FROM ISOPRENE MONOMER TO SYNTHETIC POLYISOPRENE LATEX: MANUFACTURING ROUTES AND RELATED PRODUCT PROPERTIES
Dr. Philippe Henderson, Ph.D., KRATON Polymers
Natural rubber is produced as a latex by mother nature. In order to produce a synthetic equivalent, the polymer industry has to polymerise isoprene monomer in solvent and manufacture the latex via post-emulsification of the intermediate polyisoprene (IR) solution. Direct emulsion polymerisation is no option. Therefore, the properties of a synthetic IR latex are not only a function of the emulsification step but also of the solvent polymerisation step. Most applications currently relying on natural rubber latex as a raw material could be based on a synthetic IR latex, providing that the IR is treated in accordance with its specificities by the goods manufacturer.

RESIDUAL CHEMICALS REDUCTION-LATEX PRODUCTS
Harry Bader, Akron Rubber Development Laboratory
This paper will discuss the history of leaching rubber products including the author's personal experience with the process. In addition, methods for reducing residual chemicals in products produced from natural latex will also be discussed, including cautions and exceptions to those methods.

And finally, properties of well leached products will be reviewed.
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REDUCTION OF EXTRACTABLE PROTEIN CONTENT OF NATURAL RUBBER GLOVES
Dr. A. H. Eng, Ph.D., Rubber Research Institute of Malaysia
Chlorination is a process that is being widely used in the rubber glove industries to produce powder-free gloves. Besides being able to reduce the surface tackiness, the process has also been known to be more effective in reducing the extractable protein (EP) level of natural rubber films than leaching with water. In this study, several other ways of EP reduction were investigated. Leaching in the dilute hydrochloric acid at room temperature was found to reduce the EP of the rubber films significantly. Since water soluble proteins are less soluble in acidic medium, the lower EP value observed could be due to the reaction of hydrochloride with the protein which produced insoluble derivative similar as those in chlorination. It was also found that treatment of dry rubber film with low concentration of ozone water also accelerated the removal of EP. The ozone could degrade the proteins, making them more soluble in water. The rate of EP reduction could be increased by increasing the temperature of the leaching system. It could be further enhanced by incorporating ultrasonic waves into the dry-film leaching system. The rate of EP reduction for pre-vulcanized latex films was higher than that of post-vulcanized films due to the larger surface area of pre-vulcanized latex films. The presence of ultrasonic in the leaching system did not cause deterioration to the tensile properties of both aged and unaged films.
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MODIFICATION OF POLYCHLOROPRENE COLLOIDAL DISPERSION STABILITY
Dr. Lance Christell, Ph.D., Dupont Dow Elastomers
The challenge for dispersion suppliers has been to balance the stability needed by producers to process and compound an adhesive with the end user's need for quick bond formation. For foam adhesives the quick bond property has been achieved with two-part spray technology as well as by pH reduction to destabilize the colloidal system. We will discuss newly developed technology that more effectively balances the need for compounding/processing stability and rapid bond formation in a one-component system.
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PREVULCANIZATION OF A SYNTHETIC POLYISOPRENE ELASTOMER EMULSION
Thad Plasczynski, Lord Corporation
Synthetic polyisoprene elastomer emulsions offer some very unique features and benefits that a solvent solution of the same elastomer cannot. Use of elastomer emulsions do away with solvents typically used to put these elastomers in solution. This eliminates environmental concerns over tracking and reporting solvent emissions. Another benefit is the ability to enhance the dry film properties of the emulsion with the use of pre-vulcanization methods.

Synthetic polyisoprene elastomer emulsions and solutions of polyisoprene rubber typically require compounding to enhance their dry film properties. Unlike solutions of polyisoprene rubber, polyisoprene elastomer emulsions can be pre-vulcanized. During pre-vulcanization, the rubber particles in the emulsion are vulcanized under controlled conditions. Pre-vulcanization cures the elastomer particles without radically altering the viscosity of stability of the emulsion.

Therefore, the manufacturer can pre-vulcanize the emulsion and store it for use at a later date. Additionally, for those who coat fragile fabrics, use of a pre-vulcanized coating allows one to eliminate potentially damaging heat exposures typically required to cure the coating after it is applied. This study reports some general guidelines for pre-vulcanizing a commercially available anionic polyisoprene elastomer emulsion.
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PRODUCT PERFORMANCE AND THE CHALLENGES AHEAD FOR SYNTHETIC NITRILE LATEX
John Robertson, Synthomer Limited, UK
A comparison is made between the common materials used in glove manufacture, namely nitrile, natural latex and PVC. The relative strengths and weaknesses of each material are then contrasted with nitrile to highlight the areas of improvement that are necessary for the development of the next generation of nitrile latices.
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CORRELATION OF STYRENE ACRYLIC PROPERTIES IN PAPERBOARD APPLICATIONS USING NEURAL NETWORKS
Dr. Michael Forbes, Ph.D., Omnova Solutions
Paperboard manufacturers use a variety of polymer platforms to achieve optimum product performance. Polymers range from very hydrophobic styrene butadiene copolymers to hydrophilic vinyl acetate polymers. Each polymer has advantages and disadvantages in its use for paperboard applications. A portion of the market in North American board uses vinyl acetate polymers or vinyl acrylic copolymers. More styrene acrylics are being used to widen the operating window in coating paperboard while maintaining or improving the board's final product appearance. Our work employed a neural network model to examine the influences of latex functional groups on the end use properties of coated paperboard.
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LOW TEMPERATURE CRYSTALLIZATION OF POLYCHLOROPRENE LATEX PRODUCTS
Timothy Lipinski, PolymerLatex
The ability of polychloroprene (CR) elastomers to crystallize under strain is an important factor in its unique stress-strain behavior among synthetic rubbers. Crystallization caused by low temperature storage of CR products, however, can cause undesirable changes such as increased hardness and permanent set.

The rate and amount of crystallization that occurs in CR products is influenced both by the structure of the starting polymer and also by the amount of crosslinking in the cured products. These factors and their effects on product properties are investigated. Methods to limit the amount of low temperature crystallization are detailed.
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ZINC OXIDE WITH HIGH SURFACE AREA - A WAY TO REDUCE ZINC CONTENT IN NATURAL LATEX COMPOUNDS AND IMPROVING ECOLOGICAL SYSTEMS
Bernd Hynek, Bayer
Market overview about Zinc oxide usage in the industrial areas of the world, especially for the rubber-latex industry and influences between zinc oxide types with high surface area and normal zinc types for activation of vulcanisation and their relation for environmental aspects.
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BENEFITS OF ACETYLENIC GLYCOL BASED SURFACTANTS IN RUBBER LATEX APPLICATIONS
Dr. V. V. Shah, Ph.D., Air Products and Chemicals, Inc.
Rubber latices are widely used in coagulant formulations for high quality glove manufacturing and in water based adhesive formulations. The proper choice of surfactant and its use level is critical to the development of high performance latex systems for various applications. High speed application of latex based formulations to low energy substrates place a high performance requirement on surfactants to quickly move to newly created interfaces and prevent surface defects such as retraction, fish eyes and crawling. Furthermore in glove manufacturing process, the surfactant must be able to perform consistently in the high electrolyte concentrations of a coagulant bath.

Acetylenic glycol based surfactants are successfully used in these applications. This paper will demonstrate the acetylenic glycol based surfactant's ability to provide low dynamic surface tensions and reduced foam while maintaining or enhancing other performance properties and will describe the chemistry that enables that performance.
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EXTENDING THE SHELF LIFE OF LATEX PRODUCTS
Chris Nola, R. T. Vanderbilt
In November of 1999, the Food and Drug Administration issued a Draft Guidance for comment by the general public. It is entitled Guidance For Conduction Stability Testing To Support An Expiration Date Labeling Claim For Medical Gloves. In addition to real time testing, it includes a definitive procedure for estimating the shelf life of these latex products. We vigorously applaud this first of a kind effort for consumer and responsible manufacturer protection for the latex industry. For each of these interested parties, identifying and eliminating poor quality gloves from the market is a tremendous step forward. Aside from economics it has the effect of recognizing responsible manufactures for quality work and promoting research and technology in the latex Industry.

R. T. Vanderbilt has responded to the FDA's invitation for comment by offering our criticisms of certain details of the procedures without obscuring our enthusiasm for the idea of such a protocol.

We undertook to examine in detail the test methods and results of testing with different types of medical gloves: natural latex, polychloroprene and nitrile, both lightly powdered and powder free. Secondly, we cast films of the various latex formulated compounds and surveyed ways to upgrade the shelf life of these films according to the test procedures.

The following is a report on our findings. While our work was done with thin, unfilled, unpigmented films, we emphasize that our results cannot be confined to medical gloves. The principles and the shelf life data can easily be interpolated and extended to encompass adhesives, tubing, balloons, thread, coatings and various other medical devices.
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JET DISPERSION TECHNOLOGY FOR OIL-WATER EMULSIONS
Dr. Hans Jurgen Mick, Ph.D., Bayer
Dispersion is the dominant step in the manufacture of emulsions or suspensions. The principal differences between conventional technologies, like stirred tanks, rotor stator systems, high-pressure homogenizers and the jet dispersion technology is demonstrated. The physical principles for the dispersion process and design are explained. A number of examples for the application of this technology, which includes an amino vulcanizsation accelerator, a phenolic non-staining antioxidant and a phosphate-based sulphur donor are presented. These systems are shown to be stable in water for technically relevant time periods.
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STATUS OF THE ECONOMIC RECOVERY OF THE SOUTH ASIAN LATEX INDUSTRY AND IMPACT OF LATEX ALLERGY LITIGATION ON THE INDUSTRY
Dr. R. K. Matthan, Ph.D., Polymer Consultancy Services
The economic recovery in the South Asian region has also heralded recovery of the latex products industry. However, the ongoing impact of latex allergy litigation is restructuring the industry. The techno-economic data provides an assessment of growth and the restructuring now in progress. The prospects for the South Asian latex industry over the next 3 years are forecast in this context.
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SECOND ANNUAL UPDATE ON EUROPEAN UNION, FEDERAL AND STATE EFFORTS TO REGULATE NATURAL RUBBER LATEX GLOVES
F. Samuel Eberts III, Cardinal Health, Inc.
In the past year, various European Union, U.S. Federal and State governmental initiatives have been proposed that would either ban or sharply limit the use of natural rubber latex medical gloves. For example, an Ad Hoc Working Group of the European Union, the Food and Drug Administration (FDA), the National Institute for Occupational Safety and Health (NIOSH), the Centers for Disease Control and Prevention (CDC) and a number of states have considered such proposals because of concerns about latex allergies, notwithstanding the fact that natural rubber latex gloves, particularly powdered natural rubber latex gloves, have become the number one public health defense against the spread of deadly blood-borne pathogens such as HIV and Hepatitis B and C. In light of the importance of natural rubber latex gloves as a vital public health tool used to prevent the spread of contagious and potentially lethal diseases, federal agencies and state government should be encouraging, rather than discouraging, the use of powdered natural rubber latex gloves. However, inconsistent European Commission, federal and state initiatives to ban the use of powdered natural rubber latex gloves, lacking a sound scientific basis, have potentially ominous and costly implications for physicians, hospitals, and other healthcare providers.
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REGULATORY COMPLIANCE AND ITS EFFECT ON THE NATURAL RUBBER LATEX INDUSTRY
Lillie C. Thomas, M.S., Custom Services International
Natural rubber latex is contained in more than 40,000 products used in industrial, consumer and medical applications. Natural rubber latex is also a component of many adhesives and packaging materials that come into direct contact with other products. This paper will discuss the various regulatory agencies and initiatives that apply to the natural rubber industry and how manufacturers can proactively protect themselves. As an industry, the natural rubber manufacturers are regulated in the United States by the Food and Drug Administration, the Occupational Health and Safety Administration, the Consumer Products Safety Council, the Federal Trade Commission and the Environmental Protection Agency and are also subject to ISO and ASTM standards for many of the products that are made. Further, state regulation concerning workman's compensation issues with regard to both the use of natural rubber products in specific occupations and in plant operations are becoming increasingly significant. This paper will discuss regulatory authority and its effect on the manufacturing environment. This paper will further discuss the consumer's use of regulatory requirements in litigation and product liability actions. As regulation becomes more of the business atmosphere, the natural rubber industry needs to develop specific strategies to incorporate regulatory awareness into their business paradigms.
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EXCITING POLYMER DEVELOPMENTS USING STATISTICAL TECHNIQUES
Richard E. Todd & Julie V. Bialke, BFGoodrich
New products are the life-blood of growing companies. An efficient methodology to bring new products to market quickly and successfully is a great advantage. Why do 1000 experiments when you can get the same result with only 10 experiments - faster and for less cost? Tools to accomplish this include Design of Experiments (DOE), Screening Designs, Response Surface Models. This paper gives an overview of these methodologies, in terms geared for the non-statistical layman. Some examples of these tools in use include nitrile latexes for glove dipping and an emulsion for use as a binder in fiber treatment applications.
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SBR LATICES FOR ASPHALT MODIFICATION: ADVANTAGES OF FINE POLYMER NETWORKFORMATION
Dr. Koichi Takamura, Ph.D., BASF
Asphalt pavements become too soft under strong sunlight on hot summer days but very brittle during cold nights in winter. Heavy traffic on the soft asphalt paving causes permanent deformation to the pavement, known as "rutting." Cracking of the pavement develops during winter months when the asphalt binder becomes too brittle. This means the asphalt binder works well only within its application window within which it is visco-elastic enough to dissipate stress exerted by the traffic. Polymer modification extends this application window, mostly increasing visco-elasticity at high temperature. The modified asphalt also has better fatigue resistance and extends pavement lifetime, ex 10 years vs. 15 years with and without modification, respectively.

There are two major technologies of constructing the asphalt pavement: "Hot Mix" and "Cold Paving." For the hot mix process, aggregates are heated to above 200C to remove residual water and mixed with molten asphalt of >165C. Heating of the aggregate accounts for nearly 90% of the total energy usage for this hot mix process. The cold paving uses the asphalt emulsion, which contains 65-75% asphalt, dispersed in water. Cold aggregates can be used, thus significantly reducing the energy consumption.

Optical microscopy was applied to understand the curing mechanism of the SBR latex modified, cationic asphalt emulsion. The study clearly demonstrates that majorities of latex particles remain in the aqueous phase of the asphalt emulsion and spontaneously form a continuous polymer network upon drying. The same network formation was also confirmed when the emulsion was mixed with aggregates, simulating the chip seal process.

The Polymer morphology within the cured pavement was examined under the scanning electron microscope. The sample was prepared by fracturing to expose a fresh cross-section, fixing the polymer with OsO4 and extracting asphalt with an organic solvent. Honeycomb structure of the latex polymer formed around asphalt particles was clearly observed.

A new procedure was developed to determine dynamic mechanical properties of the emulsion residue obtained under the forced airflow drying. The procedure preserves the same polymer networks existing in the real pavement. Results demonstrate advantages of the polymer network formation on the rutting resistance.

The study was also extended for the hot mix process, developing new SBR latex, which forms stable polymer networks in the asphalt during mixing. This fine network is stable even when the modified asphalt is stored for a few days at 160-170C. Advantages of the fine polymer network on the cold fracture resistance were confirmed.