Soft and hard segment ratio nuclear magnetic resonance test of polyurethane samples

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Soft and hard segment ratio nuclear magnetic resonance test of polyurethane samples
Test instrument name: VTMR NMR cross-linking density meter (Newmarket Technology)
Test sequence and parameters: CPMG sequence
Test procedure and results: T2 relaxation time reflects the chemical environment of hydrogen protons in the sample, which is related to the binding force of hydrogen protons and their degrees of freedom, and the degree of binding of hydrogen protons is inseparable from the internal structure of the sample. Relationship. The larger the hydrogen proton is bound or the smaller the degree of freedom, the shorter the T2 relaxation time, the peak position on the T2 spectrum is closer to the left, corresponding to the relaxation time of the rigid region (hard segment); otherwise, the longer the T2 relaxation time, The peak position on the T2 spectrum is relatively to the right, corresponding to the relaxation time of the motion zone (soft segment).

Table 1 Ratio of polyurethane soft and hard segments


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The test principle of NMR cross-linking densitometer is mainly based on the molecular dynamics of hydrocarbon chain protons in the polymer, and the magnetic resonance response of the cross-linked structure is used to effectively evaluate the cross-link density of polymers (such as rubber, plastic, etc.). Analyze the structural evolution of polymers in R&D and production processes, and optimize vulcanization parameters, quality verification of rubber products, analysis of aging processes, fatigue life prediction, and determination of moisture and solvent content in rubber and other elastomers. This method is used to evaluate the cross-linking structure of rubber. It is technically fast and convenient (30 seconds to 5 minutes). The test process has no damage to the sample, good reproducibility, large amount of information, and chemical cross-linking and physical cross-linking. Distinguish it. The NMR cross-linking density meter provides a new cross-linking test method, which has a good correlation with the traditional test results and has obvious advantages.
Technical indicators:
1. Magnet type: permanent magnet;
2. Magnetic field strength: 0.5±0.08T, instrument main frequency: 21.3MHz;
3. Probe coil diameter: 10mm;
4. Effective sample detection range: Φ8.5mm×H20mm;
5, sample temperature control range: 30-130 ° C;

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