Viscoelastic behavior and model simulations of poly(butylene adipate-co-terephthalate) biocomposites with carbon nanotubes: Hierarchical structures and relaxation

Abstract

Poly(butylene adipate-co-terephthalate) (PBAT) biocomposites containing carbon nanotubes (CNTs) were prepared by melt compounding. The linear viscoelasticity of composites, including creep, creep recovery and stress relaxation in the solid state, and dynamic shear flow in the molten state, were studied and then further described by the viscoelastic models, aiming at exploring relaxation of hierarchical structures of CNTs and obtaining structural parameters of CNTs in PBAT matrix. The results reveal that CNTs are dispersed mainly as flocs or small aggregates in PBAT, which is further confirmed by the structural parameters of CNTs obtained through model simulations on the dynamic rheological responses of composites. The presence of CNTs retards overall kinetics of creep and stress relaxation of PBAT. This is attributed to highly restrained viscoelastic and viscoplastic deformation of PBAT chain coils, rather than slightly confined elastic deformation of chain segments because the chain coils is in the same size-scale with the CNT flocs.

Construction and Characterization of Biodegradable Foam from High-Content Lignin-Reinforced Poly(Butylene Adipate-co-Terephthalate) Biocomposites

“…These excellent properties render PBAT a promising eco-friendly biopolymer for use as an alternative to nonbiodegradable petroleum-based polymers for a wide variety of potential applications such as food-packaging containers, waste vinyl bags, shopping bags, and mulching films. − Although PBAT shows promise as a biodegradable biopolymer, its relatively high water-vapor permeability and high production cost compared with commonly used polymers may restrict its use in some commercial applications. In recent years, numerous studies have aimed at improving the applicability of PBAT by creating blends with other polymers − and by producing composites with various reinforcements such as CaCO 3 and starch, carbon nanotubes, organoclay, − cellulose nanocrystals, zinc oxide, and natural fibers. , …”

Durability of Biodegradable Polymer Nanocomposites

“…Bleaching treatment by H 2 O 2 improved the interfacial adhesion between PLA and sugarcane leaves and thus enhanced biofilms’ tensile strength, evidenced by the increased B factor from 6.6 to 7.5. Low adhesion factors of around 1.3 were found for PBS/wine lees [ 110 ] and PBS filled with microcrystalline cellulose particles [ 138 ]. The filler–polymer bond strength was enhanced by chemical modifications of the MCC surface [ 138 ].…”

“…The most common model for creep description is the three-parameter Findley power law given by the following equation [ 110 , 139 , 148 , 149 ]: where k and n (0 < n < 1) are material parameters. The power-law models are considered empirical models without attaching importance to a physical background.…”

“…The Weibull distribution equation is also applied to model the creep recovery behaviour. The recovery strain is determined by the viscoelastic strain recovery and the residual strain caused by a viscous flow effect and is given by the following equation [ 110 ]: where is time of stress removal, and are the characteristic time and shape parameters, respectively.…”

“…Ding and coworkers have studied creep and stress relaxation of PBAT biocomposites containing CNT up to 5 wt.% [ 110 ]. The authors applied the Findley and Burgers models for creep description, while creep recovery was modelled by the Weibull distribution function given by Equation (17).…”