High performance liquid chromatography analysis method for distribution of components with different polymerization degrees of phthalonitrile resin
Technical Field
The invention relates to the field of characterization research of phthalonitrile-based resin; in particular to a high performance liquid chromatography analysis method for the distribution of components with different polymerization degrees of phthalonitrile resin.
Background
The phthalonitrile resin is a general name of high-performance thermosetting resin obtained by thermal polymerization of a phthalonitrile structure-terminated precursor, a stable high-molecular reticular structure is formed by ring polymerization of nitrile groups on a molecular structure, and a cured product of the phthalonitrile resin mainly comprises heterocyclic structures such as phthalo ring, triazine ring or isoindoline, so that the phthalonitrile resin has excellent thermal stability, corrosion resistance, irradiation resistance, flame retardance, self-extinguishment, outstanding optical performance and electrical performance, can be used as a resin matrix of a composite material with extreme service performance, and has wide application prospect in the high and new technical fields of aerospace, automobiles, electronics, machinery and the like. Prepared by the thermal polymerization addition reaction of a bisphthalonitrile monomer, the polymerization rate of the resin can be changed by changing the type of the added curing agent and the processing temperature, and the resin is also the excellent characteristic in the manufacturing application of composite materials and parts thereof.
The characterization of this class of resins is mainly structural analysis and performance evaluation. The main means currently used for structural analysis are infrared, nuclear magnetic, gel chromatography. The evaluation of the properties can be carried out by thermal analysis (TGA, DSC), Dynamic Mechanical Analysis (DMA), rheological analysis, etc. The molecular weight distribution of the phthalonitrile resin is measured, and the content distribution of high, medium and low polymerization degree components in the phthalonitrile resin can be described or used for controlling through the measurement of the molecular weight distribution. Wangwangxing et al (CN109705072A) synthesized an oligomer of phthalonitrile, characterized the resin by TGA, DMA and determined the molecular weight distribution by Gel Permeation Chromatography (GPC). Lei qin et al (CN108454135A) prepared a phthalonitrile composite material, and the mechanical properties of the material were tested by dynamic mechanics. Zhongchun (CN106947076) synthesized a phthalonitrile polyaryletherketone resin, and the structure was identified and characterized by infrared spectroscopy.
The phthalonitrile resin has a complex structure, the difference of resins prepared by different curing agents or methods is large, certain difficulties exist in characterization and evaluation, and the method is poor in universality. In view of the principle of Gel Permeation Chromatography (GPC) analysis, the difference between the structural composition of the standard sample used for drawing the standard curve and the actual sample is often large, which has a great influence on the analysis result, and such a deviation is difficult to avoid due to the limitation of the standard sample. Therefore, the method has certain limitation on the determination of the GPC molecular weight distribution of the phthalonitrile resin, relatively complex operation and high analysis cost.
Disclosure of Invention
The invention aims to provide a high performance liquid chromatography analysis method for distribution of components with different polymerization degrees of phthalonitrile resin, which adopts a reversed phase chromatography which is most convenient to operate in the high performance liquid chromatography, selects a general octadecyl (C18) chromatographic column with good universality, takes water and methanol as mobile phases, and carries out elution and separation on the components with different polymerization degrees of phthalonitrile resin in a gradient elution mode, and can confirm different requirements on the area contents of characteristic peaks of the components with different polymerization degrees, such as high, medium and low polymerization degrees according to the performance requirements of subsequent processing products on the phthalonitrile resin.
In order to achieve the purpose, the invention adopts the following technical scheme:
a high performance liquid chromatography analysis method for the distribution of components with different polymerization degrees of phthalonitrile resin selects high performance liquid reverse phase chromatography, adopts methanol water as a mobile phase, carries out gradient elution and separation to obtain the distribution of phthalonitrile resin components, divides chromatographic peaks into three types of oligomers, middle polymers and high polymers according to chromatographic peak outflow rules and sample structural characteristics, takes the sum of the contents of the chromatographic peaks of the same type as a final result, analyzes and evaluates the components of the resins, and predicts molecular weight distribution and subsequent product performance.
The method comprises the following steps:
1) a C18 chromatographic column with high generality in reversed phase chromatography is selected, and different components in a plurality of phthalonitrile resins are reserved on the chromatographic column; the separation degree and the peak symmetry degree can meet the requirements of method development, the operation is simpler and more convenient, and the method has high repeatability.
Gradient elution is carried out by adopting methanol and water in different proportions; the method has the advantages of good separation effect on various phthalonitrile resins, valuable component distribution information, good universality, small toxicity of the used solvent and low cost.
The phthalonitrile resin has more complex components, the ultraviolet-visible detector has response to most organic matters at the wavelength of 254nm, and the method is more suitable for selecting 254nm as the detection wavelength.
2) Measuring the distribution of the phthalonitrile resin with different polymerization degrees, and dividing the outflow chromatographic peaks into three categories according to the flowing universality of the chromatographic peaks and the structural characteristics of the phthalonitrile resin: an oligomer component, a middle polymer component and a high polymer component;
3) the characteristic peaks of the components with different polymerization degrees suitable for the resin are defined, the peak areas of the characteristic peaks are recorded, the content of the peak areas is calculated, the performance obtained after the resin is processed can be predicted, otherwise, the characteristic peaks can be used for controlling the requirements of the components with different polymerization degrees of the phthalonitrile resin as the subsequent material raw material, and the molecular weight distribution can be predicted and controlled.
The analysis conditions of the liquid phase reverse phase chromatography are as follows:
a chromatographic column: XDB C18150 m m.times.4.6 mm, 5 μm; detecting the temperature: 40 ℃; detection wavelength: 254 nm; mobile phase: methanol and water; sample introduction amount: 50 mu L of the solution; flow rate: 1.0 mL/min.
The gradient elution flow phase ratio changes are shown in table 1:
TABLE 1
The number average molecular weight distribution range of the phthalonitrile resin is 1000-10000.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a liquid phase evaluation method of phthalonitrile resin, which analyzes and characterizes complex resin by adopting a simple high performance liquid chromatography method to obtain the distribution conditions of components with different polymerization degrees, thereby more intuitively obtaining the information of the components with different polymerization degrees of oligomeric phthalonitrile resin. The method is applied to the component analysis and evaluation of the oligomeric phthalonitrile resin product, the performance prediction of subsequent processed products and the like through characteristic peaks and proportion information.
The method has the advantages that the method analyzes, evaluates and characterizes the components with different polymerization degrees of the phthalonitrile resin through a high performance liquid chromatography, has consistency with the result measured by a GPC (GPC) traditional method, has the same rule on the influence of the content distribution degree of the components with different polymerization degrees on the number average molecular weight (Mn), has the characteristics of convenience and quickness, can monitor the polymerization reaction in real time, and controls the proportional polymer components with different control characteristic peak areas in the reaction process, thereby achieving the purposes of anticipating the performance requirement of the product, the molecular weight distribution, the control of different polymerization degrees and the like.
Drawings
FIG. 1 is a high performance liquid chromatogram of an oligomeric phthalonitrile resin according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. The specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention, which is intended to be within the scope of the invention as defined by the appended claims.
Example 1
1) Examples liquid chromatography conditions:
an Alliance system high performance liquid chromatograph (Waters, usa) equipped with 2489 uv detector, 2695 pump, Empower workstation; methanol (chromatographically pure, world in the united states); ultrapure water, N-N-dimethylformamide (analytical grade).
A chromatographic column: XDB C18(150m m X4.6 mm, 5 μm);
detecting the temperature: 40 ℃; detection wavelength: 254 nm;
mobile phase: methanol and water;
sample introduction amount: 50 mu L of the solution;
flow rate: 1.0 mL/min.
The gradient elution flow phase ratio was varied as shown in table 1.
All samples were dissolved in N-N-dimethylformamide, diluted with methanol to give a sample having a concentration of about 2mg/mL, and filtered through a 0.22 μm oil film for further use.
2) Classifying chromatographic peaks to obtain the component distribution of the oligomeric phthalonitrile resin:
accurately weighing 50mg of phthalonitrile resin, dissolving by using N-N-dimethylformamide, fixing the volume to 25mL by using methanol, and separating the phthalonitrile resin by adopting the liquid chromatography condition described in the step 1). Classifying the effluent chromatographic peaks according to the universality rule of the effluent chromatographic peak and the structural characteristics of the phthalonitrile resin, wherein the chromatographic peaks 1, 2 and 3 are oligomer characteristic peaks, the chromatographic peaks 4, 5, 6 and 7 are middle polymer characteristic peaks, and the chromatographic peaks 8, 9 and 10 are high polymer characteristic peaks. And taking the sum of the contents of the characteristic peaks in the same category as the final contents of the components with different polymerization degrees. Specific chromatographic peak retention times and classifications are shown in table 2 and chromatograms are shown in figure 1.
TABLE 2 phthalonitrile resin characteristic Peak Classification
3) Accurately weighing 50mg of phthalonitrile resin, dissolving by using N-N-dimethylformamide, fixing the volume to 25mL by using methanol, adopting the chromatographic conditions described in the step 1), obtaining the peak distribution and the content (A%) in 4 batches of phthalonitrile resin, and comparing the number average molecular weight distribution of the corresponding batch measured by a GPC method. The distribution of the characteristic peak ratios of the 4 batches of phthalonitrile resins is shown in Table 3.
According to the method provided by the invention, the products of the batches are analyzed, the conclusion is consistent with the result measured by the GPC traditional method, and the content distribution of the components with different polymerization degrees has the same rule on the influence of the number average molecular weight (Mn), namely: the samples with relatively high polymeric fraction have higher Mn values, and the samples with higher contribution of the oligomeric fraction have lower Mn.
By adopting the liquid chromatography method provided by the invention, the total content range of the oligomer component is 60-55%, the total content range of the middle polymer component is 20-25%, the total content range of the high polymer component is 10-15%, and the controllable range of the molecular weight Mn is 2000-5000, so that the phthalonitrile resin with excellent performance or specific requirements can be obtained.
TABLE 3 phthalonitrile resin characteristic Peak proportion distribution
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.