JPH0743249B2 - Polymer spherulite analysis method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for analyzing polymer spherulites. More specifically, the present invention relates to an analysis method and apparatus for calculating useful data for obtaining the sphere diameter, spherulite distribution, number density, relative refractive index, etc. of polymer spherulites.

[0002]

2. Description of the Related Art Conventionally, as a method of analyzing a spherulite of a polymer, when the spherulite diameter is 1 μm or more, it can be directly observed with an optical microscope by transmission. In addition, if you add special functions such as dark field, polarization, and phase difference to the optical microscope, you can observe more clearly. In this case, the size is directly measured visually by comparison with the microscale.

The spherulite diameter can also be measured by a small-angle light scattering method using a monochromatic laser beam by utilizing light scattering. In the small-angle light scattering method, two polarizers are used to display a four-leaf clover-shaped H _v (horizontal and vertical polarization) scattered image. In H _v scattering, the spherulite diameter is calculated under the condition that the scattering intensity has a maximum value at a certain scattering angle θ.

Usually, a transmission electron microscope (TEM) is used when the spherulite size is too small to be measured by these methods. This is dyed with ruthenium tetroxide for electron beam and then several hundreds with an ultramicrotome.
Make ultrathin sections of thousands of Angstroms. Since ruthenium tetroxide does not easily enter the crystal part and is filled in the amorphous part, when this is applied to a TEM, lamellas in which electron beams can easily pass are observed as white streaks. When a TEM image is obtained at a magnification as low as possible so that a lamella can be seen, a wide range is observed and a spherulite pattern is easily recognized. Spherulites are observed as a lump of lamellae grown radially from a certain center, and this size (sphere diameter) is measured by a scale and converted from the magnification to the actual size.

[0005]

However, when the spherulite diameter is small (<1 μm) by a microscope and small-angle light scattering.
Is difficult to observe. In principle, the scattering phenomenon can be used up to 1/20 of the wavelength, that is, particles of several hundred angstroms, but there are problems such as the scattering angle becoming too large and the intensity becoming weak, and it is empirically difficult to measure.

Also, in electron microscopy, the smaller the spherulites, the more difficult it is to recognize the pattern, and there is no clear standard for distinguishing the spherulites, and the results may vary depending on the observer.
Furthermore, since the thickness of the slice is smaller than the size of the spherulite itself, it is not possible to know which section of the sphere is being viewed, and the pattern does not necessarily show the diameter, so statistical consideration is required. Moreover, the equipment cost is extremely high, and a high degree of skill is required for sample preparation and operation, so that it cannot be immediately used by anyone.

As described above, conventionally, there has been no apparatus capable of easily obtaining the sphere diameter of polymer spherulites, their distribution and number density, or the relative refractive index of spherulites.

The present invention covers the actual measurement range of spherulite size by one method, enables objective measurement, is inexpensive and accurate in a short time, and has many factors. It is an object of the present invention to provide an analysis device that can separately determine (size and its distribution, number density, relative refractive index). In other words, the present invention provides an analysis method and apparatus for measuring spherulite size, number density, etc., which have a great influence on polymer material properties (dielectric breakdown strength, mechanical strength, etc.) in a short time with high accuracy. The purpose is to do.

[0009]

[Means for Solving the Problems] The object is to analyze by analyzing the scattering of light in the ultraviolet to visible region or the spectroscopic characteristics of transmitted light which has not been used until now in the analysis of polymer spherulites. It is achieved by In a polymer having a spherulite structure (for example, polyethylene), the appearance of turbidity varies slightly depending on the size and number of spherulites. Therefore, the present inventors have focused on the possibility that they can be measured if they are quantified using an ordinary UV-visible spectrophotometer.

Based on this viewpoint, the present invention obtains the absorption spectrum or the scattering intensity spectrum of the polymer spherulites to be measured, and uses it as the power of the wavelength (wavelengths ^b , b: 2).
The realization number is multiplied by 4) for normalization, and the spherulite size is determined from the peak wavelength of the spectrum.

Further, using the spherulite radius a of the polymer obtained by the above-mentioned analysis method, the wavelength of the standardized spectrum is divided by 2πa, and the absorbance spectrum or scattered light spectrum is standardized with respect to the wavelength. The distribution of spherulites is calculated from the degree of spread of the normalized spectrum shape. Further, when the spherulite size is obtained, the absorbance A as the original measurement value before normalization corresponding to the peak wavelength λ ₀ indicating the polymer spherulite radius of the standardized spectrum and the scattering theory, for example, Rayleigh-Gans-Debye ( Rayleigh-G
The ans-Debye) theory and the relative refractive index m previously obtained are used to obtain the number density N, or the previously obtained number density N is used to obtain the relative refractive index m.

Further, the present invention is a spectroscopic means for obtaining the absorbance spectrum or the scattering intensity spectrum of the polymer spherulites to be measured, and the power of the wavelength to the absorbance spectrum or the scattering intensity spectrum (wavelength ^b , b: 2 to 4). Means for multiplying the absorption spectrum or scattering intensity spectrum of the polymer spherulites to be measured, and normalizing by multiplying it by the power of the wavelength (wavelength ^b , b: real number of 2 to 4) The spherulite size is determined from the peak wavelength of.

[0013]

Function: Since the existing density of spherulites in a polymer is generally not clear, the spherulite diameter cannot be obtained only from the absolute value of the absorbance. However, according to the theory of scattering, in the case of polymer spherulites, from the relative refractive index close to 1 and the size that actually exists, wavelength −2 to −4 for light in the ultraviolet to visible region.
It causes scattering of a function that changes in proportion to the power. The scattered light or the transmitted light attenuated by the scattering appears on the spectrum that is separated as this function. Since the correspondence between the numerical value of the exponent representing the power and the wavelength changes only with the size of the spherulites that are the main constituents of scattering, and does not relate to the number density, the index reflects only the size of the spherulites. Therefore, the curve obtained by multiplying the absorbance spectrum by λ ² always has a negative slope, while the curve obtained by multiplying λ ⁴ by correction has a positive slope. When multiplied by λ ^{4 + P} (P: arbitrary constant from -2 to 0),
It can be seen that the curve has a peak at a specific wavelength. Therefore, by utilizing this characteristic, the relation between the relative spherulite diameter and the index with respect to the wavelength can be derived from theory, and it is possible to correspond them in advance. That is, the slope of the curve with respect to α on the log-log graph of f (α), that is, the exponent of α of f (α) shown in Formula 2,

[0014]

[Equation 2] If is obtained, it becomes the exponent P of α in the function f (α). Focusing only on the wavelength λ in the calculation formula of turbidity, it is possible to give a peak for a specific α by multiplying it by λ ^{4 + P.} In other words, if the spectrum is normalized by the exponent of the wavelength (for example, divided by wavelength ^-b or multiplied by wavelength ^b ) for the entire wavelength range using a specific index, a curve with a peak (maximum value) is obtained. It will be rewritten.
The value of the spherulite diameter is directly obtained from the wavelength giving this peak and the ratio of the wavelength at the index used to the spherulite diameter.

Since the shape of the standardized curve changes very sensitively to the diameter of the spherulites, if the spectrum is obtained accurately, the distribution state of the spherulite diameters, for example, the standard deviation if the distribution follows the normal distribution, It is calculated from the shape and inclination. However, in this case, it is necessary to investigate to some extent what function the actual distribution matches. It is also necessary to understand the deviation from the true spectrum.

When the spherulite diameter is known, either the relative refractive index or the number density is known, and the other can be easily calculated from the absolute value of the spectrum. Generally, the relative refractive index is known depending on the type of polymer,
You will get a number density. However, if the number density is obtained by another method, it can also be a method of experimentally obtaining the relative refractive index.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

The polymeric spherulite analyzer of the present invention comprises a spectroscopic means for obtaining the absorbance spectrum or the scattering intensity spectrum of the polymeric spherulites to be measured, and the absorption spectrum or the scattering intensity spectrum obtained by the means. And a means for multiplying by a power of (wavelength ^b , b: a real number of 2 to 4), the absorption spectrum or scattering intensity spectrum of the polymer spherulites to be measured is obtained, and then the product is multiplied by the power of the wavelength to standardize The spherulite size, its distribution and number density (or the relative refractive index of the spherulite) are determined from the peak wavelength of the converted spectrum. As the spectroscopic means, for example, trade name UV- manufactured by Shimadzu Corporation
A known spectrophotometer such as 2200 can be used, and a means for multiplying the measured absorbance spectrum or scattered intensity spectrum by a power of wavelength is configured as one routine of the program software of the computer attached thereto.
Of course, the present invention is not limited to this, and for example, a known arithmetic circuit can be used.

Here, as a method of obtaining the value b (= 4 + P) of the power, for example, there is a method based on the following Rayleigh-Gans-Debye theory. If the ratio between the spherulite radius a and the peak wavelength λ ₀ is c,

[0020]

In the relationship of a = cλo

[0021]

## EQU4 ## Define α = 2πc. Then,

[0022]

[Equation 5] By

[0023]

[Equation 6] And calculate

[0024]

## EQU00007 ## With b = 4 + P, the power value b is obtained. It is shown that if the absorbance spectrum can be obtained with high accuracy, a wide range of spherulite diameters can be measured depending on the assumed value of c regardless of whether the spherulite is larger or smaller than the wavelength.

Specifically, for example, when the spherulite radius a = wavelength λ, the index P for λ of f (α) when α = 2π is −
Since it is calculated to be 1.878, the spectrum obtained by multiplying the absorbance by λ ^{2.122 shows} that the wavelength giving a peak coincides with the spherulite radius. If 2a = λ, then α = π and α in f (α)
The index P of is calculated to be −1.640, and the wavelength giving the peak by multiplying by λ ^2.360 represents twice the radius, that is, the diameter. Here, f (α) is a turbidity correction term based on the Rayleigh-Gans-Debye theory.

According to the analyzing apparatus configured as described above, a standardized spectrum can be obtained by multiplying the absorbance spectrum or the scattering intensity spectrum of the polymer spherulites by the power of a predetermined wavelength. This spectrum has a peak, and the wavelength of the peak portion has a fixed relationship with the spherulite grain size. That is, the value of the spherulite diameter can be obtained from the correlation between the wavelength giving the peak and the wavelength at the index used to normalize the spectrum having such a peak and the spherulite diameter.

[Example 1] As samples having different spherulites, three kinds of polyethylene prepared under different temperature conditions were prepared. Specifically, HFDJ-4201 Super Clean manufactured by Nippon Unicar Co., Ltd. was used as a raw material. As a result of statistically analyzing these spherulites with an electron microscope, No. The sample No. 1 had a spherulite diameter of 1.850 μm (number density of 0.217 particles / μm ³ , standard deviation of diameter of 480 nm), No. Sample No. 2 has a spherulite diameter of 1.34
0 μm (number density 0.206 / μm ³ , standard deviation of diameter 5
00 nm), No. Sample No. 3 has a spherulite diameter of 0.890 μm
(Number density 0.271 / μm ³ , standard deviation of diameter 340n
m).

When the absorbance A of each of these samples was measured in the form of a plate having a thickness of 4.5 mm, an absorbance spectrum as shown in FIG. 3 was obtained. The spectrometer used was UV-2200 manufactured by Shimadzu Corporation, and the measurement range was -4 to 5 Abs in absorbance and 0 to 999.9% T in transmittance.
Here, it suffices to simply rewrite this absorbance spectrum by simply multiplying it by the wavelength ^b , but since the experimental values include errors such as reflection / absorption and multiple scattering in addition to the scattering phenomenon, it is necessary to correct the spectrum data. There is. It is necessary to examine the parameters for correction separately from the viewpoint of both the experiment and the theory regarding the target material. Although it is a very rough method, the spectrum obtained by multiplying λ ² always has a negative slope, and the spectrum obtained by multiplying λ ⁴ always has a positive slope. )
The correction value was set so that the absolute values of the two became equal.

Here, it is assumed that 60% of the incident light is not involved in the scattering due to the reflection / absorption having a great influence. Based on this assumption, the true absorbance spectrum is tentatively obtained, and the result obtained by normalizing by multiplying the wavelength by 2.122 is shown in FIG.
The numerical value of 2.122 indicates that the wavelength giving the peak is equal to the radius of the spherulite, and No. 1 sample had a spherulite diameter of 1.540 μm and No.
No. 2 sample had a spherulite diameter of 1.320 μm and No. The results of the spherulite diameter of 1.180 μm are obtained for the three samples. Although the values are slightly different, they are relatively the same as the values obtained by the electron microscope, and the difference between the samples is clearly shown. And, since these values are close to the results by an electron microscope although they are not analyzed accurately because they are based on the correction based on a rough process, the method of the present invention is appropriate for analyzing the spherulite diameter and the like. It can be said that it proves that there is. Therefore,
If the correlation between the peak wavelength and the spherulite diameter is obtained in advance, the value of the spherulite diameter can be obtained from this more accurately. Further, using the number density obtained with an electron microscope, the relative refractive index was calculated from 1.002 to 1.003. On the contrary, if the relative refractive index is separately determined such as 1.002, it can be easily obtained from the spectra having the same number density.

Once the spherulite diameter of the polymer spherulites is obtained as described above, the diameter distribution and number density or relative refractive index are then obtained as follows.

[Diameter distribution] The horizontal axis (wavelength) of the spectrum standardized by the above method is divided by 2πa using the obtained spherulite radius a and the graph is rewritten. For example, when the peak wavelength is equal to the spherulite diameter, it is as shown in FIG. 2A, and when the peak wavelength is equal to the spherulite diameter, it is as shown in FIG. 2B. Here, if the same value of b is used as the index, the shape of this spectrum will be the same regardless of the size of the spherulite diameter. However, the spherulite diameter is distributed, for example
, The spectrum is broader than when there is no distribution. It is possible to estimate the diameter distribution by quantifying this spread from the half width or the slope of the spectrum at an arbitrary point. It is necessary to clarify the relationship between the diameter distribution and the spectrum broadening in advance by experiments and theory.

The spherulite diameter previously obtained from the peak wavelength may be slightly deviated from the true value due to an error derived from the distribution of the actual average spherulite diameter. If the distribution is obtained correctly, this will allow further evaluation of the exact mean spherulite diameter.

[Number Density] In order to obtain the number density of spherulites, the relative refractive index m between the spherulites and the other amorphous portion must be accurately grasped by experiments or theoretical calculations. When the diameter distribution is not so large, the absorbance A measured by an ultraviolet-visible light spectrophotometer is represented by the following formula 8

[0034]

[Equation 8] It is represented by. Therefore, the number density N can be obtained because all the remaining values can be obtained by using the measured absorbance at the position of the peak in FIG. 1 before normalization of the wavelength.

[Relative Refractive Index] The relative refractive index m of a spherulite can be determined in the same manner as the case of the number density N described above by previously determining the number density N by an experiment.

[0036]

As is apparent from the above description, the present invention has the following effects because the spherulite size can be evaluated by the already established UV-visible spectroscopic technique and the simple calculation of the spectrum obtained there. is there.

The measurement is extremely simple, no special skill is required, and highly accurate measurement can be performed in a few minutes. As a result, even a spherulite size distribution is included in one measurement. Further, since human judgment is not required and the subjectivity of the measurer is not included, statistical processing is not required. That is, the method of spectrum normalization using the exponentiation of the wavelength does not require subjective judgment such as pattern recognition by a human as seen in electron microscopy and is simple. As a result, there is not much room for the difference in measurement depending on the measurer and the error due to the technique, and thus highly objective measurement can be performed.

From one measurement, the average spherulite diameter (its distribution depending on the accuracy of the spectrometer) and the number density become clear.

The measurement is considerably cheaper than the conventional method. For example, since it can be measured by a commercially available spectrometer, which is much cheaper than an electron microscope, the equipment cost is about 1/10.

It is possible to measure a wide range of spherulite diameter by the same measuring method, and it is possible to measure a wide range covering the actual spherulite diameter (several hundred nm to several μm). That is, by appropriately selecting and dividing the value of the exponent between -2 and -4, or by appropriately selecting and multiplying between the second and fourth power, a wide range can be obtained regardless of the wavelength range. The spherulite diameter can be measured.

[Brief description of drawings]

FIG. 1 shows the absorbance spectrum after error correction of 2.1
It is the spectrum figure normalized by multiplying by the 22nd power.

FIG. 2 is a spectrum diagram showing the influence of the spherulite diameter distribution of the absorbance spectrum rewritten by multiplying the wavelength by the b-th power,
In the case of b = 2.122 in (A), b = 2.36 in (B).
Is the case.

FIG. 3 is an absorbance spectrum diagram of a polyethylene sample measured using a normal UV-visible spectrophotometer.

Claims (4)

[Claims] 1. An absorption spectrum or a scattering intensity spectrum of a macromolecular spherulite to be measured is obtained, which is then multiplied by a power of a wavelength (wavelength ^b , b: a real number of 2 to 4) to be standardized, and a peak of the spectrum. A method for analyzing polymer spherulites, characterized in that the spherulite size is determined from the wavelength. 2. Using the spherulite radius a of the polymer obtained in claim 1, the wavelength of the normalized spectrum is 2π.
A method for analyzing polymer spherulites, which is characterized by dividing by a and normalizing the absorbance spectrum or scattered light spectrum with respect to the wavelength, and determining the distribution of spherulites from the degree of spread of the normalized spectrum shape. 3. The absorbance A which is the original measured value before normalization corresponding to the peak wavelength λ ₀ showing the polymer spherulite radius of the standardized spectrum obtained in claim 1 and the mathematical formula 1 are used: Number 1] [Where l is the sample thickness, m is the relative refractive index, and α is 2πa /
λ ₀ , f (α) is Raylei-Ganns-Debye (Raylei
This is a turbidity correction term based on the theory of sh-Gans-Debye). ]
The number density N is obtained from the relative density m obtained in advance,
Alternatively, from the number density N obtained in advance, the relative density m
A method for analyzing polymer spherulites, characterized in that 4. A spectroscopic means for obtaining an absorption spectrum or scattered light intensity spectrum of a polymer spherulite to be measured using an ultraviolet-visible spectrophotometer, and a power of a wavelength (wavelength ^b , b:
An apparatus for analyzing polymer spherulites, characterized in that it is provided with means for multiplying by 2 to 4). [Others] There is no change in the substance of the description.