Reaction Mechanism and Mechanical Property Improvement of Poly(Lactic Acid) Reactive Blending with Epoxy Resin.

Krittameth Kiattipornpithak,Sarana Rose Sommano,Warintorn Ruksiriwanich,Kittisak Jantanasakulwong,David Rohindra,Thidarat Kanthiya,Pornchai Rachtanapun,Yuthana Phimolsiripol,Nanthicha Thajai,Noppol Leksawasdi,Krittameth Kiatiporntipthak

doi:10.3390/polym13152429

Reaction Mechanism and Mechanical Property Improvement of Poly(Lactic Acid) Reactive Blending with Epoxy Resin.

Krittameth Kiattipornpithak, Sarana Rose Sommano + Show 9 more

Open Access

https://doi.org/10.3390/polym13152429

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Journal: Polymers	Publication Date: Jul 23, 2021
Citations: 21	License type: CC BY 4.0

Affiliation: Chiang Mai University, University of the South Pacific

Abstract

Polylactic acid (PLA) was melt-blended with epoxy resin to study the effects of the reaction on the mechanical and thermal properties of the PLA. The addition of 0.5% (wt/wt) epoxy to PLA increased the maximum tensile strength of PLA (57.5 MPa) to 67 MPa, whereas the 20% epoxy improved the elongation at break to 12%, due to crosslinking caused by the epoxy reaction. The morphology of the PLA/epoxy blends showed epoxy nanoparticle dispersion in the PLA matrix that presented a smooth fracture surface with a high epoxy content. The glass transition temperature of PLA decreased with an increasing epoxy content owing to the partial miscibility between PLA and the epoxy resin. The Vicat softening temperature of the PLA was 59 °C and increased to 64.6 °C for 0.5% epoxy. NMR confirmed the reaction between the -COOH groups of PLA and the epoxy groups of the epoxy resin. This reaction, and partial miscibility of the PLA/epoxy blend, improved the interfacial crosslinking, morphology, thermal properties, and mechanical properties of the blends.

Highlights

Biodegradable polymers have attracted considerable attention in recent years owing to their environmental effects
Polylactic acid (PLA) was melt-blended with epoxy resin (0–20% w/w) to observe the effect of epoxy on the mechanical properties of the blends
The maximum tensile strength of the neat PLA was 57.5 MPa, and the addition of 0.5% epoxy enhanced the maximum tensile strength to 66.9 MPa due to crosslinking caused by the epoxy reaction

Summary

Introduction

Biodegradable polymers have attracted considerable attention in recent years owing to their environmental effects. Reactive blending of epoxy resin and PLA increased mechanical properties, melt strength, torque, toughness, and melt viscosity, but decreased crystallinity of PLA [32,33]. These improvements were due to a reaction between -COOH end groups of PLA and epoxy groups of epoxy resin [32,33]. The reaction mechanism, plasticizing effect, and morphology of epoxy resin blending with PLA have not been reported. Mechanical properties, morphology, thermal properties, thermal stability, and the reaction mechanism were investigated

Materials

Sample Preparation

Tensile Properties

Vicat Softening Temperature

Mechanical Properties

Morphology

Reaction