Nitrosoamine free preservative system for natural rubber latex
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Date
2013
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Journal ISSN
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
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).
Description
Keywords
Science and Technology, Technology, Rubber Production, Rubber Technology, Natural Rubber, Chemical