# Fully Biobased Thermoset Adhesive Precursor from Itaconic Acid and Propylene Glycol

## TL;DR

This paper introduces a sustainable, biobased adhesive precursor made from itaconic acid and propylene glycol, suitable for photocurable adhesives with strong bonding properties.

## Contribution

A scalable and sustainable method to synthesize a new biobased thermoset adhesive precursor with high purity and strong adhesion properties.

## Key findings

- The precursor, dipropylene glycol itaconate (DPG-IA), was synthesized with over 98% conversion and confirmed to be more than 99% pure.
- The adhesion strength of cured DPG-IA reached 53.6 ± 1.5 kPa on acryl-wood and 83.4 ± 4.4 kPa on acryl-glass interfaces.
- The polymerization activation energy was measured at 115 kJ/mol, and the apparent viscosity was 1050 mPa·s at 25 °C.

## Abstract

Photocurable adhesives
serve numerous practical applications,
such
as medical devices, electronics, sealing in LCDs, or glass bonding.
This work focuses on a scalable and sustainable engineering of a new
reactive precursor for photocurable adhesives, dipropylene glycol
itaconate (DPG-IA). Synthesis involved Fischer esterification, with
more than 98% conversion measured by convenient and affordable volumetric
analyses (acid number and hydroxyl value). The product’s structural
verification was provided by 1H Nuclear Magnetic Resonance
(NMR) and FT-IR analysis, confirming a highly pure yield (more than
99%). Particularly, 1H NMR and FT-IR uncovered the presence
of unsaturated double bonds, which can by radically polymerized and
from cured molecular structure. The rheological profile and curing
reactivity were investigated since they are crucial for photocurable
adhesives. The apparent viscosity reached 1050 mPa·s at 25 °C,
and the calculated flow activation energy reached 70.1 kJ/mol. DPG-IA’s
reactivity was studied by Differential Scanning Calorimetry (DSC),
uncovering the polymerization activation energy reaching 115 kJ/mol.
Eventually, the adhesion strength, achieved by the cured DPG-IA on
the acryl, wood, and glass adherents, was investigated. The measured
adhesion strength for the acryl-wood adhesion reached 53.6 ±
1.5 kPa, and for the acryl-glass system it reached 83.4 ± 4.4
kPa.