Rubber Science

PRODUCTION OF LIQUID NATURAL RUBBER BY THERMAL: DEPOLYMERIZATIONResearch Articles
Pages 1 - 7
N. M. Claramma, N. Radhakrishnan Nair & N. M. Mathew
- Abstract
- Keywords
Depolymerization of natural rubber, using a combination of mechanical and thermal energies aided by a peptiser, has been attempted. Peptiser dosage, temperature and heating time for producing liquid natural rubber (LNR) of desired viscosity were optimised. LNR can be produced by thermal depolymerization, with or without the addition of a peptiser. Possibility to produce LNR of desired viscosity by appropriately fixing the peptiser dosage, temperature and duration of heating was revealed. As degradation was found rapid at higher temperatures depolymerization at lower temperature is desirable. Properties of the liquid rubber such as Brookfield viscosity, intrinsic viscosity, iodine value and acetone extract have been determined. IR and NMR studies were also carried out. Vulcanization of LNR with sulphur resulted in very poor strength properties.

Liquid natural rubber, Depolymerization, Peptiser, Intrinsic viscosity, Brookfield viscosity.

GENERAL PROPERTIES AND IRON AND ALUMINIUM STATUS OF SELECTED RUBBER GROWING SOILS OF SOUTHERN NIGERIAResearch Articles
Pages 8 - 15
Ebong T. Eshett
- Abstract
- Keywords
Studies were conducted to determine the distribution of iron and aluminium oxides in profiles selected from rubber growing soils. The amorphous Fe and AI oxides were of much lower concentrations in these soils than their crystalline counterparts. No definite pattern of distribution of these compounds in relation to profile depth was discerned. Soils formed from coastal plain sands had the highest mean value of Fe+ AI oxides (5. 54 per cent), followed, in descending order, by soils from basalt (4 .17 per cent), basement complex rocks (3. 39 per cent) and calcareous sandstone (3.17 per cent).

Hevea brasiliensis, Soil profile, Sesquioxides, Soil property, Nigeria

JUVENILE CHARACTERS AND SEED MORPHOLOGY OF CERTAIN MODERN HEVEA CLONESResearch Articles
Pages 16 - 25
V. C. Mercykutty, Y. Annamma Varghese, J. Licy & A.O.N. Panikkar
- Abstract
- Keywords
Nine modern clones of Hevea brasiliensis were morphologically characterised at the age of 14 months, planted in the field at a spacing of 6.7 x 3. 4 m. Morphological parameters studied were nature of buds and leaf scars, shape of leaf storey and characteristics of petioles, petiolules and leaflets. The observations were confirmed with nursery plants (60 x 60 cm spacing) of the same age. Seed morphology was also used to identify the clonal trees. Clones vary in respect of the different characters studied. A combination of different characters has to be taken into consideration for the identification of clones at young age.

Hevea brasiliensis, Juvenile characters, Morphological parameters, Seed characters, Clone identification

INFLUENCE OF TEMPERATURE ON COMPRESSION SET OF NR VULCANIZATESResearch Articles
Pages 26 - 35
K. Mariamma George, P. Viswanathan Pillai & N. M. Mathew
- Abstract
- Keywords
Compression set (CS) of natural rubber vulcanizate was measured under different conditions. The temperature regime ranged from -30 to 70°C. The effects of cure system, filler, plasticizer and antioxidant on CS were also evaluated. At lower temperatures, peroxide-cured natural rubber showed higher CS than the conventionally cured rubber. Fillers, naphthenic oil and the antioxidant PBNA increased CS at all the temperatures studied.

Natural rubber, Compression set, Cure system, Filler, Plasticizer, Antioxidant

EFFECT OF IRRIGATION ON PHYSIOLOGICAL PERFORMANCE OF IMMATURE PLANTS OF HEVEA BRASILIENSIS IN NORTH KONKANResearch Articles
Pages 36 - 45
T. Mohan Krishna, C. V. S. Bhaskar, P. Sanjeeva Rao, T. R. Chandrashekar, M. R. Sethuraj & K. R. Vijayakumar
- Abstract
- Keywords
Attempts were made to quantify the optimum irrigation requirement of rubber (Hevea brasiliensis) plants in North Konkan. Basin irrigation was given at the rates of 0. 50, 0. 75, and 1.00 and drip irrigation at 0.25, 0.50 and 0.75 of crop evapotranspiration (ETc). Physiological status of irrigated and non-irrigated plants was compared. Severe inhibition of photosynthesis and transpiration and increased stomatal resistance were observed due to soil moisture stress. A significant increase in absolute growth and relative growth rate was observed in the dry season in the irrigated plants. Maximum growth was obtained with 1.00 ETc irrigation, although it resulted in attaining only fifty per cent photo synthetic rate of wet season. The water use efficiency (WUE), in terms of C0₂ /H₂0 ratio, decreased with increase in the quantity of water applied. The impact of drought and effect of irrigation on growth and physiological processes are discussed.

Hevea brasiliensis, Immature rubber, Irrigation requirement, Photosynthetic rate, Stomatal resistance. Water use efficiency, India/ Konkan

COMPARISON OF DIFFERENT PLANTING TECHNIQUES OF HEVEA IN TRIPURAResearch Articles
Pages 46 - 50
S. N. Potty, A. K. Krishnakumar & J. Rajeswari Meenattoor
- Abstract
- Keywords
Conventional brown budded stumps, two year old brown budded stumps grafted at one year's stock growth and allowed to grow without cutting back, two year old budded stumps grafted at two years stock growth and green budded stumps raised in poly bags for two months and 14 months were compared for field establishment and early growth at Tripura conditions. Fourteen months old green budded polybag plants performed better than the others with respect to plant height and number of flushes of leaves at nine months growth and girth throughout the period of study. The conventional budded stumps initially did not show good performance, but in subsequent years the difference in girth narrowed down and there was no significant difference between different treatments, except 14 month old green budded polybag plants. From the establishment point of view, the best performance was for the two months old polybag plants. Under conditions of best management, budded stumps could be used as successfully as small polybag plants.

Hevea brasiliensis, Planting technique, Tripura