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.

A Robust Experimental Model to Explore the Three-Dimensional Printing of Polylactide Parts: Solution versus Melt Extrusion

Three-dimensional (3D) printing is a simple and versatile process for producing parts of complex geometries. Although the process possesses several manufacturing advantages, such as rapid prototyping, customization, and complexity, the optimization of the 3D printing procedure remains a challenge. Here we explore the influences of various processing conditions on the mechanical properties of melt extrusion- and solution extrusion-printed polylactide (PLA) products by adopting a robust experimental design model. In addition to the commercially available melt extrusion 3D printer, a novel solution-type 3D printer has been exploited especially for this study, which consists of a solution-type plunger-actuated feeding system, stepper motors and motion components, a power supply unit, a print bed, a user interface, and connectivity. The effects of various parameters were investigated by adopting a robust experimental design. We compared the parts printed using the melt extrusion and solution extrusion methods and found that, in the melt extrusion printing, the print speed and fill density were the principal parameters affecting product quality, while in the solution extrusion printing, oven temperature, fill density, and PLA/dichloromethane (DCM) ratio were the key parameters. By scanning electron microscopy, we found that the melt extrusion-printed parts exhibit a strip-like microstructure and the solution extrusion-printed parts show a fused surface morphology. Due to the addition of solvent, the solution-printed PLA material show a different thermal profile in the differential scanning calorimeter analysis, which in turn affects the mechanical behaviour of printed parts.

Rheological and Thermal Behaviour of High Impact Polystyrene Nanocomposite

This paper presents the study of rheological and thermal behaviour of high impact polystyrene/multiwall carbon nanotubes (HIPS/MWCNTs) nanocomposite. The nanocomposite was prepared via melt mixing method. The influence of different loadings of MWCNTs on the HIPS viscosity and other rheological characteristics were analyzed experimentally. Other rheological characteristics were studied using dynamic analysis of viscosity through rotational rehometer. Glass transition temperature (Tg) were also investigated using non-isothermal differential scanning calorimeter analysis. The viscosity was found to be directly proportional to MWCNTs’ loading, up to five times the value of pure HIPS at loading level of 7.5wt% of MWCNTs. The MWCNTs loading demonstrated a marginal effect (1-2%) on the Tg.

Synthesis and Characterization of PVA/MMT Porous Nanocomposite Prepared by Directional Freeze-Drying Method

Porous PVA/MMT nanocomposites, which included a great deal of macroporous, mesoporous and a few micorporous were fabricated by directional freezing and freeze-drying. X-ray diffraction (XRD), Scan Electric Microscope (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, and Thermo gravimetric-differential scanning calorimeter analysis (TG-DSC) were used characterize the samples. Results showed that the morphology and the interactions between MMT and PVA of the obtained porous nanocomposites were influenced by nanoparticle size, colloid concentration , aging time etc.O-H bond in PVA and Si-O bond in MMT, "acetate" in PVA and O-H bond in particle flat of MMT which occurred coupling constituted hydrogen bonding which enhanced the driving power to help PVA molecules insert into interlayer spaces of MMT.

A Linear Relationship between the Mechanical, Thermal and Gas Barrier Properties of MAPE Modified Rubber Toughened Nanocomposites

Composites based on high density polyethylene (HDPE), ethylene propylene diene monomer (EPDM) and organophilic montmorillonite (OMMT) clays were prepared by melt compounding followed by compression molding. The addition of clay as well as compatibilizer agent (maleic anhydride polyethylene (MAPE)) considerably improved the tensile properties of nanocomposites systems. The largest improvement in mechanical and thermal properties occurred at clay loading levels of 4% (2-8 wt %) with MAPE system. Interestingly, the increased in tensile properties also resulted in improve in thermal and barrier properties. Differential scanning calorimeter analysis (DSC) revealed that the barrier property of nanocomposite was influenced by the crystalline percentage of nanocomposite. Along with crystalline percentage, the crystallization temperature, Tc and melting temperature, Tm were also improved with OMMT and MAPE agent. The d-spacings of the clay in nanocomposites were monitored using x-ray diffraction (XRD) and the extent of delamination was examined by transmission electron microscope (TEM). The wide angle of XRD patterns showed the increased interplanar spacing, d of clay layers, indicating enhanced compatibility between polymer matrix and OMMT with the aid of MAPE agent. TEM photomicrographs illustrated the mixed intercalated and partial exfoliated structures of the nanocomposites with OMMT and MAPE agent.

Effects of solvents on post-irradiation grafting of styrene onto fluoropolymer films

Due to the interest in the development of low cost membranes with similar capabilities to Nafion®, grafting of styrene on fluorinated polymers by simultaneous irradiation and pre-irradiation methods at high temperature (higher than 50 °C) followed by sulfonation has been a process studied broadly. However, there is very little information about grafting yield at room temperature after simultaneous irradiation. Previous works reported that the surface morphology of the styrene grafts has showed an uneven profile under the studied conditions. This work aims to evaluate the grafting of styrene onto these films after simultaneous irradiation (in post-irradiation condition), using different solvent in periods until 28 days at room temperature. Films of poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) were immersed in styrene/toluene 1:4 or styrene/methanol 1:4 and then submitted to gamma radiation at 40 and 80 kGy doses. The degree of grafting (DOG) was determined gravimetrically and physical and chemical changes were evaluated by infrared spectroscopic analysis (FTIR), differential scanning calorimeter analysis (DSC), thermogravimetric analysis (TGA), and also by scanning electron microscopy (SEM). For PTFE films, the highest DOG was achieved using toluene as solvent while for PVDF films, the highest DOG was achieved with methanol. Surface images of the grafted films by SEM technique have presented a strong effect of the solvents on the films morphology. Finally, PVDF-g-PS in styrene/methanol film revealed higher DOG, although the surface showed small cavities and discontinuities. On the contrary, the surface of PTFE-g-PS in styrene/toluene presented homogeneous surface.

The Effect of Tungsten Addition on the Thermal Stability and Microstructure in the Electroless Ni-P-W Composite Coating

Ni-P-W composite deposit on the mild steel substrate was derived by the electroless process. The composition of the eletroless coating was Ni-10.7wt.%P-8.7wt%W analyzed by electron probe microanalysis (EPMA). The coating was annealed at various temperatures from 350oC to 600oC for 4h and the structure at different heat-treated temperature was studied by X-ray diffraction, and transmission electron microscope (TEM). The crystallization behavior was evaluated by the differential scanning calorimeter analysis with continuously heating from room temperature to 550oC at different heating rates. The hardness at all depths of the coating on the substrate could be acquired by the nanoindentation. From the DSC analysis, the onset temperature and crystallization temperature were 397.7oC and 405.5oC, respectively, at the heating rate of 10oC/min. The activation energy of the Ni-P-W coating was 307 kJ/mol analyzed by Kissinger, and Augis and Bennett methods with different heating rates. The Ni-P-W coating showed an amorphous structure in the as-deposited state and exhibited a relatively low hardness of approximately 6.8 GPa. As temperature was raised to 380oC, the hardness was slightly increased to 8.7 GPa due to the partial precipitation of Ni and Ni3P in the amorphous matrix. On heating to 500oC for 4 h, the hardness reached the maximum value of 12.3 GPa with a grain size of 33.1 nm and followed by gradual degradation above 500oC.