Master of Science By research

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Browsing Master of Science By research by Author "Liyanage, NMVK"

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    item: Thesis-Abstract
    Evaluation of the applicability of natural polymers as coupling agents in imparting reinforcement action of silica fillers in NR latex films
    (2014-06-30) Gnanaratna, WDSN; Liyanage, NMVK
    The results of an evaluation of the applicability of natural polymers (NPs) as coupling agents in imparting reinforcement action of silica fillers in natural rubber (NR) latex films are described in this research investigation. Three types of NPs namely; chitin, chitosan and cellulose were used for this investigation. Standard extraction processes were used for the extraction of chitin and chitosan. A commercially available grade of cellulose was used for this investigation without purification. Modification of surface of silica particles with NPs was affected by two techniques; in-situ surface modification, and surface modification through a sol-gel process. Coupling action of these NPs was compared with that of the most widely used commercially available coupling agent silane, Si69. A range of stable aqueous colloidal dispersions of precipitated silica were prepared with the use of NPs and Si69. In-situ surface modification performed with NPs and Si69. With NPs, the surface modification was done at four different proportions as 2.5%, 5%, 7.5% and 10% by weight of silica. With Si69, the modification was done at two different proportions as 5% and 10% by weight of silica. Sol-gel surface modification performed with chitosan was done at two different proportions as 5% and 10% by weight of silica. Interactions between polar groups of silica and functional groups of the NP which hinder aggregation of silica particles were confirmed by FTIR spectroscopy. The dispersion stability of the unmodified/modified filler (UMF/MF) dispersions was assessed by observing the phase separation upon standing. Dispersion stability of MF dispersions prepared using both surface modification method is much better than that of UMF dispersions. The particle size distribution of unmodified/ modified filler dispersions was measured by using “Fritsch” particle size analyzer. The particle size of the modified filler with cellulose was found to be lower than that of UMF dispersion. Effectiveness of NPs in enhancing reinforcing action of silica in NR latex was evaluated through investigation of mechanical properties of vulcanized films cast from NR latex compounds containing modified/unmodified fillers in different proportions. Distribution of unmodified/modified fillers within the rubber matrix was investigated through metallurgical microscope and scanning electron microscope by examining micrographs of surfaces of dipped NR latex films and micrographs of cross sections of cast NR latex films containing modified/unmodified fillers respectively. High colloidal stability of modified fillers with NPs indicates that are capable of acting as colloidal stabilizers for silica dispersions. Some of the NPs tested were found to be capable of conferring an appreciable enhancement in reinforcing action of silica in NR latex films. Micrographs graphs of the filled NR latex films revealed that same NPs have conferred uniform distribution of filler particles within the rubber matrix.
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    item: Thesis-Full-text
    Reinforcement of carboxylated acrylonitrile-butadiene rubber latex films by surface modified fillers
    Liyanaarachchi, LADA; Liyanage, NMVK
    Carboxylated acrylonitrile butadiene rubber (XNBR) latex is a widely used synthetic copolymer of acrylonitrile and butadiene with a small amount of a third monomer containing carboxylic groups. Some of the mechanical properties of XNBR latex are not adequate for certain applications and should be enhanced. Incorporation of reinforcing fillers is most widely used technique for that purpose. Silica filler is used in dry rubber industry as a reinforcement agent, but difficult to use in latex applications due to some problems associated with dispersing silica resulted by its surface chemistry. Surface of silica should be modified in order to use as a reinforcing filler in latex applications. In the present investigation, XNBR latex was filled with a series of surface modified precipitated silica. Surface modification of silica was affected by two methods i.e. non aqueous medium modification and aqueous medium modification, with the use of some synthetic polymers (SP). Three types of SPs, containing hydrophillic and hydrophobic groups that are methacrylic acid and 2-ethyl hexyl acrylate, respectively in different ratios were synthesized and used at a concentration of 3 % by weight of silica for the modification. The effectiveness of the SPs in enhancing reinforcing ability of silica in XNBR latex films was evaluated through investigation of mechanical properties of a range of vulcanized films cast from filled XNBR latex compounds containing modified filler in different concentrations in the range of 5 to 20 phr loadings. One of the well known non-sulphur vulcanization systems of XNBR, crosslinking with zinc oxide was used during the study. Latex films were cast from filled latex by several routes with different process sequences in order to investigate the importance of each step of the process to find out the most suitable step for filler addition. Some of the mechanical properties important for rubber latex applications, such as tear strength, of modified silica filled cast films improved over unmodified silica filled cast films. Optimum tear strength of cast films filled with modified fillers was observed at 20 phr filler loading, while films containing 15 phr filler loading gave optimum tensile properties. Morphological studies done by scanning electron microscopy illustrated improved distribution and lower size of modified filler particles within the XNBR matrix indicating surface modification has reduced filler aggregation. SPs used for the modification are capable of enhancing reinforcing action of silica filller in XNBR latex films. The extent of enhancement of physical properties of filled cast films depends on the hydrophillic/hydrophobic ratio of SPs used for surface modification of silica. Highest physical properties were observed for the vulcanizates containing silica modified with the most hydrophobic SP, which is thought to be the result of better rubber filler interactions created by the entanglement of rubber chains with hydrophobic side groups present in this particular SP.
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    item: Thesis-Full-text
    Reinforcement of carboxylated nitrile rubber latex films by surface modified nanosilica
    Ramasinghe, RLP; Liyanage, NMVK
    Carboxylated acrylonitrile butadiene rubber (XNBR) is synthetic elastomer which inherent number of physical and chemical properties such as comparable barrier protection, good puncture and chemical resistance and high durability under storage. Although that there is a problem associated with synthetic elastomers that they are typically not self-reinforcing elastomers. Therefore, reinforcing fillers are incorporated to improve the properties of the compounds. Silica is extensively used for latex products. Nanofillers can impart more advanced properties to the final nanocomposite than micro fillers. Surface modification has been introduced to avoid the incompatibility between inorganic filler silica and organic XNBR matrix Role of surface modifiers in this study play dual role, as a capping agent: to control the size of nanoparticles & as a coupling agent: to develop compatibility between rubber and filler. Synthetic surface modifiers i.e. Polymethacrylic acid & Polymethacrylic acid ethyl hexyl acrylate and natural surface modifiers i.e. cellulose, collagen, chitosan & gelatin were used in this study. The FTIR analysis confirm that the surface of nanosilica particles has been successfully modified with acrylic polymers, forming ester bonds between carboxylic groups of acrylic polymers and surface silanol groups of nanosilica. TGA confirms the successful surface modification resulting lower weight loss; indicating small number of free surface silanols groups are present on the silica surface. XRD analysis revealed the amorphous nature of unmodified and all modified nanosilica particles. SEM results help to monitor the particle shape, size and agglomerations of synthesized particles. Evaluation of XNBR vulcanizate properties of micro silica, unmodified nanosilica, acrylic polymer modified nanosilica and natural polymer modified nanosilica filled vulcanizates was carried out. The results show that addition of small quantities of nanosilica causes an increase of mechanical properties of XNBR vulcanizates, while high filler loading of nanosilica appear to decrease the mechanical properties due to the aggregation of nanosilica particles. 2% PMAA and 2% cellulose modified nanosilica filled vulcanizates show balance strength with stretch & comfort properties for the glove manufacturing.