Browsing by Author "Attanayake, A."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Effect of Clone type on Storage Hardening and Gel Content of Raw Natural Rubber
    (Uva Wellassa University of Sri Lanka, 2016) Delman, H.W.O.C.; Kaliyadasa, P.E.; Arachchi, M.P.; Attanayake, A.
    Latex is the only non-synthetic elastomer in wide use derived from the milk-like liquid of the Rubber tree. At present the country ranks among the world's top ten largest producers and 7111 largest exporter of natural rubber. Even though Sri Lanka is the one of the leading manufacturer of raw rubber, most of the product is carried out in other countries and those rubbers should be kept under storage conditions until use. During transportation or upon storage natural rubber exhibits different storage properties. Hence, rubber industry has increase the requirement for quality and uniformity of natural rubber. The objective of this study was to assess effects of clone type on gel content and storage hardening of natural rubber. Ten different clones rubber were used as samples in this study which are RRISL 201, 202, 203, 205, 206, 211, 216 217, 219 and RRISL 222. Properties of raw rubber were analyzed using standard methods of Gel content, Mooney viscosity, stress relaxation rate, Green strength, Initial plasticity and Hardening plasticity. Minitab 16 statistical software was used to analyze the qualities of nine replicates from ten different clones. Most clones were showed medium and hard viscosities and none of clones reported low viscosities. Correlation between Mooney viscosity and Initial Wallace plasticity were analyzed using regression and identified that there is a relationship among them. The RRISL 203 clone gave relatively high Mooney viscosity, Po, stress relaxation rate and green strength. Therefore it can be concluded that RRISL 203 clone consisted high molecular weight. As all the tested properties of RRISL 217 clone have met the specification requirements for rubber processing, can be successfully used in product manufacturing. Key Words: Gel content, Storage hardening, Mooney viscosity, Green strength, Initial plasticity, clones
  • No Thumbnail Available
    Item
    Effect of Residual Diammonium Hydrogen Phosphate Content on Properties of Natural Rubber Centrifuged Latex
    (Uva Wellassa University of Sri Lanka, 2021) Siriwardhana, M.W.H.N.M.; Attanayake, A.; Lochana, E.A.L.; Senevirathna, A.M.W.K.
    Natural rubber particle, a polyisoprene core is surrounded by a shell of non-rubber components, proteins and phospholipids. Natural PO43- are added to ammonia preserved latex due to the hydrolysis of phospholipid layer around the rubber particle. Although this process contributes to the stability of the latex this could produce a waste sludge; a precipitate of magnesium with phosphate. In centrifuged latex (CL) manufacturing process PO43- are added as diammonium hydrogen phosphate (DAHP) before centrifugation in order to remove residual Mg2+ present in field latex to the level of 80-100 ppm. In most cases, added DAHP will leave excess PO43- in latex as most manufacturers added it without estimating the remaining Mg2+ present in latex. It results in a high amount of PO43- in latex as a considerable amount of PO43- are released from the natural process of hydrolysis with storage time. This study aimed to determine the variation of residual PO43- content of CL with storage time and its ultimate effect on latex property development. A series of centrifuged latex samples were prepared by adding 0 g (control sample), 3 g, 6 g, 9 g, 12 g, and 15 g of 15% DAHP. Changes of the latex characteristics such as mechanical (MST) and chemical stability time (CST), PO43- and Mg2+ concentration, viscosity were determined with time. All the testing were carried out according to ISO procedures. High ammonia preserved CL showed a considerable amount of natural PO43- of about 300-200 ppm with storage time. The PO43- content of latex is not a stable amount and showed several fluctuations with time due to several chemical reactions within the latex sample. The excess amount of PO43- in the latex leads to a decrease in viscosity and stability of latex due to colloidal destabilization. The control sample showed the highest MST (315 seconds) and CST (97 seconds) with storage time than other samples revealing that there is no need for the addition of DAHP if the Mg2+ content of field latex is below 100 ppm in manufacturing CL. Keywords: Latex; Diammonium; Phosphate; Magnesium; Destabilization; Colloidal