CN116297299A - A Method for Measuring Polymer Crystallinity Based on Terahertz Time-Domain Spectroscopy - Google Patents
A Method for Measuring Polymer Crystallinity Based on Terahertz Time-Domain Spectroscopy Download PDFInfo
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Abstract
本发明涉及聚合物结晶度测量技术，旨在提供一种基于太赫兹时域光谱的聚合物结晶度测量方法。包括：以氮气为参考样品，以干燥处理后的结晶性聚合物样品作为待测样品；分别采集参考样品和待测样品的太赫兹时域光谱；对获得的太赫兹时域光谱进行快速傅里叶变换，得到太赫兹吸收光谱；确定待测样品在太赫兹吸收光谱中的太赫兹特征峰；对待测样品的太赫兹吸收光谱进行曲线拟合，并根据太赫兹特征峰计算峰面积；计算聚合物样品结晶度。本发明能够有效反映聚合物结晶区的产生和所占比例，从而快速、简单、无损地确定其相对结晶度；能够最大程度上弥补现有传统检测技术的缺陷，具有实际应用价值。
The invention relates to polymer crystallinity measurement technology and aims to provide a polymer crystallinity measurement method based on terahertz time-domain spectroscopy. Including: taking nitrogen as a reference sample, and taking a dried crystalline polymer sample as a sample to be tested; respectively collecting the terahertz time-domain spectra of the reference sample and the sample to be tested; performing fast Fourier analysis on the obtained terahertz time-domain spectra leaf transformation to obtain the terahertz absorption spectrum; determine the terahertz characteristic peak of the sample to be tested in the terahertz absorption spectrum; perform curve fitting on the terahertz absorption spectrum of the sample to be tested, and calculate the peak area according to the terahertz characteristic peak; calculate the aggregation crystallinity of the sample. The invention can effectively reflect the generation and proportion of polymer crystallization regions, so as to quickly, simply and nondestructively determine its relative crystallinity; it can make up for the defects of the existing traditional detection technology to the greatest extent, and has practical application value.
Description
技术领域technical field
本发明属于聚合物结晶度测量技术，具体涉及一种基于太赫兹时域光谱的聚合物结晶度测量方法。The invention belongs to polymer crystallinity measurement technology, in particular to a polymer crystallinity measurement method based on terahertz time-domain spectroscopy.
背景技术Background technique
聚合物材料是指由许多相同的、简单的结构单元通过共价键重复连接而成的高分子量化合物(一般在103～107)。聚合物中规则排列的区域称为结晶区，而无序排列区域被称为非晶区，结晶区所占百分比称为结晶度。在实际晶态聚合物中，结晶区和非晶区通常是同时存在的。聚合物的结晶程度显著影响其各种物理机械性能。例如，同一种聚合物材料，一般来说其结晶度越高，熔点就越高。因此，不管对于理论研究还是实际应用方面，结晶度是一个描述聚合物性质的重要指标，定量计算其相对数值也是一个十分重要的工作。Polymer materials refer to high-molecular-weight compounds (generally 10 3 -10 7 ) composed of many identical and simple structural units linked repeatedly through covalent bonds. The regularly arranged regions in the polymer are called crystalline regions, while the disorderly arranged regions are called amorphous regions, and the percentage of crystalline regions is called crystallinity. In actual crystalline polymers, crystalline and amorphous regions usually exist simultaneously. The degree of crystallinity of a polymer significantly affects its various physical and mechanical properties. For example, generally speaking, the higher the crystallinity of the same polymer material, the higher the melting point. Therefore, no matter for theoretical research or practical application, crystallinity is an important index to describe the properties of polymers, and quantitative calculation of its relative value is also a very important work.
目前，测量聚合物结晶度的常用方法有X射线衍射法、中红外光谱法、差示扫描量热法和密度测定法等。其中，X射线衍射法的测量计算被样品纯度和测试基底所限制，不同的测试基底对结晶度计算结果影响显著，同时也会对样品产生电离辐射。中红外光谱一般应用于材料的定性分析，而对于聚合物结晶度的定量计算则被结晶相和非晶相的吸收峰显著程度、分离程度所限制，此外，中红外光谱大多数基于吸收峰强度差值计算结晶度，此方法缺乏严谨性。差示扫描量热法会对样品完全破坏；密度测定法的计算结果误差范围较大。因此，现有的传统结晶度检测技术在一定程度上很难满足聚合物材料表征领域的快速发展。At present, the commonly used methods for measuring the crystallinity of polymers include X-ray diffraction, mid-infrared spectroscopy, differential scanning calorimetry, and densitometry. Among them, the measurement and calculation of the X-ray diffraction method is limited by the purity of the sample and the test substrate. Different test substrates have a significant impact on the crystallinity calculation results, and will also generate ionizing radiation to the sample. Mid-infrared spectroscopy is generally used in the qualitative analysis of materials, while the quantitative calculation of polymer crystallinity is limited by the significance and separation of the absorption peaks of crystalline and amorphous phases. In addition, mid-infrared spectroscopy is mostly based on the intensity of absorption peaks The difference calculates the degree of crystallinity, and this method lacks rigor. Differential scanning calorimetry will completely destroy the sample; the calculation results of densitometric method have a large error range. Therefore, the existing traditional crystallinity detection technology is difficult to meet the rapid development in the field of polymer material characterization to a certain extent.
如今，振动光谱技术由于其无损性、穿透性和瞬态性等优点得到蓬勃发展。其中，太赫兹光谱学是一种新兴的直接测量偶极跃迁的非破坏性技术。0.1～10THz，0.03～3mm波段被称为太赫兹区域。通过太赫兹时域光谱系统可以得到样品在太赫兹波段的折射率、吸收系数、介电常数等光学物理信息。Nowadays, vibrational spectroscopy is flourishing due to its non-destructive, penetrating and transient properties. Among them, terahertz spectroscopy is an emerging non-destructive technique to directly measure dipole transitions. 0.1 ~ 10THz, 0.03 ~ 3mm band is called the terahertz region. Through the terahertz time-domain spectroscopy system, optical and physical information such as the refractive index, absorption coefficient, and dielectric constant of the sample in the terahertz band can be obtained.
太赫兹波对聚合物的高阶结构非常敏感，可以直接观察聚合物的晶体结构。与X射线衍射法类似，聚合物在太赫兹波段中的振动模式来源于其本身的结晶区，而其非晶区由于缺乏长程结构而无明显的光谱特征，从而导致了太赫兹光谱形状随聚合物结晶度的变化而变化。常规太赫兹测量技术获得的太赫兹光谱目前仍只是局限于材料的定性表征，未实现对聚合物结晶度的有效测量，其最大原因在于聚合物在庞大单元的影响下导致其振动模态难以很好解析。本发明提出通过太赫兹吸收光谱拟合后的积分面积，提供一种有效的计算聚合物结晶度的方法。Terahertz waves are very sensitive to the high-order structure of polymers, and can directly observe the crystal structure of polymers. Similar to the X-ray diffraction method, the vibration mode of the polymer in the terahertz band comes from its own crystalline region, while its amorphous region has no obvious spectral features due to the lack of long-range structure, which leads to the shape of the terahertz spectrum varying with the polymerization. Changes in the crystallinity of the compound. The terahertz spectrum obtained by the conventional terahertz measurement technology is still limited to the qualitative characterization of the material, and the effective measurement of the crystallinity of the polymer has not been realized. Good analysis. The invention provides an effective method for calculating the crystallinity of a polymer through the integrated area after fitting the terahertz absorption spectrum.
发明内容Contents of the invention
本发明所需要解决的技术问题为：克服现有技术的不足，提供一种基于太赫兹时域光谱的聚合物结晶度测量方法。The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a polymer crystallinity measurement method based on terahertz time-domain spectroscopy.
为解决上述技术问题，本发明的解决方案是：In order to solve the problems of the technologies described above, the solution of the present invention is:
提供一种基于太赫兹时域光谱的聚合物结晶度测量方法，包括以下步骤：A method for measuring crystallinity of polymers based on terahertz time-domain spectroscopy is provided, comprising the following steps:
(1)以氮气为参考样品，以干燥处理后的结晶性聚合物样品作为待测样品；分别采集参考样品和待测样品的太赫兹时域光谱；(1) Take nitrogen as a reference sample, and use the dried crystalline polymer sample as the sample to be tested; respectively collect the terahertz time-domain spectra of the reference sample and the sample to be tested;
(2)对获得的太赫兹时域光谱进行快速傅里叶变换，得到太赫兹吸收光谱；(2) Fast Fourier transform is performed on the obtained terahertz time-domain spectrum to obtain a terahertz absorption spectrum;
(3)确定待测样品在太赫兹吸收光谱中的太赫兹特征峰；(3) Determine the terahertz characteristic peak in the terahertz absorption spectrum of the sample to be tested;
(4)对待测样品的太赫兹吸收光谱进行曲线拟合，并根据太赫兹特征峰计算峰面积；(4) Curve fitting is performed on the terahertz absorption spectrum of the sample to be tested, and the peak area is calculated according to the terahertz characteristic peak;
(5)计算聚合物样品结晶度。(5) Calculate the crystallinity of the polymer sample.
作为本发明的优选方案，步骤(1)中作为参考样品的氮气纯度在97％以上。As a preferred version of the present invention, the nitrogen purity of the reference sample in step (1) is above 97%.
作为本发明的优选方案，所述步骤(1)中所述测量的操作内容具体包括：As a preferred solution of the present invention, the operation content of the measurement described in the step (1) specifically includes:
在室温条件下，使用太赫兹时域光谱仪对待测样品进行光谱采集；采集过程中持续以氮气吹扫，保持测试环境相对湿度始终小于3％；将获取的太赫兹时域光谱数据以txt格式保存。At room temperature, use a terahertz time-domain spectrometer to collect spectra of the samples to be tested; continuously purging with nitrogen during the collection process, keeping the relative humidity of the test environment always less than 3%; save the acquired terahertz time-domain spectral data in txt format .
作为本发明的优选方案，所述步骤(2)具体包括：As a preferred version of the present invention, the step (2) specifically includes:
分别记录参考样品和测试样品的太赫兹电场的频域谱，并按下述公式对得到的太赫兹时域光谱进行快速傅里叶变换，得到太赫兹吸收光谱：Record the frequency-domain spectrum of the terahertz electric field of the reference sample and the test sample respectively, and perform fast Fourier transformation on the obtained terahertz time-domain spectrum according to the following formula to obtain the terahertz absorption spectrum:
式中，T(ω)为传递函数；ω为角频率；Esample(ω)和Ereference(ω)分别为样品信号和参考信号；n(ω)为折射率；c为光速3×108m/s；i为虚数单位；a(ω)为吸收系数；k(ω)为消光系数；d为样品厚度。In the formula, T(ω) is the transfer function; ω is the angular frequency; E sample (ω) and E reference (ω) are the sample signal and reference signal respectively; n(ω) is the refractive index; c is the speed of light 3×10 8 m/s; i is the imaginary unit; a(ω) is the absorption coefficient; k(ω) is the extinction coefficient; d is the sample thickness.
作为本发明的优选方案，所述步骤(3)具体包括：As a preferred version of the present invention, the step (3) specifically includes:
对太赫兹吸收光谱进行分析，根据待测样品的光谱特征来确定太赫兹特征峰。The terahertz absorption spectrum is analyzed, and the terahertz characteristic peak is determined according to the spectral characteristics of the sample to be tested.
作为本发明的优选方案，所述步骤(4)具体包括：As a preferred version of the present invention, the step (4) specifically includes:
(4.1)基于洛伦兹振子模型，利用洛伦兹函数对待测样品的太赫兹吸收光谱进行曲线拟合；(4.1) Based on the Lorentz oscillator model, use the Lorentz function to perform curve fitting on the terahertz absorption spectrum of the sample to be measured;
(4.2)根据拟合曲线中待测样品的太赫兹特征峰的情况，以结晶区和非晶区的积分强度作为峰面积，分别记作Icrystal和Iamorphous。(4.2) According to the terahertz characteristic peak of the sample to be measured in the fitting curve, the integrated intensity of the crystalline region and the amorphous region is used as the peak area, which is recorded as I crystal and I amorphous , respectively.
作为本发明的优选方案，所述步骤(5)具体包括：As a preferred version of the present invention, the step (5) specifically includes:
根据下式计算待测样品的结晶度XC：Calculate the crystallinity X C of the sample to be tested according to the following formula:
XC＝Icrystal/(Icrystal+Iamorphous)X C ＝I crystal /(I crystal +I amorphous )
式中，XC为待测样品的结晶度，Icrystal为拟合曲线中结晶区的峰面积，Iamorphous为拟合曲线中非晶区的峰面积。In the formula, X C is the crystallinity of the sample to be tested, I crystal is the peak area of the crystalline region in the fitting curve, and I amorphous is the peak area of the amorphous region in the fitting curve.
与现有技术相比，本发明的有益技术效果是：Compared with the prior art, the beneficial technical effect of the present invention is:
1、本发明基于太赫兹吸收光谱，利用洛伦兹函数拟合曲线，能够有效反映聚合物结晶区的产生和所占比例，从而快速、简单、无损地确定其相对结晶度。1. Based on the terahertz absorption spectrum, the present invention uses the Lorentz function to fit the curve, which can effectively reflect the generation and proportion of the polymer crystallization region, so as to determine its relative crystallinity quickly, simply and nondestructively.
2、本发明提供的聚合物结晶度测量方法，其结晶度测量值与差示扫描量热和X射线衍射法获得的数据接近，测量精确度符合实际应用需求。在此前提下，本发明与差示扫描量热和X射线衍射法相比，具有快速、无损的额外好处。因此，本发明能够最大程度上弥补现有传统检测技术的缺陷，具有实际应用价值。2. The crystallinity measurement method of the polymer provided by the present invention is close to the data obtained by differential scanning calorimetry and X-ray diffraction, and the measurement accuracy meets the actual application requirements. Under this premise, the present invention has the additional advantage of being fast and non-destructive compared with differential scanning calorimetry and X-ray diffraction. Therefore, the present invention can make up for the defects of the existing traditional detection technology to the greatest extent, and has practical application value.
附图说明Description of drawings
图1为本发明方法的流程图；Fig. 1 is the flowchart of the inventive method;
图2为聚合物样品太赫兹吸收光谱曲线拟合过程示意图；Fig. 2 is a schematic diagram of the curve fitting process of the polymer sample terahertz absorption spectrum;
图3为本发明测量所得结晶度结果与X射线衍射法测量所得结晶度结果的对比图；Fig. 3 is the comparison chart of the obtained crystallinity result measured by the present invention and the obtained crystallinity result measured by X-ray diffraction method;
图4为本发明测量所得结晶度结果与差示扫描量热法测量所得结晶度结果的对比图。Fig. 4 is a comparison chart of crystallinity results measured by the present invention and crystallinity results measured by differential scanning calorimetry.
具体实施方式Detailed ways
下面结合附图和实施例对本发明作进一步说明。The present invention will be further described below in conjunction with drawings and embodiments.
本发明提供的基于太赫兹时域光谱的聚合物结晶度测量方法，包括以下步骤：The polymer crystallinity measurement method based on terahertz time-domain spectroscopy provided by the present invention comprises the following steps:
(1)以氮气为参考样品，以干燥处理后的结晶性聚合物样品作为待测样品；分别采集参考样品和待测样品的太赫兹时域光谱；(1) Take nitrogen as a reference sample, and use the dried crystalline polymer sample as the sample to be tested; respectively collect the terahertz time-domain spectra of the reference sample and the sample to be tested;
所述测量的操作内容具体包括：在室温条件下(如24℃)，使用太赫兹时域光谱仪对氮气和待测样品分别进行光谱采集，采集过程中以高纯氮气持续吹扫以保持测试环境相对湿度始终小于3％；其中待测样品至少采集三次，每次采集进行1024次扫描，将获取的太赫兹时域光谱数据以txt格式保存。The operation content of the measurement specifically includes: at room temperature (such as 24°C), use a terahertz time-domain spectrometer to collect spectra of nitrogen and the sample to be tested, and continuously purse with high-purity nitrogen to maintain the test environment during the collection process. The relative humidity is always less than 3%; the sample to be tested is collected at least three times, and each collection is scanned 1024 times, and the acquired terahertz time-domain spectral data is saved in txt format.
本发明针对待测样品进行光谱采集是在氮气环境中进行的，因此以氮气(测试背景)作为参考样品。所以在得到待测样品的太赫兹光谱后，需消除氮气的影响。In the present invention, the spectral collection of the sample to be tested is carried out in a nitrogen environment, so nitrogen (test background) is used as a reference sample. Therefore, after obtaining the terahertz spectrum of the sample to be tested, it is necessary to eliminate the influence of nitrogen.
(2)对太赫兹时域光谱进行快速傅里叶变换，得到太赫兹吸收光谱；具体包括：(2) Perform fast Fourier transform on the terahertz time-domain spectrum to obtain the terahertz absorption spectrum; specifically include:
分别记录参考样品和测试样品的太赫兹电场的频域谱，按下述公式对得到的太赫兹时域光谱进行快速傅里叶变换，得到太赫兹吸收光谱：Record the frequency-domain spectrum of the terahertz electric field of the reference sample and the test sample respectively, and perform fast Fourier transformation on the obtained terahertz time-domain spectrum according to the following formula to obtain the terahertz absorption spectrum:
式中，T(ω)为传递函数；ω为角频率；Esample(ω)和Ereference(ω)分别为样品信号和参考信号；n(ω)为折射率；c为光速3×108m/s；i为虚数单位；a(ω)为吸收系数；k(ω)为消光系数；d为样品厚度。In the formula, T(ω) is the transfer function; ω is the angular frequency; E sample (ω) and E reference (ω) are the sample signal and reference signal respectively; n(ω) is the refractive index; c is the speed of light 3×10 8 m/s; i is the imaginary unit; a(ω) is the absorption coefficient; k(ω) is the extinction coefficient; d is the sample thickness.
(3)对太赫兹吸收光谱进行分析，根据待测样品的光谱特征来确定太赫兹特征峰。(3) Analyze the terahertz absorption spectrum, and determine the terahertz characteristic peak according to the spectral characteristics of the sample to be tested.
(4)基于洛伦兹振子模型，利用洛伦兹函数对待测样品的太赫兹吸收光谱进行曲线拟合；(4) Based on the Lorentz oscillator model, the Lorentz function is used to perform curve fitting on the terahertz absorption spectrum of the sample to be measured;
根据拟合曲线中待测样品的太赫兹特征峰的情况，以结晶区和非晶区的积分强度作为峰面积，分别记作Icrystal和Iamorphous。According to the terahertz characteristic peaks of the samples to be measured in the fitting curve, the integrated intensities of the crystalline region and the amorphous region were used as the peak areas, which were recorded as I crystal and I amorphous , respectively.
由于实验数据点是不连续的，因此本发明利用数学函数模型对实验数据进行拟合，以获取更好的实验结果，并以拟合后的曲线用作结晶度的计算基础。Since the experimental data points are discontinuous, the present invention uses a mathematical function model to fit the experimental data to obtain better experimental results, and uses the fitted curve as the basis for calculating the crystallinity.
(5)根据下式计算待测样品的结晶度XC：(5) Calculate the crystallinity X C of the sample to be tested according to the following formula:
XC＝Icrystal/(Icrystal+Iamorphous)X C ＝I crystal /(I crystal +I amorphous )
式中，XC为待测样品的结晶度，Icrystal为拟合曲线中结晶区的峰面积，Iamorphous为拟合曲线中非晶区的峰面积。In the formula, X C is the crystallinity of the sample to be tested, I crystal is the peak area of the crystalline region in the fitting curve, and I amorphous is the peak area of the amorphous region in the fitting curve.
具体实施例1Specific embodiment 1
本实例以聚乳酸作为待测样品，以纯度在97％以上的氮气作为参考样品。In this example, polylactic acid is used as the sample to be tested, and nitrogen with a purity of more than 97% is used as the reference sample.
(1)通过溶液结晶法分别制备7个不同结晶度的聚乳酸薄膜，干燥处理后作为待测样品，防止水分影响太赫兹时域光谱测量结果；(1) Prepare 7 polylactic acid films with different crystallinity by solution crystallization method, and use them as samples to be tested after drying treatment to prevent moisture from affecting the measurement results of terahertz time-domain spectroscopy;
使用大恒光电子公司生产的太赫兹时域光谱仪对参考样品和待测样品分别进行测量操作，以采集太赫兹时域光谱。所有测量操作均在室温(24℃)条件下进行，待测样品平均进行三次测量，每次测量包括1024次扫描；测量过程中用高纯氮气持续吹扫以保持测试环境相对湿度始终小于3％；将获取的太赫兹时域光谱数据以txt格式保存。Use a terahertz time-domain spectrometer produced by Daheng Optoelectronics Co., Ltd. to perform measurement operations on the reference sample and the sample to be tested respectively to collect terahertz time-domain spectra. All measurement operations are carried out at room temperature (24°C). The sample to be tested is measured three times on average, and each measurement includes 1024 scans; during the measurement process, high-purity nitrogen is continuously purged to keep the relative humidity of the test environment less than 3%. ; Save the acquired terahertz time-domain spectral data in txt format.
(2)对得到的太赫兹时域光谱进行快速傅里叶变换，得到相应的太赫兹吸收光谱：记录参考样品和测试样品的太赫兹电场的时域图谱，按前述公式对得到的时域频谱和太赫兹光谱吸收进行快速傅里叶变换，得到太赫兹吸收光谱。(2) Perform fast Fourier transform on the obtained terahertz time-domain spectrum to obtain the corresponding terahertz absorption spectrum: record the time-domain spectra of the terahertz electric field of the reference sample and the test sample, and compare the obtained time-domain spectrum according to the above formula Perform fast Fourier transform with terahertz spectral absorption to obtain terahertz absorption spectrum.
(3)对太赫兹吸收光谱进行分析，根据聚乳酸的光谱特征来确定太赫兹特征峰。(3) Analyze the terahertz absorption spectrum, and determine the terahertz characteristic peak according to the spectral characteristics of polylactic acid.
以图2为例，在图中，聚乳酸的太赫兹光谱中2.01THz处的相对吸收强度显著高于附近频率的吸收强度，呈现波峰状态，确定此处为聚乳酸的特征峰频率。Taking Figure 2 as an example, in the figure, the relative absorption intensity at 2.01THz in the terahertz spectrum of polylactic acid is significantly higher than that at nearby frequencies, presenting a peak state, which is determined to be the characteristic peak frequency of polylactic acid.
(4)基于洛伦兹振子模型，利用洛伦兹函数对待测样品的太赫兹吸收光谱进行曲线拟合；根据拟合曲线中待测样品的太赫兹特征峰的情况，以结晶区和非晶区的积分强度作为峰面积，分别记作Icrystal和Iamorphous。(4) Based on the Lorentz oscillator model, use the Lorentz function to perform curve fitting on the terahertz absorption spectrum of the sample to be tested; according to the terahertz characteristic peak of the sample to be tested in the fitted curve, the The integrated intensities of the regions are taken as the peak areas and are denoted as I crystal and I amorphous , respectively.
以图2为例，与X射线衍射法计算结晶度相同，在图中，通过洛伦兹函数拟合，基线划分拟合曲线程两个区域：结晶相(黑色区域)和非晶相区域(斜划线区域)，点划线上半部分为结晶相所引起得特征振动，出现显著特征峰，下半部分为非晶相所引起的振动，并未出现特征峰。Taking Figure 2 as an example, it is the same as the crystallinity calculated by the X-ray diffraction method. In the figure, by fitting the Lorentz function, the baseline divides the fitting curve into two areas: the crystalline phase (black area) and the amorphous phase area ( Diagonal line area), the half of the dotted line is the characteristic vibration caused by the crystalline phase, and a significant characteristic peak appears, and the lower half is the vibration caused by the amorphous phase, and no characteristic peak appears.
(5)根据下式计算待测样品的结晶度XC：(5) Calculate the crystallinity X C of the sample to be tested according to the following formula:
XC＝Icrystal/(Icrystal+Iamorphous)X C ＝I crystal /(I crystal +I amorphous )
式中，XC为待测样品的结晶度，Icrystal为拟合曲线中结晶区的峰面积，Iamorphous为拟合曲线中非晶区的峰面积。In the formula, X C is the crystallinity of the sample to be tested, I crystal is the peak area of the crystalline region in the fitting curve, and I amorphous is the peak area of the amorphous region in the fitting curve.
在本实例中，经计算最终得到了7个聚乳酸待测样品的结晶度结果，分别为18.1％、21.4％、25.1％、25.7％、26.4％、28.5％和31％。In this example, the crystallinity results of 7 polylactic acid samples to be tested are finally calculated, which are 18.1%, 21.4%, 25.1%, 25.7%, 26.4%, 28.5% and 31%.
结果评价：Result evaluation:
为了评价本发明测量方法的准确性，引入相关系数R的概念。In order to evaluate the accuracy of the measurement method of the present invention, the concept of correlation coefficient R is introduced.
相关系数R具体是指：反映变量之间相关关系密切程度的统计指标。相关系数是按积差方法计算，同样以两变量与各自平均值的离差为基础，通过两个离差相乘来反映两变量之间相关程度，表达式为：The correlation coefficient R specifically refers to: a statistical index that reflects the closeness of the correlation between variables. The correlation coefficient is calculated according to the product difference method. It is also based on the deviation between the two variables and their respective average values. The degree of correlation between the two variables is reflected by multiplying the two deviations. The expression is:
其中，xi和yi分别表示第i个待测聚乳酸样品中晶型含量的实际值和计算值，
因此，根据R值的大小可以评价结晶度的计算准确性。R值越接近1，计算结果与实际值越接近。Therefore, the calculation accuracy of crystallinity can be evaluated according to the value of R. The closer the R value is to 1, the closer the calculated result is to the actual value.
如图3、4所示，本发明测量所得结晶度结果与采用X射线衍射法和差示扫描量热法测量所得结晶度结果进行比对，所得7个聚乳酸样品结晶度(计算值)与X射线衍射法和差示扫描量热法测量的数据的相关系数均大于0.98。因此，可以证明根据本发明提供的测量方法所获得的结晶度结果满足准确性要求，具有实际应用意义。As shown in Figures 3 and 4, the crystallinity results measured by the present invention are compared with the crystallinity results measured by X-ray diffraction and differential scanning calorimetry. The correlation coefficients of the data measured by X-ray diffraction method and differential scanning calorimetry are all greater than 0.98. Therefore, it can be proved that the crystallinity results obtained by the measurement method provided by the present invention meet the accuracy requirements and have practical application significance.
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