Processability, property, and morphology of biodegradable blends of poly(propylene carbonate) and poly(ethylene-co-vinyl alcohol)

Novel Simple Approach for Production of Elastic Poly(propylene carbonate)

The simple approach of increasing the elastic properties of atactic poly(propylene carbonate) (PPC) with Mn = 71.4 kDa, ĐM = Mw/Mn = 1.86, and predominantly carbonate units (>99%) is suggested by selecting the appropriate hot pressing temperature for PPC between 110 and 140 °C. Atactic PPC is synthesized through ring-opening copolymerization of (rac)-propylene oxide and CO2 mediated by racemic salen complex of Co(III). Hot pressing PPC results in the release of a small amount of propylene carbonate (PC), sufficient to lower the glass transition temperature from 39.4 to 26.1 °C. Consequently, increasing the pressing temperature from 110 to 140 °C generates materials with a reduced modulus of elasticity (from 1.94 to 0.09 GPa), yield strength (from 38 to 2 MPa) and increased tensile elongation (from 140 to 940%). Thermomechanical analysis has shown a significant expansion in sample volume by hundreds of percent within the 80-130 °C range. PPC also displays large, reversible deformations, which can be utilized by creating shape memory materials.

Enhanced Properties of Biodegradable Poly(Propylene Carbonate)/Polyvinyl Formal Blends by Melting Compounding

Polyvinyl formal (PVF) was first synthesized via the reaction of poly(vinyl alcohol) (PVA) and formaldehyde. The synthesized PVF exhibits a high decomposition temperature, glass transition temperature, and low melting point compared to pristine PVA. The synthesized PVF can be melt processed at temperatures much lower than PVA. Poly(propylene carbonate) (PPC) and the as-made PVF were melt blended in a Haake mixer. The mechanical properties, thermal behaviors, and morphologies of PPC/PVF blends were investigated. Compared to the pure PPC, PPC/PVF blends show higher tensile strength and Vicat softening temperature. Thermogravimetric (TGA) result reveals that the thermal stabilities of PPC/PVF blends decreased with the increase of the content of PVF. Scanning electron microscopy (SEM) observation indicates that the interfacial compatibility of the PVF and PPC matrix is better than that of the PVA and PPC matrix. The PPC/PVF blends show much better comprehensive properties compared to pure commercial PPC, which provides a practical way to extend the application of PPC copolymer.

Biodegradable and Toughened Composite of Poly(Propylene Carbonate)/Thermoplastic Polyurethane (PPC/TPU): Effect of Hydrogen Bonding

The blends of Poly(propylene carbonate) (PPC) and polyester-based thermoplastic polyurethane (TPU) were melt compounded in an internal mixer. The compatibility, thermal behaviors, mechanical properties and toughening mechanism of the blends were investigated using Fourier transform infrared spectra (FTIR), tensile tests, impact tests, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and dynamic mechanical analysis technologies. FTIR and SEM examination reveal strong interfacial adhesion between PPC matrix and suspended TPU particles. Dynamic mechanical analyzer (DMA) characterize the glass transition temperature, secondary motion and low temperature properties. By the incorporation of TPU, the thermal stabilities are greatly enhanced and the mechanical properties are obviously improved for the PPC/TPU blends. Moreover, PPC/TPU blends exhibit a brittle-ductile transition with the addition of 20 wt % TPU. It is considered that the enhanced toughness results in the shear yielding occurred in both PPC matrix and TPU particles of the blends.