Polymer fiber modification

Electric discharge methods are known [31] to be very effective for nonactive polymer substrates such as polystyrene, polyethylene, polypropylene, etc. They are successfully used for cellulose-fiber modification to decrease the melt viscosity of cellulose-polyethylene composites [32] and to improve the mechanical properties of cellulose-polypropylene composites [28]. 

Analog-to-glass fibers silanes are used as coupling agents for natural fiber polymer composites. For example, the treatment of wood fibers with product A-175 improves wood dimensional stability [53]. In contrast, a decrease of mechanical properties was observed for coir-UP composites after a fiber modification with di-chloromethylvinyl silane [54]. The treatment of mercer-... 

Dye setting, control of, 9 493-498 Dyesite content, of polymer fibers, 11 195 Dye solubility, modification of, 9 509 Dye stability, in color photography, 19 263 Dyestuff migration, 9 231-232 Dyestuff production trends in, 9 294t United States, 9 295 West European, 9 294t Dyestuffs industry, growth of, 9 238-239 Dye-transfer inhibition system, 10 284 Dye transfer system, in color photography, 19 242... 

Polyethylene terephthalate modification hexsaazocyclanes by additives was carried out and fibers were formed. Additives introduction did not influence on the process of formation, and, consequently on the polymer fiber properties. 

Fig. 6 Functionalization of polymer fibers for nerve regeneration, (a) Functionalization with adsorption or covalent binding of ECM molecules to electrospun polymer fibers [169]. (b) Functionalization by blending of ECM molecules with synthetic polymers before electrospinning [93]. (c) Functionalization by chemical bulk modification of the electrospinnuig solution [158]...

Plasma Modification of Polymer Fibers and Polymer Membranes... 

Table 9-15. Modification of Properties of Polymer Fibers after Plasma Treatment...

Polymer fiber Plasma gas Plasma treatment conditions Modification of fiber properties... 

The properties of acrylic ester polymers depend largely on the type of alcohol from which the acrylic acid ester is prepared [26]. Solubility in oils and hydrocarbons increases as the length of the side chain increases. The lowest member of the series, poly(methyl acrylate), has poor low-temperature properties and is water sensitive. It is therefore restricted to such applications as textile sizes and leather finishes. Poly(ethyl acrylate) is used in fiber modifications and in coatings and poly(butyl acrylate) and poly(2-ethylhexyl acrylate) are used in the formulation of paints and adhesives. 

A number of polymer and fiber modifications have been devised to overcome this problem, although none has been successful enough to allow acrylics to compete in successfully easy-care apparel markets. The fibers may be treated with compounds such as ammonium sulfide [433], hydrazine derivatives [434,435], thiosemicarbazides [436], silicone oils [437], and emulsions of polysiloxane and polyepoxide [438]. Some success has been achieved by incorporating comonomers that increase the wet glass transition temperature of the polymer or make the copolymer more water-resistant [439-444]. Sheath-core fibers have been reported [445] in which the core polymer is stable under hot-wet conditions and the sheath polymer is used to compensate for deficiencies in dyeability. 

Cheng, C., Liye, Z., Zhan, R.J., 2006. Surface modification of polymer fiber by the new atmospheric pressure cold plasma jet. Surf. Coat. Technol. 200, 6659-6665. 

Supercritical modification of polymers was studied by several scientists to improve or change the properties of polymers. Polymers can either be chemically or physically modified. Examples of chemical modifications are the functionalization of polymers (grafting) or a chemical reaction of the functional groups of polymers to obtain new materials [38, 39]. Examples of physical modifications are the preparation of polymer blends, impregnation of polymers with additives [46], or foaming of polymers [59-61]. Another studied topic of polymer modification and impregnation is the supercritical dyeing of polymer fibers [40, 41). 

Here we discuss the alkali treatment and the silane treatment, which are the most common treatments used for fiber modification. Effect of various treatments on the mechanical properties of the polymer matrix is shown in Table 14.2. 

The interface is a region at least several molecular layers thick with properties intermediate between those of the fiber and matrix phases and arises due to the peculiar restrictions on molecular motions in this zone. Matrix molecules may be anchored to the fiber surface by chemical reaction or adsorption and determine the extent of interfacial adhesion. Fiber modification reduces hydrophilicity of the fiber and improves the physical/chemical interactions between the fiber and matrix. Treatment makes the surface of the fiber very rough and provides better mechanical interlocking with the polymer matrix. 

Sis et al. prepared composites based on poly (lactic acid) (PLA)/poly (butylene adi-pate-co-terephthalate) (PBAT)/kenaf fiber using a melt blending method [39]. A PLA/ PBAT blend with the ratio of 90 10 wt%, and the same blend ratio reinforced with various amounts of kenaf fiber were prepared and characterized. The addition of kenaf fiber reduced the mechanical properties sharply due to the poor interaction between the fiber and polymer matrix. Modification of the composite by (3-aminopropyl)tri-methoxysilane (APTMS) showed improvements in mechanical properties, increasing up to 42.5, 62.7 and 22.0% for tensile strength, flexural strength and impact strength, respectively. The composite treated with 2% APTMS successfully exhibited optimum... 

ITowever, it has some disadvantages, mainly the incompatibility between the hydrophilic fibers and hydrophobic thermoplastic matrices, which can negatively affect the mechanical properties. This requires appropriate treatments to enhance the adhesion between the fiber and matrix [13]. Fiber modification is necessary to increase the adhesion between the hydrophilic natural fibers and the hydrophobic polymer matrix at the interface. Many investigations have been carried out by a number of researchers. However, different methods and chemicals were used. Accordingly, this crucial factor will be discussed in detail later. 

Yip,J.,Chan,K.,Sin,K.M.,Lau,K.S.(2004)Comprehensive study of polymer fiber surface modifications. Part 1 high-fluence UV-excimer-laser-induced structures. PoZym. Int., 53, 627-633. 

A variety of discontinuous (short) functional fillers may be combined with thermoplastic or thermoset matrices to produce composites. The fillers may differ in shape (fibers, platelets, flakes, spheres, or irregulars), aspect ratio, and size. When the fully dispersed (exfoliated or deagglomerated) fillers are of nanoscale dimensions, the materials are known as nanocomposites. They differ from conventional microcomposites in that they contain a significant number of interfaces available for interactions between the intermixed phases. As a result of their unique properties, nanocomposites have great potential for applications involving polymer property modification utilizing low filler concentrations for minimum weight increase examples include mechanical, electrical, optical, and barrier properties improvement and enhanced flame retardancy. 

Michler, G.H., Baltd-Calleja, F.J., Nano- and Micromechanics of Polymers Structure Modification and Improvements of Properties (2012) Carl Hanser Verlag, Munich, Section 12.2, Hot Compacted Oriented Films/Fibers, ... 

The new fiber-modification technique is based on cationic acrylic copolymer. Pretreatment of cellulosic fiber with polymer is believed to offer an opportunity for increasing both the substantivity and reactivity of fibers towards reactive dyes under neutral conditions. The nature of a reactive polymer resin is such that it may react with nucleophilic sites in cellulosic fibers or in the polymer itself, thus fixing the polymer to the substrate. During subsequent dyeing, further reactions between the polymer and the dyestuff, the fiber and the dyestuff, and the fibre and the polymer and can be expeeted to take plaee, forming crosslink within the fibers. 

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