Leather and Footwear Journal

Volume 15, no 3

Contents
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Dose-Dependent Effects of Gamma Irradiation on Collagen in Vegetable Tanned Leather by Mobile NMR Spectroscopy
- Pages 139-150
  Claudiu ŞENDREA^1,2*, Elena BADEA^1,3, Ioana STĂNCULESCU^4,5, Lucreția MIU¹, Horia IOVU²
  - ¹National Research and Development Institute for Textile and Leather (INCDTP), ICPI Division, Ion Minulescu 93, 031215 Bucharest, Romania, claudiusendrea@yahoo.com
  - ²Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 1-7 Polizu Str., 011061 Bucharest, Romania
  - ³Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Craiova, 107 Calea Bucuresti, 200512 Craiova, Romania
  - ⁴Horia Hulubei National Institute for Physics and Nuclear Engineering (HH-IFIN), Radiation Processing Center, Magurele, Romania
  - ⁵University of Bucharest, Department of Physical Chemistry, 4-12 Regina Elisabeta Av., Bucharest, Romania
  ABSTRACT. The dose dependent effect of gamma irradiation on collagen in vegetable tanned leather was studied by unilateral nuclear magnetic resonance (NMR). Examination of the irradiated samples after 1 week of treatment revealed variations of both spin-lattice (T1) and spin-spin (T2) proton relaxation times. To evaluate the long-term effects of gamma irradiation, the irradiated samples were further exposed to accelerated ageing at 40°C and weekly alternate 30% and 75% relative humidity (RH) for 12 weeks. The synergistic action of temperature and relative humidity caused distinct variations of both T1 and T2 relaxation times suggesting distinct modifications within the collagen fibril structure. Structural variations were attributed to cross-linking, the prevalent pattern at 25 kGy dose, while polypeptide chain scission was shown to be prevailing at higher doses.
  
  KEY WORDS: collagen, vegetable tanned leather, gamma irradiation, unilateral NMR
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Safety Assessment of Shoes Fit for Driving
- Pages 151-158
  Yuguo FENG^1,2, Ting LI², Jianxin WU³, Bo XU², Wuyong CHEN², Jin ZHOU^2,3*
  - ¹College of Applied Technology of Xihua University, Sichuan Province, Chengdu 610065, P. R. China
  - ²Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University, Sichuan Province, Chengdu 610065, P. R. China, zj_scu@qq.com
  - ³Science Lab, Zhejiang Red Dragonfly Footwear Co., LTD., Zhejiang Province, Wenzhou 325100, P. R. China
  ABSTRACT. This study was aimed to explore a suitable heel height of shoes for driving. Fourteen healthy female students were recruited and five pairs of footwear with varied heel heights were randomly arranged to each participant; their insole plantar pressure and ankle motion in plantar and dorsal direction whilst stepping on the power and break pedal were recorded in a Suzuki 1.3L AT car, where the driving position was on the left side. One-mask model was used and peak pressure (PP) (Kpa), contact area (CA) (cm2) and pressure time integral (PTI) (s·Kpa) under forefoot area were calculated. Our results show that in terms of ankle motion, it increased with the relative heel height; in terms of insole pressure, only the CA was sensitive to the augment of relative heel height. Based on the significant differences, 30 mm heel height was a criterion; when the heel height exceeded 30 mm, the ankle motion range and CA were significantly increased. Overall, the safe heel-height of driving shoe should not exceed 30 mm.
  
  KEY WORDS: driving, safety, insole pressure, ankle motion, high-heeled footwear
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Investigation of the Effect of Varied Schoolbag Weight on the Health of Primary Students: A Quantitative Plantar Pressure Study
- Pages 159-168
  Nan ZHOU, Jin ZHOU, Luming YANG, Wuyong CHEN*
  - National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu, 610065, China, wuyong.chen@163.com
  ABSTRACT. The aim of this study was to explore the effects of varied schoolbag weight on biomechanics of primary students in terms of planter pressure distribution, so as to clarify the threshold of the safety weight bearing for primary students. Sixty healthy children from primary school between the grade 1 to 6 were recruited and those with any scoliosis or foot injury were excluded. Changes of plantar pressure with weight bear increasing in terms of parameters of mean pressure (MP), contact area (CA), pressure-time integral (PTI) and Timecost were measured and the data were analyzed by model of ANOVA with significant level of 0.05 and confident interval of 95%. Our results show that pressure of 0% BW, 5% BW and 10% BW were significantly lower than those of 15% BW and 20% BW under the majority of foot regions, particularly at the medial forefoot and rearfoot. Thereby, our study suggested that the weight of primary students' bag should not exceed 15% BW.
  
  KEY WORDS: primary students, school bag, foot biomechanics, safety weight bearing
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Protein Biofertilizer Development and Application on Soybean Cultivated Degraded Soil
- Pages 169-178
  Rodica Roxana CONSTANTINESCU^1*, Gabriel ZĂINESCU², Daniela Simina ŞTEFAN³, Carmen SȊRBU⁴, Petre VOICU⁴
  - ¹Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Romania, rodica.roxana@yahoo.com
  - ²INCDTP - Division: Leather and Footwear Research Institute, 93 Ion Minulescu, Bucharest, Romania
  - ³University Politehnica of Bucharest, Department of Analytic Chemistry and Environmental Engineering, 1-7 Polizu, Bucharest, Romania
  - ⁴Research Institute for Soil Science and Agrochemistry, Bucharest Romania
  ABSTRACT. This paper addresses the priority area of greening tanneries by recovering hide waste as fertilizing biocomposites. The paper presents the development of protein biofertilizers and their application in agriculture for plant growth and remediation of nutrient-poor soil. The aim was to obtain protein biofertilizers and apply them to soybean crop having the effect of stimulating the metabolism, speeding the productive phase, stimulating the defense system of the plant. We also obtained healthy plants and increases in production quality upon application of fertilizing biocomposites based on collagen hydrolysate. The highest increase of production was recorded for variants to which the protein biofertilizer was applied before sowing.
  
  KEY WORDS: pelt waste, protein biofertilizer, soil, soybeans
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The Synthesis and Application of Phosphorus-Nitrogen Flame Retardant Retanning Agent
- Pages 179-188
  Jinwei ZHANG^{1, 2}, Fan CHENG³, Zhengwu AI^{1, 2}, Wuyong CHEN^{1, 2*}
  - ¹Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University, Chengdu 610065, China, wuyong.chen@163.com
  - ²National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065, China
  - ³Haining Leather Research Institute, Haining 314400
  ABSTRACT. In order to improve the fire resistance of leather to meet the higher fire-safety requirement, a phosphorus-nitrogen flame retardant retanning agent (M-THPS-U for short) was synthesized and used to treat leather. The vertical flame test, oxygen index test, smoke density, mechanical properties, thickness increase, and shrinkage temperature were used to evaluate the properties of M-THPS-U, and the dosage of M-THPS-U was optimized at the same time. Furthermore, the hide powder treated with M-THPS-U was used to study the flame resistance effect by thermogravimetry (TG) and microscopy. The results showed that the fire resistance of leather was improved obviously by using 5% of M-THPS-U. With the increase of M-THPS-U dosage, the mechanical properties dropped, but the fire resistance, thickness increase and shrinkage temperature of the leather raised. The TG results indicated that the fire retardant could promote the fire resistance of leather by accelerating leather fiber converting into char and decreasing the temperature at break down. In short, not only does M-THPS-U improve the fire resistance of leather, but it also has retanning and filling effects.
  
  KEY WORDS: leather, phosphorus-nitrogen flame retardant, retanning
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Effects of Stress State while Dried on Leather Mechanical Properties
- Pages 189-202
  Wei TIAN¹, Jing DU¹, Keyong TANG^1*, Fang WANG¹, Kang ZHAO¹, Mădălina ALBU²
  - ¹College of Materials Science and Engineering, Zhengzhou University, Henan 450001, P. R. China, keyongtangzzu@yahoo.com
  - ²INCDTP - Division Leather and Footwear Research Institute, Collagen Department, 93 Ion Minulescu Str., 031215, Bucharest, Romania
  ABSTRACT. After being chrome tanned, the wet blue was retanned, neutralized, and fatliquored with Coripol MK to get different leather samples. Under the condition of ambient drying and vacuum drying, different forces were applied on above leather samples to provide different stress states, i.e., uniaxial stress state and biaxial stress state. The effect of different stress while dried on leather mechanical properties was investigated. Combined with the SEM results of grain and cross section, the change patterns were discussed. They indicate that after drying with stretching, the tensile strength and the stiffness of the samples are increased while the elongation at break is decreased. Compared with the sample being biaxial stress processed, the sample with a uniaxial stress process is higher in tensile strength and lower in elongation at break. After being dried and stretched, the grain smoothness of the sample becomes better. Uniaxial stretching increases the orientation degree of the collagen fiber in the sample, while biaxial stretching may separate the collagen fiber bundles. On the basis of the work, a simplified fiber structure model during stretching was proposed.
  
  KEY WORDS: stress state, leather, mechanical property, tensile strength, elongation at break, fiber orientation
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