2021 Annual Meeting

Exploration of Curing Conditions for Producing a Soybean Oil-Based Thermosetting Polymer for Potential Use As a Renewable Matrix for Composites

Due to increased environmental concerns, there is interest in exploring bio-based monomers and polymers to produce thermosetting resins and ultimately composites. Our project focuses on thermosetting polymers, meaning they become irreversibly hardened after being cured. Traditionally, thermosetting polymers are produced from petroleum-based chemicals. We are interested in replacing the traditional methods with bio-based alternatives, which are also targeted as possible matrix materials for natural-fiber or natural-particle reinforced composites.

Solid polymers were prepared from a bio-based liquid mixture consisting of acrylated epoxidized soybean oil (AESO) and isobornyl methacrylate (IBM), cured, with a free radical initiator. Previous work from other Bucknell students proved a two step curing sequence of 120 C followed by 160 C to be successful for an 80:20 ratio of AESO to IBM - this produced a solid with mechanical properties appropriate for future composite formation.

A further goal is to optimize curing time and temperature for this system. Minimizing temperature is desirable because it makes the process easier to work with, and potentially makes samples less susceptible to cracking and forming bubbles. The lower temperature is also less likely to damage the plant-based fillers. Combinations of different temperatures and times have been studied for curing AESO and IBM to get an understanding of when curing is complete, and also what minimum temperature can be used to produce a solid polymer. Results from material properties tests were compared to determine how the method of curing affects the physical characteristics. Mechanical analysis included testing the hardness with a durometer and deformation in compression and bending on a universal testing machine.

Modification of the initiator system with promoters, such as Cobalt(II) Naphthenate, is also being explored in an attempt to achieve curing at lower temperatures and time. It is expected that the addition of this promoter will speed up the process and require less heat. The outcome desired from experimenting with different promoters is to achieve a cure at or near room temperature.