Study On Softening Of Ageing Cattlehide Leather And Its Structures And Properties Study On Softening Of Ageing Cattlehide Leather And Its Structures And Properties

Historical leathers are precious treasures of Chinese ethnic peoples. Leather was used by people from ancient time and its history is far earlier than other textiles. Leather is the important evidence that reflects the development of human civilization. Due to the rich history, culture and technology information it contains, historical leather is more valuable compared with other cultural relics. However, the main composition of historical leather is protein. Because protein is easy to be aged and to be degraded by light, heat, humidness and microorganism, water and oils of leather disappeared and collagen fibers were gradually degraded when historical leather was under different hostile environments chronically. Then historical leather became dry, hard, moldy and its colour changed. In order to exhibit, conserve and research historical leather better, we need to restore its original colour and flexibility as much as possible.Therefore, light aged and heat aged cattlehide leathers were selected as historical leather alternative samples in this research. And the chromatism, the surface topography, the flexibility, the tensile stress, the breaking elongation, the structure and the thermal property of different historical leather alternative samples have been studied. Then the preparation of softening agent and its formulation design have been systematically researched through orthogonal experiments. The acid-base property, the emulsion stability, the acid-base resistance property, the colour, the flowability and the storage stability of softening agent have also been tested. At last, historical leather alternative samples have been softened by softening agent and the chromatism, the surface topography, the flexibility, the tensile stress, the breaking elongation, the structure and the thermal property of historical leather alternative samples after softening have been researched, too. The main results and conclusions of above research are shown as follows:After light ageing and heat ageing, the colour of leather changed and became darker; a large number of serious cracks appeared on leather’s surface and the size of heat aged leather reduced; the flexibility, the tensile stress and the breaking elongation of leather decreased dramatically; the thermal stability of sample decreased a little:through the analysis of the infrared, we found the main reason is that the collagen molecules degraded, the peptide chains of main molecular chain was broken, the triple helical structure changed to be random coil structure and molecule alignment decreased. This resulted in the decrease in different properties of leather.After softening, historical leather alternative sample’s surface became more glossy; SDBS residues was found in the leather’s pores through SEM and no other residues were found; because of the surfactants’coating on collagen fibers and the existence of oil in collagen fibers’ gaps, the crosslinking and the distance between collagen fibers reduced and decreased respectively. As a result, the leather flexibility was improved; the tensile stress and the breaking elongation changed a little; lanolin had adverse effects on the thermal stability of sample, and others did not. what’s more, through the analysis of the infrared, the main functional groups of collagen changed little and some new absorbance peaks of softening agent appeared. Through comprehensive comparison and analysis, the optimal formula of softening agent was:20g modified castor oil,2.5g hydrophilic amino silicone oil,2.5g span-80,25g water,0.0005g2-octyl-4-isothiazolin-3-one and0.0005g tea saponin.Softening agent was effective for historical leather alternative sample. After softening, the flexibility and the colour of sample were improved with no disadvantage influence on leather. What’s more, the softening mechanism was briefly stated in this paper, it provided a theory basis for the softening of historical leather alternative sample. This study is of great importance that it is useful to softening agent’s application on historical leather.