Rubber Science

EVALUATION OF HEVEA GERMPLASM: 1. VARIABILITY IN EARLY GROWTH PHASEResearch Articles
Pages 195 - 198
Saji T. Abraham, C. P. Reghu, Jayashree Madhavan, P. J. George, S. N. Potty, A. O. N. Panikkar & P. Saraswathy.
- Abstract
- Keywords
One hundred genotypes from the wild germplasm of Hevea brasiliensis were subjected to a preliminary study on variation. Observations on girth, height, leaf area, bark thickness, juvenile yield, total number of latex vessel rings and density of latex vessels per ring were made. General mean values of the wild germplasm for all the characters except for height, single leaf area and density of latex vessels per ring were found to be lower than that for the controls. MT 999 showed a higher value for total number of latex vessel rings and density of latex vessels per ring. Juvenile yield of the wild germplasm was very low compared to that of the controls. Among the three provenances- Acre, Rondonia and Matto Grosso, the genotypes from Matto Grosso showed a general superiority for all the characters except girth, height and leaf area. Yield, leaf area and total number of latex vessel rings gave higl1er estimates of GCV, H² and GA.

Hevea brasiliensis, Germplasm, Provenance, IRRDB collection, Variability, Heritability

BLOCK CO-POLYMERS BASED ON NATURAL RUBBER AND POLYURETHANE OLIGOMERS OF ETHYLENE GLYCOL-TOLUENE DIISOCYANATEResearch Articles
Pages 199 - 205
C. J. Paul & M. R. Gopinathan Nair
- Abstract
- Keywords
A series of segmented block co-polymers based on hydroxyl-terminated liquid natural rubber of number average molecular weight 3000 were synthesized by one-shot and two-shot processes in solution. The hard segment consisted of polyurethane formed from toluene diisocyanate and ethylene glycol. The materials were characterized by infrared spectroscopy, thermal analysis, mechanical testing and SEM studies. Block co-polymers synthesized by the two-shot process were found to possess superior mechanical properties to those produced by the one-shot process. With increasing hard segment content, the properties compared varied from soft to rigid elastomers and then to rubber toughened plastics. This variation in behaviour was consistent with the sample morphology, which, in fact, depended upon the relative fractions of the soft and hard segments. All of these short-segment block co-polymers showed nearly complete phase separation.

Liquid natural rubber, Block co-polymer, polyurethane, phase segregation, thermoplastic elastomer

A COMPUTER MODEL FOR ASSESSING AGRO-CLIMATIC AND EDAPHIC FEASIBILITY FOR RUBBER CULTIVATION IN THE TRADITIONAL TRACTResearch Articles
Pages 206 - 216
T. Vilasachandran, K. Usha, V. S. Motial & M. R. Sharma
- Abstract
- Keywords
A computer model has been designed to assess the agro-climatic and edaphic feasibility of an area in traditional tract for commercial rubber cultivation. This model devised in Lotus 1-2-3 employing 'nested@ IF function' is useful to indicate the suitability of an area against each agro-climatic and edaphic factor based on pre- defined suitability indices and to infer the overall agro-climatic and edaphic suitability of an area for commercial rubber cultivation. The model can accommodate changes in suitability indices and is user friendly.

Lotus 1-2-3, Nested @ IF function, Suitability indices, Hevea

STABILITY AND AGEING OF ENR GUMS BY THERMOGRAVIMETRY AND IR SPECTROPHOTOMETRYResearch Articles
Pages 217 - 222
T. K. Chaki, Sanjoy Roy & B. R. Gupta
- Abstract
- Keywords
Thermogravimetric analysis of epoxidized natural rubber (ENR) was carried out. The T_maxvalues of ENR showed shift to higher values relative to natural rubber. However, the integral procedural decomposition temperature (IPDT) and apparent activation energy decreased with increasing epoxidation level. Low temperature (70°C) air aged samples were studied by IR spectroscopy. The peak intensities of carboxyl, hydroxyl, hydrofuran etc. were found to increase. Some.new peaks like ether, lactone etc. were detected. Dielectric studies and gel content analysis were performed with the aged and unaged ENR samples.

Epoxidized natural rubber, Ageing, IR study, Stabilizer, Dielectric study

EARLY GROWTH PERFORMANCE OF SOME HEVEA CLONES IN KONKAN REGION OF WESTERN INDIAResearch Articles
Pages 223 - 228
M. A. Nazeer, Joseph G. Marattukalam, T. R. Chandrasekhar, Kavitha K. Mydin, D. Premakumari & A. O. N. Panikkar
- Abstract
- Keywords
Fifteen clones of Hevea brasiliensis were evaluated for their early growth performance in the non traditional rubber growing tract of the Konkan. The vigour of the clones at the age of four years was assessed in terms of ten morphological and anatomical traits. Clonal variation was studied and correlations worked out. On the basis of a growth index clones RRII 6, RRII 208, RRIM 605, PB 311, RRII 105 and PB 260 were identified as better adapted to the stress situation in the Konkan tract.

Hevea brasiliensis, Early performance, Growth index, Non-traditional area, Konkan, India

STUDIES ON MICROCELLULAR SOLES BASED ON NR-EVA BLENDSResearch Articles
Pages 229 - 237
Alex T. Koshy, Baby Kuriakose, Sabu Thomas & Siby Varghese
- Abstract
- Keywords
Blends of natural rubber (NR) and ethylene vinyl acetate copolymer (EVA) were evaluated for technological properties relevant to microcellular sheets for hawai sandals. The effects of blend ratio and loading of precipitated calcium carbonate and china clay on the cell structure and technological properties were studied. The results indicated that with increase in the proportion of EVA in the blend, abrasion resistance, split tear strength, compression set and shrinkage were increased. The pattern of the microcells changed with EVA content of the blend and this was found to influence the properties. Between china clay and calcium carbonate the latter imparted higher split tear strength and expansion and lower compression set and abrasion resistance.

Natural rubber, Ethylene vinyl acetate, Blends, Microcellular sole, Cell structure