Effects of Poly(vinyl butyral) as a Macromolecular Nucleating Agent on the Nonisothermal Crystallization and Mechanical Properties of Biodegradable Poly(butylene succinate)

Silica Aerogel-Rubber Composite: A Sustainable Alternative for Buildings' Thermal Insulation

Silica aerogel composites with recycled tire rubber have been synthesized and evaluated for their potential use for thermal protection in buildings. The present work describes for the first time the preparation of silica-based aerogel composites containing recycled rubber tires reinforced with polyvinyl butyral (PVB) by hot pressing. The developed composite was extensively characterized regarding its physical, morphological, thermal and mechanical features, and the results showed their properties were relevant, leading to composites with different properties/performances. The obtained bulk density values were satisfactory, down to 474 kg·m^-3, and very good thermal properties were achieved, namely, thermal conductivity as low as 55 mW·m^-1·K^-1 for composites with silica aerogel, recycled tire rubber and PVB. The most promising composites were those based on low bulk density and thermal conductivity values, and they were thermally stable, indicating their suitability for thermal insulation applications.

Dependence of Crystallization Behavior of Interacting Telechelic Poly(butylene succinate) Oligomer on Molecular Weight

A large spherulite structure deteriorates the mechanical properties of crystalline polymers, and therefore various methods have been explored to increase primary nucleation density. Recently, chain-end modification has been proposed as an effective approach for regulating polymer crystal nucleation. However, the relevant nucleation mechanism still requires investigation. Therefore, in this work, 2-ureido-4[1H]-pyrimidinone (UPy) units, which can form stacks via quadruple hydrogen bonds with each other, are introduced as end groups for the preparation of interacting telechelic poly(butylene succinate) (PBS-UPy) oligomers with different molecular weights (Mns). The crystallization, especially the nucleation behavior of PBS-UPy, is studied in detail by comparing with the corresponding pre-polymer, the hydroxyl-terminal PBS (PBS-OH). The thermal properties of PBS-UPy exhibit similar Mn-dependent tendency to those of PBS-OH, but with weaker total crystallization rate. The spherulite growth rate is significantly reduced, whereas the primary nucleation density is highly promoted, after introducing UPy groups. Further investigation reveals that the mechanism of UPy stacks’ influence on nucleation ability changes from inhibition to promotion with respect to Mn. Even under an inhibition of nucleation ability, the final nucleation density is obviously increased because of a significant decline of the growth rate. In addition, the change in the impact of UPy stacks on nucleation ability is speculated to originate from the memory expression feasibility of ordered conformation in the melt during crystallization.

Phase Transitions in Poly(vinylidene fluoride)/Polymethylene-Based Diblock Copolymers and Blends

The crystallization and morphology of two linear diblock copolymers based on polymethylene (PM) and poly(vinylidene fluoride) (PVDF) with compositions PM23-b-PVDF77 and PM38-b-PVDF62 (where the subscripts indicate the relative compositions in wt%) were compared with blends of neat components with identical compositions. The samples were studied by SAXS (Small Angle X-ray Scattering), WAXS (Wide Angle X-ray Scattering), PLOM (Polarized Light Optical Microscopy), TEM (Transmission Electron Microscopy), DSC (Differential Scanning Calorimetry), BDS (broadband dielectric spectroscopy), and FTIR (Fourier Transform Infrared Spectroscopy). The results showed that the blends are immiscible, while the diblock copolymers are miscible in the melt state (or very weakly segregated). The PVDF component crystallization was studied in detail. It was found that the polymorphic structure of PVDF was a strong function of its environment. The number of polymorphs and their amount depended on whether it was on its own as a homopolymer, as a block component in the diblock copolymers or as an immiscible phase in the blends. The cooling rate in non-isothermal crystallization or the crystallization temperature in isothermal tests also induced different polymorphic compositions in the PVDF crystals. As a result, we were able to produce samples with exclusive ferroelectric phases at specific preparation conditions, while others with mixtures of paraelectric and ferroelectric phases.

Polyether Single and Double Crystalline Blends and the Effect of Lithium Salt on Their Crystallinity and Ionic Conductivity

In this work, blends of Poly(ethylene oxide), PEO, and poly(1,6-hexanediol), PHD, were prepared in a wide composition range. They were examined by Differential Scanning Calorimetry (DSC), Polarized Light Optical Microscopy (PLOM) and Wide Angle X-ray Scattering (WAXS). Based on the results obtained, the blends were partially miscible in the melt and their crystallization was a function of miscibility and composition. Crystallization triggered phase separation. In blends with higher PEO contents both phases were able to crystallize due to the limited miscibility in this composition range. On the other hand, the blends with higher PHD contents display higher miscibility and therefore, only the PHD phase could crystallize in them. A nucleation effect of the PHD phase on the PEO phase was detected, probably caused by a transference of impurities mechanism. Since PEO is widely used as electrolyte in lithium batteries, the PEO/PHD blends were studied with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), and the effect of Li-salt concentration was studied. We found that the lithium salt preferentially dissolves in the PEO phase without significantly affecting the PHD component. While the Li-salt reduced the spherulite growth rate of the PEO phase within the blends, the overall crystallization rate was enhanced because of the strong nucleating effect of the PHD component. The ionic conductivity was also determined for the blends with Li-salt. At high temperatures (>70 °C), the conductivity is in the order of ~10⁻³ S cm⁻¹, and as the temperature decreases, the crystallization of PHD was detected. This improved the self-standing character of the blend films at high temperatures as compared to the one of neat PEO.

Poly(butylene succinate-co-butylene acetylenedicarboxylate): Copolyester with Novel Nucleation Behavior

Big spherulite structure and high crystallinity are the two main drawbacks of poly(butylene succinate) (PBS) and hinder its application. In this work, a new type of copolyester poly(butylene succinate-co-butylene acetylenedicarboxylate) (PBSAD) is synthesized. With the incorporation of acetylenedicarboxylate (AD) units into PBS chains, the crystallization temperature and crystallinity are depressed by excluding AD units to the amorphous region. In contrast, the primary nucleation capability is significantly strengthened, without changing the crystal modification or crystallization kinetics, leading to the recovery of total crystallization rate of PBSAD under the same supercooling condition. The existence of specific interaction among AD units is found to be crucial. Although it is too weak to contribute to the melt memory effect at elevated temperature, the interaction continuously strengthens as the temperature falls down, and the heterogeneous aggregation of AD units keeps growing. When the aggregating process reaches a certain extent, it will induce the formation of a significant amount of crystal nuclei. The unveiled nucleation mechanism helps to design PBS copolymer with good performance.

Effect of polyvinyl acetals on non-isothermal crystallization behaviour and mechanical properties of poly(ε-caprolactone)

Melt shearing made the crystallinity of as-received PCL increased and the crystallization temperature raised by 7.7 °C. Polyvinyl acetals increased the spherulite size of PCL from a few microns to 200 μm and PVB improved the Young’s modulus of PCL by 67%.

POLYVINYL BUTYRAL (PVB), VERSETILE TEMPLATE FOR DESIGNING NANOCOMPOSITE/COMPOSITE MATERIALS:A REVIEW

In current article, the versatile behaviour of Polyvinylbutyral (PVB)and its ability to form composite materials withvarious inorganic species is reported. PVB has hydrophilic vinyl alcohol groups and hydrophobic vinyl butyral groups. These groups behave as promoters of polymer adhesive and binders for organic moieties. The composite materials of PVB have been synthesized viaphysical as well as chemical both protocols. PVB is used as a constituent part in the formation of composite, induces a specific property in a resulting one which are utilized by various ways since it has stronger in binding ability, sharper optical clarity and able for providing flexibility and toughness in the formed composite. Varioussophisticated instrumentation techniques eg FTIR, XRD, FESEM, TEM etc. are reported for characterizations of samples. The composite materials have excellent film formation properties, and can be potential candidate for photoelectric as well as photovoltaic applications. The inorganic conducting species which do not have film formation ability can be useful by composite formation along with PVB. The green protocols for synthesis of composites may also useful for biological applications. 

How to regulate the isothermal growth rate of polymer spherulite without changing its molecular composition?

A new method has been invented to control the spherulite growth rate of isothermally crystallized PBS without changing its molecular composition.

Enhanced crystallization rate of biodegradable poly(butylene succinate-co-ethylene succinate) by poly(butylene fumarate) as an efficient polymeric nucleating agent

PBF may significantly enhance the nonisothermal melt crystallization behavior of biodegradable PBES by acting as an efficient polymeric nucleating agent.