Itaconimide telechelics of polyethers, synthesis, and their impact on mechanical properties of unsaturated polyester resins

Abstract

The present work focuses on the evolution in the mechanical properties of an unsaturated polyester resin (UPR) on blending with itaconimide‐end terminated polyethers, namely, polypropylene glycol (I‐PPG), polyethylene glycol (I‐PEG), and polytetra methylene oxide (I‐PTMO). Blends of an unsaturated polyester (UPR, based on propylene glycol, terephthalic, and maleic acids) resin with different loading of itaconimide end‐capped telechelics were investigated for their mechanical and thermal properties. Blending with these additives enhanced the mechanical and thermal properties of the crosslinked UPR. The impact strength and fracture toughness values were improved by more than 100% by small quantities of the additives. The improvement in fracture properties was correlatable primarily to a decrease in overall crosslink density. The distribution of the polyether chains in the cured matrix as dictated by the reactivity ratios of styrene and polyether macromer was found to have a role in deciding the properties. The properties were found to be the best for the blend toughened with I‐PPG with a molecular weight 2000 g/mole at a loading of 2.5 parts per hundred parts. On comparison with the resin blended with a maleimide‐encapped polyether of same molecular weight, the itaconimide end‐capped polyether was found to provide a better toughening of the UPR matrix. This could a priori be explained based on a difference in distribution of the end‐capped polyether as a consequence of the difference in the copolymerization behavior of itaconimide and maleimide functionalized telechelics toward UPR. The itaconimide enters into a random copolymerization with styrene and the probability for formation of the continuous sequences of the itaconic group is about 60%. This will permit polyether segments to come close enough to form micro or even sub‐micron clusters of the polyether which eventually forms the micro crystallites of poly ether that act as a crack stopper. This possibility cannot be envisaged in maleimides which forms invariably an alternating sequence with styrene. The morphological features as reflected in scanning electron microscopic analyses tallied with these observations. This work could help identify the ways for obviating the inherent brittleness of the UPR systems.

On the toughening of unsaturated polyester resins using nadimide end‐functionalized polyether telechelics

“…In previous works, maleimide-and itaconimide end-capped polyethers were chosen as the reactive oligomers. [16,17] The toughening effect was found to depend not only on the nature of the polyether but also on its concentration in the blend as well as how the end groups react or copolymerize with styrene/maleic groups. The reactivity of the end group of the polyether with styrene decides the spatial distribution of the polyether in the cured matrix.…”

“…In this backdrop, we examined maleic and itaconic end-capped polyethers and found that the terminal group does have an important role in deciding the toughening of the UPER. [16,17] It is of interest to see the impact of these polyethers when nadimide becomes their end group. Nadimide possesses an isolated unsaturation in its backbone.…”

“…Keeping this in mind we fixed the polyether ends with three different groups, all capable of co-reacting with styrene but in their characteristic manner decided by the reactivity ratio. In this perspective, the end groups were chosen as maleic, [16] itaconic, [17] and nadic (present paper).…”

“…In previous work, we had examined the toughening effect of maleimide and itaconimide endfunctionalized polyethers in the same UPER. [16,17] In this paper, we examine the capabilities of nadimide endcapped telechelics of various polyethers in comparison to maleimide telechelics of the same for their capacity in toughening the conventional UPER. There are no reports of such studies so far.…”

Preparation A Cross-Linked Copolymer By Using Unsaturated Poly(2-Butene Maleate) Polyester and Methyl Methacrylate

“…Many other glycols and anhydrides or acids can be used to alter the character of unsaturated polyesters. E.g., terephthalic acid and isophthalic acid are chosen to obtain much better chemical and thermal resistance, whereas longchain aliphatic acids, such as succinic acid or adipic acid, enhance the flexibility but reduce the thermal and chemical resistance [10,11].…”