Cold crystallization behavior of poly(lactic acid) in its blend with acrylic rubber; the effect of acrylic rubber content

Understanding the crystallization process of polymer blends is of great importance for designing their process conditions, especially when the crystallization occurs during heating, so‐called cold crystallization. In this paper, the cold crystallization behavior of poly(lactic acid) (PLA) in its blends with acrylic rubber (ACM) was studied as a function of ACM content, using various techniques including differential scanning calorimetry, polarized optical microscopy and rheological methods. It was found that the addition of 10 wt% ? 20 wt% ACM to the PLA accelerated its cold crystallization. However, on using a greater amount of ACM up to 30%, the rate of crystallization was not further increased. In the ACM‐rich blends, the crystallizable PLA domains were distributed inside the amorphous ACM matrix and consequently confined crystallization occurred. The observed effects are discussed in terms of the interplay between chain mobility enhancement and the influence of phase boundaries. © 2017 Society of Chemical Industry     

Effect of pH on Aerobic Granulation and Treatment Performance in Sequencing Batch Reactors

Two sequencing batch reactors were operated to investigate the effect of influent alkalinity and reactor pH on aerobic granulation. In the first reactor R1 with high influent alkalinity the pH was adjusted in the neutral range, and in the second reactor R2 with low alkalinity the pH was held within the acidic range. The R1‐dominating species were bacteria and the appearance time of granules was three weeks after reactor start‐up. On the other hand, the acidic environment of R2 provided favorable conditions for fungal growth, and rapid granule formation occurred within the first week of operation. The varying microbial structure of granules resulted in different reactor performance in terms of evolution time and morphology of granules, suspended solids in the reactors, settling ability of granules, effluent quality of treated wastewater, and physical strength of the granules.     

Integration of signals/systems and electromagnetics courses through the design of a communication system for a cardiac pacemaker

The integration of multiple concepts and courses through laboratory design projects are part of a new experimental program at the University of Utah, supported by the National Science Foundation, the College of Engineering, and the University of Utah. One such project is the design of an FSK communication system for a cardiac pacemaker, which combines labs from the junior-level "signals and systems" courses and the junior-level electromagnetics course, which are both taught in the same semester. The electromagnetic and the signal and system labs are briefly described in this paper.     

Algae-based sorbents for removal of gallium from semiconductor manufacturing wastewater

Removal of various soluble metallic impurities from wastewater in semiconductor fabrication plants is a critical issue facing the microelectronics industry. Considering the large volume of wastewater and a highly variable concentration of these contaminants, finding a robust adsorption process using a low-cost sorbent is of great value and interest to this industry. Of particular interest is the development of a flow-through abatement method for treating the process-tool effluent before it is mixed with other wastewaters. In this work, a strain of freshwater green algae (Chlorella sorokiniana), representing an algae-based sorbent, and a simulated wastewater, containing soluble gallium as the metallic impurity, are used as model compounds. The choice of gallium is based on its increased use, and the lack of related adsorption data compared to the information available for other metals such as copper and arsenic. Both batch and continuous-flow operations were used in this study. Comprehensive process models were developed and validated for both batch and flow systems. These models were found to be valuable for understanding the process steps as well as for obtaining the fundamental parameters that are needed for process design and scale-up. The sorbent was found to have high adsorption capacity even at low pH values (14.1 mg/g at pH of 2.3, and 38.5 mg/g at pH of 2.8). Based on the comparison of adsorption rate and capacity with data on previously studied and conventional sorbents, such as activated carbon and ion-exchange resins, the use of this algae-based sorbent is potentially an attractive option for the removal of gallium from the process-tool wastewater.     

A new empirical model for quiescent annealing of binary co-continuous polymer blends

The high sensitivity of the morphology and final properties of co-continuous polymer blends to thermal annealing has motivated many researchers to study the evolution of their morphology during thermal annealing process. In this work, phase coarsening of a low interfacial tension polylactic acid/polycaprolactone blend and a medium interfacial tension polylactic acid/polyethylene blend during quiescent annealing was studied in detail. To this aim, characteristic length scale of the microstructure of the polymer blends was determined at different annealing times. It was found that the phase size in both blends increased linearly by time at the early stage of the annealing and then the phase coarsening rate gradually decreased at longer times. Finally, the phase size of the blends approached a finite size. The mechanisms involved in the observed phase coarsening behavior were discussed in detail. Linear and exponential phase coarsening models in the literature could not explain the observed phase coarsening behavior in the studied blends. A new empirical model was presented which showed a very good agreement with both the obtained results in this work and the previous experimental data in the literature. The obtained results indicate the significant potential of the new model in analyzing phase coarsening behavior of co-continuous polymer blends.

     

Synthesis,characterization, and soil biodegradation study of polyamides derived from the novel bioactive diacid monomer 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid

A new bioactive diacid monomer, 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid ( 6 ), was synthesized in three steps. This monomer can be regarded as biologically active aromatic diacid and may be used in the design of biodegradable and biological materials. This monomer was polymerized with several aromatic diamines by step‐growth polymerization to give a series of biodegradable and highly thermally stable polyamides (PAs) with good yield (70–82%) and moderate inherent viscosity between 0.38–0.68 dL/g in a system of triphenylphosphite/pyridine/N‐methyl‐2‐pyrolidone/CaCl_2. The new aromatic diacid 6 and all of the PAs derived from this diacid and aromatic diamines were characterized by Fourier transform infrared, ¹H‐NMR, ¹³C‐NMR, and elemental analysis techniques. The thermal stability of the PAs was determined by thermogravimetric analysis and differential scanning calorimetry techniques under a nitrogen atmosphere, and we found that they were moderately stable. The soil biodegradability behavior of 6 and all of the PAs derived from this diacid and aromatic diamines were investigated in culture media, and we found that the synthesized diacid 6 and all of the PAs were biodegradable under a natural environmental. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A method for rejecting 3k-th harmonics in bandpass 6N-path filters

In this paper, a method for 3 -th ( ) harmonics rejection in 6 -path filters is proposed, and the related analysis is provided. Using a single-ended-input to differential-output structure, the filter selectivity around even harmonics are also suppressed. Accordingly, a proof-of-concept band-pass filter is designed, and postlayout simulations in the 90-nm CMOS technology are carried out, which covers an input frequency range from 200 MHz to 1.2 GHz with a channel bandwidth of 10 to 15.5 MHz. The achieved third harmonic rejection at 1-GHz local oscillator (LO) frequency is about 43 dB. Over the entire radio frequency (RF) range, the in-band IIP3 and noise figure are better than 1.5 dBm and 5.3 dB, respectively. The power consumption of the analog circuitry is 21 mW from the 1.2-V supply, whereas the digital clock generation circuitry consumes between 0.9 and 5.2 mW, depending on the center frequency of the filter.     

Raman-based silicon photonics

This paper reviews recent progress in a new branch of silicon photonics that exploits Raman scattering as a practical and elegant approach for realizing active photonic devices in pure silicon. The large Raman gain in the material, enhanced by the tight optical confinement in Si/SiO2 heterostructures, has enabled the demonstration of the first optical amplifiers and lasers in silicon. Wavelength conversion, between the technologically important wavelength bands of 1300 and 1500 nm, has also been demonstrated through Raman four wave mixing. Since carrier generation through two photon absorption is omnipresent in semiconductors, carrier lifetime is the single most important parameter affecting the performance of silicon Raman devices. A desired reduction in lifetime is attained by reducing the lateral dimensions of the optical waveguide, and by actively removing the carriers with a reverse biased diode. An integrated diode also offers the ability to electrically modulate the optical gain, a unique property not available in fiber Raman devices. Germanium-silicon alloys and superlattices offer the possibility of engineering the otherwise rigid spectrum of Raman in silicon.