Rubber Science

PINK DISEASE OF HEVEA BRASILIENSIS IN NORTHERN WEST BENGAL AND NORTH EAST INDIA
Pages 91-97
G.C. Mondal, H.K. Deka & Shammi Raj &Sabu P. Idicula
- Abstract
- Keywords
A survey was carried out in 180 locations covering in northern West Bengal and North East India, from August to November, during 1990-2011,on pink disease of rubber (Hevea brasiliensis) caused by Corticium salmonicolor (Berk. & Br.). The incidence of pink disease on rubber was higher in northern West Bengal than Meghalaya and Assam. Maximum incidence of pink disease was observed on four to six-year-old rubber plants at Rango (7.5%) followed by Jiti rubber estate (3.0%) in northern West Bengal. The disease was noticed on the main trunk of five-year-old rubber plants at Rango and Jiti rubber estates during September, 2001 for the first time in northern West Bengal and caused a total loss of the affected trees. Weather factors like monthly rainfall (mm), number of rainy days, maximum temperature (oC) and relative humidity (%) from July to September during 1996-2011 are also reported. The monthly rainfall above 500 mm and more than 17 continues rainy days were the major predisposing factors influencing the development of pink disease.

Climatic factors, North East India, North West Bengal, Pink disease

PEROXIDE VULCANIZATION OF POLYMERS
Pages 98-126
Rejitha Rajan, Siby Varghese & K.E. George
- Abstract
- Keywords
The present article reviews the use of different organic peroxides used for the crosslinking of various types of rubbers. The rubbers include both unsaturated and saturated elastomers as well as elastomer blends. The use of co-curing agents (coagents) to improve the vulcanizate properties is also discussed. Peroxide cure depends upon a number of factors like type and concentration of peroxides, type of elastomers, compounding ingredients like fillers, antioxidants, processing aids etc. However, by the proper selection of elastomers and coagents, peroxide cure systems can be effectively used as an alternative to sulphur cure system.

Coagent, Natural rubber, Organic peroxide, Vulcanization

SUPERIOR PROCESSING RUBBER FROM RADIATION CROSS-LINKED NATURAL RUBBER LATEX
Pages 127-134
Joy Joseph P.S. Sadeesh Babu & K.N. Madhusoodanan &Rosamma Alex
- Abstract
- Keywords
Superior processing (SP) natural rubber was prepared by blending different proportions of fresh and radiation vulcanised natural rubber latex, followed by coagulation and drying. The Mooney viscosity of SP rubber increased as the proportion of cross-linked rubber increased. Cross-linked and uncross-linked rubber blended in 20/80 proportion (P20) recorded very good mechanical and processing characteristics compared to pure NR. The better processing characteristics were attributed to the higher viscous nature of the modified rubber in gum and carbon black filled mixes. It was observed that the P20 rubber had a higher level of vulcanisation than the pure NR. The improved processability and vulcanisation characteristics were ensured from the analysis of viscoelasticity cure characteristics, physical property evaluation and filler dispersion characteristics. Blending of fresh natural rubber latex and radiation vulcanised latex in suitable proportions offer a very simple method to produce SP rubber with enhanced processing characteristics and mechanical properties.

Radiation vulcanisation, Natural rubber latex, Viscoelasticity, Processing rubber

STABLE FREE RADICAL ASSISTED SCORCH CONTROL IN PEROXIDE VULCANIZATION OF EPDM
Pages 135-145
Benny George & Rosamma Alex
- Abstract
- Keywords
This study demonstrates the capability of a nitroxide stable free radical, 2, 2, 6, 6-tetramethylpiperidine 1- oxyl (TEMPO), to induce sulphur/accelerator like scorch control in peroxide vulcanisation of EPDM. Two commercially used peroxides; butyl 4,4-di(tert-butylperoxy) valerate (BPV) and Di(tert-butyl peroxyisopropyl) benzene (BBPIB) with cure temperatures of 160 oC and 175 oC respectively were used for vulcanisation. TEMPO induced scorch in both systems and the cure curves resembling typical sulphur/ accelerator cure curves were obtained. The reduction in cross-link density with the addition of TEMPO was significantly less in BBPIB system. Addition of 4phr of trimethylolpropane trimethacrylate (TMPTM) could regain the loss of cross-links due to the scavenging action of TEMPO. The vulcanisate properties of the EPDM/ BBPIB /TEMPO/ TMPTM system were determined and compared with a control EPDM compound. The mechanism of scorch control by the stable free radical is also discussed.

Peroxide vulcanization, Scorch control, Stable free radicals

OPTIMIZATION OF PROCESS PARAMETERS FOR STABLE ZnO DISPERSIONS
Pages 146-152
Anand K, Shera Mathew &Thomas Kurian & Siby Varghese
- Abstract
- Keywords
As most of the nanomaterials are very expensive, the concept of stable ultrafine dispersions with uniform size distribution is gaining commercial importance. For optical applications including transparency and also for reducing the additive concentration, ultrafine particles should be uniformly dispersed in the polymer matrix. Dispersion of ZnO has been a consistent issue because of its strong tendency to form aggregates. Present research work focuses on combining ball milling and ultrasonication to produce stable aqueous dispersions of ZnO with consistent size distribution. Milling time and concentration of surface active agent (SA) were followed through, dynamic light scattering (DLS) and Zeta potential measurements. It was observed that 12h milling with 2-3 wt per cent SA was found to be the optimum conditions for the preparation of ZnO dispersion. Effect of ultrasonication on ball milled samples resulted in dispersions with reasonable stability.

Ball milling, Ultrafine ZnO, Dispersion, Ultrasonication, Zeta potential