The combination of high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polypropylene (PP) is frequently found in polymer waste streams. Because of their similar density, they cannot be easily separated from each other in the recycling stream. Blending of PP/ polyethylenes (PEs) in different ratios possibly eliminate the sorting process used in the regular recycling process. PP has fascinating properties such as excellent processability and chemical resistance. However, insufficient flexibility limits its use for specific applications. Blending of PP with relative flexible PEs might improve its flexibility. This is a unique approach for recycling or upcycling, which aims to maintain or improve the properties of recycled materials. The effects of the branched-chain structures of PEs on the crystallization behavior and the related mechanical properties of such blends were investigated. The overall kinetics of crystallization of PP was significantly influenced by the presence of PEs with different branched-chain structures. The presence of LDPE was found to decrease the overall crystallization rate while the addition of HDPE accelerated the crystallization process of the blends. No negative effect on the mechanical performance and the related crystallinity was observed within the studied parameter range.

We have investigated bottom-up chemical synthesis of quaternary ammonium (QA) groups exhibiting antibacterial properties on stainless steel (SS) and filter paper surfaces via nonequilibrium, low-pressure plasma-enhanced functionalization. Ethylenediamine (ED) plasma under suitable conditions generated films rich in secondary and tertiary amines. These functional structures were covalently attached to the SS surface by treating SS with O 2 and hexamethyldisiloxane plasma prior to ED plasma treatment. QA structures were formed by reaction of the plasma-deposited amines with hexyl bromide and subsequently with methyl iodide. Structural compositions were examined by electron spectroscopy for chemical analysis and Fourier transform infrared spectroscopy, and surface topography was investigated with atomic force microscopy and water contact angle measurements. Modified SS surfaces exhibited greater than a 99.9% decrease in Staphylococcus aureus counts and 98% in the case of Klebsiella pneumoniae. The porous filter paper surfaces with immobilized QA groups inactivated 98.7% and 96.8% of S. aureus and K. pneumoniae, respectively. This technique will open up a novel way for the synthesis of stable and very efficient bactericidal surfaces with potential applications in development of advanced medical devices and implants with antimicrobial surfaces.

Cold plasma conditions offer a novel route for synthesizing and depositing macromolecular structures on various organic and inorganic surfaces, and to functionalize in a controlled manner even the most inert polymeric substrates. The energies of active species of plasma are high enough to split all chemical bonds from organic and organometallic derivatives and consequently, tailored macromolecular structures can be created through controlled recombination of plasma generated charged and neutral molecular fragments. Nonmacromolecular forming active species of organic-or inorganic-origin can interact with polymeric surfaces creating desired, new thin layer structures through in situ or ex-situ recombination mechanisms initiated between the plasma generated active sites of the condensed and gaseous phases. Understanding the plasma induced reaction mechanisms developed in the gas phase and on the surfaces which limit the discharge opens up rational ways to create materials with advanced surface characteristics, such as chemical inertness, advanced hydrophobicity or hydrophilicity, selective reactivity (molecular recognition), intense surface roughness, etc.

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Polyester (PET) swatches are treated with an electrical discharge plasma of a reactive atmosphere (tetrachlorosilane) to graft chlorosilane groups, subsequently hydrolyzed to very hydrophilic hydroxysilane groups. The Kawabata evaluation system for fabrics (KES-FB), high resolution microscopy, and surface tension measurements are used to investigate the physical properties of the fabrics before and after plasma exposure. The results show that the surface parameters are considerably modified by the treatment.

Polyethylene and glass surfaces were functionalized under dichlorosilane-RF-cold-plasma environments and were employed as substrates for further in situ derivatization reactions and immobilization of papain. Surface functionality changes of RF-plasma-exposed surfaces were monitored under 40 kHz continuous discharge environments. The nature and morphology of derivatized substrates and the substrates bearing the immobilized enzyme were analyzed using survey and high resolution ESCA, ATR-FTIR, and fluorescence of chemical derivatization techniques. Spacer molecules intercalated between the substrates and the enzyme significantly increased the enzyme activity (comparable with the that of the free enzyme). Computer-aided conformational modeling of the substrate-spacer systems corroborated with experimental data indicated that an optimal distance might exist between the enzyme and the substrate. The activity of free and immobilized papain was monitored using benzoyl arginine ethyl ester assay. The pH data were recorded every 0.3 s over 25 min. The Michaelis-Menten kinetic constants were evaluated for immobilized enzymes. It was shown, that the immobilized papain retains most of its activity after several washing/assay cycles.

SYNOPSISExtensive research has been carried out in recent years using fluorocarbon plasmas for modification and depositions on polymer substrates. In some cases anomalous results have been obtained that are not explainable based on conventional fluorine chemistry. In this investigation pure polypropylene films were exposed to carbon tetrafluoride plasmas in a Pyrex glass reactor. A t short reaction times (less than 1 min) significant amount of silicon was detected by ESCA on the surface of the films. Analysis of liquid nitrogen trapped fluorocarbon plasma gases and molecular fragments indicated high concentrations of silicon and carbon containing species, the former indicative of ablation and etching reactions of the glass reactor walls. The production of a relatively high quantity of fluorosilicon derivatives was explained by the greater affinity of silicon for fluorine than for carbon, with the tendency to readily form SiF,. These fluorosilicon radical and ionic species generated under cold plasma conditions can easily react with polymeric substrates causing unexpected surface modifications. In addition Si-F bonds could be readily hydrolyzed to SiOH islands on the surface of the substrate to impart anomalous characteristics.

Flame retardant cellulosic materials have been produced using a silicon dioxide (SiO 2 ) network coating. SiO 2 network armor was prepared through hydrolysis and condensation of the precursor tetraethyl orthosilicate (TEOS), prior coating the substrates, and was cross linked on the surface of the substrates using atmospheric pressure plasma (APP) technique. Because of protection effects of the SiO 2 network armor, the cellulosic based fibers exhibit enhanced thermal properties (characterized by TGA and DSC) and improved flame retardant (proven by ASTM D1230-99). Furthermore, the surface analysis (XPS and SEM) confirmed the presence of the SiO 2 network attached to the substrates even after intense ultrasound washes.