Browsing by Author "Gunapala, PY"

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item: Thesis-Abstract
A Study of natural rubber latex - filler interaction
Peris, CN; Gunapala, O; Gunapala, PY
An attempt has been made to evaluate natural rubber latex - filler interaction. 1800- peel test of flexible to rigid joints was performed to determine the peel strength of natural rubber latex -kaolin joints in order to evaluate the interaction of natural rubber latex with standard rubber grade kaolin and activated one by ion exchange reaction with amino -functional derivatives. Experimented natural rubber latex compounds were pre vulcanized with sulphur and ionization radiation. Radiation vulcanization was performed using 60 Co source irradiator, originally designed for sterilization of medical products, with reduced gamma rays dose rate. Its suitability for radiation vulcanization of locally produced natural rubber latex was confirmed experimentally. Obtained results showed that the peel off test device was acceptable for evaluation of natural rubber latex -filler interaction irrespective of the vulcanization system used with latex compound. Peel test results displayed the influence of modified fillers on the peel strength values of tested laminates. Increased peel strength values of the samples containing modified kaolin were attributed to better interaction of the filler with rubber polymer. It was investigated, that facilitated interaction observed with natural rubber latex and modified kaolin resulted in improved properties of filled natural rubber latex compounds of both vulcanization system, and irradiated one was more susceptible within the experiment performed. Preference in mechanical stability time, viscosity factor and tensile was given to radiation vulcanization natural rubber latex (RVNRL). Reinforcing effect of modified filers in natural rubber latex compounds was lower of that observed earlier with dry rubber compounds. The reason for it could be associated with partial deactivation of the active centres initially brought by modification the phenomenon that have to be studied and overcome in the future. However, it is hoped that carried out research positively contributes to the understanding the mechanism of reinforcement of rubber polymers with fillers and development of the technologies upgrading cheap local mineral resources to use them more beneficially in natural rubber formulation technology. Another aspect covered by research related to development of radiation vulcanization technology that gives a definite support for introduction to local latex based manufacturing industries.
item: Conference-Extended-Abstract
Chemical recycling of PET from waste soft drinks bottles to recover Terephthalic Acid
(2009) Udayakumara, SV; Gunapala, PY; Gunapala, O
This project aims to develop an efficient and low cost chemical recycling method to extract valuable terephthalic acid (TPA) from post consumer Poly (ethylene Terephthalate) (PET) in Sri Lanka. PET waste from soft drink bottles was subjected to alkaline hydrolysis using NaOH to produce sodium terephthalate. Reaction was carried out under different hydrolysis conditions including varying Ethylene glycol to PET ratios, reaction temperature and time. After completing the reaction, mixture was diluted with sulfuric acid to precipitate TPA that was separated by filtration. Characterization and identification of purified TPA were performed using Fourier Transformation Infrared techniques.
item: Conference-Extended-Abstract
Design of conventional extruder die for production of semi rigid PVC pipe
(2009) Gunapala, O; Gunapala, PY; Tilakasena, U
The research was directed to design an extruder die for production of semi rigid poly-vinyl-chloride ( PVC) pipes widely used as an outlet pipe in washing machines, that are very popular not only at homes but in a number factories located in Sri Lanka, belonging to certain industries including dyeing, protective clothing etc. Nevertheless extrusion dies for production of semi rigid pipes have been neither produced nor designed in Sri Lanka. Theoretical approach in the research project was based on rheology and thermodynamics of plasticized PVC melt that enabled design of the extrusion die considering the specialties of the selected material and processing limitations. The carried out research consisted of two parts. Firstly to come up with a general solution package that was used to derive dimensions when information about the input material and the expected output was given. Secondly, using the package to design the die for a special application of the desired dimensions. An Excel spread sheet was developed that embodied the theoretical aspects of the research project. Changing the indicated input parameters, spread calculated and produced the dimension of the desired die. A sequence of calculations and AutoCAD diagrams were produced for the specific die requirements. With this information at hand, Sri Lankan industries can start manufacture of the extruder dies for production of plasticized PVC pipes on a good theoretical basis ensuring success, instead importing.
item: Thesis-Abstract
Design of thermo forming machine
Hettiarachchi, HANR; Gunapala, PY; Gunapala, O
An attempt has been made to design vacuum forming machine which is capable of producing "Small plant growing Horticultural HIPS tray" in a economical speed. these trays has high demand in all over the world's horticultural industry but used thermo-forming as a manufacturing process which tooling cost quite high compared with vacuum forming. at the same time small quantity of product not accepted by the manufactures and simple epoxy moulds and wood mould can't used in this thermoforming machine. at the same time European made thermoforming machine is high expensive compared with normal roll feed vacuum forming machines. so my aim was to design vacuum forming machine which is capable of producing this type of product at a economical way. This research aimed to design most critical components of this vacuum forming machine with clear understanding of it's practical operational requirement. Basically heater oven ; vacuum system; mold and plug moving system and mould design covered in this research. High Impact Polystyrene (HIPS) used as the plastic material for this "Horticulture tray production" and this machine capable of using .O.8mm - 0.25mm thick HIPS and PP (polypropylene) sheets reels as input material. Pneumatically operated mould and plug moving system incorporated with chill water cooling jacket as a mould base for each and every mould used. Electric Infra-red ceramic heaters used as the heating source for sheet heating ..These heaters mounted on top and bottom ovens where sheet feeding through these two. Vane type vacuum pump selected according to match the vacuum requirement and this vacuum system consists of vacuum surge tank, vacuum line and operating solenoid valves.
item: Thesis-Abstract
Designing of a profile extrusion die
(2014-06-06) Samarawickrama, UDA; Gunapala, PY
Designing of the proposed profile extrusion die had few main tasks. One was to find out the most suitable type of die and the other was to calculate important operating parameters like pressure drop. The next is to calculate the land and calibration dimensions. Due to complex nature of the proposed profile, it was approximated to a slit die for the purposes of calculating pressure drops anddie swell / draw down ef-fects. Based on the thickness calculated for die, product and equilibrated swell state were used to calculate the dimensions of the complex die land and calibrator. When designing the die, due consideration was given to phenomenon like ,melt flow instabilities and shrinkage on cooling.Only top half of the PVC trunking profile was designed in this exercise, as trials are needed to validate the models selected and based on these val-ues only, progress onwards could be envisaged.
item: Conference-Abstract
Development of breathing monolayer plastic packaging
(2008) Gunapala, O; Gunapala, PY; Illangarathne, SSKP
The importance and relevance of development of permeable polymeric materials become apparent due to accelerating demand on breathing packaging in food processing, pharmaceutical, and horticultural industries. The present research was pursued to develop breathable plastic packaging suited for desired level of moisture permeable applications. The monolayer plastic films differed by resin composition were extruded on blown film equipment and two types of packages differed by architecture were prepared from the films extruded .To evaluate the package quality the shelf life of fresh mushrooms packed in the packages was studied. Water vapor transmission rate and other performance properties of plastic films were determined. Results demonstrated good breathability of the developed packaging. Preference was given to the filled polyolefin compounds. Importance of filler particle size, treatment and processing conditions, including biaxial orientation was shown. Use of local fillers and traditional single layer extrusion equipment did not contribute to the cost significantly, making packaging affordable easily by local consumers.
item: Thesis-Abstract
Development of extrusion technology of breathable film for industrial applications
Illangarathne, SSKP; Gunapala, O; Gunapala, PY
The present research was pursued to develop breathable plastic packaging suited for desired level of moisture permeable application. The monolayer plastic films differed by resin composition were extruded by blown film equipment and two types of packaging with different architecture were prepared from the films extruded. To evaluate the package quality, the shelf life of fresh mushrooms packed in the packages was studied. Water vapour transmission rate and other performance properties of plastic films were determined. Results demonstrated good breathability of the developed packaging. Preference was given to the filled polyolefin compounds. Importance of filler particle size, treatment and processing conditions, including biaxial orientation were shown .Use of local filler and traditional single layer extrusion equipment did not contribute to the cost significantly, making packaging affordable easily by local consumer.
item: Conference-Abstract
Effect of Papain on the biodegradability of polyethylene modified by Chitosan
(2008) Samarasekara, AMPB; Gunapala, PY
The objective of this research was to impart biodegradability to polyethylene. Chitin and Chitosan were main additives extracted from the fishery waste. Chitosan, a natural polymer, was one prospective contender for imparting biodegradability to Polyethylene. Papain a natural enzyme was used in addition to enhance biodegradability. The biodegradability of Polyethylene blend was studied using low molecular weight chitosan in the presence and absence of papain. The soil degradation test was performed to evaluate degree of biodegradability. Results obtained showed that specimens buried in the soil were degraded by almost 60% after six months 1.vhen papain was added and the test sample was completely disintegrated after one year. The combinations of chitosan, papain and polyethylene showed the appreciable biodegradable properties of Low Density Polyethylene products after industrial and domestic applications.
item: Conference-Full-text
Effect of the surface chemistry of kaolin on the properties of filled rubber compounds
(2001) Ranasinghe, ARMWWK; Gunapaia, O; Gunapala, PY
An attempt has made to activate the inert structure of Rubber grade kaolin clays through ion-exchange process. Counter ions absorbed by unsatisfied silicon, oxygen and hydroxyl ions at the edges of planar surfaces of kaolinite mineral to preserve electrical neutrality were replaced with complex organic ions containing active functional groups (amine, hydroxyl, carboxyl) in their organic radicals. Strongly attached to the clay surface these complex ions project their organic aryl or alkyl radicals outwards to suspending medium rubber matrix making inorganic kaolin surface effectively organic and therefore hydrophobic one. Such change in kaolin surface facilitated rubber- filler interaction owing to better wetting of the filler surface with organic rubber polymer and formation of sufficient density grafted polymer layer bonding the rubber matrix to filler. Carried out physico-mechanical testing of filled rubber compounds showed that modification of kaolin with chosen basic electrolytes ionized in aqueous medium was effective. Increase in strength characteristics has made possible in commercial practicability of rubber formulation technology the substitution of expensive reinforcing fillers with lowest in cost appropriately modified kaolin Clay.
item: Conference-Abstract
Extraction and modification of chitosan from fishery waste to develop biodegradable polyethylene films
(2006) Gunapala, PY; Samarasekara, AMPB
Polymers made of petroleum by products have come into wide use throughout the world. With an increase of their applications, the treatment of waste polymers has become a serious environmental problem because of the difficulty of ensuring refilling land and burning. The principle methodologies of waste management of polymer based products are mechanical recycling, incineration and biodegradation. Mechanical recycling and incineration have technological and ecological limitations but biodegradation is an environmental friendly economical process compared to above two methods. Conventional polyethylene products can take longer than 100 years to degrade, but a biodegradable product has the ability to break down, safely and relatively quickly, by biological means, into the raw materials of nature and disappear into the environment. Therefore these polymers can be considered as a solution for the plastic waste disposal problem.
item: Thesis-Abstract
Extraction and modification of lignin resin for rubber compounds
(6/23/2011) Sagarika, APT; Gunapala, PY
The aim of this work was related to development of economically viable method of extraction of lignin from sawdust in order to produce additive capable to improve physical mechanical and aging properties of rubber compounds. Five methods were developed and performed to isolate lignin from sawdust. They were delignification, acidolysis with 5M Hydrochloric acid, acidolysis with 10M Hydrochloric acid, ethanolysis and extraction with acetone. Chemical structure of produced lignin samples was identified with Furior Transform Infra Red spectrometer (FTIR). Analysis of FTIR spectra showed good' conformity of all wave numbers at which specified peaks of experimented and reference lignin samples were observed. Acidolysis of sawdust with 10M hydrochloric acid was found the most efficient for lignin extraction. This lignin was proceeded as a filler for rubber compounds. Properties of rubber compounds extended with produced lignin samples were determined. The test results showed that lignin was capable to improve properties of rubber compounds to the level achieved with carbon black and imported lignin filler samples, as well as resistance of rubber to prolong heat aging. An attempt was made to synthesize commercial antioxidants for rubber from extracted lignin sample. Methodology was developed and performed. Synthesized products were 2,4,6 three-tert-butyl phenol and 2,6 di-tert butyl paracresol. Alcoholic and methoxyl groups present earlier in extracted lignin samples were replaced with methyl and tertiary butyl groups. These groups are particularly capable to donate hydrogen to an alkyl peroxy radical. The effects of substituent groups in the transition state involved not only electron transfer to the peroxy radical but electron delocalization in the aromatic ring. So synthesized products were expected to act as effective antioxidants in rubber compounds. Rubber compounds with experimented antioxidants were prepared and their properties carefully investigated. Test results showed excellent resistance of rubber compounds to heat aging, that proved with high level of confidence antioxidation activity of synthesized products.
item: Conference-Extended-Abstract
Extraction of lignin from sawdust for rubber compounding
(2003) Gunapala, PY; Gunapala, O; Sagarika, APT
The increasingly stringent requirements of rubber product consuming industries have put demand on Sri Lankan rubber processing industry to provide rubber parts with better performance such as high tensile strength, good tear resistance and low abrasion. The economic recession and competition from abroad are other major challenges facing Sri Lankan rubber industry. To satisfy customer needs and meet competition local rubber industrialists have to realize the importance in basic research and their investment, Special attention is to be brought to upgrade and develop rubber formulation technologies based on cheap and locally available raw materials.
item: Thesis-Abstract
Modelling of the vulcanization process of thick-walled natural rubber articles
(7/2/2011) Weragoda, VSC; Gunapala, PY; Munasinghe, RGNDS
A computer-based technique was developed to render the state of cure in thick-walled natural rubber compounds as measured by the oscillating disk rheometer torque. The method was based on a mathematical function derived to replicate the rate of change in the rheometer torque with respect to the curing time and the curing temperature. The mathematical function was able to trace the temperature related changes in the rheometer curves of different rubber compounds exceptionally well, at a 99.9% level of certainty. This was used to model the vulcanisation process for thick-walled articles through a deterministic simulation approach, which was made it possible to predict the scorch time, curing time, and the time for onset of reversion to a precision within ±5%, as verified against programmed a temperature profile curing in a rheometer. This study also investigated the variation of the thermal conductivity and the thermal diffusivity of rubber compounds during the curing process, to determine the effectiveness of such variations in estimating the curing time of thick-walled rubber articles. The experiments were carried out using a modified hot wire technique. The coefficient of variation in the thermal diffusivity was estimated at 20%, and the same for the thermal conductivity was found to be 15%, for the compounds tested. The simulation model showed that this variation was not significant in affecting the curing time.
item: Conference-Extended-Abstract
Modification of mineral fillers with amino-functional derivatives
(2002) Thambawita, IS; Gunapala, O; Gunapala, PY
Fillers playa major role in the rubber industry with respect to their effect on properties of vulcanised rubber and the compound's cost. For most applications rubber compounds are loaded with reinforcing carbon black fillers to increase hardness, stiffness, strength, resistance to tear and abrasion. Approximately 90% of the world's carbon black production is consumed by rubber industries. Carbon blacks are imported to Sri Lanka and in spite of high cost are not easily available in the local market.
item: Thesis-Abstract
Modification of mineral fillers with aminofunctional derivatives
(2014-07-07) Thambawita, IS; Gunapala, O; Gunapala, PY
Effect of mineral fillers modified with amino-functional derivatives on properties of natural rubber compounds was studied. To improve the performance of rubber compounds, three types of locally available mineral fillers; kaolin, kaolinite and quartz were modified through ion-exchange process and used as reinforcing fillers. The clays were thus modified with three types of organic quaternary ammonium ions. They were thiourium, ammonium succinimate and para ammino phenolate. Sieve fractionating and sedimentation analysis were performed to find the particle size distribution of the tested fillers. Cation exchange capacities of tested fillers were determined using Kjedhal experiment. Obtained results were used to perform the ion-exchange reaction keeping stoicheometrically balanced ratios of modifying exchangeable cations and kaolins Modified and unmodified fillers were compounded with rubber. Physico -mechanical properties of rubber compounds such as tensile, aging, resistance to flex cracking, crack growth, and abrasion were determined and analyzed. To evaluate the interaction of rubber with filler surface bound rubber content and swelling tests were performed. Differential Thermal Analysis (DTA) and Differential Thermal Gravimetric Analysis (DTG) were used to confirm the course of ion-exchange reaction. Microphotographs were taken to evaluate the quality of dispersion and distribution of fillers in rubber compounds. Obtained results demonstrated advantages of rubber compounds filled with modified fillers. Better performance was achieved on account of improved compatibility and intensified interaction of modified fillers with rubber. It was found that reinforcing effect introduced to rubber by thiourium cations modified clay was especially strong. Proposed mechanism of reinforcement of rubber with thiourium cations modified clay referred to formation of chemical links across rubber-filler interface. Effect of particle size of the clay fines on cation exchange capacity and reinforcing capability of modified fillers was established. Larger contactar aera and increased cation exchange capacity of the small size filler particles permitted arrangement of increased number of active centers on the surface of the filler particles that resulted in strong reinforcing effect similar to that, achieved with carbon blacks.
item: Conference-Full-text
Modified clay as a filler in rubber compounding
(1998) Gunapala, PY; Sivasundaram, M
Elastomer formulations have changed continuously in order to achieve optimum cost-performance characteristics. The surface modification of low cost mineral fillers had an impact on the rubber industry, because ii made possible to convert non reinforcing mineral fillers into reinforcing ones and displace expensive carbon black fillers from rubber compound. Therefore low cost mineral filler such as china clay has been upgraded by surface modification to obtain creditable performance as reinforcing filler in rubber industry. Also this modified filler has improved the quality of rubber compound through better dispersion of ingredients added to the mix. But primary advantage of the modification has been related to the interfacial adhesion between rubber and filler, since the modificator, acting as a surfactant provides the bond formation across modificator-clay interface as well as rubber-modificator interface.
item: Thesis-Abstract
Natural rubber to filler interaction study by determining creep rupture strength
(6/15/2011) Liyanage, DS; Gunapala, PY; Gunapala, O
Creep rupture of clay-rubber composites was studied by 1800 peel test of flexible to rigid joints to evaluate the rubber-filler interaction. Static load providing separation of specimen at equilibrium peel rate, corresponding to 10-8 m/sec, the rate at which a kinetic segment of a hydrocarbon chain moves in an elementary event of thermal motion, was treated as peel strength of a specimen at creep rupture. A methodology was developed to measure the peel strength at creep rupture in an open air and liquid medium active towards the interface of joined materials. Series of monohydric alcohols was selected since lower alcohols are strongly hydrogen bonded solvents whilst higher alcohols tend to strong dispersion interaction. The change in peel strength values due to variation of solubility parameter of the selected alcohols was used for identification of molecular bonds established across rubber filler interface. Decreasing in the peel strength values with increasing in despersive component of the solubility parameter of the hostile medium indicated the presence of dispersion bonds across rubber-filler interface. Hydrogen and polar bonds were identified by decreasing the peel strength values due to increasing polar component of the solubility parameter of the alcohols to which a specimen was exposed, while stability of joints to action of hostile medium, proved the presence of chemical bonds established across the rubber - filler interface. Obtained peel-strength values correlated well with bound rubber content, ensuring that the results have realistically characterized rubber-filler interaction. The chemical nature of the filler surface was the main factor influencing it, that has made possible in commercial practicability the modification of the inert filler in order to enhance its effect on rubber properties.
item: Thesis-Abstract
Physico-mechanical properties of modified kaolin clay filled rubber compounds
Ranasinghe, ARMWWK; Gunapala, O; Gunapala, PY
An attempt has made to activate the inert structure or Rubber grade kaolin clays through ion-exchange process. Counter ions absorbed by unsatisfied silicon. oxygen and hydroxyl ions at the edges of planar surfaces of kaolinite mineral to preserve electrical neutrality were replaced with complex organic ions containing active functional groups (amine, hydroxyl, carboxyl) in their organic radicals. Strongly attached to the clay surface these complex ions project their organic aryl or alkyl radicals outwards to suspending medium rubber matrix making inorganic kaolin surface effectively organic and therefore hydrophobic one. Such change in kaolin surface facilitated rubber-filler interaction owing to better wetting of the filler surface with organic rubber polymer and formation of sufficient density grafted polymer layer bonding the rubber matrix to filler. Carried out physico-mechanical testing of tilled rubber compounds showed that modification or kaolin with chosen basic electrolytes ionized in aqueous medium was effective. Increase in strength characteristics has made possible in commercial practicability of rubber formulation technology the substitution of expensive reinforcing fillers with lowest in cost appropriately modified kaolin Clay.
item: Conference-Full-text
Processing aids for rubber compounding
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1995-03) Gunapala, PY; Adikary, SU; Dharmawardena, G; Dias, WPS
This paper reviews some aspects of rubber-filler interaction in the presence of resins. Laboratory investigations conducted by us with optical methods, power traces. DTA , DSC curyes and treatment of samples with various solvents and tests for physico-mechanical properties were used to demonstrate specificity in behaviour of selected resins and to discuss a concept which could explain mechanism of reinforcement in the presence of various resins, intimate analysis has snown capability of certain resin to promote wetting properties and give high true contact between iubber and carbon black particles, thereby best owing favourable physicc-mechanical properties to the compound. Information of this type can assist not only the compounders bat also can give theoretical explanation about additional reinforcement in the presence of selected resins.
item: Conference-Extended-Abstract
Reinforcing activity of modified filler
(2003) Gunapala, O; Gunapala, PY
Sri Lankan rubber industries process approximately 90,000 tons of natural rubber per year for manufacture of tire tread. footwear. flooring, pneumatic tubes, rugs. dipped product and many others. Large quantities of reinforcing and non-reinforcing fillers are required to obtain rubber product of desirable quality. The fillers used commonly are carbon black. silica. mica. china clay. Reinforcing fillers usually consume large amount of energy when processed and treated, so that their cost is sharply affected by the market price increases of energy. Mineral fillers are non-reinforcing by nature, less energy sensitive and not susceptible to price increase. They are available and widely distributed in Sri Lanka. It was shown in earlier research that modified mineral fillers could be used as quite economical and versatile substitute for expensive imported reinforcing fillers. The purpose of this paper is to establish the factors, effecting the reinforcing activity of modified fillers and optimization of rubber -rnodified filler composite formula for industrial usage.