Fiber modification, surface conditions

Semiquantitative elemental analysis was performed on the fiber samples by SEM-EDAX. The Ti content on the surface ranged around 90-95% and in the interior from 65 to 90%, depending on the conditions of PAN fiber modification. The inner core contained a higher percentage of titanium when the modifications were performed at 20°C, compared to -10°C. Thus temperature possibly affects the rate of titanium monomer diffusion as well as reaction rate of the -C-N group and the titanium monomer. 

Nonwovens The textile and paper industries are based on the two oldest (wet and dry) processes. Manufacturers of nonwovens for plastics draw on both. With the wet, there are basically two types namely the Fourdrinier and cylinder machine types that have been modified. In addition, two basic types exist for the process formation of the web and application of the bonding agent or system where mechanical carding of fibers is used. The particular equipment and method of operation to be used, with their many modifications, is influenced by desired requirements such as mechanical properties, softness, surface condition, tenacity, etc. There are certain t) es of so-called nonwoven fabric that are directly formed from short or chopped fiber as well as continuous filaments. They are produced by loosely compressing together fibers, yarns, rovings, etc. with or without a scrim cloth carrier assembled by mechanical, chemical, thermal, or solvent methods. Products of this type include melted and spun-bonded fabrics. 

When any polymer is to be used as film, plate, fiber, or molded material, the surface properties are as important as the bulk properties. In comparison with the large number of works devoted to the development of new polymers, relatively minor efforts have been directed to the modification of polymer surface. In particular, owing to the difficulties of studying chemical and physical properties of polymer surface, few articles have been published on the correlation between the condition of surface treatments and the imparted surface properties. 

Drzal et al. 90) have investigated the effect of interphase modification on interfacial moisture absorption. The fibers used were a surface treated and a surface treated and finished type A carbon fiber in the same epoxy matrix studied previously. Three equilibrium exposure conditions were investigated. 20 °C, 70 °C and 120 °C were selected for moisture equilibration of single fiber samples and for the neat epoxy resin. The interfacial shear strength was measured both in the saturated and the dehydrated cases and compared to the initial dry values. 

In a similar way, a well-adhered surface modification of BC fibers can be achieved with Ti(>2 nanoparticles (with a diameter of about 10 nm) by the hydrolysis of titanium tetraisopropanolate adsorbed onto the fibers. It was observed that the titania-coated surface appears to be dense and have low porosity and to consist of near-spherical grains. By washing with sodium carbonate solution, the TiC>2 films were not removed during neutralization. It seems that the particles have formed strong interactions with BC. The coated membranes showed substantial bactericidal properties under UV radiation and white light (containing a small fraction of UV) conditions, too. This effect is caused by the photocatalytic destruction of the bacterial cells. 

It was noted by MacDiarmid and Epstein as early as 1989 that PAn salts may also be deposited as films on a variety of substrates by immersing the substrate in the polymerization mixture.29 In fact, during standard chemical polymerization, one often observes the deposition of a thin, extremely adherent green emeraldine salt (ES) film on the walls of glass reaction vessels, as well as the bulk precipitation of PAn/HA powder. By judicious manipulation of the polymerization conditions such as reagent concentrations/ratios and modification of the substrate surface, one can maximize the surface deposition as opposed to polymer precipitation.30 This phenomenon has been developed into a widely useful in situ polymerization technique for the preparation of PAn films on a variety of insulating surfaces such as glass and plastics, as well as on fibers and fabrics. 

A theory for cavitation was outlined, and preliminary calculations for four fiber treatment conditions were discussed. The theory corroborates the experimental results and reinforces the Idea that liquid mixtures of strong and weak swelling agents can be used to control surface modification. 

The fibers were immersed in solution of Ti(NEt2)4/benzene for 48h at 10°C. The concentration of Ti(NEt2)4 in benzene was varied to determine the effect on fiber structure. The modified fibers were pyrolyzed under different conditions, which are summarized in Table I. Fig. 1 is an SEM micrograph of the surface of such a fiber, thermally processed in argon. Table II summarizes the modification of PAN fibers by the monomer Ti(NMe2). Here no solvent was used as the monomer was less viscous and easier to handle. Fig. 2 is an SEM micrograph of a cross section of a... 

Abstract A wide variety of natural fibers can be applied as reinforcement or fillers in composites. Bast fibers, such as fiax and hemp, have a long history of cultivation and use. They are characterized by low weight and excellent range of mechanical properties. The properties of bast fibers are influenced by conditions of cultivation, retting, and processing. Pretreatment and surface modification of bast fibers is conducted for optimization of the interfacial characteristics between fiber and matrix as well as improvement of their mechanical properties. Application of bast fibers as reinforcement to replace the glass fibers to composite manufacture brings positive environmental benefits. 

The research results confirm that the application of silica-organic compounds for modification of cellulose fiber surface considerably improves strength properties of composites [50, 51, 72-75]. Raj et al. [72] found that the modification of cellulose fibers with silanes as well as with isocyanate caused improvement of mechanical properties of composites based on polypropylene matrix. However, studies conducted by Hornsby et al. [76] do not confirm that. His results prove that processing flax fibers with silanes has no effect on mechanical properties of composites based on polypropylene matrix. These contradictory conclusions are probably the effect of a complex anatomical structure of cellulose fiber and/or application of suitable conditions of modification reaction. 

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