Mehmet Akalin

Influence of flame retardants on the mechanism of pyrolysis of cotton (cellulose) fabrics in air

A revised model for the influence of flame retardant treatments on the pyrolysis behaviour, in air, of cotton (cellulose) fabrics is proposed. This is based on extensive studies of a set of commercially flame retarded cotton fabrics using a range of experimental techniques, e.g., Py-FTIR, Py/GC and GC-MS, thermal analysis, oxygen index/smoke-CO-CO2 evolution. The samples studied were the condensed phase active ammonium polyphosphate (Amgard TR), a phosphonium salt-urea-polycondensate (Proban CC) from Albright and Wilson and a phosphonopropionamide (Pyrovatex CP) from Ciba-Geigy, together with two vapour phase active treatments: ammonium phosphate-ammonium bromide (Amguard CD, Albright and Wilson) and an antimony(III) oxide-aliphatic bromide (Flacavon H14/587) formulation from Schill and Seilacher. The results obtained are collated and interpreted to provide an overall view of the pyrolysis mechanism of cellulose in air. The pyrolysis can be characterised by three stages: Stage I, 300–400°C, involves two competing pathways which yield aliphatic char and volatiles. During Stage II, 400–800°C, some of the aliphatic char converts to an aromatic form. Both chars are partially oxidised to evolve CO and CO2. Above 800°C, Stage III, char and any remaining hydrocarbon species are further oxidised mainly to CO2 and some CO. The influence of the various flame retardant types on these various Stages are discussed with respect to their retardant roles.

FTIR analysis of gases evolved from cotton and flame retarded cotton fabrics pyrolysed in air

The gaseous products produced by pyrolysing various samples of cotton and flame retarded cotton fabrics in air at different temperatures (300–1200 °C) were identified and quantified via FTIR. CO and CO2 evolutions were investigated in detail. The flame retardant samples showed enhanced CO and CO2 concentrations at lower pyrolysis temperatures (300–450 °C). These evolutions showed similar temperature dependence behaviour for all samples tested. At higher temperatures (450–800 °C), a second pyrolysis stage is identified where product evolution increased in concentration towards respective maximum values within this range. At higher temperatures still (800–1200 °C) pyrolysis product oxidation occurred which thus reduced the concentrations of all oxidisable products. The relative evolutions of both CO and CO2 are commensurate with the known vapour phase and condensed phase activities of bromine- and phosphorus-nitrogen-containing flame retardants, respectively.

Investigation of electromagnetic shielding properties of needle-punched nonwoven fabrics with stainless steel and polyester fiber:

In this study, electromagnetic shielding properties of needle-punched nonwoven fabrics were investigated. The paper evaluates and compares the electromagnetic shielding of needle-punched nonwoven fabrics produced from stainless steel/polyester and normal polyester fibers. Stainless steel/polyester fiber and normal polyester fiber were blended at specified ratios in the experimental study. Webs were produced from the fibers with the carding machine and then bonded with the needle-punching machines. The thickness and electromagnetic shielding properties of the needle-punched fabrics were tested. An electromagnetic shielding effectiveness (EMSE) device was used for measuring the electromagnetic shielding. The experimental study indicated that as the conductive stainless steel fiber ratio in nonwoven fabrics increases, the EMSE also increases at low, medium and high frequencies. Satisfactory electromagnetic shielding values were obtained at wide bandwidth, i.e. 1200–3000 MHz. The highest EMSE values of the needle-punched nonwoven fabric with 25% conductive steel fiber were, respectively, 6 dB at 0–300 MHz low frequency, 12 dB at 300–1200 MHz medium frequency and 18 dB at 1200–3000 MHz high frequency. It was found that 90% of electromagnetic waves were shielded by nonwoven fabric at high frequencies, 85% at medium frequencies and 80% at low frequencies.

Smoke, CO2 and CO Evolution from Cotton and Flame Retarded Cotton: Part 2. Behaviour of Single Layer Fabrics in Air at Elevated Temperatures

Smoke, CO and CO2 emissions have been determined from un treated cotton and flame retarded cotton fabrics at elevated temperatures. The flame retardants studied at commercial levels of applications were ammonium polyphosphate (Amgard TR), ammonium polyphosphate—ammonium bromide (Amgard CD), a phosphonium salt-urea-polycondensate (Proban CC), a phos phono-propionamide (Pyrovatex CP) and an antimony (III) oxide-aliphatic bro mide (Flacavon H14/587) formulation. Combustion product analyses were undertaken at elevated temperatures (225-300°C) in air under burning conditions (above the respective temperature oxygen index) and non-flaming pyrolysis. Under both conditions smoke densi ties and CO concentrations increased with temperature. Carbon dioxide con centrations under non-flaming conditions showed similar increases but under burning conditions, decreased with increasing temperature. At a given temper ature, the P- and N-containing retardants reduced smoke density under burn ing conditions and increased it under pyrolysis relative to pure cotton below 350°C. These same flame retardants reduced CO and CO2 formation at each temperature from burning fabrics but produced little change with respect to cotton under non-flaming conditions. The presence of aliphatic bromine in the Sb2O3—bromine synergistic system caused significant increases in smoke density and CO and CO2 concentrations with respect to all other fabrics under pyrolysis in air. The observed trends are analysed in terms of current knowledge of pyrolysis and combustion mechanisms.

Smoke and CO Evolution from Cotton and Flame Retarded Cotton. Part 1: Behaviour of Single Layer Fabrics under LOI Conditions

The limiting oxygen indices of two different area densities of untreated and phosphorus-containing flame retardant cotton fabrics (Proban CC, Amgard TR, Amgard CD) have been determined at 20 and 100°C. Simultaneous smoke and CO evolutions from all the fabrics have been determined at respective LOI and (LOI + 0.010) oxygen concentration conditions at 20 and 100°C. At 20 ° C, flame retardants present greatly increased smoke generation whilst little if any change in CO generation (except for the bromine-containing Amgard CD) occurred. Whilst increase in temperature to 100°C reduced fabric LOI and increased apparent and specific smoke optical densities its effect on CO generation was not straightforward. Lightweight, bromine-free flame retarded fabrics showed increased CO formation whilst for the heavier fabrics, increased area density and/or presence of bromine stabilised or reduced CO evolution.

Properties of Polypropylene Composite Produced with Silk and Cotton Fiber Waste as Reinforcement

The importance of polymer composites among industrial materials is due to their improved mechanical properties. In recent researches, mechanical and physical properties have been improved by way of making composites with fiber reinforcement. Silk and cotton fibers used in the textile industry have good physical and mechanical properties. In this study, composite structures were produced by using recycled Poly Propylene, PP, polymer with silk and cotton waste as fiber reinforcement in different ratios. The fiber dimensions of silk and cotton wastes were between 1 mm, 2.5 mm, and 5 mm. They were mixed in the ratios of PP/silk and cotton waste 97%/3 and 94%/6. The mixture of polymer composite was prepared with double screw extruder. The sample was tested for tensile strength, elongation, yield strength, elasticity modulus, izod impact strength, melt flow index (MFI), heat deflection temperature (HDT), and vicat softening temperature. Thermal transitions of the materials were determined with Differential Scanning Calorimeter (DSC) and micro-structure properties were observed with a Scanning Electron Microscope (SEM).

Characterization and evaluation of antimicrobial properties of electrospun chitosan/polyethylene oxide based nanofibrous scaffolds (with/without nanosilver)

Various ratios (30/70%, 70/30%, 50/50% with and without nanosilver) of chitosan (CS; 60–120.000 g/mol) and polyethylene oxide (PEO; 600.000 g/mol) blended nanofibers in the nanofibrous scaffolds were obtained by using electrospinning at ambient atmosphere. Homogenous CS solutions were prepared in 90% aqeous acetic acid. PEO was dissolved in deionized water. Nanosilver dispersion was prepared and added to the 50/50% blend of CS/PEO solution. Properties of all blended solutions were determined by measuring viscosity and conductivity. Differential scanning calorimeter, Fourier transform infrared spectroscopy, scanning electron microscopy analysis and tensile tests were conducted to investigate the characteristics of the final nanofibrous composite structures. Beadless and uniform nanofibers were obtained and the average diameter of the fibers ranged from 63 ± 23 nm to 108 ± 51 nm. The antimicrobial effectiveness of the nanofibrous scaffolds was investigated against Escherichia coli and Candida albicans, and satisfactory results were obtained.

The effect of needle-punched nonwoven fabric thickness on electromagnetic shielding effectiveness

In this study, the effect of nonwoven fabric thickness on electromagnetic shielding effectiveness (EMSE) was investigated and there was found to be a correlation between the thickness of needle-punched nonwoven fabric and EMSE. The production of needle-punched nonwoven fabrics from stainless steel staple fiber in the experimental study was carried out. Stainless steel staple fibers provided by Bekaert were used as a raw material. The webs were formed using a wool-type carding machine. The webs were bonded using needling punching machines. The pre-needled, twice-needled and thrice-needled nonwoven fabrics at three different thicknesses were produced. The experimental studies were carried out using large-scale production machines instead of small-scale laboratory-type machines. EMSE measurements of produced needle-punched nonwoven fabrics, in addition to physical properties such as strength, elongation and thickness, were performed. The coaxial transmission line method specified in ASTM D4935-10 was utilized to test the nonwoven fabrics and the needle-punched nonwoven fabrics were tested in the frequency range from 15 to 3000 MHz. It was understood that needle-punched nonwoven fabric thickness was a very important parameter for EMSE. It was found that as the frequency increases, EMSE values of needle-punched nonwoven fabrics showed continuously increasing tendency by starting from a specific frequency in the frequency range of 15–3000MHz. There were no significant differences between absorption and reflection values of needle-punched nonwoven fabrics produced at different thicknesses. It was found that pre-needle-punched, twice-needled and thrice-needle-punched nonwoven fabrics produced from the conductive stainless steel staple fibers in our study have, respectively, highest EMSE values of 22, 25 and 27 dB between 2100 and 2400 high frequency ranges.

Investigation of electromagnetic shielding properties of boron, carbon and boron–carbon fibre hybrid woven fabrics and their polymer composites

Abstract The growth of the electronic industry and the widespread use of electronic equipment in communications, computations, automations, biomedicine, space and other purposes have led to many electromagnetic interference (EMI) problems as systems operate in close proximity. It is likely to become more severe in the future, unless proper EMI control methodology and techniques are used to meet the electromagnetic compatibility requirements. In recent years, electromagnetic (EM) waves in the 1–10 GHz range are broadly used in wireless communication tools and local area networks. In the future, the usable range of EM waves will tend to shift further to higher frequency regions with the development of information technology as well as electronic devices. As a consequence, the seriousness of problems such as EMI of electronic devices and health issues is ever rising. In this study, electromagnetic shielding effectiveness, absorbance and reflectance properties of the boron, carbon and boron–carbon plain woven fabrics and boron/polyester, carbon/polyester, and boron–carbon/polyester hybrid composites were investigated. Using a coaxial transmission line holder set-up, the (EMSE), reflectance and absorbance of various fabrics and composites were carried out in the frequency range from 15 to 3000 MHz.

Comparing Heuristic and Simulation Methods Applied to the Apparel Assembly Line Balancing Problem

Marmara University, Faculty of Technology, Department of Textile Engineering, Istanbul, Turkey E-mail: mkayar@marmara.edu.tr Abstract In this study, general information on assembly line and simulation and researches on assembly line balancing are theoretically analysed. Afterward time studies with respect to blouse production, which will be analysed in assembly line balancing, are conducted and information, which is necessary for assembly line balancing, is obtained. In parallel with the data obtained, the assembly line is firstly balanced by the Hoffman method, which is one of the heuristic methods. Then the assembly line is balanced again using the Arena Simulation program and results which belong to two different assembly line balancing resolutions are given. The aim of the study is to create an assembly line which has highest line efficiency by using an optimum number of machines and operators as well as highlight the applicability of the Hoffman method to ready-to-wear assembly lines.