紫外照射对皮胶原结构和性能的影响
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摘要
本文采用波长为312nm的紫外光对未鞣、铬鞣、戊二醛鞣、坚木栲胶鞣、氯化石蜡加脂、天然大豆磷脂加脂、亚硫酸化大豆磷脂加脂羊皮胶原进行处理,系统地研究了紫外光照射时间对羊皮胶原干热稳定性、热降解行为、力学性能、透水汽性能、尺寸稳定性、表面形貌及聚集态结构的影响。
对胶原纤维的干热收缩行为的研究发现,UV照射对皮胶原的干热收缩行为影响较大。未鞣、鞣制和加脂皮胶原的干热收缩温度随照射时间的延长呈先增大后降低的趋势。干热收缩率则随照射时间的延长不断降低。与未鞣皮胶原相比,在相同的照射时间下,鞣制后的皮胶原其抵抗UV照射破坏的能力明显增强。鞣制皮胶原的干热收缩温度和干热收缩率降低趋势明显减缓。其中以单宁处理的皮胶原抵抗UV破坏的能力最强,戊二醛处理的皮胶原抵抗UV破坏能力最差。与铬鞣皮胶原相比,加脂后皮胶原抵抗UV照射破坏的能力有所降低。其中以亚硫酸化大豆磷脂加脂过的皮胶原抵抗能力最差。这可能与加脂剂中双键的含量有关。
本文还研究了UV照射前后皮胶原热降解行为。对样品进行TG分析后,采用Coats-Redfern和Horowitz-Metzge法计算了其热降解活化能。结果发现,未鞣皮胶原的热降解活化能随紫外照射时间的延长呈先增大后降低的趋势；经长时间的紫外照射后(≥8h),未鞣、鞣制、加脂皮胶原的热降解活化能都有所降低,其中以未鞣皮胶原降低最多,坚木鞣皮胶原降低最少,而加脂后的试样其降低量要高于未加脂的试样。
本文还研究了UV照射对皮革力学性能、透水汽性能、尺寸稳定性能、表面形貌的影响。结果发现,皮革的拉伸强度随照射时间的延长呈先增大后降低的趋势；断裂伸长率和拉伸断裂能随着照射时间的增加逐渐降低。透水汽性能随照射时间的延长呈先增大后降低的趋势；而皮革的面积随照射时间的延长不断降低。从SEM图片上发现,长时间的UV照射使样品表面出现较多的龟裂裂纹。红外图谱分析的结果表明,紫外照射使胶原分子内和分子间的氢键断裂,导致其三股螺旋结构部分被破坏。
In the present study, the pickled goat skins were tanned by different chemicals including chrome tanning agent, glutaraldehyde tanning agent, and quebracho extract, respectively. The wet blues were fatliquored by paraffin fatliquoring agent, granulesten fatliquoring agent, and sulphitated granulesten fatliquoring agent, respectively. The samples were treated with UV irradiation (wavelength 312nm) for different time intervals. The mechanical properties, thermal stability, thermal degradation behaviour, water vapor permeability, dimensional stability, and morphology of goatskin collagen matrices before and after UV irradiation were investigated. The influence of UV irradiation on the molecular structure of collagen was studied by infrared spectra.
The dry heat shrinkage behaviors of the collagen fibers were performed by using the thermal platform microscopy. It was shown that UV irradiation affects the dry heat shrinkage behaviors obviously. The dry heat shrinkage temperature (Ts) of native, tanned and fatliquored collagen fibers increases at the first few hours of UV irradiation (0-4h) and decreases after irradiation for longer time (8-64 h). Increasing UV irradiation time leads to a decrease in shrinkage ratio. For the same irradiation time, the UV irradiation exerted more dramatic effect on the un-tanned collagen matrix, compared with the tanned and fatliquored ones. The dry heat shrinkage temperature showed that quebracho extract tanned goatskin collagen fibers have better stability against UV irradiation than native and other tanning agents treated goatskin collagen fibers. Un-fatliquored samples have better stability against UV irradiation than the fatliquored one.
The thermal degradation behaviors of native, tanned and fatliquored before and after UV irradiation collagen fibers were investigated as well. The thermal degradation behaviors of samples were characterized by using thermo-gravimetric thermal analyzer (TG), and both methods of Coats-Redfern and Horowitz-Metzge were applied to calculate the thermal degradation activation energy of the samples. The results showed that the thermal degradation activation energy of native collagen fibers increases at the first few hours of UV irradiation (0-4h) and decreases after irradiation for longer time (8-64 h). The thermal degradation activation energy of tanned and fatliquored collagen fibers decreases after long time of UV irradiation.
The mechanical properties of goatskin leathers before and after UV irradiation were investigated. It was found that the tensile strength of the goatskin matrices increases slightly in the first few hours of irradiation (0-4 h), and decreases dramatically after longer time (8-64 h) of UV irradiation. Increasing UV irradiation time leads to a decrease in elongation at break and tensile fracture energy. The water vapor transmission rate decreases at the first few hours of UV irradiation (0-4 h) and increases after irradiation for longer time (8-64 h). UV irradiation results in a continuous decrease in sample dimension.
Scanning electron microscopy observation suggested that UV irradiation induces crack and loss of skin tone. ATR-IR spectra of goatskin collagen showed that after UV irradiation, the positions of Amide A and AmideⅡbands were shifted to lower wavenumbers. There was not any significant alteration in the position of Amide I bands of collagen after UV irradiation. It was indicated that phototransformation occurred during UV irradiation and changed the conformational state of collagen.
对胶原纤维的干热收缩行为的研究发现,UV照射对皮胶原的干热收缩行为影响较大。未鞣、鞣制和加脂皮胶原的干热收缩温度随照射时间的延长呈先增大后降低的趋势。干热收缩率则随照射时间的延长不断降低。与未鞣皮胶原相比,在相同的照射时间下,鞣制后的皮胶原其抵抗UV照射破坏的能力明显增强。鞣制皮胶原的干热收缩温度和干热收缩率降低趋势明显减缓。其中以单宁处理的皮胶原抵抗UV破坏的能力最强,戊二醛处理的皮胶原抵抗UV破坏能力最差。与铬鞣皮胶原相比,加脂后皮胶原抵抗UV照射破坏的能力有所降低。其中以亚硫酸化大豆磷脂加脂过的皮胶原抵抗能力最差。这可能与加脂剂中双键的含量有关。
本文还研究了UV照射前后皮胶原热降解行为。对样品进行TG分析后,采用Coats-Redfern和Horowitz-Metzge法计算了其热降解活化能。结果发现,未鞣皮胶原的热降解活化能随紫外照射时间的延长呈先增大后降低的趋势；经长时间的紫外照射后(≥8h),未鞣、鞣制、加脂皮胶原的热降解活化能都有所降低,其中以未鞣皮胶原降低最多,坚木鞣皮胶原降低最少,而加脂后的试样其降低量要高于未加脂的试样。
本文还研究了UV照射对皮革力学性能、透水汽性能、尺寸稳定性能、表面形貌的影响。结果发现,皮革的拉伸强度随照射时间的延长呈先增大后降低的趋势；断裂伸长率和拉伸断裂能随着照射时间的增加逐渐降低。透水汽性能随照射时间的延长呈先增大后降低的趋势；而皮革的面积随照射时间的延长不断降低。从SEM图片上发现,长时间的UV照射使样品表面出现较多的龟裂裂纹。红外图谱分析的结果表明,紫外照射使胶原分子内和分子间的氢键断裂,导致其三股螺旋结构部分被破坏。
In the present study, the pickled goat skins were tanned by different chemicals including chrome tanning agent, glutaraldehyde tanning agent, and quebracho extract, respectively. The wet blues were fatliquored by paraffin fatliquoring agent, granulesten fatliquoring agent, and sulphitated granulesten fatliquoring agent, respectively. The samples were treated with UV irradiation (wavelength 312nm) for different time intervals. The mechanical properties, thermal stability, thermal degradation behaviour, water vapor permeability, dimensional stability, and morphology of goatskin collagen matrices before and after UV irradiation were investigated. The influence of UV irradiation on the molecular structure of collagen was studied by infrared spectra.
The dry heat shrinkage behaviors of the collagen fibers were performed by using the thermal platform microscopy. It was shown that UV irradiation affects the dry heat shrinkage behaviors obviously. The dry heat shrinkage temperature (Ts) of native, tanned and fatliquored collagen fibers increases at the first few hours of UV irradiation (0-4h) and decreases after irradiation for longer time (8-64 h). Increasing UV irradiation time leads to a decrease in shrinkage ratio. For the same irradiation time, the UV irradiation exerted more dramatic effect on the un-tanned collagen matrix, compared with the tanned and fatliquored ones. The dry heat shrinkage temperature showed that quebracho extract tanned goatskin collagen fibers have better stability against UV irradiation than native and other tanning agents treated goatskin collagen fibers. Un-fatliquored samples have better stability against UV irradiation than the fatliquored one.
The thermal degradation behaviors of native, tanned and fatliquored before and after UV irradiation collagen fibers were investigated as well. The thermal degradation behaviors of samples were characterized by using thermo-gravimetric thermal analyzer (TG), and both methods of Coats-Redfern and Horowitz-Metzge were applied to calculate the thermal degradation activation energy of the samples. The results showed that the thermal degradation activation energy of native collagen fibers increases at the first few hours of UV irradiation (0-4h) and decreases after irradiation for longer time (8-64 h). The thermal degradation activation energy of tanned and fatliquored collagen fibers decreases after long time of UV irradiation.
The mechanical properties of goatskin leathers before and after UV irradiation were investigated. It was found that the tensile strength of the goatskin matrices increases slightly in the first few hours of irradiation (0-4 h), and decreases dramatically after longer time (8-64 h) of UV irradiation. Increasing UV irradiation time leads to a decrease in elongation at break and tensile fracture energy. The water vapor transmission rate decreases at the first few hours of UV irradiation (0-4 h) and increases after irradiation for longer time (8-64 h). UV irradiation results in a continuous decrease in sample dimension.
Scanning electron microscopy observation suggested that UV irradiation induces crack and loss of skin tone. ATR-IR spectra of goatskin collagen showed that after UV irradiation, the positions of Amide A and AmideⅡbands were shifted to lower wavenumbers. There was not any significant alteration in the position of Amide I bands of collagen after UV irradiation. It was indicated that phototransformation occurred during UV irradiation and changed the conformational state of collagen.
引文
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