Investigation On The Quantitation Of Si-OH In MQ Silicon Resin

The MQ silicon resin is widely used in fields such as air space,new energy vehicles,electronics,medicine and architecture,silicon hydroxyl is the active group in the MQ silicon resin,and its content has a significant effect on the physical and chemical properties of the MQ silicon resin and its second processing products,such as the transmittance,the combination of silicone rubber,and reinforcement property.At present,the sensitivity and accuracy of silicone hydroxyl determination method in MQ silicone resin are not satisfactory.However,by chemical derivatization of silanization and esterification,the sensitivity of the determination of silyl hydroxyl was significantly improved by transforming the silyl hydroxyl group into the phenyl or naphthalene group sensitive to UV detection.And the GPC separation technology can reduce the influence of hydroxyl in water and alcohol on the quantitation of silicone hydroxyl in MQ silicone resin(polymer),improve the accuracy of the quantitation of silicone hydroxyl.At present,this technology has been mature and applied to the detection of active silicone hydroxyl groups in several types of MQ silicone resins.The main research contents are as follows:(1)Quantitative study of silicon hydroxyl in MQ silicon resin based on derivatization of dimethyl phenyl chlorosilaneStandard sample was synthesized by reaction of MQ silicone resin and dimethyl phenyl chlorosilane,and the standard sample was obtained by column pure separation and purification.According to infrared spectrum to determine whether the hydroxyl content reaction is thorough;the purity was analyzed by GPC-UV.~1H-NMR spectroscopy was used to determine the content of phenyl in standard samples,and then the complete derivatization of silicon hydroxyl was achieved by optimizing the experimental methods and conditions.Finally,the same sample was selected at the same concentration and in different concentration ranges to verify the methodology.Its low intra day and inter day reproducibility indicates that the analysis method is relatively stable and reliable.(2)Quantitative study of silicon hydroxyl in MQ silicone resin based on derivatization of p-methoxybenzoyl chlorideThe standard sample methyl p-methoxybenzoate was synthesized by reaction of methanol and p-methoxybenzoyl chloride,and the content of phenyl was calculated by ~1H-NMR resonance analysis,and the purity of the standard sample was determined by GC-MS and GPC-UV detection.P-methoxybenzoyl chloride was selected as the derivatization reagent,and the experimental method and conditions were optimized to realize the complete derivatization of trace silicon hydroxyl in methyl MQ silicone resin.The results of the two methods were compared:the acylation derivatization reagent corrosion is weak,can effectively avoid the damage of the instrument;the acylation method has lower reproducibility and better stability;the reaction time of acylation is shorter;acylation derivatization reagent is cheap,less dosage,and easy to remove.(3)Quantitative study of silicone hydroxyl in MQ silicone resin based on2-naphthalene formyl chloride derivatizationThe purity of methyl 2-naphthoate standard sample was determined by GPC-UV detection,and the actual content of naphthyl in standard sample was calculated by corresponding peak area.The hydroxyl content in vinyl MQ silicone resin was quantitatively studied by using 2-naphthalyl chloride as derivatization reagent,and the experimental methods and conditions were optimized to achieve the complete derivatization of trace hydroxyl in vinyl MQ silicone resin.Compared with silanization,the detection limit and quantitation limit decreased by 10 times,and the sensitivity was further improved.