Effect of extrusion process melt temperature on polyurethane catheter surfaces

Determination of optimum process melt temperature of medical-grade polyurethane (PU) is an indispensable challenge witnessed during the catheter manufacturing process. This resin does not contain a uniform crystal structure but exists in an amorphous state. The lower shore hardness PU material, used in catheter manufacture, has just a “melt temperature range” instead of a definite melt temperature. This temperature plays a significant role in shaping the catheter surfaces, which directly interact with human tissues and cause health-care-associated issues. The objective of this work is to evaluate the effects of variations in the melt temperature during the extrusion process of medical catheters on their outer surfaces. Medical PU, Pellethane, was used for this study and 12 Fr (4.0?mm) catheters were manufactured with optimal validated parameters, excluding melt temperature. The manufactured catheters were examined under Optical Microscopy and Atomic Force Microscopy (AFM) for surface topography studies. Wettability studies were carried out using a Goniometer for evaluating the water contact angles. The effects of melt temperature on the surface roughness (R_a) and wettability of the catheter surfaces were analyzed through analysis of variance (ANOVA). The conclusion was that the process melt temperature variations have a significant effect on catheter R_a and its wettability characteristics.     

Streamlined life cycle assessment of residue utilization options in <Emphasis Type="Italic">Tongkat Ali </Emphasis>(<Emphasis Type="Italic">Eurycoma longifolia</Emphasis>) water extract manufacturing process

Life cycle assessment (LCA) is often used to compare alternative process options in terms of their overall impact on the environment to easily identify the most environmentally friendly alternative. In this work, a streamlined LCA study was conducted to assess three different residue utilization schemes for Tongkat Ali (Eurycoma longifolia) extract production. The case study was firstly simulated using a batch process simulation software. The results of mass and energy balances obtained from the simulation software were then subjected to life cycle analysis. By evaluating the different schemes for using the fibrous residue from the extraction process, the potential for environmental process improvement was identified. Overall, use of the residue as process fuel was found to be the most environmentally friendly option. It produces the least emissions and reduces resource usage per unit of product than the other options evaluated.     

Effect of high permeability on the accurate determination of permittivity for Mn-Zn ferrite cores

This work presents a field-circuit-coupled method to investigate differences between intrinsic and measured permittivities for a Mn-Zn ferrite. Electric and magnetic fields in a flat cylindrical ferrite, which is used here to construct a ferrite capacitor, are solved analytically. Then, complex power supplied to the capacitor is calculated. On the basis of the complex power, parameters in an equivalent circuit for the ferrite capacitor are extracted. The paper examines the validity of the developed mathematical model. Numerical results show that for a ferrite with high permeabilities, measured permittivities follow intrinsic values well at low frequency but fail to embody the intrinsic values when the frequency runs above several hundred kilohertz. Numerical results also demonstrate that the dimensions of the sample under investigation play a role in measurement errors. The larger the radius of the cylindrical ferrite is, the higher the errors are. Correction curves are generated, from which the measured permittivities can be corrected to reflect the intrinsic values.     

Synthesis of resource conservation network with sink–source interaction

This article presents a mathematical model for the synthesis of resource conservation networks with interception placement. A comprehensive superstructure that incorporates all possible network configurations is used to facilitate the formulation. The synthesis task involves the allocation and interception of process sources to satisfy process sinks and environmental constraints. In particular, the interaction between the sinks and sources is addressed as the subject of the present study. Two literature case studies are solved to illustrate the proposed approach.     

Targeting and design for batch regeneration and total networks

Resource conservation for batch processes is gaining good attention in recent years. This is mainly due to the recent trend in chemical engineering that focuses on product engineering, as well as in the rise of various low volume and high value-added products (e.g. pharmaceutical, specialty chemicals, etc.) in the market. In this study, a systematic procedure to perform targeting and design of a batch resource conservation network (RCN) involving material regeneration and waste treatment (also known as a total RCN) is proposed. The procedure is applicable for all fixed-schedule-type batch RCNs with mass storage facilities. Literature examples are used to elucidate the proposed procedure.     

Competition between Superconductivity and Charge-density Wave Order in Na0.3CoO2⋅1.3H2O

Three samples of Na_0.3CoO₂⋅1.3H₂O that differed in sample age showed different ordering: after three and five days, superconductivity with T _c∼4.5 K but different superconducting condensates; after 40 days, no superconductivity but charge-density wave order at T _CDW∼7 K. A pair-breaking action that progresses with sample age and acts preferentially in one of two electron bands produces the changes in the superconducting condensate, and ultimately destroys the superconductivity. Theoretical calculations predicted the charge-density wave transition.     

Microwave-Assisted Aging of Organic–Inorganic Hybrid Nanocomposite of α-Naphthaleneacetate in the Lamella of Zn-Al-Layered Double Hydroxide

Microwave-assisted aging Zn-Al-layered double hydroxide with nitrate as the interlayer anion (ZANOL) and its nanohybrid with an organic moiety, -naphthaleneacetate (ZANAN), was done and the resulting properties of the materials compared. The results showed that intercalation of the -naphthaleneacetate (NAA) anion into the Zn-Al layered double hydroxide lamella is readily accomplished, resulting in the expansion of the interlayer spacing from 9.0 Å in the layered double hydroxide to 20.0 Å in the nanohybrid. This expansion accommodates the NAA anion of larger size than nitrate, as indicated by its molecular structure. For both methods, the resulting materials afforded a well-ordered organic–inorganic nanolayered structure. The Zn to Al ratio of the resulting nanocomposite is lower than the ratio present in the mother liquor at the beginning of the reaction, which implied less incorporation of aluminum ions from the mother liquor into the inorganic metal hydroxide layers. By using the microwave-assisted method, however, slightly more Al³⁺ ions were incorporated into the inorganic metal double hydroxide layers. In general, there is not much difference in the physicochemical properties of ZANANs aged by either the microwave or the conventional oil bath method. For both methods, longer aging time slightly enriched the organic content of the resulting nanohybrid and the inorganic Zn to Al ratio remained the same, independent of the aging time.