The effect of MDI on the structure and mechanical properties of poly(lactic acid) and poly(butylene adipate- co-butylene terephthalate) blends

Hongwei Pan; Zonglin Li; Jia Yang; Xin Li; Xue Ai; Yanping Hao; Huiliang Zhang; Lisong Dong

doi:10.1039/c7ra10745e

The effect of MDI on the structure and mechanical properties of poly(lactic acid) and poly(butylene adipate- co-butylene terephthalate) blends

RSC Adv. 2018 Jan 25;8(9):4610-4623. doi: 10.1039/c7ra10745e. eCollection 2018 Jan 24.

Authors

Hongwei Pan^{1

2}, Zonglin Li^{1

2}, Jia Yang³, Xin Li³, Xue Ai⁴, Yanping Hao¹, Huiliang Zhang¹, Lisong Dong¹

Affiliations

¹ Key Laboratory of Polymer Ecomaterials, Chinese Academy of Sciences, Changchun Institute of Applied Chemistry Changchun 130022 China hlzhang@ciac.ac.cn +86-431-85262689.
² University of Chinese Academy of Sciences Beijing 10080 China.
³ Changchun University of Technology Changchun 130012 China.
⁴ College of Chemical and Environmental Engineering, Shandong University of Science and Technology Qingdao 266510 China.

Abstract

In this work, poly(lactic acid) and poly(butylene adipate-co-terephthalate) (PLA/PBAT 50/50) were melt-blended in the presence of 4,4'-methylene diphenyl diisocyanate (MDI) which acted as a reactive chain extender. The mechanical properties, phase morphology, thermal behavior and crystalline structure of the blends were investigated. Fourier transform infrared measurements revealed that some remarkable chemical interaction had taken place between the two polymers and MDI. Upon increasing the content of MDI, the blends showed increased tensile strength and elongation at break. With the addition of 0-2 wt% MDI, the impact strength of PLA/PBAT-MDI blends increased from 7.0 kJ m^-2 to 70.0 kJ m^-2. A large shift towards each other in terms of the glass transition temperature was observed by DMA and DSC analysis. SEM micrographs showed not only a reduction in the PBAT phase size but also a significant increase in interfacial adhesion between the PLA and PBAT phases with increasing of MDI. Furthermore, the toughening mechanism of the oriented samples was confirmed by wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) images; it was possible for the smaller crystallites of blends to form during the course of chain extension.