Phase Transitions of Polarised PVDF Films in a Standard Curing Process for Composites

The article reports on the influence of annealing PVDF in an autoclave process on the PVDF phase composition. DSC, FTIR and XRD measurements serve to observe the phase changes in an already stretched, polarised and β-phase rich film. Annealing was conducted between 90 and 185 ∘C to cover a broad range of curing processes in an autoclave. The β-phase is found to be stable up to near the melting range at 170 ∘C. At 175 ∘C, the non-piezoelectric α-phase dominates and the piezoelectric γ- and γ′-phases appear. The γ-phase grows at elevated temperatures and replaces the β-phase. This observation stresses the importance of developing new methods to reactivate the polarisation after annealing, in particular for the integration of PVDF as a sensor in laminated structures, such as CFRP.

Growth And Characterization Of L-Arginine Doped Succinic Acid Single CrySTAL (LASA)

Under room temperature condition semi-organic crystals of L-Arginine mixed with succinic acid were grown from a solution maintained in aqueous from by slow evaporation solution growth method. Spectral analysis Fourier transform infrared and power diffraction by X-rays was used to determine the structural behavior of the grown LASA crystals. The lower cut off wavelength values 240 nm and efficiency transparency was confirmed using ultraviolet-Vis-NIR spectrum. The efficiency of second harmonic generation has been carried out for the grown LASA crystals and the detailed discussion about the results obtained was recorded. The thermal stability and melting range of the grown mixed crystal was carried out using thermogravimetric and Differential Scanning Calorimeter analysis.

Plastic drawing response in the biaxially oriented polypropylene (BOPP) process: polymer structure and film casting effects

Processing isotactic polypropylene (iPP) from cast film into biaxially oriented polypropylene (BOPP) involves plastic drawing of a semi-crystalline morphology in the melting range of iPP, where the crystal phase is reduced and the polymer has high mobility. The literature claims that plastic drawing in general and at elevated temperatures in particular depends predominantly on the structure of the amorphous entanglement network. We investigated this aspect using laboratory-scale biaxial drawing experiments. Three iPP homopolymer types differing in chain isotacticity and molecular weight distribution were extruded into 200-μm-thick primary sheets using 10 different extrusion settings. The sheets were biaxially drawn on a laboratory stretcher at 157°C and 160°C, recording the respective stress-strain curves. These curves were evaluated according to a rubber elasticity model to obtain the network modulus, GN, of the entanglement network. The effects of iPP type, the extrusion parameters, the resulting cast film properties, and the draw temperature on GN are discussed.

Melting ranges of heterophase systems Zr – Si – ZrB2 – ZrSi2-MoSi2 and Zr – Si – HfB2 – HfSi2 – MoSi2

The work is devoted to studying the melting ranges of the base Zr – Si eutectic composition depending on the content of the heterophasic powder component in the ZrB2 – ZrSi2 – MoSi2 and HfB2 – HfSi2 – MoSi2 systems in an amount of 30 – 90 % obtained by the method of self-propagating high-temperature synthesis (SHS). The melting range of the mixture Zr – Si was 1420 – 1440 °C, while the addition of SHS-powders ZrB2 – ZrSi2 – MoSi2 led to an increase in the melting onset temperature Тmelt.onset to 1460 – 1560 °С and the complete melting temperature Tmelt.complete to 1480 – 1670 °C. The addition of HfB2 – HfSi2 – MoSi2 powders had a weak effect on the values of Тmelt.onset (1390 – 1430 °С), but led to an increase in the values of Tmelt.complete to 1510 – 1550 °С. X-ray phase analysis showed that the remelted samples contained ZrB2/HfB2, ZrSi2/HfSi2, MoSi2 phases and Si, with the number of phases being directly proportional to the content of SHS powders in the composition of the Zr – Si mixture. The ingots were characterized by a homogeneous structure consisting of a silicon matrix, ZrSi2/HfSi2, MoSi2 disilicide grains, with ZrB2/HfB2 diboride inclusions.

Morphology of Aluminum Alloy Foams Produced with Dolomite via Partial Sintering of Precursors

Highly expanded, low-cost aluminum-based foams were successfully produced via powder metallurgy using dolomite as foaming agent. Nickel additions (5–15 wt.%) were explored in order to reduce the temperature disparity between dolomite decomposition and the melting range of the metallic matrix. Specific Al–Ni compositions provide appropriate viscosities for effective encapsulation of CO2 gas released during dolomite decomposition. A partial sintering step of compacted precursors was introduced prior to foaming, which resulted in high porosity levels (~86%) and significant volume expansion (~250%) in the final product. The partial sintering technique was a key determining factor in obtaining stable, highly expanded cellular structures with homogeneous pores, averaging 3 mm in size and being morphologically comparable with ALPORASTM foams.

Compliance with Amended General Chapter USPMelting Range or Temperature

Laboratories measuring melting temperature according to USP<741> Melting Range or Temperature, must comply with the amended calibration and adjustment requirements described in this regulation. Compliance is ensured by adjusting the instrument with secondary reference standards, traceable to USP, followed by verification of accuracy using USP primary reference standards.

Compliance with Amended General Chapter USPMelting Range or Temperature

Laboratories measuring melting temperature according to USP<741> Melting Range or Temperature, must comply with the amended calibration and adjustment requirements described in this regulation. Compliance is ensured by adjusting the instrument with secondary reference standards, traceable to USP, followed by verification of accuracy using USP primary reference standards.