||Polymer is highly related to our daily life, the analysis of its structure, chemical properties, and physical poperties is very important during manufacture quality control. Analysis procedure always accompany with tedius pretreatment to purify it before further detection. However, both synthetic and natural polymer has quite low volatility and solubility, common solvent system won’t dissolve it. Therefore, many studies have focused on using pyrolysis-GC/MS for analysis by decomposing it to deectable low molecular weight compound. Thermogravimetry-MS is also one of commonly used instrument to study thermal stability of material through monitoring weight loss during heating. Compare to high vacuum operating environment in conventional mass spectrometry, atmospheric pressure ionization mass spectrometry has advantages of less or non-pretreatment, rapidness, and high throughput analysis to detect target compound with effective and less complicated methods.|
At the first part of thesis, the study focused on development of interface to connect Pyrolyzer and low-temperature plasma ionization mass spectrometry, neutral pyrolysates was directly transferred to ionization source and interacted with reactive species generateed from low-temperature plasma, and proceed Penning ionization as major ionization mechanism. Poly(ethylene glycol), poly(bisphenol A carbonate), cellulose, polylactic acid and many polymer materials were analyzed under various temperature. The result show that intact oligomer molecular ions can be detected, even higher pyrosis temperature(600℃) was used, , intact pyrolysates and monomer ions still can be detected without fragment peak induced from ionization source. Non-polar polyethylene and long chain normal alkane were also analyzed, it is well known that normal alkane has higher boiling point and can’t be easily ionized under room temperature, but it can be ionized using Py-LTP MS under 400℃, spectra signal were detected as [M+O-3H]+ and [M-H]+, signal of normal alkane with carbon number up to 120 can also be detected. From above result, it can be concluded that electron and plasma species has higher kinetic energy to increase its opportunity to interact with gas phase analyte, and enhance the ionization efficiency of low-temperature plasma.
At the second part of thesis, the study focused on development of interface to connect thermogravimetry analyzer and low-temperature plasma ionization mass spectrometry, during conventional TGA-MS development, it is important to avoid condensation of evolved gas, and maintain the compatibility of high vacuum operating environment, therefore, the interface was constructed using home-made heated transfer line, and proceed ionization under ambient environment. During analysis of acetysalicyclic acid, polycaprolactam, and poly(butylene succininate), dynamic temperature was set from 30℃ to 650℃ at 20℃/min, variation of mass spectra signal can be recorded and observed with arising temperature and weight-loss. Further study on real sample, such as non-reuseable polypropyleny plate, not only Pyrolysates signal can be observed, but anti-oxidant signal from additive can also be detected. The above results show that TGA-LTP MS can rapidly monitoring thermal stability and thermal degradation mechanism on-line, provide a useful, direct, and rapid method to analyze polymer material during synthesis and development.