Complete collection of detection and analysis methods of polymer materials

Date：2022-04-24 14:44:04 Views：1430

Polymer materials, as the name suggests, are materials based on polymer compounds. The polymer material industry should not only provide a large number of new products and materials with rapid changes for industrial and agricultural production and people's clothing, food, housing and transportation, but also provide more and more effective high-performance structural materials and functional materials for the development of high technology. The component analysis of polymer materials is a process of qualitative and quantitative analysis of unknown components of samples to be tested through a variety of separation technologies and various analytical instruments. Since the composition analysis of polymer materials is so complicated, it is very important to choose the appropriate analysis method. The following mainly introduces the composition detection and analysis methods of polymer materials for your reference.

1. Infrared spectroscopy (FTIR)

Infrared spectrum represents the molecular structure by means of the wavelength position of infrared absorption band and the strength and shape of absorption band, so it is often used to identify the structure of unknown substances or to qualitatively identify chemical groups and compounds. The absorption intensity of infrared absorption band is related to the molecular composition or the content of its chemical groups, so it can be used for quantitative analysis and compound purity identification. At present, infrared detection is mainly used for qualitative analysis. Usually, the spectrum of the sample is compared with that of the standard or literature. It can also be retrieved by computer spectrum library and identified by similarity. Infrared spectrum analysis runs through the whole process of analysis, from the initial information collection, to the subsequent monitoring of each compound component, and then to the analysis of compound structure after purification.

2. Gas chromatography-mass spectrometry (GC-MS)

GC-MS is often used in the separation, qualitative and quantitative analysis of additives in polymer materials. Generally, the auxiliaries in polymer materials are separated from resin, and then different auxiliaries are separated by gas chromatography column. Then, they are qualitatively compared with the standard spectrum in mass spectrometry and quantitatively combined with standard samples. In practical application, it is mainly used to analyze some organic additives with low boiling point and good thermal stability.

3. Thermogravimetric analysis (TGA)

Thermogravimetric analysis is the process of measuring the weight of samples with temperature or time by using program temperature control. Polymer materials will decompose, oxidize and volatilize with the increase of temperature, accompanied by the change of quality. By recording the relationship between quality and temperature, combined with the analysis results of other instruments, deduce the reasons for the change of quality, and then quantify the main components, additives, fillers, carbon black, etc.

4. Differential scanning calorimetry (DSC)

DSC uses programmed temperature control conditions to directly measure the energy absorbed or released by the sample in the process of heating, cooling or constant temperature. With the increase of temperature, polymer materials will have physical changes and accompanied by energy changes. The physical changes, such as melting point and glass transition temperature, can be detected by recording the relationship between energy and temperature, so as to realize the qualitative analysis of materials.

5. Elemental analysis (XRF)

X-ray excites the surface elements of polymer materials to make them have energy band transition, and then return to the ground state to emit fluorescence. Some elements in polymer materials are qualitative and semi quantitative by detecting the emitted fluorescence. This method is relatively easy to operate and can be used to confirm the basic information in the early stage of polymer material composition analysis. It is a qualitative and semi quantitative method.

6. Nuclear magnetic resonance (NMR)

NMR spectrum is divided into hydrogen spectrum and carbon spectrum, that is, to determine the structure of organic compounds by the chemical shift value of hydrogen atom or carbon atom, coupling constant and the area of absorption peak respectively. It is one of the best methods for the accuracy of structural information and the predictability of recommendation for unknown structures. Nuclear magnetic resonance spectroscopy can accurately provide information about hydrogen and carbon in organic compounds, as well as the functional groups, structural units and connection modes composed of them. In the component analysis of polymer materials, some separated and purified substances can be accurately identified by NMR, and the purity of samples is required to be relatively high.

7. Inductively coupled plasma emission spectrometry (ipc-oes)

ICP-OES is a common metal element analysis method, which is not suitable for polymer materials. However, because the general qualitative and semi quantitative element analysis methods can not carry out accurate quantification, the detection limit is not enough for the determination of some trace elements. ICP-OES is qualitative according to a series of characteristic wavelengths produced by atoms from ground state to excited state, and then quantitative according to the intensity of spectral line and standard working curve. It has the characteristics of low detection limit and high accuracy. Quantitative analysis of inorganic components is often used in the composition analysis of polymer materials.

8. Pyrolysis gas chromatography (Py-GC-MS)

Py-GC-MS is connected with a cracker on the sample injector of GC-MS. when the high polymer enters the high-temperature cracker, it will be cracked into volatile small molecules and enter GC-MS for separation and detection together with low molecular compounds. Compared with infrared absorption spectroscopy, it plays an irreplaceable role in analyzing various forms of polymer samples, including identifying non fusible thermosetting resins, identifying homopolymers with similar composition, distinguishing copolymers and blends. In addition, it can also be used to analyze some additives in polymer materials. In the actual analysis process, in order to reduce the blindness of analysis, it is required to have a preliminary grasp of the cracking spectrum of common polymer materials or additive systems in order to ensure more accurate detection.

9. High performance liquid chromatography (HPLC)

HPLC is based on classical chromatography, which improves the column efficiency by changing the mobile phase to high-pressure transportation. This method has a wide range of application, can make up for the shortcomings of GC-MS, and is suitable for the analysis of some organic additives with high boiling point, poor thermal stability and large relative molecular weight. However, compared with GC-MS, due to the lack of MS assistance, other means should be used for qualitative analysis in the actual analysis process, which is not suitable for blind sample analysis or preliminary information collection.

10. X-ray diffraction (XRD)

XRD is a method to obtain the characteristics of X-ray signal after diffraction by using the diffraction phenomenon of X-ray in the crystal. After processing, the diffraction pattern is obtained to analyze the phase or compound structure. It is a method to determine the phase and crystal state of compounds. It is often used to identify the structure of inorganic compounds in the composition analysis of polymer materials. However, XRD is suitable for the analysis of crystalline, microcrystalline or quasi crystalline compounds, not amorphous compounds.

11. X-ray photoelectron spectroscopy (XPS)

XPS uses X-ray to act on the sample surface to produce photoelectrons. By analyzing the energy distribution of photoelectrons, photoelectron spectroscopy is obtained to study the composition and structure of the sample surface. This method is often used to determine the valence state of compounds, so as to obtain the structure of compounds. XRD can not identify amorphous inorganic compounds, and XPS can make up for this deficiency.

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