Browsing by Author "Udayangani, G.G.D."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Nitrosoamine Free Preservative System For Natural Rubber Latex
    (Uva Wellassa University of Sri Lanka, 2013) Udayangani, G.G.D.
    Latex preservation is the physical and/or chemical stabilization of natural rubber (NR) latex against microbial growth and putrefaction, as well as the stabilization against coagulation of colloidal rubber particles. There is a good market for preserved latex concentrate, as it is an important raw material with a wide range of applications. Preservatives can effectively inhibit the bacterial growth in fresh NR latex. Hence the formation of acidic compounds resulting from bacterial activity in the latex is inhibited or even avoided, which in turn inhibits coagulation. Although several methods have already been developed for the short- term and long-term preservation of fresh NR latex; many of these methods still suffer from one or more disadvantages. This invention relates to a method for the provision of an alternative or an improved method for the preservation of latex concentrate over a period of six months. The most commonly used preservative system of commercial importance which are the high ammonia (HA) and the low ammonia-TMTD/ZnO composite system (LA-TZ) have certain drawbacks. Since Tetramethylthiurumdisulfide (TMTD) forms carcinogenic nitrosamine, present invention is mainly focused on the elimination of TMTD from the preservative system and provision of a nitrosoamine free preservative system for latex concentrate to stabilize the latex over a period of six months. Furthermore, TMTD is an allergen and it can cause dermatitis as well. Also it causes discolorations in latex. Since the field latex provides an optimum environment for microbial growth, in the absence of a proper preservation, the carbohydrates which the latex contains are oxidized in to volatile fatty acids due to the microbial activities. These acids then tend to destabilize the latex which results the coagulation of rubber particles. The preservative activities for treated latex concentrate with new developing system (NDS) was tested based on the measurements of volatile fatty acids (VFA) number test. Moreover the other properties of the preserved latex samples were tested by Total Solid Content (TSC) test, Mechanical Stability Time (MST) test, Dry Rubber Content (DRC) test, and Potassium hydroxide (KOH) number test. Key Words: Natural rubber, Volatile Fatty Acids, Tetramethylthiurumdisulfide, Mechanical Stability Time, New Developing System, Total Solids Content.
  • No Thumbnail Available
    Item
    Nitrosoamine free preservative system for natural rubber latex
    (Uva Wellassa University of Sri Lanka, 2013) Udayangani, G.G.D.; Nilmini, A.H.L.R.; Sirimanne, P.M.
    colloidal dispersion of rubber particles in an aqueous medium, containing usually from about 20% to about 40% w/w rubber particles (dry rubber) and about 5% w/w non-rubber compounds, including carbohydrates, proteins, phospholipids and metal salts. Since it provides an optimum environment for microbial growth, in the absence of a proper preservation, the carbohydrates which the latex contains are oxidized in to short chain volatile fatty acids due to microbial activities. These acids destabilize the latex which results the coagulation of rubber particles (Blackley, 1997). Preservatives can effectively inhibit the bacterial growth in fresh NR latex. Hence the formation of acidic compounds resulting from bacterial activity in the latex is inhibited, which in turn inhibits coagulation. Since the most widely used preservative, Tetramethyl thiurumdisulfide (TMTD) forms carcinogenic nitrosamine, present invention is mainly focused on the provision of a nitrosoamine free preservative system for latex concentrate to stabilize the latex over a period of six months. Volatile fatty acid number is an important measure of the level of deterioration and stability of the latex. Therefore the preservative activities of new developing system (NDS) for treated latex concentrate was tested based on the measurements of volatile fatty acids (VFA) number test. The current study was carried out at the Rubber chemistry & Technology laboratories of Rubber Research Institute, Ratmalana. Three experimental trials with different treatments of NDS were conducted during this study. The trial (I) was carried out to find out the optimum concentration of NDS in preservation of natural rubber latex. In order to compare the efficiency of NDS with the conventional preservative, the VFA number of the latex, treated with ammonia/TMTD/ZnO (TZ) system and NDS was determined respectively. In trial (II), the effect of NDS on latex preservation in combination with a co-activator was determined. The effect of ammonia on the activity of novel preservative and the appropriate combination of ammonia and NDS to preserve and stabilize the latex were evaluated in trial (III).The appropriate combination was used to prepare centrifuged latex and other properties of the concentrated latex such as total solids content (TSC), dry rubber content (DRC), pH, KOH number, Brookfield viscosity were measured according to ISO standard methods and compared with the centrifuged latex preserved by adding 0.2% ammonia (NH 3), 0.025% of 1:1 mixture of tetramethylthiuramdisulphide (TMTD) and Zinc oxide (ZnO) combination as a control sample.VFA values of trial (I) and (II) were analyzed using one way analysis of variance (ANOVA) with MINITAB statistical package 16.0 version. The Experiment trials were done using complete randomized design (CRD). Means comparison of results was done by using the least significant difference (P<0.05) test (LSD).