CN115901843A - Method for monitoring curing degree of PI coating on line - Google Patents
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Abstract
The invention discloses a method for monitoring the curing degree of a PI coating on line, belonging to the technical field of optical fiber preparation. The method disclosed by the invention is simple in steps and convenient and fast to operate, can quickly monitor the curing degree of each PI coating in the drawing preparation process of the PI optical fiber on line, ensures the curing quality of each PI coating after coating, avoids the foaming problem caused by insufficient curing of the PI coating, improves the efficiency and yield of PI optical fiber preparation, and has good practical value and application prospect.
Description
Technical Field
The invention belongs to the technical field of optical fiber preparation, and particularly relates to a method for monitoring the curing degree of a PI coating on line.
Background
Polyimide (PI) is a high-performance material with good thermal stability, chemical resistance and excellent mechanical properties, has important applications in the fields of structural or functional materials such as high-performance fibers and films, thermosetting or thermoplastic resins, and the like, and is also widely applied to the preparation process of optical fibers, and is used for forming a PI coating on the periphery of the optical fiber and finally forming a PI optical fiber.
In general, PI is mostly produced by a two-step process, i.e. PAA is synthesized first and then cured to PI by chemical or thermal means, and for this reason, the curing process of PI often has a great influence on its final properties. During the heat treatment curing process of the PI coating, the PI coating is mainly subjected to the following processes: volatilizing residual moisture and solvent at 50-150 deg.c; volatilizing water in the imidization reaction at the temperature of 150-350 ℃; degrading the generated CO within the temperature range of 300-400 DEG C 2 。
Currently, the more applied techniques for the characterization of the coating curing process mainly include TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry). The TGA method is a method for judging the curing degree of a material by measuring the relation between the mass and the temperature of a substance, and because the solid content of the PI coating is low and the solvent occupies more than 80 percent of specific gravity, the thermal weight loss of a test piece is small during actual test, the test accuracy for representing the curing degree by using the ratio of the mass before and after curing is poor, and the measurement equipment possibly has test errors, so that the final representation result has low reliability, and the method cannot be accurately applied to the judgment of the curing degree of the PI coating.
In contrast, for the DSC method, the heat A emitted when a completely uncured sample is cured is measured PAA And the reaction heat A remaining after the sample is cured to a certain extent PI The degree of cure was evaluated as the difference between the two and the proportion of heat evolved from the fully uncured sample undergoing cure, as shown below.
For the DSC method, it is generally applicable to the case where the sample itself does not shift, which cannot be accurately used for PI curing degree determination in the process of on-line preparation of PI optical fiber; and degree of cure for PI fiberIn the case of off-line determination (optical fiber preparation is completed), since the overall curing degree of the PI optical fiber is already high, A is caused PI The method is small, so that the test results of different test pieces are difficult to reflect difference, and the determination of the curing degree of the PI coating is difficult to accurately complete. In summary, the DSC method is also not suitable for evaluating the curing degree of PI fibers.
Based on the analysis, it is obvious that the existing TGA method and DSC method cannot accurately determine the coating curing degree of the PI optical fiber, and have certain application limitations.
Disclosure of Invention
Aiming at one or more of the defects or the improvement requirements in the prior art, the invention provides a method for monitoring the curing degree of a PI coating on line, which can realize the accurate monitoring of the curing degree of each level of coating in the preparation process of the PI optical fiber, quickly evaluate the curing degree of each level of coating and ensure the preparation precision and the processing quality of the PI optical fiber.
In order to achieve the above object, the present invention provides a method for on-line monitoring of the curing degree of a PI coating, which comprises the following steps:
(1) Selecting a PI optical fiber complete curing standard sample, carrying out infrared spectrum test on the complete curing standard sample, selecting a variation peak and a reference peak from an infrared spectrum of the complete curing standard sample, and calculating the ratio A' of peak areas of the variation peak and the reference peak;
(2) Respectively arranging external test equipment with a detection lens corresponding to at least part of curing equipment when the PI optical fiber is drawn on line, so that the PI optical fiber passes through the external test equipment and the detection lens is over against the periphery of the PI optical fiber, and measuring infrared spectrum data of the PI optical fiber after the PI coating is cured corresponding to the periphery of the PI optical fiber;
(3) Drawing infrared spectrograms of all levels by using the infrared spectroscopic data, selecting a variation peak and a reference peak from the infrared spectrograms, calculating to obtain a ratio A of the variation peak to the reference peak area of the PI coating after all levels are cured, and calculating the curing degree of the PI coating of all levels according to the following formula:
in the formula, I is standard curing degree; a is the ratio of the variation peak of the corresponding measuring point of the measured optical fiber to the reference peak area; a' is the ratio of the peak of the variation to the peak of the reference peak in the fully cured standard fiber.
As a further improvement of the invention, in the process (1), a test process of the curing degree of the liquid PI coating is also carried out, and the process is as follows:
selecting a certain amount of liquid PI coating to perform infrared spectrum measurement, obtaining peak areas of a variation peak and a reference peak from an off-shore spectrum, and calculating the ratio A of the variation peak and the reference peak 0 (ii) a Accordingly, the relative cure of the PI coating is calculated as follows:
wherein I' is relative curing degree; a. The 0 Is the ratio of the variation peak in the liquid PI coating to the reference peak area.
As a further improvement of the invention, the peak of the change is 1350cm -1 The wavelength corresponds to the vibrational peak of the C-N bond in the imide.
As a further improvement of the invention, the peak area of the change peak is 1310-1410 cm in the infrared spectrum -1 The area between peaks in the wavelength range.
As a further improvement of the invention, the reference peak is 1520cm -1 The wavelength corresponds to the vibration peak of the benzene ring.
As a further improvement of the invention, the peak area of the reference peak is 1480-1530 cm in the infrared spectrum -1 The area enclosed by the peaks in the wavelength range.
As a further improvement of the present invention, in the process (1), the completely cured standard is obtained by the following process:
selecting a plurality of optical fiber finished products which are coated and cured with the PI coatings, carrying out thermocuring on the optical fiber finished products, controlling the thermocuring temperature to be 250-450 ℃, controlling the acting time to be 0.5-4 h, and carrying out infrared spectrum measurement values at a plurality of time points until the ratio of the variation peak to the reference peak area is not changed any more.
As a further improvement of the present invention, the external test equipment includes 1 to 12 groups of detection lenses arranged at intervals in the drawing direction of the PI optical fiber, and the number of the detection lenses in each group of detection lenses is 1 to 8 in the circumferential direction of the PI optical fiber;
and/or
The external test equipment comprises 1-64 detection lenses arranged on the periphery of the PI optical fiber.
As a further improvement of the invention, the external test equipment is provided with a plurality of detection lenses, and the distance between two adjacent detection lenses in the external test equipment is 2-20 mm;
and/or
The acquisition frequency of each detection lens is 0.03125-5 Hz.
As a further improvement of the invention, the external test equipment is also provided with data processing equipment which is electrically connected with each external test equipment through a data cable and is used for receiving infrared spectrum data transmitted by each external test equipment and obtaining an infrared spectrogram according to the infrared spectrum data;
and/or
The infrared spectrum test dynamically collects the near infrared spectrum of the PI coating, and the test wavelength of the PI coating is 600cm -1 ～2000cm -1 。
The above-described improved technical features may be combined with each other as long as they do not conflict with each other.
Generally, compared with the prior art, the technical scheme conceived by the invention has the following beneficial effects:
(1) The invention relates to a method for monitoring the curing degree of a PI coating on line, which selects a complete curing standard sample corresponding to a PI optical fiber to be detected, carries out infrared spectrum test on the PI optical fiber to be detected and the complete curing standard sample respectively, selects a variation peak and a reference peak from an infrared spectrum, and calculates the ratio of the variation peak to the reference peak to the peak area of the variation peak to the reference peak respectively, so as to quickly obtain the standard curing degree corresponding to the PI coating, complete the online monitoring of the curing degree of the PI coating, provide basis for the regulation and control of relevant process parameters in the prior drawing process of the PI optical fiber, ensure the accuracy of the PI coating preparation in the online drawing process of the PI optical fiber, avoid bubbles of the PI coating, and improve the yield of the PI optical fiber preparation.
(2) According to the method for monitoring the curing degree of the PI coating on line, disclosed by the invention, the liquid PI coating is subjected to infrared spectrum test, the ratio of a variation peak in an infrared spectrum to a reference peak area is correspondingly calculated, and a curing degree test formula of the PI coating is correspondingly corrected according to the ratio, so that the test of the relative curing degree of the PI coating is further completed, and the accuracy of the determination of the curing degree of the PI coating is further improved.
(3) According to the method for monitoring the curing degree of the PI coating on line, the reference peak and the variation peak are combined and optimized, the actual generation reason of each vibration peak is fully considered, the generation of each vibration peak can be ensured to correspond to an accurate chemical bond, the acquisition accuracy of infrared spectrum test data is ensured, the acquisition accuracy of peak area data is further ensured, and the curing degree of the corresponding PI coating is accurately obtained.
(4) According to the method for monitoring the curing degree of the PI coating on line, disclosed by the invention, a large amount of data can be quickly and accurately obtained by arranging the external test equipment consisting of a plurality of detection lenses and optimally setting the acquisition parameters of the detection lenses; meanwhile, the data with larger errors can be accurately abandoned by carrying out normal distribution analysis on the collected data, the accuracy of subsequent infrared spectrum drawing is ensured, the reliability of obtaining each parameter in the process of calculating the curing degree is improved, and the reliability of judging the curing degree of the PI coating is further ensured.
(5) The method for monitoring the curing degree of the PI coating on line has simple steps and convenient operation, can quickly measure the infrared spectrum data of the PI coating on the periphery of a complete curing standard sample and a multi-stage curing drawn optical fiber in a near infrared spectrum measuring mode, can quickly complete the on-line monitoring of the curing degree of each stage of PI coating in the drawing preparation process of the PI optical fiber by utilizing the corresponding selection of a variation peak and a reference peak and the corresponding design of a curing degree calculation formula, avoids the foaming problem caused by insufficient curing of the PI coating, ensures the efficiency and the yield of the PI optical fiber preparation, and has better practical value and application prospect.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a system for on-line monitoring of PI coating cure in an embodiment of the present invention;
FIG. 2 is an infrared spectrum of a corresponding measuring point in the embodiment of the present invention;
in all the figures, the same reference numerals denote the same features, in particular:
1. coating equipment; 2. a curing device; 3. external test equipment; 4. detecting a lens; 5. a data processing device; 6. a display device; 7. an optical fiber; 8. a data cable.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature "under," "beneath," and "under" a second feature may be directly under or obliquely under the second feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Example (b):
for the method for monitoring the curing degree of the PI coating on line in the preferred embodiment of the invention, the method is applied to the multi-stage coating production scene of the PI optical fiber, and the near infrared spectrum of the corresponding PI coating after coating and curing at each stage is dynamically acquired(600cm -1 ～2000cm -1 In range), the spectral specific peak position is used to correspond to the complete PI coating cure.
Specifically, in order to collect the near infrared spectrum of each stage of coated and cured optical fiber in real time, an external testing device 3 is respectively disposed at the rear end of each stage of curing device of the PI optical fiber preparation line, as shown in fig. 1, and the near infrared spectrum of the surface coating of the drawn optical fiber after the last stage of curing is collected by the external testing device.
In the monitoring system shown in fig. 1, it can be seen that during the drawing process of the PI optical fiber, a multi-stage coating and multi-stage curing are required, i.e. a multi-stage coating apparatus 1 and a multi-stage curing apparatus 2 are arranged on the drawing flow line. In a preferred embodiment, the number of coating and curing steps is preferably 1 to 5. Correspondingly, the external testing equipment 3 is respectively arranged at the rear end of each stage of curing equipment 2, so that the cured PI optical fiber can correspondingly penetrate through the external testing equipment 3 and correspondingly complete data acquisition of corresponding measuring points.
Specifically, taking the preferred embodiment shown in fig. 1 as an example, the optical fiber drawing tower in this case includes a three-stage coating assembly, that is, 3 coating devices 1 (such as coating cups) and 3 curing devices 2 (such as multi-stage curing furnaces, resistance wire heating or graphite heating furnaces); accordingly, the external test devices 3 are respectively provided at the rear ends of the curing devices 2 (the external test device 3 at the lowermost end is omitted in the drawing).
Meanwhile, a plurality of detection lenses 4 are integrated in the external testing device 3 in the preferred embodiment, and each detection lens 4 is respectively arranged right opposite to the periphery of the optical fiber 7 penetrating through the external testing device 3 and used for measuring infrared spectrum data of a corresponding measuring point on the periphery of the optical fiber 7. In the preferred embodiment, the detection lenses 4 are preferably a plurality of groups arranged at intervals in the optical fiber drawing direction, and each group preferably includes a plurality of groups arranged at intervals in a ring shape.
When actually setting up, external test equipment 3 prefers to make with high temperature resistant corrosion-resistant alloy material, not only compromises the demand of workable, still can reduce by a wide margin and in the long-term use because of receiving the deformation that high temperature brought, avoids the corruption of the corrosive gas that probably produces to external test equipment built-in electrical components in the solidification reaction, improves the stability of this equipment. Meanwhile, the external testing device 3 in the preferred embodiment is preferably a cylindrical structure with a ring-shaped closed or non-closed ring shape, for example, the cylindrical structure in the preferred embodiment, the detecting lenses 4 are arranged in a distributed manner in the circumferential direction of the inner circumference of the external testing device 3, accordingly, during actual measurement, the optical fiber 7 passes through the inner cavity of the testing device 3, and the detecting lenses 4 are distributed on the outer circumference of the optical fiber 7. In practical application, the closed cylindrical structure can completely ensure that the circumferential direction of the optical fiber 7 has test point positions; the non-closed cylindrical structure sacrifices part of test point positions, but when the external test equipment 3 is installed and disassembled, the operation is more convenient on the premise of ensuring no collision with the optical fiber 7.
In more detail, the number of the detection lenses 4 is selected to be 1 to 64 arranged at intervals on the periphery of the PI optical fiber to be tested, and preferably includes 1 to 12 groups arranged at intervals in the optical fiber drawing direction, and each group of the detection lenses 4 is preferably 1 to 8, and when actually arranged, the plurality of detection lenses 3 in a group are arranged at intervals in the ring direction of the drawn optical fiber. By utilizing the interval arrangement of the detection lenses 4 in the annular direction, multiple groups of data of the same optical fiber 7 section area can be acquired at one time, and the phenomenon that the optical fiber 7 rotates in the wire drawing process to cause inaccurate data is avoided; correspondingly, multiple times of scanning of the same measuring point can be realized by utilizing the axial interval arrangement of the detection lens 4, the number of data acquisition is increased, and the accuracy of data acquisition of the detection lens 4 is ensured.
In more detail, a data cable 8 is respectively disposed corresponding to each external testing device 3, and a data processing device 5 (for example, a computer host) and a display device 6 (for example, a display) are correspondingly disposed, so that each external testing device 3 is electrically connected to the data processing device 5 through the data cable 8, and is configured to transmit the measuring point data acquired by each external testing device 3 to the data processing device 5, complete the data processing here, and generate a corresponding infrared spectrogram (an absorbance-optical wavelength schematic diagram), as shown in fig. 2. Then, according to the test of each external test device 3, the infrared spectrum data acquisition of each level of PI coating can be completed, and the curing degree of each level of coating can be judged on the basis of the infrared spectrum data acquisition.
Further, in a preferred embodiment, the determination of the cure degree of the PI coating is accomplished by the following formula:
wherein I is the degree of cure; a is the ratio of the variation peak of the corresponding measuring point of the measured optical fiber to the reference peak area; a' is the ratio of the peak of variation in the fully cured standard fiber (fully imidized fiber) to the reference peak area.
Further, identification and selection of reference and variation peaks:
for the reference peak and the variation peak in the above formula, both are characteristic peaks of the infrared absorption spectrum. The reference peak is the peak position with small or unchanged change and the change peak is the peak position with strong absorption as the selection principle. In the actual measurement, it is preferably 1520cm -1 The vibration peak of benzene ring at wavelength is reference peak, and is preferably 1350cm -1 The vibration peak corresponding to the C-N bond in the imide at the wavelength is a variation peak.
As can be readily seen from the illustration shown in FIG. 2, 740cm is found in the IR spectrum of the PI coating -1 Wavelength sum 1780cm -1 The vibration peak at the wavelength was also more pronounced and was not selected as a change peak because of the dichromatic effect, 740cm -1 The wavelength band is very sensitive to the dichroic absorption of the infrared beam. As the curing temperature increases, more imine chains are formed and are formed in the same direction. Therefore, the intensity of the absorption band depends on the experimental conditions, and a slight variation in the measurement conditions may cause a significant data deviation. So too does it, 740cm -1 The degree of cure of the wavelength band does not show reliable results under high temperature treatment. Furthermore, 1780cm -1 The band height is affected by the overlap of the anhydride and carbonyl groups of the imine, and samples processed at lower temperatures may have large positive errors in the resulting band height and area due to the too low to be determined absorption band of the imine. In contrast, for 1350cm -1 The band is calculated because the band is less affected by the dichroic effect and the band area results in less deviation than the band height results.
To verify the theoretical effect of the dichroic effect, the peak areas and peak heights measured for the 5-stage fully cured standard samples are listed in Table 1, from which the 1350cm samples were tested -1 The area and height of the absorption band of the wave band are most stable, and the consistency is better; in contrast, 740cm -1 And 1780cm -1 The performance is relatively poor. Meanwhile, as can also be seen from table 1, the standard deviation of the measurement result of the absorption band area is smaller than that of the measurement result of the absorption band height for the measurement result of the same wavelength, indicating that the result obtained by the absorption band (energy band) area is better than that obtained by the absorption band (energy band) height with less deviation.
TABLE 1 Peak area and Peak height test data Table for fully cured standards at different wavelengths
In more detail, in a preferred embodiment, the reference peak area corresponds to 1480 to 1530cm -1 The area enclosed by the peaks in the wavelength range, such as 1520cm in FIG. 2 -1 The area of the triangular region above the dotted line at the wavelength; accordingly, the peak area of the change corresponded to 1310 to 1410cm -1 The area enclosed by the peaks in the wavelength range, 1350cm in FIG. 2 -1 The area of the triangular region above the dotted line at the wavelength.
Further specifically, in a preferred embodiment, the method for on-line monitoring of the curing degree of the PI coating comprises the following processes:
(1) In the preparation stage, selecting a PI optical fiber complete curing standard sample, and determining the ratio A 'of a variation peak in a PI coating to a reference peak area, wherein the ratio A' is used as a reference value for determining the curing degree;
specifically, in practice, the selection of the fully cured standard is preferably subjected to the following procedure: selecting a plurality of optical fiber samples (which are finished optical fibers and have finished PI coating and curing processes) drawn in the same batch with the optical fiber to be measured, carrying out thermocuring on the optical fiber samples until the ratio of the variation peak to the reference peak area is not changed any more, and taking the samples as a complete curing standard sample.
In more detail, the temperature condition of the re-solidification in the preferred embodiment is preferably 250-450 ℃, the action time is preferably 0.5-4 h, the value of the infrared spectrum measurement is carried out at a plurality of time points, for example, the value is carried out once every 30min until the ratio of the variation peak to the reference peak area is not changed, the test method clamps the optical fiber sample to be tested at the center of the external test equipment 3, and the peak area is also 1480-1530 cm -1 Wavelength 1310-1410 cm -1 Wavelength.
(2) In the determination stage, infrared spectrum data of the optical fiber cured by the corresponding curing equipment 2 are collected by utilizing each external testing equipment 3, and infrared spectrum testing data corresponding to each stage of cured optical fiber are respectively obtained;
according to the different set quantity of the detection lenses 4 in the external test equipment 3, the quantity of the test data after curing corresponding to each level is different, in the preferred embodiment, the data processing equipment 5 processes the test data of each level by adopting a normal distribution probability density function formula, and discards the data with larger deviation in the test data.
(3) And drawing an infrared spectrogram by using the data of each level, selecting a change peak and a reference peak from the spectrogram, correspondingly calculating peak areas of the change peak and the reference peak of the PI coating, calculating a ratio A of the change peak to the reference peak area of the cured PI coating of each level, correspondingly calculating the curing degree of the cured PI coating of each level according to the following formula, and finishing the online monitoring of the curing degree of the PI coating of each level.
Correspondingly, in the actual production process, the curing conditions of the coatings at all levels can be correspondingly judged through online monitoring of the curing degree of the PI coatings at all levels, once insufficient curing of the PI coatings at corresponding levels is found, relevant production parameters of the optical fiber, such as the optical fiber drawing speed, the optical fiber curing temperature, the optical fiber curing time and the like, can be timely adjusted, the coating and curing accuracy of the PI optical fiber coatings is fully ensured, the coating foaming problem is improved, the yield of the PI optical fiber is improved, and the preparation and application cost of the PI optical fiber is reduced.
It should be noted that the problem of foaming of the coating can be improved by controlling the curing degree of the PI coating, and the reason for this is that when the coating is not completely cured, the solvent in the coating is not completely volatilized, and after the coating of the next coating, the incompletely cured inner coating is sealed in the coating, and the coating expands and foams when exposed to high temperature. In the actual operation process, the higher the curing degree of the coating is, the more sufficient the solvent volatilization in the coating is, the less the problem of coating foaming is, so that the problem is promoted to accelerate the volatilization of the solvent in the corresponding coating by optimizing the curing condition, and the aims of improving the foaming problem and improving the production quality of the PI optical fiber are fulfilled.
Further, in the determination process of the degree of curing in the step (3), the degree of curing of the corresponding PI coating is determined by comparing the peak area ratio of the optical fiber to be measured with the peak area ratio of the completely cured standard sample, and at this time, the determined degree of curing is the standard degree of curing, which is a result when the degree of curing of the liquid coating is not considered or the degree of curing of the liquid coating is regarded as 0.
However, in actual measurement, the degree of cure of the PI coating in a liquid state is often not 0. Therefore, in a preferred embodiment, the curing degree of the PI coating in the liquid state is also determined, and the calculation formula of the curing degree is further optimized, so as to obtain the relative curing degree of the PI coating, which is as follows:
in the preparation stage, the liquid PI coating curing degree is tested, at the moment, a certain amount of PI coating is selected and uniformly spread on a spectrometer test platform, an infrared spectrometer is used for measuring, infrared spectrum data of the liquid PI coating are collected, the data collected by the infrared spectrometer are processed into infrared spectrum by a data processing device 5, and then the ratio A of a variation peak to a reference peak of the PI coating is measured by the data processing device 5 0 (ii) a Correspondingly, the calculation formula of the standard curing degree can be correspondingly corrected, and the following calculation formula of the relative curing degree is obtained:
wherein I' is relative curing degree; a is the ratio of the variation peak of the corresponding measuring point of the measured optical fiber to the reference peak area; a' is the ratio of the variation peak in the fully cured standard fiber (fully imidized fiber) to the reference peak area; a. The 0 Is the ratio of the peak of variation in the liquid PI coating (uncured coating) to the reference peak area.
The method for monitoring the curing degree of the PI coating on line is further described by an embodiment as follows.
In this example, two stages of a multi-stage curing draw tower were selected for measurement and the standard and relative cure levels of the PI coatings after the two stages of curing were determined accordingly.
Specifically, in the preparation stage, a bottle of completely uncured Polyimide (PI) coating is taken, 1-2 ml of liquid coating is poured on an infrared spectrometer test platform, after the liquid coating is uniformly spread out, an infrared spectrometer is used for measuring, data collected by the infrared spectrometer are processed into an infrared spectrum by a data processing device 5, and ratio data of a change peak and a reference peak area are obtained according to the infrared spectrum.
It should be noted that, in practical application, the process of generating the infrared spectrum according to the infrared spectrum data and obtaining the corresponding peak area by using the infrared spectrum data can be realized by using software such as OMNIC, iC IR, bruker, and the like, and by taking the maximum transmittance points of the two wings of the spectrum band as the tangent of the spectral absorption, as the baseline of the spectrum line, the intersection point of the vertical line and the baseline at the wave number is analyzed, and the distance from the peak of the maximum absorption peak is the peak height. Quantification is generally performed by calibration curve method or comparison with standard sample, which is a relatively mature technique and will not be described herein.
In the preparation stage, the PI optical fiber drawn in the same batch as the optical fiber to be measured is selected and divided into a plurality of sections of samples, for example, 4 sections shown in the preferred embodiment, each section of sample is subjected to the heat re-curing treatment, the temperature range of the heat re-treatment curing is controlled to be 300-350 ℃, and the curing time is controlled to be 60min, 90min, 120min and 180min respectively, as shown in table 2 below.
Table 2 test data table for fully cured standards
| Off-line resolidification time of optical fiber | 60min | 90min | 120min | 180min |
| Area of peak change | 1.7886 | 1.8617 | 1.8846 | 1.8846 |
| Reference peak area | 0.6473 | 0.6496 | 0.6496 | 0.6496 |
According to the test data in the above table, it can be easily seen that the peak area of the variation peak does not change after re-curing for 2h (120 min), and at this time, the PI optical fiber sample is determined as the full-cure standard sample, and the peak area ratio at this time is taken as the full-cure standard value.
Furthermore, in the measuring stage, the drawing preparation of the optical fiber is carried out by controlling a multi-stage drawing tower, the drawing speed is preferably 3-10 m/min, and the drawing is carried out from a fixed drawing end. Correspondingly, multi-stage coating and multi-stage curing of the PI coating are sequentially performed between the fixed wire take-up end and the silicon rod.
Meanwhile, the external test equipment 3 located at the rear end of each stage of curing equipment starts to collect data, in the embodiment, 8 detection lenses are fixedly arranged in the external test equipment 3, and infrared spectrum data collection of 8 collection points is carried out. In actual setting, the spacing distance of each collection point is preferably finely adjusted according to the drawing speed.
It is further preferable that the distance between two adjacent detecting lenses 4 in the external testing device 3 is 2-20 mm, wherein 2mm is the minimum distance excluding the mutual crosstalk between two detecting lenses 4 when measured, and if the distance is too close, the crosstalk of optical signals between the two detecting lenses is very easy to occur. Meanwhile, the drawing speed is 10m/min (17 cm/s), the drawing speed is calculated according to the fluctuation of +/-2 m/min, the drawing speed is calculated according to the condition that 12m/min =20cm/s, the scanning time can be set to be 1-64 times according to the acquisition of a single detection lens 4 within 2-5 seconds, the scanning frequency of the detection lens 4 is 0.03125-5 Hz, and 20 x 0.03125=0.625cm =6.25mm. In actual measurements, data for accurate infrared absorption can be captured at the second set at 6.25mm spacing or the third set at 13.5mm spacing or the fourth set at 19.75mm spacing when the first set of hoop scans are not aligned. Therefore, the upper limit of the distance between two adjacent detection lenses 4 is set to be 20mm, so that a certain measuring point of the moving optical fiber 7 can be scanned for multiple times in the drawing process, and the data accuracy is ensured.
In actual operation, after the acquisition is started layer by layer and the temperature of the thermosetting furnace is stable, the multi-level points are independently controlled and acquired according to N-level curing, and the acquisition of infrared map data of the cured PI coatings of different levels is completed.
Further, during data processing, the data is processed by the data processing device 5 and presented on the display device 6 in the form of a matrix, for example, 8 points per stage, each point being scanned 10 times, 8 × 10 data being collected in total, resulting in 8 × 10 spectrograms, for each spectrogram, at 1520cm -1 Vibration peak of benzene ring at wavelength is reference peak, and is 1350cm -1 Corresponding to C in imide at wavelengthThe vibration peak of the N bond is a variation peak, and the reference peak area corresponds to 1480-1530 cm -1 The area of a triangular region sandwiched by peaks in the wavelength range, the peak area of variation corresponding to 1310-1410 cm -1 The area of the triangular region bounded by the peaks in the wavelength range. And simultaneously, respectively carrying out normal distribution analysis on the reference peak position and the change peak position area of all spectrograms, calibrating a central area with the frequency of more than 20, and selecting the reference peak position area mean value and the change peak position area mean value of the area as the curing degree reference peak area and the change peak area of the PI coating. Accordingly, the standard cure and relative cure of the PI coatings of each stage can be obtained by filling the data in table 3 below.
TABLE 3 PI CURING MEASUREMENT TABLE IN PREFERRED EXAMPLE
The liquid coating cure was not considered or was considered to be 0% when the coating cure was measured, and it can be seen in this example that the standard cure for the liquid PI coating was 6.2%, not 0%. Liquid coatings of different formulations may exhibit different degrees of curing, and if the degree of curing of the liquid coating is not considered, the liquid coating is directly calculated by using a formula of standard degrees of curing, so that the test result is distorted. Therefore, the invention further optimizes the calculation formula of the curing degree, obtains the relative curing degree of the PI coating, and also embodies the reliability and the accuracy of the method for testing the curing degree.
The method for monitoring the curing degree of the PI coating on line has the advantages of simple steps and convenience in operation, can quickly measure the infrared spectrum data of the PI coating on the periphery of a full-curing standard sample and a multi-stage curing drawn optical fiber in a near infrared spectrum measurement mode, can quickly complete the on-line monitoring of the curing degree of each stage of PI coatings in the drawing preparation process of the PI optical fiber by utilizing the corresponding selection of a variation peak and a reference peak and the corresponding design of a curing degree calculation formula, avoids the foaming problem caused by insufficient curing of the PI coatings, ensures the efficiency and the yield of the PI optical fiber preparation, and has good practical value and application prospect.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method for monitoring the curing degree of a PI coating on line is characterized by comprising the following steps:
(1) Selecting a PI optical fiber complete curing standard sample, carrying out infrared spectrum test on the complete curing standard sample, selecting a variation peak and a reference peak from an infrared spectrum of the complete curing standard sample, and calculating the ratio A' of peak areas of the variation peak and the reference peak;
(2) Respectively arranging external test equipment with a detection lens corresponding to at least part of curing equipment when the PI optical fiber is drawn on line, so that the PI optical fiber passes through the external test equipment and the detection lens is over against the periphery of the PI optical fiber, and measuring infrared spectrum data of the PI optical fiber after the PI coating is cured corresponding to the periphery of the PI optical fiber;
(3) Drawing infrared spectrograms of all levels by using the infrared spectrograms, selecting a variation peak and a reference peak from the infrared spectrograms, calculating to obtain a ratio A of the variation peak to the reference peak area of each level of the PI coating after curing, and calculating the curing degree of each level of the PI coating according to the following formula:
wherein I is standard curing degree; a is the ratio of the variation peak of the corresponding measuring point of the measured optical fiber to the reference peak area; a' is the ratio of the peak of the variation to the peak of the reference peak in the fully cured standard fiber.
2. The method for on-line monitoring of the curing degree of PI coating according to claim 1, wherein in the process (1), a test process of the curing degree of liquid PI coating is also performed, which process is as follows:
selecting a certain amount of liquid PI coating for infrared spectrum measurement, obtaining peak areas of a variation peak and a reference peak from an infrared spectrum of the PI coating, and calculating a ratio A of the variation peak and the reference peak 0 (ii) a Accordingly, the relative cure of the PI coating is calculated as follows:
in the formula, I' is relative curing degree; a. The 0 Is the ratio of the variation peak in the liquid PI coating to the reference peak area.
3. The method for on-line monitoring of the curing degree of PI coatings of claim 1 or 2, characterized in that the peak of the variation is 1350cm -1 The wavelength corresponds to the vibrational peak of the C-N bond in the imide.
4. The method for on-line monitoring of the curing degree of the PI coating as claimed in claim 3, wherein the peak area of the variation peak is 1310-1410 cm in the infrared spectrum -1 The area between peaks in the wavelength range.
5. The method for on-line monitoring of PI coating cure level of claim 3 wherein said reference peak is 1520cm -1 The wavelength corresponds to the vibration peak of the benzene ring.
6. The method for on-line monitoring of the curing degree of the PI coatings as claimed in claim 5, wherein the peak area of the reference peak is 1480-1530 cm in the infrared spectrum -1 The area enclosed by the peaks in the wavelength range.
7. The method for on-line monitoring of the curing degree of PI coatings as claimed in any one of claims 1-2 and 4-6, wherein in the process (1), the full curing standard is obtained by the following process:
selecting a plurality of optical fiber finished products which are coated and cured with the PI coatings, carrying out thermocuring on the optical fiber finished products, controlling the thermocuring temperature to be 250-450 ℃, controlling the acting time to be 0.5-4 h, and carrying out infrared spectrum measurement values at a plurality of time points until the ratio of the variation peak to the reference peak area is not changed any more.
8. The method for on-line monitoring of the curing degree of the PI coatings according to any one of claims 1-2 and 4-6, wherein the external test equipment comprises 1-12 groups of detection lenses which are arranged at intervals in the drawing direction of the PI optical fiber, and the number of the detection lenses in each group of detection lenses is 1-8 in the annular direction of the PI optical fiber;
and/or
The external test equipment comprises 1-64 detection lenses arranged on the periphery of the PI optical fiber.
9. The method for on-line monitoring of the curing degree of the PI coatings according to claim 8, wherein the external test equipment comprises a plurality of detection lenses, and the distance between two adjacent detection lenses in the external test equipment is 2-20 mm;
and/or
The acquisition frequency of each detection lens is 0.03125-5 Hz.
10. The method for the on-line monitoring of the curing degree of the PI coatings as claimed in any one of the claims 1 to 2, 4 to 6 and 9, wherein a data processing device is further arranged corresponding to the external test devices, is electrically connected with each external test device through a data cable, and is used for receiving infrared spectrum data transmitted by each external test device and obtaining an infrared spectrogram according to the infrared spectrum data;
and/or
The infrared spectrum test dynamically collects the near infrared spectrum of the PI coating, and the test wavelength of the PI coating is 600cm -1 ～2000cm -1 。
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116382380A (en) * | 2023-06-05 | 2023-07-04 | 四川馨香源环保科技有限公司 | Basalt fiber composite board spraying state detection control system |
| CN117907259A (en) * | 2024-03-20 | 2024-04-19 | 深圳市聚芯源新材料技术有限公司 | Epoxy structural adhesive curing detection device and detection method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116382380A (en) * | 2023-06-05 | 2023-07-04 | 四川馨香源环保科技有限公司 | Basalt fiber composite board spraying state detection control system |
| CN116382380B (en) * | 2023-06-05 | 2023-08-18 | 四川馨香源环保科技有限公司 | Basalt fiber composite board spraying state detection control system |
| CN117907259A (en) * | 2024-03-20 | 2024-04-19 | 深圳市聚芯源新材料技术有限公司 | Epoxy structural adhesive curing detection device and detection method |
| CN117907259B (en) * | 2024-03-20 | 2024-05-14 | 深圳市聚芯源新材料技术有限公司 | Epoxy structural adhesive curing detection device and detection method |
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