Leather and Footwear Journal

Volume 14, no 1

Contents
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3D Design Method for Flat Footwear Soles
- Pages 5-16
  Cornelia LUCA, Răzvan MOCANU
  - "Gheorghe Asachi" Technical University of Iasi, Faculty of Textile, Leather and Industrial Management, Romania, e-mail: cionescu@tex.tuiasi.ro , razvan_mocanu@yahoo.com
  ABSTRACT. Research conducted on soles reveals that footwear details can be obtained in a wide variety of models by moulding. Soles are complex three dimensional objects. When assembling with the uppers, they have to correspond to the interior sole contour. That is why it is necessary that sole design be done with high accuracy and in strict accordance to the last. Nowadays, there are specialized software applications which can perform computer aided design processes for footwear. This paper presents a method, developed by the authors, of footwear flat soles 3D design using PowerSHAPE-e software of Delcam system. Computer-aided design used in this paper highlights several important advantages that include: increased design quality; soles three dimensional viewing, which can lead to immediate decisions regarding the acceptance of newly developed models; the complexity of mould cavities execution can be appreciated, without the need of making prototypes; the outlines of construction templates are accurately obtained for the mould cavities and for all size numbers; calculations can be easily done to determine the soles volume for the entire size number volumes, with implications on estimating polymer blend consumption and so on.
  
  KEY WORDS: footwear, shoe soles, shoe sole design, sole moulds
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The Crosslink Density of Ethylene-Vinyl-Acetate Copolymer/Triallylcyanurate Mixture Cross-linked by Electron Processing
- Pages 17-26
  Maria Daniela STELESCU ¹, Elena MĂNĂILĂ^2*, Gabriela CRĂCIUN², Daniel IGHIGEANU, Dana GURĂU¹
  - ¹National Research & Development Institute for Textiles and Leather, Division: Leather &Footwear Research Institute, 93 Ion Minulescu St., 031215, Bucharest, Romania, e-mail: dmstelescu@yahoo.com
  - ²National Institute for Laser, Plasma and Radiation Physics, Electron Accelerators Laboratory, 409 Atomistilor St., 077125 Magurele, Romania, e-mail: elena.manaila@inflpr.ro
  ABSTRACT. Vulcanization by electron beam (EB) irradiation involves the interaction of electron energy and an elastomer. The interaction results in formation of free radicals by dissociation of molecules in the excited state or by interaction of molecular ions. The free radicals or molecular ions can react by connecting directly to the polymer chains or by initiating grafting reactions. The chemistry of the process is based on macroradical formation from elastomer chains, which recombine causing structuring. This paper presents the effect of ionizing radiation on mixtures based on ethylene-vinyl acetate copolymer (EVA) and triallylcyanurate (TAC). Samples were subjected to electron beam treatment with doses ranging between 50 kGy and 500 kGy. The induced crosslinking of EVA/TAC samples was evaluated with gel fraction (crosslinked polymer content) and crosslink density determination. The cross-linking density of the samples was determined on the basis of equilibrium solvent-swelling measurements (in toluene at 23-25°C) by applying the well-known modified Flory-Rehner equation for tetra functional networks, where values of the solubility parameter were calculated according to Small, Hoy and Krevelen. Sol-gel analyses and crosslink density have shown that samples tend to cross-link as a result of electron beam irradiation. As EB dose increases, there is an increase of gel fraction, of volume fractions of polymer in the samples at equilibrium swelling (Î½2m) and of cross-link density (Î½), and a decrease of swelling ratio G (toluene soluble polymer quantity). The highest value of crosslinking rate was obtained for the sample irradiated with a dose of 350 kGy.
  
  KEY WORDS: ethylene-vinyl-acetate-copolymer, triallylcyanurate, cross-linking, electron beam
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System for Measuring the Walking Speed of a Human Subject on a Force Plate
- Pages 27-38
  Viorel GHEORGHE¹, Ana Maria VASILESCU^2*, Mirela PANTAZI²
  - ¹Politehnica University - Faculty of Mechanical Engineering and Mechatronics, Bucharest, Romania, e-mail: viorel.gheorghe@gmail.com
  - ²INCDTP - Division: Leather and Footwear Research Institute, 93 Ion Minulescu, Bucharest, Romania, e-mail: icpi@icpi.ro
  ABSTRACT. This paper presents the development of a system for measuring the walking speed on a force plate that measures ground reaction. The walking speed measurement system must meet the following criteria: minimal impact on the force plate, easy installation/dismantling, speed must be detected "without contact" and speed of subject must be detected irrespective of the subject's clothing colour, it must provide the possibility of using several types of force plate, it must allow the addition of new functions and have a competitive price. Ground reaction force was measured using the AMTI's AccuGait force plate and the NetForce component, while analysis was performed using the BioAnalysis module. To assess the three components of the ground reaction force provided by the force plate, for a subject not wearing shoes, walking at different speeds, two measurement sessions were organized: placing optical barriers of the walking speed measurement system at distances of 2.5 m and 0.7 m, respectively. Upon analyzing the values obtained in this case study, we can observe an increase in values of the following components: vertical component, Fz, medio-lateral component, Fy and anterior-posterior component, Fx at the speed of 2.33 m/s, compared to those obtained at 0.6 m/s. By comparing values provided by the force plate with optical barriers of the walking speed measurement system placed at distances of 2.5 m and 0.7 m, respectively, very small differences can be noticed. Therefore, the position of optical barriers does not affect the measurement of ground reaction force components.
  
  KEY WORDS: speed, walking, ground reaction force
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Hybrid Bipolymeric Structures Based on Butadiene-co-Acrylonitrile and Styrene-Butadiene Rubber Reinforced with Nanoparticles
- Pages 39-52
  Laurenția ALEXANDRESCU¹*, Maria SONMEZ¹, Mihaela NIȚUICĂ¹, Dana GURĂU¹, Natalia POPA²
  - ¹INCDTP - Division Leather and Footwear Research Institute, 93 Ion Minulescu St., Sector 3, 031215-Bucharest, Romania, email: icpi@icpi.ro, laura_alexandrescu@yahoo.com
  - ²Politehnica University of Bucharest, 313 Splaiul Independenței, Sector 6, 060402-Bucharest, Romania
  ABSTRACT. This work reports new polymeric structures based on butadiene-co-acrylonitrile and butadiene-styrene rubbers, reinforced with nanoparticles of functionalised clay by the addition of ingredients such as protective agents, accelerators, plasticizers, etc., in order to obtain polymeric structures with predetermined characteristics. These were developed on a roller mill and their composition is designed so as to be processed into finished products by press molding, using the optimum processing technological parameters. Determining the optimal batch and ingredients in the structure of hybrid bipolymeric compounds based on general purpose polymers used in the footwear industry and optimum technological processing conditions led to obtaining qualitative performance in terms of physical-mechanical properties higher than those imposed by standards in force, especially concerning hardness, resistance to petroleum oils and resistance to high temperature for a long time. Polymer structures were characterized in terms of behavior in aggressive environments, high temperature resistance, physical-mechanical properties (normal state and after accelerated aging).
  
  KEY WORDS: bipolymeric structures, butadiene-co-acrylonitrile, butadiene-styrene, nanoparticles
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