Development of Polyoxymethylene/Polylactide Blends for a Potentially Biodegradable Material: Crystallization Kinetics, Lifespan Prediction, and Enzymatic Degradation Behavior.

Jianhua Li,Xiaodong Wang,Yatao Wang,Dezhen Wu

doi:10.3390/polym11091516

Jianhua Li, Xiaodong Wang + Show 2 more

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https://doi.org/10.3390/polym11091516

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Abstract

This paper reported the development of polyoxymethylene (POM)/polylactide (PLA) blends for a potentially biodegradable material. A series of POM/PLA blends at different weight ratios were prepared by melt extrusion with a twin-screw extruder, and their mechanical properties, crystallization behavior and kinetics, thermal degradation kinetics and stability, lifespan prediction and enzymatic degradation behavior were investigated extensively. POM and PLA were found to be partially miscible in the melt state at low temperature and become phase-separated at elevated temperatures, and their blends exhibited a typical lower critical solution temperature behavior. There were two distinct glass transition temperatures (Tg) observed for POM/PLA blends at any mass ratios when quenched from the homogeneous state, and both POM and PLA domains showed an apparent depression in their respective Tg’s in the blends. Owing to the partial miscibility between two domains, the tensile strength and impact toughness of POM/PLA blends gradually decreased with an increase of PLA content, but their flexural strength and modulus presented an increasing trend with PLA content. The studies on non-isothermal and isothermal crystallization behaviors of the blends indicated that the crystallization rates of the blends decreased continually with increasing the PLA content, confirming that the crystallization of POM domain was controlled by the molecular-confined mechanism. The introduction of PLA into POM not only led to a slight increase of thermal stability of POM domain at low PLA contents but also shortened the lifespan of the blends, favoring the natural degradation of the blends. The POM/PLA blends exhibited an improvement in partially biodegradable performance with an increase of PLA content and their mass loss reached up to 25.3 wt % at the end of 48-h enzymatic degradation when 50 wt % of PLA was incorporated.

Highlights

As sustainable development has become a worldwide tendency, there is growing awareness of the importance of biodegradable polymeric materials and their products in our ordinary daily life
As seen in the phase diagram of POM/PLA blends in Figure 1a, this blending system exhibits a series of typical cloud temperatures dependent on the blending compositions due to a phase separation occurring at the critical solution temperature
The development of relative degree of crystallinity seems to become slower when the PLA content is further improved. These results indicate that the loading of PLA significantly influences the isothermal crystallization of POM domain in the blend

Summary

Introduction

As sustainable development has become a worldwide tendency, there is growing awareness of the importance of biodegradable polymeric materials and their products in our ordinary daily life. Polymers 2019, 11, 1516 and eventually end up as non-degradable waste at the end of their service life. These pollutants from polymeric materials inevitably influence the soil, rivers, lakes, oceans and even food chain on which human beings depend. The disposal of polymer wastes by incineration leads to enormous environment pollution while reducing landfill sites. These factors have contributed to the development of environmentally friendly polymers that degrade completely under composting conditions after the end of their service life. The exploitation of renewable and biodegradable materials and the restrictions of the use of traditional polymeric materials are considered as two important means to avoid an overdependence on fossil energy resources, which can effectively reduce the environmental pollution and carbon emissions [2]

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