Type I and Type IV Circumallergenic Thin Films from Guayule and Hevea Natural Rubber

Natural rubber latex from the Brazilian rubber tree, Hevea brasiliensis, is commonly used for thin film barrier applications in products such as condoms, medical gloves, and dental dams.  Type I and Type IV latex allergy sensitization and subsequent allergic reactions from Hevea natural rubber latex products have created an industry demand for thin film barriers that are circumallergenic (circumvent the allergic response). Also, both natural and synthetic thin film products are prone to causing Type IV contact dermatitis allergies, attributed to residual thiazole, thiuram, and carbamate accelerators. 

We have developed Type IV hypoallergenic natural rubber thin films.  Latex films were cured with the accelerators diisopropyl xanthogen polysulphide (DIXP) and alkyldithiocarbamate (ZDNC) (Robinson Brothers Ltd., West Bromwich, UK).  DIXP is consumed during the vulcanization process, and skin tests have shown that ZDNC does not cause dermal reactions or delayed contact hypersensitivity, thus eliminating Type IV allergy sensitization.  In addition, DIXP contains no nitrogen, phosphorous and metallic elements, and so is unable to form the volatile and carcinogenic N-nitrosamine compounds during vulcanization, reducing occupational hazards for latex industry workers.  

DIXP and ZDNC were compounded in two different natural rubber lattices that do not elicit a Type I latex allergy sensitization.  Circumallergenic natural rubber latex from the plant species Parthenium argentatum, commonly referred to as guayule, was used because its proteins do not cross-react with antibodies raised against Hevea associated allergic proteins.   Ultra-low protein natural rubber latex from the plant species Hevea brasiliensis was used to make thin films as well.

Formulations in both lattices generated films which exceeded the ASTM 3577 surgical glove specifications.  A multivariate stochastic regression technique was used to demonstrate the individual effect of DIXP, ZDNC, and film thickness on tensile properties of films made from each latex.  Comparative analysis of multivariate models provides insight into compounding variations attributed to differences in Guayule vs. Hevea latex composition and chemistry.