Solid Natural Rubber Based Methods

Adhesives come in several forms and include pressure-sensitive adhesives (which must have characteristics of both a liquid and a solid), mbber-based adhesives (essentially all mbbers can be used with solvent natural mbber based, neoprene based, styrene butadiene rubber (SBR) based), hot melt adhesives, and natural produce adhesives. Structural adhesives require high-strength materials and are often used instead of welding or other methods of joining. For example, structural adhesives are used to attach bodywork to automobile chassis in some makes of car. Epoxy-based thermosets, phenolics, polyurethanes, acrylics, cyanoacrylates. 

The chemistry involved with crosslinking of diene-based systems is largely speculative. Since crosslinked systems, by their nature, are completely insoluble, all analytical procedures which require solutions of the polymers are unusable. IR spectroscopic techniques are of limited value because the spectrum of polystyrene blocks out most frequencies other methods are difficult in the solid state. Most work reported in this area is based on measuring the fraction of insolubles and some indication of how tightly crosslinked the insoluble component has become (by a swelling index test). The presence of occluded polystyrene in the gel fraction of typical rubber-modified plastics further complicates the issue, although Karam and Tien have attempted to allow for this problem through a modification of the Flory-Rehner equation. 

A new method based on thermomechanical analysis of solid (not dissolved) polymer was used to study the topology and molecular structure of different kinds of sulphur (mineral and two polymeric types), commonly used as vulcanising agents for diene rubbers. It was found that a significant difference existed in their MWDs and in their degrees of crystallinity. Both mineral and polymeric sulphurs had a polymeric nature. 9 refs. EASTERN EUROPE POLAND RUSSIA Accession no. 645667... 

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