the silicon rubber under different aging condition is obtained by the test of XPS and nuclear magnetic resonance.

Step 3, XPS and NMR test result to be analyzed

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

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:

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

In formula: B---constant;

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

α---empirical constant;

τ---digestion time, d;

Y---represent ageing properties index, if Selective Pressure compression permanent deformation ε is as aging characteristics index, then y=1-ε;

In certain temperature range, Arrhenius formula is obeyed between velocity constant K and aging temperature T:

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;

The defining method of undetermined parameter α is successive approximation method, and its criterion is that the undetermined parameter α of after being accurate to radix point 2 makes 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---during i-th temperature, the trial value of the compression set rate of its jth testing site;

---during i-th temperature, the predicted value of the compression set rate of its jth testing site.

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

Y＝a+bX (4)

In formula:

$Y=\mathrm{lgy};a=\mathrm{lgB};b=-\frac{K}{2.303};X={\mathrm{\τ}}^{\mathrm{\α}}$

Adopt Least Square Method parameter a and b:

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

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

The velocity constant under p test temperature can be tried to achieve thus the test constant B tried 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 log-transformation, obtains:

W＝C+DZ (8)

In formula:

$W=\mathrm{lgK};C=\mathrm{lgA};D=-\frac{E}{2.303R};Z=T^{-1}$

Adopt Least Square Method 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 can trying to achieve the velocity constant K under p test temperature is thus:

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

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 to attempt, constantly reduce and attempt interval and attempt interval.When empirical constant α is a number being accurate to 2 significant digits, and when making I value minimum, this number is exactly that it is separated.

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

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

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:

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

Then the upper limit of the fiducial limit of W is:

W＝C+DZ+tS _W(15)

Be can find t value in formula in the numerical tabular of 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, then W and Z linear correlation, equation is set up; Otherwise then W and Z is linearly uncorrelated, equation is untenable.

2, utilize energy of activation to change the change analyzing agine mechaism

Utilize the computing method of energy of activation above, application Matlab program calculation goes out the parameter in method.By calculating when empirical constant α value is 0.38, I value is minimum is 0.05799.The value of α is brought into formula (5), (6) obtain a _iand b _i, and then try to achieve test constant B and aging speed constant K at each temperature.Map to 1000/T 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, when 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 silicon rubber thus in ageing process, along with the rising of temperature of reaction, three reaction velocitys occurred all are accelerated, and silicone hydroxyl attack main chain forms the fastest of this reaction rate of crosslink bond increase, and proportion of therefore this reaction increases, and the energy of activation that the energy of activation of this reaction reacts relative to other is lower, therefore overall energy of activation declines.

The above; be only the present invention's preferably embodiment; these embodiments are all based on the different implementations under general idea of the present invention; and protection scope of the present invention is not limited thereto; everyly be familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within 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 and become the method that energy of activation analyzes silicon rubber agine mechaism, it is characterized in that,

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

First hot oxygen accelerated aging test is carried out to silicone rubber test pieces, the fixture of experiment 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 testing provides for Wuxi Ke Laimu environmental science and technology company limited, its operating room is of a size of 450x450x500mm, temperature fluctuation≤± 0.5K;

Silicon rubber baking oven accelerated aging test is carried out 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 adjustment universal program ", pre-service is carried out to all samples; With reference to GB GB/T 1683, put into by sample among fixture, put 4 samples in each fixture, the spacing of each sample 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 carried out to the test of X diffraction light electronic energy spectrum and nuclear magnetic resonance test

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

Nuclear magnetic resonance apparatus is Bruker AVANCE III 400WB; Nuclear magnetic spectrometry is equipped with the gauge orifice of 4 millimeters, and the X passage of its probe is 79.50 megahertzes, and other passages carry out adjusting to 400 megahertzes; Dry fine-powdered sample is contained in closed titanium rotor, rotates with the frequency of 5kHZ, altogether carries out 10000 scanning and record to each sample;

The element spectrogram of the silicon rubber under different aging condition is obtained by the test of XPS and nuclear magnetic resonance;

Step 3, XPS and NMR test result to be analyzed

Learn from the result of XPS, along with the increase of aging temperature and digestion time, in silastic material, C element content reduces gradually, and 0 constituent content increases gradually, this is because dioxygen oxidation silicon rubber side base causes the increase of oxygen element, formation hydrocarbon is lost in air and causes carbon to reduce, and carry out peak-fit processing to element silicon, Si element has following three kinds of chemical environment SiO in siloxane ₂c ₂, SiO ₃c, SiO ₄chemical bond energy position corresponding is respectively 101.9,102.8,103.6; The peak of these three chemical bond energy positions is carried out to the calculating of peak area, draw the relative scale of these three kinds of environment under different aging condition; Learn under being all aging 57h, along with aging temperature is increased to 150 DEG C again to 180 DEG C by 120 DEG C, SiO ₂c ₂relative content from 51% to 27% again to 23%, to reduce gradually, and SiO ₃the relative content of C from 43% to 48% again to 63% in raising trend gradually; See the increase facing to aging temperature and digestion time from the result of nuclear magnetic resonance, the relative content of silicone hydroxyl reduces, and SiO ₃c and SiO ₄relative content be increase, learnt by the change of the relative content of silicone hydroxyl thus, silicon rubber main side base that occurs in ageing process is aging formation silicone hydroxyl, but along with aging carrying out, silicone hydroxyl attack siloxane main chain forms cross-linked structure and ring texture, by above chemical detection test can analyze silicon rubber ageing process comprise side base be oxidized by oxygen crosslinked, to react with moisture in air and form silicone hydroxyl, silicone hydroxyl and main chain and react and form the main reaction of cross-linked structure three;

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:

In formula: B---constant;

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

α---empirical constant;

τ---digestion time, d;

Y---represent ageing properties index, if Selective Pressure compression permanent deformation ε is as aging characteristics index, then y=1-ε;

In certain temperature range, Arrhenius formula is obeyed between velocity constant K and aging temperature T:

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;

The defining method of undetermined parameter α is successive approximation method, and its criterion is that the undetermined parameter α of after being accurate to radix point 2 makes the I value in formula (3) minimum;

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

---during i-th temperature, the predicted value of the compression set rate of its jth testing site;

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

Y＝a+bX (4)

In formula:

Adopt Least Square Method parameter a and b:

The velocity constant K under p test temperature can be tried to achieve thus _i=-2.303b _iwith the test constant B tried to achieve like this in formula (1) is:

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

W＝C+DZ (8)

In formula:

Adopt Least Square Method parameter C and D:

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

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

From above formula, find out that I is the function about empirical constant α, convert different α values and attempt, constantly reduce and attempt interval and attempt interval.When empirical constant α is a number being accurate to 2 significant digits, and when making I value minimum, this number is exactly that it is separated;

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

The standard deviation calculation method of W is as follows:

In formula:

Then the upper limit of the fiducial limit of W is:

W＝C+DZ+tS _W(15)

Be can find t value in formula in the numerical tabular of 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, then W and Z linear correlation, and equation is set up; Otherwise then W and Z is linearly uncorrelated, equation is untenable;

(2) energy of activation is utilized to change the change analyzing agine mechaism

Utilize the computing method of energy of activation above, application Matlab program calculation goes out the parameter in method, and by calculating when empirical constant α value is 0.38, I value is minimum is 0.05799, the value of α is brought into formula (5), (6) obtain a _iand b _i, and then try to achieve test constant B and aging speed constant K at each temperature, with lgK, 1000/T is mapped, 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, when 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 silicon rubber thus in ageing process, along with the rising of temperature of reaction, three reaction velocitys occurred all are accelerated, and silicone hydroxyl attack main chain forms the fastest of this reaction rate of crosslink bond increase, therefore the proportion of this reaction increases, and the energy of activation that the energy of activation of this reaction reacts relative to other is lower, therefore overall energy of activation declines.