基于热重-质谱联用技术测定EVA的方法探究

Determination Method of EVA by Thermal Gravimetric Analysis Coupled with Mass Spectrometry

乙酸乙烯酯-乙烯共聚物乳胶粉(EVA)应用广泛,其检测技术的发展至关重要。本研究利用热重-质谱联用技术(TG-MS),在质量维度上建立了一种对EVA进行定量分析的方法。通过热重-红外-气质联用仪探究了EVA的热解过程,结果表明EVA的热解可分为三个阶段,其中第二阶段脱乙酰化步骤产生大量的乙酸能被清晰识别,同时在此步骤中也有低分子量的(CH)_(n)碎片和丙酮产生。随着热解温度升高,分子量较大的苯环衍生物和(CH)_(n)碎片在高温下被检测到。这表明在脱乙酰过程中聚合物主链末端发生了断链反应,随着温度的升高,不饱和烯烃结构热解产生芳香挥发物。通过在线质谱监测等温脱乙酰化反应,确定酮类物质的生成并不会影响脱乙酰化反应的进行,因此使用乙酸对EVA进行定量分析是合理的。通过MS信号与乙酸质量关联,建立了EVA的定量分析方法,为分析样品中EVA的定量检测提供了一种新方案。

Ethylene-co-vinyl acetate(EVA)is widely used in daily life and the development of its detection technology is very important.In this study,the thermal gravimetric analysis coupled with mass spectrometry(TGA-MS)was applied to develop a method for the direct quantitative analysis of EVA without further sample pretreatment.The degradation of EVA as measured by the combination of TGA with Fourier transform infrared spectrometer(FTIR)and gas chromatograph-mass spectrometer(GC/MS)consists of three steps.The results show that a large amount of acetic acid produced in the deacetylation step of second stage can be clearly identified,while(CH)_(n) fragments and acetone produced in this step.With the increase of pyrolysis temperature,benzene derivatives and large(CH_(2))fragments are detected.This indicates the chain scission reactions occurring at the end of the polymer main chain during deacetylation.Isothermal deacetylation reaction is monitored by MS which determines that the formation of ketones does not affect deacetylation.MS signal intensities of acetic acid linearly responding to EVA concentrations,therefore the quantitative analysis of EVA can be clearly identified by acetic acid.This method is easier operation and rapid to test the concentration of EVA,at the same time it can be a viable complement to existing methods.