Poly (lactic acid) blends with excellent low temperature toughness: A comparative study on poly (lactic acid) blends with different toughening agents

Poly (lactic acid) (PLA) blends with different toughening agents were prepared by melt compounding, and the effects of toughening agents on the toughness of PLA, especially the low-temperature toughness, were investigated. All blends were immiscible systems, but the rheological Cole-Cole diagram showed that the blends had certain compatibility, and the interfacial bonding of PLA/Ethylene/butyl methacrylate/Glycidyl Methacrylate Terpolymer (GEBMA) blend was the best. With addition of the toughening agents, all blends showed improvement of the tensile and impact toughness both at room temperature and low temperature. GEBMA was the best toughening agent, the elongation at break and impact strength at room temperature and low temperature were greatly improved. The elongation at break, tensile strength and impact strength of PLA blend with 20 wt% GEBMA at -20 °C was 55.8 MPa, 195.9% and 18.8 kJ/m², respectively, which showed the reinforcement and super ductility at low temperature. However, the toughening effect of Poly (propylene carbonate) polyurethane (PPCU) at low temperature was poor. The T_g and interfacial bonding were the main factors affecting the toughness of the blends, especially at low temperature. The lower the T_g and the better the interfacial bonding, the better the toughness of the blends.

Fiber-induced crystallization in polymer composites: A comparative study on poly(lactic acid) composites filled with basalt fiber and fiber powder

The poly(lactic acid) (PLA) composites with the silane coupling agent treated basalt fiber (SBF) and basalt fiber powder (SBFP) were prepared. The crystalline morphology, mechanical properties, and heat resistance of PLA/SBF/SBFP composites were investigated. The results indicated that SBF or SBFP not only acted as heterogeneous nucleating agents for PLA crystallization but also improved the mechanical properties and heat resistance of PLA. Morphological analyses showed that SBFP could play nucleating role to reduce the spherulites size of PLA, and SBF could restrict the mobility of PLA chains and construct interface crystallization for PLA during isothermal crystallization process. The composites with higher SBF loading, the "Transcrystalline-network" built in the composites significantly improved the heat resistance properties of PLA. Due to the synergistic effect of SBF and SBFP, the PLA/SBF/SBFP composites showed high heat deformation temperature (HDT), especially after isothermal crystallization, the HDT increased to 150.5 °C for the PLA/SBF/SBFP 50/10/40 composite, much higher (about 190%) than that of pure PLA (71.7 °C).

Unusual strain-dependent thermal conductivity modulation of silver nanoflower-polyurethane fibers

Thermal management of stretchable and wearable electronic devices is an important issue in enhancing performance, reliability, and human thermal comfort. Here, we constructed a unique experimental setup which investigated the strain-dependent thermal conductivity. The thermal conductivity of flower-shaped silver nanoparticle (silver nanoflower)-polyurethane (Ag-PU) composite fibers was systematically investigated as a function of strain. The strain-dependent temperature distribution of the Joule-heated fiber was measured using an infrared camera, and the thermal conductivity was obtained from the 1-dimensional Fourier's conduction model. There was a monotonic decrease in both lattice and electronic thermal conductivity with stretching at 25 °C. However, there was an initial increase in lattice and total thermal conductivity in the low strain region (<10%), when the fiber was stretched at 45 °C, although the electronic thermal conductivity decreased monotonically. The softening of the polymer at increased temperatures enhanced Poisson's ratio. Resultantly, the fiber cross-sectional area and radial-direction inter-particle distance between silver nanoflowers decreased. This could increase the thermal transport in conductive fibers by modulating the interfaces between silver nanoflowers and polyurethane. A further stretching decreased the lattice thermal conductivity due to the significantly increased axial distance between silver nanoflowers and the decreased filler fraction. The weft-knitted fabric also demonstrated an increased thermal conductance in the low strain region (≤30%) at 45 °C.

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

The FTIR spectrum of the PLA (a) and the PBAT (b) reacted with MDI.

A study on the mechanical, thermal properties and crystallization behavior of poly(lactic acid)/thermoplastic poly(propylene carbonate) polyurethane blends

PPCU was prepared by using PPC and polyols as the raw materials and diphenyl-methane-diisocyanate (MDI) as the extender chain. The impact strength and elongation at break of PLA were remarkably enhanced by blending with PPCU.