Different techniques used for the mass coloration of polyester fibers are discussed in this article. Dope-dyed fibers have been produced starting from PET bottle wastes. Dope dyeing has been carried out both by the incorporation of pigments during drying before melt extrusion and by masterbatch addition. Fibers produced using different pigments and at different add-ons have been evaluated for color fastness properties and loss of mechanical properties due to dope addition. It has been shown that fibers having excellent fastness properties with little loss in mechanical properties could be obtained by either of these techniques. Fibers produced by recycling PET bottle wastes have been compared with those obtained by recycling polyester fiber wastes and virgin fiber grade polyesters melt spun under identical conditions. It has been demonstrated that bottle wastes yield fibers having properties equivalent to those of virgin polyester but probably cost similar as fiber wastes. Molded automotive carpets developed from recycled fibers from PET bottle wastes have shown excellent mechanical and fastness properties. It is inferred that using dope-dyed fibers based on PET bottle wastes in automotive applications may ensure a high benefit to cost ratio.
Poly(ethylene terephthalate) bottle-grade (BG) waste was converted into spinnable chips and spun on a laboratory-scale melt-spinning apparatus into filaments. Virgin fiber-grade (FG) polyester chips were blended with BG waste during melt spinning so that the influence of blending on the fiber properties could be studied. Subsequently, the scaling-up of the process was carried out in a polyester recycling plant so that staple fibers could be obtained. In this part of the study, the spinning of blends of BG waste and FG waste was carried out. The BG waste was found to be superior feed stock for melt processing. Fibers with unique properties were obtained from the BG waste. Staple fibers obtained by the blending of FG and BG waste showed properties different from those of fibers spun from BG waste alone. This study also showed that using blends of BG and FG waste could improve the melt processing and staple-fiber properties.
Gravimetric absorption test system (GATS) is used to measure the absorption capacity, absorption rate and drying rate of knit hoses, prepared from different fibres. The fibres studied are cotton, polyester and variety of modified polyesters. The study has shown that desorption or drying rate is at least two orders of magnitude lower than absorption rate. This finding implies that drying is the limiting process in moisture management. Further experiments on knit fabrics made from polyester and cotton, show that the drying rates are independent of fibre type in the constant-rate period, while the drying rates in the falling-rate period are dependent on fibre type. Subsequently, it is shown on the polyester fabric that drying rate in the falling-rate period depends on water concentration. Based on this understanding, an approach for enhancing drying rate in the falling-rate period is defined. The approach is demonstrated on knit hoses prepared from cotton and polyester yarns in alternating stripe form. The drying rate in the falling-rate period is found to be higher in the polyester-cotton stripe knit hose. A hypothesis for the observed enhancement in drying rate by wicking is put forth in terms of the internal movement of water from polyester to cotton portion. Experimentally, it is shown that 16% improvement in drying time is achieved in the case of the polyester-cotton stripe samples. Further, indications of internal water movement from polyester to cotton portion have been obtained by tracking the surface temperatures of the knit hoses during drying by infrared (IR) thermography.
Activated carbon in the form of a regular fabric obtained using viscbse rayon precursot is a new generation adsorbent material having superior sorptional properties and is finding varied defence applications. CarbQnisation and activation mechanisms and properties and applications of adsorbent carborl fib~s, made from viscose rayon precursor are reviewed in this paper. j activated carbon having superior adsorption potential has gone on unabated since the first application of carbon in canisterS in the First World War. Activated carbons derived from coconut shell, wood and coal are well-known and so are the advantages and disadvantages associated with them.. Activated carbon derived by carbonisation and activation of viscose rayon fabric (Figs 1 and 2) is the latest addition to the above list. The full poltcntial of this adsorbent carbon fabric has not yet been realised, but this form of,carbon has begun to replace traditional carbon in devices. like face let masks. In this review, an attempt has been made to I.
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