Field Stability Tests of Polyethylene Composites with Organomineral Biocidal Additives in Aqueous Environments

Laboratory and field stability tests for a composite based on low-density polyethylene with an organomineral biocidal additive to the effects of aqueous media have been carried out. As an organomineral additive, polyhexamethyleneguanidine hydrochloride (a high-molecular-weight nontoxic biocide used in antiseptic solutions) immobilized on an inorganic carrier (montmorillonite) was used to improve the quality of distribution of the organomineral additive in a thermoplastic polymer (without loss of the biocidal properties of polyguanidine) and to prevent polyguanidine from being washed out of the composite during operation. The composition and structure of the composite with an organomineral additive remain unchanged after exposure to distilled water and model seawater. Field tests of the composites in seawater at a depth of 1.5 m in a tropical climate revealed that there were no polyguanidine leaching from the material even after 21 months of exposure of the samples. The samples without an organomineral additive undergo insignificant photo-oxidative aging, whereas the molecular structure of the polymer in the composite with the additive is unchanged. Thus, the studied organomineral additive has a photostabilizing effect on polyethylene. When the samples are exposed to seawater, there is a slight decrease in the strength of the samples and an increase in the elastic modulus, which is associated with an increase in the degree of crystallinity of polyethylene during aging.