Electron Microscopy of Hevea Latex Gels

Abstract

Abstract The use of preserved concentrated Hevea latex for the production of rubber articles has given birth, during the last decades, to a number of quite new technological methods in rubber manufacture. Starting from an aqueous rubber dispersion of low viscosity as a raw material, instead of the very tough viscoelastic solid rubber, may be advantageous in many respects. Latex technology, however, also presents its particular difficulties and drawbacks, one of which is concerned with the problem of the reinforcement of rubber. Reinforcing fillers like carbon black, which enhance the tear strength and abrasion resistance of masticated rubber, do not exhibit the same beneficial effect on the properties of rubber films cast from latex ; the same is true of all fillers if added in appreciable amounts, with the notable exception of resorcinol-formaldehyde resins formed in situ. Nevertheless, the strength of vulcanized cast films from latex is excellent in comparison with vulcanized sheets of masticated solid rubber. In order to get more insight into the factors which control the rheological and mechanical properties of wet as well as dried and vulcanized latex gels, an extensive study has been undertaken, part of which has been concerned with an elucidation of the structure of these gels by means of electron microscopy. The purpose of this paper is to describe the experimental methods for obtaining electron micrographs and to present some of the results. The rheological and mechanical properties will be discussed in forthcoming publications, one of which has appeared in print already.