Rubber Science

EARLY GROWTH PERFORMANCE OF CERTAIN HEVEA CLONES FROM ON-FARM TRIALS IN GARO HILLS OF MEGHALAYAResearch Articles
Pages 275 - 280
M.J. Reju*, Ram Phool Singh, Umesh Chandra, D. Panda***, P. Khoyamthem**** & Gitali Das**&Kavitha K. Mydin
- Abstract
- Keywords
Two on-farm trials (OFTs) were established in 2009 at Mendipather, North Garo Hills, Meghalaya. The trials were initiated to study the performance of certain selected clones of Hevea brasiliensis in farmers’ fields and the clones were planted in the fields of two progressive farmers at Mendipather. Six clones viz., RRIM 600, PB 235, RRII 203, RRII 417, RRII 422 and RRII 429 were planted in blocks. Data on girth and other secondary characters recorded during the initial years have been analysed in the present study. The highest girth was recorded in RRII 429 followed by RRII 417 whereas the lowest girth was recorded in RRII 422 in Field 1. In Field 2, maximum girth was recorded in PB 235 followed by RRII 203 and minimum was in RRII 422. Maximum bark thickness was recorded in PB 235 closely followed by RRII 429 whereas the lowest bark thickness was recorded in RRII 422. Performance of the clones based on absolute girth suggests the superiority of PB 235 and RRII 429 over RRIM 600 in the local agro-climatic conditions of North Garo Hills.

North Garo Hills, Meghalaya, Growth, Hevea brasiliensis

PETIOLAR NECTARY MORPHOLOGY: A TOOL FOR CLONE IDENTIFICATION IN HEVEAResearch Articles
Pages 281 - 285
P. Deepthy Antony&Jayashree Madhavan*
- Abstract
- Keywords
Crop improvement programmes in different rubber growing countries have resulted in the availability of a large number of clones for commercial cultivation. Due to the narrow genetic base, the available morphological variation among the commercially cultivated Hevea clones is also low making clone identification a cumbersome process. The present study explores the utility of morphological features of petiolar nectaries for clone identification. Morphological features of petiolar nectaries were recorded from one to two year old plants of forty nine Hevea clones which included size of the cluster, number of glands, appearance and shape of the nectaries. Based on the descriptors, the clones could be grouped into different classes and it was found that the character was stable over different seasons in young plants. Hence, it can be used as a descriptor for clone identification along with other descriptors available for Hevea.

Extrafloral, Hevea, Petiolar nectaries, Clone identification

OPTIMIZATION OF EPDM RECLAIM IN EPDM COMPOUNDSResearch Articles
Pages 286 - 293
Jinu Jacob George&Siby Varghese
- Abstract
- Keywords
Ethylene-propylene rubbers (EPDM) continue to be one of the most widely used and fastest growing synthetic rubbers being used in specialty and general-purpose applications. In this study, EPDM-reclaim has been used as partial replacement for virgin EPDM, which eventually reduce the production cost, provided the material properties do not deteriorate significantly. Characterisation of vulcanisates illustrate that addition of up to ten parts of EPDM reclaim to virgin rubber do not significantly deteriorate vulcanisate properties. Tensile, tear, and hardness properties were maintained almost as that of the virgin EPDM vulcanisate. Also, there is no drastic increase in heat build-up after reclaim addition. There is only a marginal reduction in thermal stability with the incorporation of EPDM reclaim. The above results were well supported by swelling analysis and dispersion study which show that as the reclaimed rubber content increases, the level of dispersion gradually deteriorates. From the findings it may be concluded that incorporation of up to 10 parts reclaimed EPDM is justifiable in EPDM vulcanisates.

EPDM, Reclaimed EPDM rubber, Mechanical properties

DEGRADATION BEHAVIOUR OF NANO SILICA AND NANO TITANIA FILLED NATURAL RUBBER LATEX NANOCOMPOSITESResearch Articles
Pages 294 - 304
K. Anand & Siby Varghese&Thomas Kurian*
- Abstract
- Keywords
The shelf-life of natural rubber latex products are highly dependent on various environmental factors. To improve the quality as well as performance, fine particle dispersions are employed in their formulations. The degradation behaviour of silica (SiO₂) and Titania (TiO₂) nanoparticles incorporated natural rubber latex (NR) nanocomposites against various degrading agents viz. thermal, γ-radiation, UV radiation and chlorination were studied. The properties such as tensile strength, elongation at break and modulus were recorded after exposing the latex films to various degrading environments. Compared to the gum vulcanizates, addition of nano SiO₂ and nano TiO₂ improved the tensile strength even after ageing. Enhanced UV resistant properties were noticed for nano titania latex composites from mechanical property measurements. Nano SiO₂ (0.3 phr) imparted maximum tensile strength after chlorination.

Nano TiO2, Nano SiO2, Mechanical properties, Natural rubber, Degradation, UV radiation