Noaman Ul-Haq

Preparation of antibacterial cotton fabric using chitosan-silver nanoparticles

The aim of this study was to prepare antibacterial cotton fabric using chitosan-silver nanoparticles (CS-AgNPs). CS-AgNPs were used as finishing agent for 100 % pure cotton fabric. AgNPs were prepared by Turkevich method. CSAgNPs were synthesized by mixing chitosan solution with silver nanoparticles. Fourier transform infrared (FTIR) spectrometer technique supported the formulation of CS-AgNPs. Cs-AgNPs crystalline peaks were in perfect agreement with JCPDS card no. 89-3722. Two gram negative bacteria Escherichia coli, Pseudomonas aeruginosa and two gram positive bacteria Bacillus cereus, Staphylococcus aureus were used to test the bacterial efficacy of synthesized AgNPs and CSAgNPs. Scanning electron micrograph of cotton fabric revealed the presence of CS-AgNPs on the surface of cotton fabric. The presence of small amount of silver nanoparticles in the composite was enough to enhance antibacterial activity significantly compared to pure chitosan.

Cleaner production technologies in desizing of cotton fabric

Desizing is one of the key processes for the pretreatment of cotton fabric wet processing. Prior to dyeing and printing, it is essential to remove the sizes coated on fabric. Cleaner production technologies, using which hazardous material is substituted with -amylase, an eco-friendly material, are applied for desizing of cotton fabric. The enzymatic desizing process is human-, machine-, and environmentally-friendly. Four different types of machines were used to investigate the aspects and results of enzymatic desizing. Unlike acid and oxidative desizing, biodegradation of sizes does not damage fabric and emit greenhouse gases (CO2), respectively. The highest quality of desizing was observed by using winch technology. The degree of desizing on TEGEWA scale was 8. The amount of desizing agent used was 0.5–4.0 kg/1000 liters. In winch (batch) desizing, the degree of whiteness was 76%, which is 1.5 times higher than grey fabric, but pad steam (continuous) desizing process showed 69% degree of whiteness, which is 1.35 times higher than grey fabric. The competitive results were achieved in continuous process with efficient time. This article reveals the benefits, processes and results of eco-friendly technology within the framework of textile wet process industry.

Dynamic Mechanical Characterization of the Crosslinked and Chain-extended HTPB Based Polyurethanes

The viscoelastic response of two different polyurethane (PU) systems (crosslinked and chain-extended) based on hydroxyl terminated polybutadiene (HTPB) were analyzed and compared. The PU elastomers were fabricated by reacting HTPB with isophorone diisocyanate. A tri-functional alcohol (1,2,6 hexanetriol) and a bi-functional aliphatic diol (1,4 butanediol) were used as the crosslinking agent and the chain extender respectively. Hydrogen bonding between the hard segments is indentified by the IR spectroscopy. The segregation of these segments was manifested by dynamic mechanical analysis at characteristic frequency over a wide range of temperature. The intensity and temperature location of the relaxation peaks was identified and discussed. The phenomenon of viscous dissipation was evaluated by recording the viscoelastic parameters as a function of temperature across a series of frequencies. The results obtained indicate that the chain-extended polymer is phase segregated and more sensitive to temperature rise via viscous dissipation as compared to crosslinked polymer. Both the polymers showed similar glass transition temperature (Tg) and characteristic relaxation times. Master curves for the polymer systems investigated are produced and discussed.

Effect of concentration of Surfactant on the Exfoliation of Graphite to Graphene in Aqueous Media

Graphite was exfoliated to graphene by tip sonic using sodium cholate as a surfactant in the presence of Millipore water as a medium. The use of water as a solvent for exfoliation purposes is very important due to its environmentally friendly nature and almost no cost, contrary to organic media. Two different concentration ratios of surfactants are used in the present work. As a result, graphene dispersions with two different concentrations of 5 mg/ml and about 7 mg/ml respectively were obtained in aqueous media. It was observed that the optimum concentration of surfactant has an effective role in the exfoliation of graphite to graphene. Concentrations of graphene dispersions were studied through UV spectroscopy, while Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to study the quality of the exfoliated graphene flakes.

The effect of large area graphene oxide (LAGO) nanosheets on the mechanical properties of polyvinyl alcohol

Abstract Large area graphene oxide sheets were synthesized, dispersed in water and used as nanofiller for mechanical improvement in terms of Young’s modulus and ultimate tensile strength (UTS) of polyvinyl alcohol (PVA) at low loading. The molecular level dispersion and interfacial interactions between the graphene oxides and polymeric matrix PVA were the real challenges. An excellent improvement in mechanical properties at 0.35 wt% loading was observed. Modulus improved from 1.58 GPa to 2.72 GPa (~71% improvement), UTS improved from 120 MPa to 197 MPa (~65% improvement), and in spite of these improvements, interestingly, there was no fall in elongation at break at this loading.

Synthesis of Cyanate Ester Based Thermoset Resin by Using Copper (II) Oxalate as Catalyst and its Application in Carbon Fiber Composites

Polymer matrix plays a crucial role in the development of advanced light weight composite materials, and is mainly responsible for thermal and mechanical properties. These polymer matrices are usually thermosetting plastics due to their ease of processing. Thermoset resins were prepared using different compositions of dicyanate ester of bisphenol A and polyether imide and carbon fiber laminates were prepared by wet layup technique. Small amount of epoxy (diglycidyl ether of bisphenol A) was also added to the composites to improve the (interfacial) bonding between the carbon fiber and the resin. The Copper (II) oxalate with 1,5-pentanediol was used as a catalyst for the first time to reduce the curing time from eight hours to four hours. The catalyst has also reduced the curing temperature from 400°C to 250°C. The catalyst Copper (II) oxalate is commercially available. The plasticizer has improved the thermal and mechanical properties of the matrix significantly. The addition of epoxy to the thermoset resin improved the (interfacial) bonding between the resin and carbon fiber. FTIR results suggest that the polymerization reaction of dicyanate results in the formation of trizine ring with phenolic group. SEM results show the interaction of bisphenol A dicyanate (BPADCy) monomer to form polymer matrix. SEM images also represent a uniform anchoring of matrix on the individual carbon filament. It is clear from thermal analysis that sample having 85% BPADCy and 15% polyetherimide (BPR-2) shows the greater thermal stability which is due to the reaction of epoxy with cyanate matrix.

7Effects on Thermal and Ablative Properties of Phenolic Resin (Novolac) Blended Acrylonitrile Butadiene Rubber

In this work we investigated the ablative response and thermal properties of phenolic resin (PR) blended acrylonitrile butadiene rubber (NBR) composites. PR was added to NBR in the proportion of 0, 5, 10, 20, 30, 40 and 50 phr by means of two-roll laboratory mill. PR remarkably improved ablation resistance and thermal properties of NBR/PR composite. The linear and mass ablation rates reduced to 21.3 % and 26.1 % respectively. The char content deposition increased from 0.19 to 26.8 %. Char layer produced by PR, obviously reduced the erosion rate of the NBR/PR composite relative to neat NBR (without PR). Detailed morphological studies of the composite and post-test (ablation) microstructure of char revealed that higher loading of PR in the rubber composite produced dense char layer firmly intact to the substrate. Furthermore, thermal stability of the composite improved by 22–23 ºC, however, thermal conductivity of the composite slightly increased by 0.115 W/mK for 50 Phr of PR loading as compared to the neat.

Comparison of the Polymer/Composite Based on Polyurethane with Different –OH Backbone

Polyurethanes with two different types of –OH backbones castor oil (CO) and hydroxyl terminated polybutadiene (HTPB) were synthesized by using moderately reactive iso-phorone diiscocayante (IPDI) as curing agent. IR spectroscopy and mechanical property evaluations were carried out to elucidate the structure-property relationship of the polymer. It was found that the polymer, intersegment bonding had significant effects on the ultimate tensile properties. The CO based polymer exhibited far better mechanical properties than that of HTPB based polymer. However, a reverse behavior was observed in the composites. Composite fabricated with HTPB based polymer matrix showed four times the tensile strength of CO based composite. SEM comparison of the fractured composites revealed better wetting and adhesion properties with HTPB. Dynamic mechanical testing results indentified a relationship between the viscoelastic parameters and frequency of the applied load.