Double Dielectric Barrier (DBD) plasma-assisted deposition of chemical stabilized nanoparticles on polyamide 6,6 and polyester fabrics

The development of new multifunctional textiles containing nanoparticles (NPs) has had a special interest in several applications for pharmaceutical, medical, engineering, agricultural, and food products.[1-2] Cu, Zn and especially Ag NPs exhibit strong antibacterial activities on a broad spectrum of bacteria.[3-5] Most of the antimicrobial textiles coated with NPs are not able to perform a controlled release of the antibiotic species. Thus, the immobilization of NPs in the substrate or its inclusion in polymeric matrix is essential to control the NPs antibiotic effect with time. Dielectric barrier discharge (DBD) plasma technology is one of the most effective non-thermal plasma sources.[6] However, an even dispersion and coating of NPs onto fabrics remain a challenge due to the high degree of aggregation of metal NPs.[7] Some capping agents were described to increase the suspension stability such as citrate and SDS.[8] In this work, Ag, Zn, and Cu NPs deposition on DBD plasma pre-treated polyamide 6,6 (PA66) and polyester (PES) were tested for the production of durable antibacterial textiles. SEM-EDX analysis and the effect of some NPs stabilizers (e.g. sodium citrate, sodium alginate and Polyvinyl alcohol (PVA)) was analysed by dynamic light scattering (DLS) in term of size, polydispersity index and zeta potential. XPS analyses prove the DBD efficacy in providing oxygen species onto the fabric’s surfaces. The SEM analyses prove the deposition of the Ag and Cu NPs onto the PES and PA66 fabrics. No zinc was detected. However, antimicrobial tests in PES shows that all the NPs have an antimicrobial effect but Cu and Zn show activity only in S. aureus and Ag only in E.coli. Cu shows a reasonable dispersion onto the fibres but PVP coated AgNPs display a high level of aggregation even after 1 hour of ultrasonic treatment. To solve instability and aggregation problems, NPs suspensions were prepared in different concentrations (1, 2.5 and 5 wt%) of citrate, alginate and PVA using water and ethanol as control by ultrasonic bath. In table 1 are resumed the best results obtained for each NP compared to water as control. Ethanol and PVA were disregarded due to the highest instability and lowest ζ potential, respectively. XPS, SEM and antimicrobial data shows lack in coating uniformity. It is clear that doesn't exist a univocal dispersant and concentration for all NPs. Despite the improving in ζ potentials and stability of the colloids, the obtained sizes still show a high degree of aggregation.info:eu-repo/semantics/publishedVersio

Aromatic polyesters via transesterification of dimethylterephthalate/isophthalate with bisphenol-A

As a part of our work in the area of transesterification chemistry, we have studied the transesterification of dimethyl terephthalate/isophthalate with bisphenol-A for the synthesis of aromatic polyester. The process comprises two steps. The first step comprises preparation of aromatic polyester prepolymer by reacting the dimethyl esters of terephthalic/isophthalic acids and bisphenol-A in the melt phase via catalyzed interchange reaction. The second step involves the postpolycondensation of aromatic polyester prepolymer under reduced pressure, eliminating the by-product and driving the equilibrium of the reversible reaction to the formation of a high molecular weight aromatic polyester. In both steps, methanol is eliminated as a by-product. The method explored is the simplest one, permits the use of commercial materials as the feed stock, and leads to a low boiling by-product that can be recycled

Effect of latex concentration on epoxidation of natural rubber (NR) latex

Effect of latex concentration on the extent of epoxidation and physical properties of epoxidized natural rubber (ENR) was evaluated as a function of latex concentration in the range of 20-60% by weight. The epoxidation rate increased with increasing latex concentration. Physical properties and sequence distribution of an epoxy group of ENR with 30 mol % epoxy content was invariant with the latex concentration employed for epoxidation

Oxidative polymerization of 2,6-dimethylphenol by copper(II)chloride-amine complexes: effect of amines on polymerization activity

2, 6-Dimethylphenol (2,6-DMP) undergoes oxidative polymerization with CuCl2.2H2O-aliphatic amine complexes in a 70:30(v/v) o-dichlorobenzene-ethanol solvent. Unlike pyridine, polymerization occurs even in the absence of added base. Apart from basicity, factors such as steric effects and nature of ligand coordination to Cu(II) have profound effect on catalyst reactivity