Browsing by Author "De Silva, NGH"

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item: Thesis-Full-text
Investigation of high volume bio materials as potential colourants and finish chemicals for fibrous substrates
(7/22/2011) Wijayapala, UGS; De Alwis, A; De Silva, NGH
The modern consumer (1990 onwards) is aware of the toxic chemical residues on textiles/garments (resulting from dyes and chemicals used) which can have carcinogenic/ dermatological and allergic effects on the wearer, especially because textiles are in contact with human skin for 24 hours of the day. The second aspect deals with the 'pollution' (air/water) at each of all stages in production of textiles. The third concern is about the 'ecological' problems during disposal (of garbage / on incineration). The aim of this research is to show feasibility of producing high quality natural dyes from plants, creating new opportunities for both farmers and the fabric / garment industry in line with the current consumer trends towards eco-friendly natural products. The direct national benefit is shown. Environmental and economical factors too need to be considered to make this viable in the long run. Investigation of the traditional dyeing techniques and dye producing plants with special reference to Sri Lanka, and development of natural dyes and investigation of their suitability as textile dyes were the two major objectives of this research study. Research investigations based on the comprehensive analysis of 10 best dye yielding plants which have been chosen from 47 dye yielding plants in Sri Lanka are presented. The available raw material spectrum had been reviewed. The ten (10) selected species are Kothala Himbutu (Salacia reticulata), Weniwal tCoscinium fenestratum), Rambutan (Nephelium lappaceum), Mangus tGarcinia mangostana), Big onion skin (Allium cepa) , Marigold (Tegetus erecta), Tea (Camellia sinensis), Jak (Artocarpus heterophyllus), Walmadata (Rubia cordifolia) and Turmeric (Curcuma domestica). Some of the above plant extracts have not been used before in textile dyeing. Environmental performance was another aspect of the research. Results from effluent characteristics of best dyeing solutions reveal significant reduction in pollution potential. The concept of ready to use dye concentrates is also presented
item: Conference-Extended-Abstract
Investigation of leaves and saw dust of jak tree as potential colouring agent for textile substrates
(2006) Samudrika, UG; De Silva, NGH; De Alwis, A
Synthetic dyes are largely consumed for colouration purposes for a long time. But now there has been increasing interest in natural dyes as, public become aware of ecological, environmental and health problems related to the use of synthetic dyes. So the main aim is as a developing country, always we have to concern about the prevailing demand.
item: Conference-Full-text
Investigation of the use of water by the textile industry in Sri Lanka-part 1
(1998) De Silva, NGH
The textile sector is one of the high water consuming operations among all industries. Studies on water use by their respective textile industries have been conducted by many countries such as USA, India and Great Britain. Information available facilitates the finisher to realise the actual position about the country levels of water usage and take appropriate action. if required, to optimise water utilisation with final objectives of economy of production and pollution prevention. This study has to cover as much a wide cross section of textile finishing facilities to get a realistic view about the country situation. In this Part I of the paper four of the biggest mills have been surveyed and information presented according to the widely accepted formats, i.e. in terms of unit operations of finishing treatments by the number of litres per kilogram (l/kg) processed. Information has also been presented in terms of the variable parameters such as machine type, dye class type or chemical type for better analytical possibility. The finisher would then be able to decide on any conservation measures necessary by comparison with (target) figures available from various sources. Il is intended to cover the medium and some small scale textile finishing facilities in the next part of this study to complete the full cross-section of the Sri Lankan textile finishing sector.
item: Thesis-Abstract
Positive environmental management via waste minimisation in a textile washing factory
(6/11/2011) Wijayapala, S; De Alwis, A; De Silva, NGH
Textile and garment Industry is an important industry sector in the Sri Lankan economy. The finishing part comprises the final step in textile processing and it is known as a sector with high polluting potential. In the textile washing sector considerable quantities of water is used only once usually and is discharged without any recovery. To stay competitive this industry needs to be modernized and definitely needs better performance in the environmental management sector. This project was limited to looking at the environmental management aspects and that too with only a single pollutant stream -water. The sector of the textile industry considered is the textile washing industry. A garment washing plant is analyzed with the objective of promoting water recycling and waste minimization practices. Initially typical practices were reported, followed by a water balance for the system . Results of the water audit presented here forms the first essential element of the waste minimization process. Water stream is considered from the inlet to the exit, and the consideration is given to methods of conservation possible of this valuable natural resource while obtaining the optimal use in the process. The time that water was assumed to be a limitless low-cost resource has already passed. Today there is an increasing awareness of the danger to the environment caused by over-extraction and use of water. There is now considerable incentive to reduce both consumption and waste water production. The selection of the washing industry was selected for this study under that consideration. This industry sector today uses significant quantities of water and most of the factories neither utilize waste minimization nor water recycling techniques. The waste treatment methods are also not adequate. Thus there is a tremendous potential on savings on one hand and a need on the other hand. It was shown that it is feasible to utilize groundwater after treatment. Manganese is not appearing to be a major problem. The problem chemical appears to be the presence of iron. Iron can be removed from groundwater using several operations. This eliminates the transport of water from outside and serves many environmental needs such as reduced traffic, removing reliance on outside sources and events etc. A pilot plant was constructed in the laboratory and four methods of iron removal were analyzed. Ozonation was studied as a method of reducing this wastage. In this manner there would be a reduced demand on the freshwater resource as well as reduced discharge of effluents. Thus the situation would lead to a facility whereby the waste minimization has taken place and a facility with positive environmental management. It has been shown that this technology offers many advantages to the industry including the recycling option. Ozonation in addition provided abilities to provide the required input quality as well in addition to being able to reduce COD, BOD and the most importantly Color of effluents. It was seen that processes are carried out with less attention being paid to the overall efficiencies but only towards meeting production targets and/or meeting deadlines. The feasibility of recycling waste water was shown. The practice of this would be a major improvement on the current environmental performance.
item: Conference-Full-text
Positive environmental management via waste minimization in a textile washing facility.
(1998) Wijayapala, S; De Silva, NGH
Existing and developing national environment protection regulations have made it mandatory for all industries to establish a treatment system for wastewater to bring down all toxic, hazardous and offensive components to specified levels before releasing to the environment. The paper looks at the garment washing industry in the textile sector. The industry sector today uses significant quantities of water and none of the factories utilise waste minimisation nor water recycling techniques. A washing plant is analysed with the objective of promoting water recycling and waste minimisation practices. Initially typical practices are given, followed by a water balance for the system. Results of the water audit presented here forms the first essential element of the waste minimisation process. The method suggested look at the iron removal process to utilise ground water and then (eliminating water transport needs) to advance filtration to make recycling feasible. Iron is the key limiting factor in utilising the available ground water supply. These steps would preserve the water resource and would eliminate the current wasteful practices adopted by the industry.
item: Conference-Extended-Abstract
Shade variations in narrow fabric dyeing - a case study
(2003) De Silva, NGH
This paper looks at the problems of a local narrow fabric manufacturer supplying its products to garment factories of the same group. The basic raw materials are (i) Filament yarns of Nylon 6. Nylon 66. Polyester and Lycra: (ii) Dyes and Chemicals. The yarns arc converted to narrow fabrics as per buyers' requirements by weaving or knitting machines and dyed and finished to match buyers' swatches using imported dyes and chemicals. To match the colour shade of the buyer's swatch. a computerised colour matching package namely "Data Color" is used to obtain few closely matching recipes. Using these recipes the respective fabrics are dyed and finished in laboratory scale equipment. These dyed sample swatches are sent for buyer's approval and the bulk is dyed using the buyer approved recipe.
item: Thesis-Abstract
A Study of indigenous dye producing plants and their derivatives in textile dyeing
(3/28/2011) Gunaratne, KPN; Wijayapala, S; De Silva, NGH
With the discovery of synthetic dyes all colour industries, not only textile industry had turned to the more economical, reproducible, high colour fast and easy to use synthetic dyes and abandoned the natural dyeing tradition which had prevailed as the only colouring technology till then. But recently a revival in the natural dye in technology has occurred as solutions to the environmental pollution arising out of the wet processing of textiles as well as to the growing trend of dye toxicity and all ergie s to the textile consumers. Natural dyes provide not only a good alternative to the environmental pollution arising from synthetic dyes but also provide low toxicity and allergic reactions while giving unique and fascinating colours which are not achieve able from synthetic dyes. A thorough review to the historic background of the origin and progression of natural dyeing techniques in the world with specific concern to Sri Lanka was carried out .During this review a search was also made into the reasons for the erosion of this valuable tradition of natural dyeing. Through a survey of the natural dye producing plants world over, a list of indigenous dye producing plants in Sri Lanka was preparedand investigated the possibility of using one of these plant sources to develop a new natural dye based on its extraction. In selection of this plant source the major concern was given to the fact that it should be abundant as a waste material in Sri Lanka. Black tea, which is highly available as a waste (dust) from tea factories and domestic sources (brewed tea) were used to extract polyphenols, which are an abundant form of natural compounds in tea. These were used as the coupling component to produce a zocompounds by coupling with different diazonium salts. Both polyphenols and azo compounds were separated and solidified and thus obtained azo compounds had variable colour shades depending on their respective diazonium salts. The possibility of applying these azo compounds as in-situ azo dyes on 100% cotton and ready-madeinsoluble disperse azo dyes using HTHP conditions on 100% polyester, 100% nylonand 100% wool were investigated. Different azo compounds produced different colourshades on different fabric types as well as on the same fabric type. Optimisation of dye bath conditions to improve the take up of polyphenols by cotton using the in-situ application of azo dyes was also carried out. The colours produced on cotton were not very bright and showed moderate colour fastness to washing, good colour fastness to rubbing while the brilliant colours produced on polyester showed good to very good wash, rub and sublimation fastness, after reduction clearing. The colour depth and fastness on nylon and wool were better than those on polyester. The light fastness of all the azo dyed samples was poor and should be improved using suitable after treatments. The percentage yield of polyphenols for both used and unused black tealeaves and the percentage yield of different azo compounds obtained from unused black tea leaves were calculated. The study was basically carried out with the aim of investigating the traditional dyeing techniques and indigenous dye producing plant sources in Sri Lanka and to assess the possibility of using polyphenols from one of the selected plant resources. Tea, which is abundantly available as tea waste (dust) from factories and brewed tea leaves fromdomestic sources was selected as the natural source of dye or dye intermediate for textile dyeing.
item: Conference-Extended-Abstract
Tea polyphenols as an indigenous natural plant resource in preparation of azo dyes for dyeing textiles
(2003) Gunararne, KPN; Wijayapala, S; De Silva, NGH
For thousands of years. until as recently as the discovery ofthe first synthetic dye in 1RS6. all colouring substances were of natural (vegetable. animal, lichen and mineral) origin. After the discovery of first synthetic dye, there was a gradual decrease in the use of natural dyes. which were more expensive and in many ways more difficult to use. Today. many of the natural dyes have been replaced by synthetic dyes. The major problem threatening the textile industry today is the environmental pollution, arising out of the wet processing of the textiles. The production of synthetic dyes involves many violent reactions. using. manv hazardous petroleum based primary chemicals as well as the production of hazardous intermediates. Therefore it is high time that the over utilization of synthetic dyestuffs should be thought about in the context of health of the people and environment. Natural dvcs extracted or developed from natural resources exhibit better biodegradability. higher compatibility with the environment and also a lower toxicity and allergic reactions not to mention the unique and fascinating colours.
item: Thesis-Abstract
Technological improvements in garment dyeing & finishing for sustainable development
(3/28/2011) Kumarasena, NWS; De Silva, NGH
Burdens to the environment with industrialization have extended to a greater extent than the assimilating capacity of it. The textile wet processing is a heavy consumer of water and energy. It also discharges environmentally hazardous substances. But the apparel sector with their affiliated garment washing and dyeing plants is one of the main income generators in Sri Lanka. Hence the discovery of any mean to mitigate those impacts while sustaining the industry would be immensely useful. This study has focused on two main approaches to accomplish the sustainable development in the garment dyeing facility. The approaches are maximizing Right First Time dyeing and Implementation of the Cleaner production options. Majority of the textile dyeing plants in Sri Lanka does not maintain any statistics on Right First Time dyeing. The percentage is acutely low in Garment dyeing. The root causes for the dyeing defects and shade variations in the dyed garments are analyzed in detail in this study. Cause and effect diagram, which is considered to be a powerful tool among seven quality tools, was used here as the tool for the analysis. Preventive measures are suggested for each root cause, subsequently. Application of Cleaner Production options to the industry is another approach for the sustainable development. The novel technologies, which are affordable, such as Ultra low liquor ratio machines, improved efficient washing systems, were deeply reviewed in this study. Switching on to such technology changes is utmost important for industries in order to, not only for the environmental compliance but also for sustainability in competitive global market. Modification of processes and formulas by critically analyzing them and making trials on them was another proven mean for the sustainability. Possibilities of implementing 3R-Reduce, Reuse and Recycle on water and other resources were looked into in the project. Good house keeping procedures are highlighted options in Cleaner production and some of the quantified studies have been covered in this project. Plenty of new options in material substitutions, Process controls, new byproducts etc. are also suggested for the industries to implement in order to demonstrate world-class ecologically sound performance.
item: Conference-Extended-Abstract
Ultra sound technique in natural dye application to textiles
(2007) Samudrika, UG; De Silva, NGH; De Alwis, AAP; Vankar, PS
The conventional method of textile dyeing has been to boil the fabric or yarn in dye bath, till the desired color is obtained. Enormous amount of heat is consumed in terms of heating the dye bath. Some dyes, which are heat sensitive, cannot be used in conventional dyeing because prolonged heating decomposes the dye molecules. The dye uptake by the fabric is also far from exhaustion and as a result fair amount of dye is wasted and gives rise to significant environmental pollution. The study carried out is to couple a different dyeing technique with natural dyes and to observe process effectiveness.