Thermal Properties and Thermal Decomposition Gas Characteristics of Natural Protein Fibers

To study thermal properties and thermal decomposition gas characteristics of natural protein fibers， Fourier transform infrared spectroscopy （FT-IR） and Raman spectroscopy （Raman） were used to scan spectra of fibers. Thermogravimetry-infrared spectroscopy （TG-IR） and pyrolysis gas chromatography-mass spectrometry （PY-GC-MS） were applied to determine the thermal properties and gas products of fibers， so as to analyze the correlation between the chemical structure， thermal properties and gas products of fibers. The results showed that the main difference in the molecular structure between the two natural protein fibers is that wool contains cysteine residues with disulfide bonds， while mulberry silk contains a specific amino acid sequence such as alanine-glycine-alanine. The slow thermal decomposition process of fibers is divided into three stages， in the second stage at 200~500 ℃， the mass loss rate of fibers is greater than 55%. During this stage， the three substances containing ammonia （NH3）， CO groups and C—H alkanes in gas products are important sources of the “burned hair odor”. In addition， substances containing —COS— groups in wool products are important sources of the pungent odor similar to sulfur. The fiber is thermally decomposed instantaneously at 550 ℃， six types of substances with a relative content higher than 3% in the gas products，including phenol， p-cresol， hydroxyundecanoic acid lactone， indole， octadecanoic acid and cis-9-octadecenoic acid methylester in the gas products are important sources of the “burned hair odor”， and CS2 with a relative content of 0.85% in the products is an important source of the pungent odor similar to sulfur. The research results provide a new idea for the evaluation of fiber thermal properties and combustion odor， and also have application value in the exploration of high-temperature application scenarios of fibers.