Rubber Processing Industry Research Articles

Novel Sulfur Vulcanization Accelerators Based on Mercapto-Pyridine, -Pyrazine, and -Pyrimidine

Abstract Sulfur vulcanization accelerators derived from 2-mercaptobenzothiazole (MBT) have been a staple for the rubber processing industry for over 65 years. Most noteworthy are the sulfenamide derivatives, which provide various combinations of scorch delay and cure rate, depending upon the basicity and steric nature of the sulfenamide N-substituent(s). While the effect of the amine moiety on benzothiazole sulfenamide accelerator performance has been well documented, the effect of the S-linked heterocyclic moiety of the sulfenamide has been investigated to a much lesser extent. Thus, to gain a better understanding of the role of the heterocycle, a variety of novel disulfides and sulfenamides based on pyridine have been synthesized and tested. The performance of the pyridine based accelerators have been compared to each other and to the various benzothiazole analogues. Until recently, the corresponding sulfenimides (compounds containing two divalent thiol moieties attached to an amine nitrogen ) seem to have received little attention in the rubber industry. Sulfenimides based on pyridine, pyrazine and pyrimidine have therefore also been synthesized and tested. The differences in preparation and vulcanization activity for the benzothiazole sulfenimides and sulfenamides are described, as well as some rudimentary differences which have appeared in the early stages of mechanistic work. It has been discovered in the course of this work that other heterocyclic thiols may be substituted for 2-mercaptobenzothiazole in the basic sulfenimide structure to gain advantages both in faster cure rate and extended scorch delay. The behavior of these novel sulfenimides in common rubber cure systems is presented together with representative physical properties of the rubber vulcanizates.

Carcinogenic and co-carcinogenic studies of thiram on mouse skin

Thiram (tetramethyl thiuram disulfide), a carbamate fungicide, is used in the rubber processing industry as an accelerator and vulcanizing agent. Previous studies evaluated the tumorigenic potential of thiram in rodents, but failed to provide conclusive results. In the present study the tumorigenic potential of thiram was evaluated in Swiss albino mice by a two-stage initiation-promotion protocol and a long-term in vivo bioassay for carcinogenicity. Results revealed that following tumour initiation with thiram and promotion with 12- O-tetradecanoyl phorbol 13-acetate, skin tumours developed, mostly at the site of treatment (dorsal skin) in single and multiple dose-initiated animals. Similarly, papillomatous growths were observed on the dorsal skin of the mice initiated with a single subcarcinogenic dose of dimethylbenzanthracene and promoted with thiram. Thiram failed to provoke tumorigenesis when tested as a complete carcinogen for up to 52 wk and thereafter the study was terminated due to increased mortality. It is concluded that thiram has both tumour initiating and tumour-promoting potential in both sexes of Swiss albino mice following topical exposure at the tested dose level.

The way forward

Far reaching proposals to bring about major changes in school curricula have been put forward by a special Study Group set up by the Rubber and Plastics Processing Industry Training Board to examine the education/training of Young People.

Tobacco Use, Occupation, Coffee, Various Nutrients, and Bladder Cancer2

In a Canadian population-based case-control study of 480 males and 152 female case-control pairs, the relative risk for development of bladder cancer for ever used versus never used cigarettes was 3.9 for males and 2.4 for females, with a dose-response relationship in both sexes. A reduced risk was associated with the use of filter cigarettes compared to nonfilter cigarettes. After control for cigarette usage, a significant risk was noted for male pipe smokers. For male ex-smokers the risk after 15 years of no smoking was less than one-half that of current male smokers. Bladder cancer risk was found for workers in the chemical, rubber, photographic, petroleum, medical, and food processing industries among males and for workers occupationally exposed to dust or fumes among both sexes. Bladder cancer risk was elevated for males consuming all types of coffee, regular coffee, and instant coffee and for females consuming instant coffee, but no dose-response relationship was found. Risk was found for males consuming water from nonpublic supples but not for females. No risk was observed in males or females consuming nitrate-containing foods, beverages other than coffee, or fiddlehead greens. Hair dye usage in females and phenacetin usage in males and females carried no risk. Divergent findings by area for aspirin suggested that an overall association was not causal. Reevaluation of the data on artificial sweeteners confirmed a significant bladder cancer risk in males and a dose-response relationship. The cumulated population attributable risk for bladder cancer was 90% for males from cigarette smoking, industrial exposure, and exposure to nonpublic water supplies and 29% for females from cigarette smoking, industrial exposure, and instant coffee consumption.

Developing the export potential of small firms

The aim of this article is to review the work currently being conducted at Durham University Business School to help small firms to develop their export potential. It describes the evolution of an Export Planning, Organisation, Research and Training System (EXPORTS). The foundation stone of the system is a training programme developed in conjunction with the Rubber and Plastics Processing Industry Training Board. Much of the article describes the development and evolution of this course. A keynote of the article is the progress that can be made with in‐company work providing the Training Board is willing to involve Training Advisers actively in course development and implementation. This innovative programme is evaluated and the routes to further action identified and reviewed.

The Industrial Training Levy (Rubber and Plastics Processing) Order 1974

The Secretary of State after approving proposals submitted by the Rubber and Plastics Processing Industry Training Board for the imposition of a further levy on employers in the rubber and plastics processing industry and in exercise of powers conferred on him by section 4 of the Industrial Training Act 1964 as amended by paragraph 2(2) of Part I of Schedule 2 to the Employment and Training Act 1973, and of all other powers enabling him in that behalf hereby makes the following Order:—

The Industrial Training Levy (Rubber and Plastics Processing) Order 1973

The Secretary of State after approving proposals submitted by the Rubber and Plastics Processing Industry Training Board for the imposition of a further levy on employers in the rubber and plastics processing industry and in exercise of powers conferred by section 4 of the Industrial Training Act 1964 and now vested in him, and of all other powers enabling him in that behalf hereby makes the following Order:—

The Industrial Training Levy (Rubber and Plastics Processing) (No. 2) Order 1972

The Secretary of State after approving proposals submitted by the Rubber and Plastics Processing Industry Training Board for the imposition of a fur‐ther levy on employers in the rubber and plastics processing industry and in exercise of his powers under section 4 of the Industrial Training Act 1964 and of all other powers enabling him in that behalf hereby makes the follow‐ing Order:—

The Industrial Training Levy (Rubber and Plastics Processing)Order 1972

The Secretary of State after approving proposals submitted by the Rubber and Plastics Processing Industry Training Board for the imposition of a fur‐ther levy on employers in the rubber and plastics processing industry and in exercise of his powers under section 4 of the Industrial Training Act 1964 and of all other powers enabling him in that behalf hereby makes the follow‐ing Order:—

Automation in the Tyre Curing Process

The Rubber processing industry has steadily improved and modernised the tyre moulding machine. In association the Instrument industry has developed instruments that minimise on-machine commissioning and servicing, time, through simplicity of design and careful attention to the problems of instrument adjustment. In tyre manufacture this reduces the down time on mould change giving greater flexibility to the production programme

The Industrial Training Levy (Rubber and Plastics Processing) Order 1969

The Secretary of State after approving proposals submitted by the Rubber and Plastics Processing Industry Training Board for the imposition of a further levy on employers in the rubber and plastics processing industry and in exercise of her powers under section 4 of the Industrial Training Act 1964 and of all other powers enabling her in that behalf hereby makes the following Order:—