Insect-trapping glues made of natural rubber: Effects of nonrubber components and rubber molar mass on performance

Abstract

An easy-to-prepare glue was produced from natural rubber (NR) latex and environmentally benign chemicals for use in control of insect pests in greenhouses. The effects of non-rubber components and the molar mass (MM) of NR in the latex and the glue on adhesion performance of the glues are reported. Glues were produced using five latex types: commercial high-ammonia concentrated latex (HA), fresh latex (FL), skim latex (SK), urea deproteinized latex (UD), and saponified latex (SP). The latexes’ characteristics (e.g., protein content, phospholipid content, gel content, and molar mass of NR chains) and the characteristics of the resulting glues (i.e., drying time, molar mass of NR chains, and adhesion performance) were evaluated by principal component analysis (PCA). The NR glues made of HA and SP latex types were found to have an adhesion performance comparable to commercial insect trapping glues. The HA latex was natural, more economical, and required less processing than the SP latex. PCA demonstrated that the adhesion performance of the glues correlated strongly to the gel content and the molar mass of the NR chains in the glue and the latex. Increased values of all these variables improved the cohesive strength of the glue. The HA glue was tested in a greenhouse to confirm its effectiveness: it showed an insect capturing efficacy of ∼68% of a commercial glue. The lower performance was caused by an absence of vulcanization, leading to creep behavior and degradation of the rubber chains in the hot environment of the greenhouse.