Pollen fillers for reinforcing and strengthening of epoxy composites

Abstract

Pollen grains have the potential to be effective plant-based biorenewable fillers in polymer matrices due to their high modulus, strength, chemical stability, and unique nanoscale architectures. In this work, we present evidence for the effectiveness of pollen as a reinforcing filler in epoxy matrices, characterized as a function of pollen loading and surface treatment. Composites prepared with unmodified native defatted ragweed pollen (D) displayed decreased mechanical properties and increasing glass transition temperatures (T g ) with increasing pollen loading. A soft interphase was observed to form around native pollen that is likely due to incompletely cured epoxy, resulting in decreased mechanical properties. However, pollen treated via a common base-acid (BA) surface preparation was a load-bearing, toughening filler in epoxy composites, displaying simultaneously increased tensile strength (by 47%) and strain at break (by 70%), improving interfacial morphology (absence of soft interphase), and increasing T g at 10 wt% pollen loading. Elastic modulus improves by 14% with 10 wt% BA pollen loading, and fitting of the modulus with the Halpin-Tsai and Counto models results in an estimated pollen exine modulus of 8 GPa, the first reported pollen modulus measurement from composite studies. Improvements in mechanical properties in BA pollen versus D pollen likely result due to crosslinks with the epoxy matrix due to the presence of protic functional groups (hydroxyls or carboxyls) on the BA surface. BAtreated ragweed pollen shows promise as a toughening filler for imparting higher strength to polymers without increasing mass.

Hemp hurd and alfalfa as particle filler to improve the thermo‐mechanical and fire retardant properties of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

“…This behavior can constitute a limitation in several applications. A possible improvement of the elongation and impact properties could be achieved with filler surface treatments or by the addition of an adhesion promoter additive . As expected, these treatments involve an increase in the costs and the possibility of a no longer biodegradable composite.…”

The atypically high modulus of pollen exine

“…The resulted polymer -pollen composite showed an 80% increase in tensile strength and a wider glass transition [2]. Similarly, ragweed pollen were recently reported to result in a 47% increase in tensile strength, a 70% increase in strain at break and a 14% increase in modulus of epoxy composites at 10 wt% pollen loading [3]. Uddin et al [4,5] have demonstrated the oral delivery of vaccines to mice via ragweed pollen and the potential for pollen to be used for controlled release of pharmaceuticals has been reviewed [6].…”

A brief overview of RF sputtering deposition of boron carbon nitride (BCN) thin films

“…Composites are applied in a wide range of applications because of their promising properties [117][118][119][120][121][122][123][124][125]. To illustrate, the corrosion behavior of BCN films has been attracted a growing attention of researchers to allow their application in different environments.…”