[en] The relationship between photosynthetic efficiency, dry matter accumulation and yield in five genotypes of paddy derived from a single cross between Jaya X Halubbalu was studied. Photosynthetic efficiency of younger leaves, on the main tiller was higher than in the older leaves. A significant positive correlation between RuDPcase activity and photosynthetic efficiency was observed in these genotypes. Also a similar positive correlation between dry matter production and photosynthetic efficiency during vegetative period but not during post-anthesis period was observed. Genotypes with high photosynthetic efficiency and also the genotypes with high LAD produced higher dry matter. A reduction in LAD or in photosynthetic efficiency during the post-anthesis period and thus a reduction in source capacity which occurred specially in late types resulted in a lesser ratio between productive and total tillers and also higher percent sterility. Differences in yield amongst the genotypes were not significant, since in the late types MR. 333 and MR. 335, the post-anthesis dry matter production was low due to lesser source capacity. But in the early types, though the total dry matter was less, the post-anthesis source capacity was high. The importance of post-anthesis leaf area of photo-synthetic efficiency in productivity in genotypes of rice is highlighted. (author)

[en] There is a bright future for radiation vulcanised natural rubber latex but there are problems in manufacturing it as the centrifuged latex to be used for radiation has to be kept for at least a month or sometimes even three to six months before adding sensitisers and even then the latex sometimes coagulates on adding the sensitisers. By this invention, the field latex is stabilised by an anionic soap before centrifuging so that it has a high machanical stability and hence can be used even within one week of the manufacture of the centrifuged latex. The use of low ammonia centrifuged latex is recommended. The addition of any of the following namely TMTD/ZnO, ZEDC/ZnO, HNS, HH or bactericides is recommended as the secondary stabiliser for the field latex and the addition of any of the following namely TMTD/ZnO, ZEDCZnO, HNS, HH or bactericides is recommended as the secondary stabiliser for centrifuged latex. ZEDC/Zno

[en] Investigation showed that a combination of 2-ethylhexyl acrylate (2-EHA) and carbon tetrachloride as a sensitizer system for radiation vulcanization of natural rubber latex is effective to reduce the vulcanization dose. This combination is effective over a wide range so that it can be selected depending on the radiation cost and chemical cost. Swelling data indicate that the addition of carbon tetrachloride to 2-EHA increases the efficiency of the crosslinking reaction. A combination of 1 phr carbon tetrachloride and 1 phr 2-EHA will lead to a more economical system than the system using 5 phr carbon tetrachloride as sensitizer. (author)

[en] The effect of heating and leaching on the mechanical properties of radiation vulcanized natural rubber latex (RVNRL) film was investigated. It was found that heating and leaching improved tensile strength of film considerably. The tensile strength could increase as high as 25 % upon heating alone and as high as 75 % upon leaching and drying. The increase in the tensile strength was attributed to reduced moisture content, better particle cohesion and improved entanglement of molecular chains. Complete leaching and drying of RVNRL was found to be important to obtain better and consistent results on the mechanical properties of films from RVNRL. (author)

[en] Radiation vulcanized natural rubber latex (RVNRL) film has poor aging characteristics especially after it has been subject to leaching. The effect of the addition of antioxidants on the aging properties of RVNRL obtained using carbon tetrachloride and n-butyl acrylate (n-BA) as sensitizers respectively were evaluated. Antioxidant 2'2'-methylene-bis-(4-methyl-6-tert-butylphenol) containing 0.8 phr was found to be the most effective for RVNRL produced by using CCl₄ as sensitizer and antioxidant 2,4-Bis[(octylthio)methyl]-o-cresol containing 1.0 phr for RVNRL produced by using n-BA as sensitizer. Antioxidant 2-mercaptobenzimidazole showed slightly less effective but gave less tendency for discolouration compared to 2.4-Bis[(octylthio)methyl]-o-cresol when used in the n-BA system. (author)

[en] There is a bright future for radiation vulcanised natural rubber latex (RVNRL) but there are problems in manufacturing it as the centrifuged latex to be used for radiation has to be kept for at least a month or sometimes even three to six months before adding the sensitisers and even then the latex sometimes coagulates on adding the sensitisers. This paper describes a process by which the latex can be stabilised by addition of an anionic soap before centrifuging so that it has a high mechanical stability and hence can be used even within one week of the manufacture of the centrifuged latex

[en] Radiation vulcanization of natural rubber latex (RVNRL) can be used to make large quantities of specially stabilized latex. It is possible to obtain RVNRL films of tensile strength over 25 MPa. The films could be either coagulant dipped or cast. It is very important to determine the correct radiation dose which gives the maximum tensile strength. Cross linking density or prevulcanized relax modulus (PRM) at 100% is a reliable property to control the prevulcanization

[en] Radiation Vulcanization of natural rubber latex has been developed extensively through various research and development programme. During these investigations many data was collected and from these data it was proved that radiation vulcanized natural rubber latex (RVNRL) can be used as a new material for industry (RVNRL symposium 1989; Makuuchi IAEA report). This material has been extensively tested in making of dipped goods and extruded products. However these investigations were confined only to laboratory experiments and these experiments mainly reflected material properties of RVNRL and only a little was observed about its behavior in actual production scale operation. The present exercise was carried out mainly to study the behavior of the material in production scale by irradiating latex on a large scale and producing gloves in a production scale plant. It was found that RVNRL can be used in conventional glove plants without making major alteration to the plant. Quality of the gloves that were produced using RVNRL is acceptable. It was also found that the small deviation of vulcanization dose will affect the crosslinking density of films. This will drastically reduce the tensile strength of the film. Crosslinking density or pre-vulcanized relax modulus (PRM) at 100% is a reliable property to control the pre vulcanization of latex by radiation