Ahmed H. Hassanin

Improving high-altitude UV–Vis resistance of PBO braided tendons of NASA’s super pressure balloons

Super pressure balloons (SPBs) are used by the National Aeronautics and Space Administration (NASA) for ultra-long duration ballooning (ULDB) missions which carry various scientific explorations to support space and earth sciences research activities. The resistance to photo-degradation of load-bearing braided tendons of SPBs is critical to the success of ULDB missions. Recognizing the critical need to improve UV and visible light (UV–Vis) protective performance of p-phenylene-2, 6-benzobisoxazole (PBO) braids, North Carolina State University and NASAs Balloon Program collaborated to investigate the effectiveness of sheath extrusion method in improving the UV–Vis resistance of tendons. This study included two PBO tendon types – 48,000 (48k) denier tendons and 72,000 (72k) denier tendons. Using a sheath extrusion method, the tendons were covered with UV protective sheath of low-density polyethylene containing two types of UV inhibitors – TiO2 rutile nanoparticles and PolyOne PE White CC®. Bare and sheathed tendons were subjected to artificial UVB exposure in the lab as well as to both high altitude and ground exposure during flight missions conducted by NASA. Protection against radiation exposure was evaluated by determining the loss of tensile strength after exposure. UV–Vis protection of tendons improved with an increase in sheath thickness as well as UV inhibitor content in the sheath. The results also showed that 72k denier braids had higher resistance against UV degradation compared to 48k denier braids. In-flight exposure results confirmed the comparative UV protective performance of tendons exposed to accelerated artificial UVB exposure in lab. 72k denier tendon covered with sheath containing 10% PE White CC® (sheath thickness of 0.37 mm) experienced the lowest strength loss among all tendon samples to high-altitude exposure during flight missions. The study has also utilized UV–Vis transmittance of the sheath covering the braids as a method of evaluating the performance of the protective sheaths.

Nanocomposite Multilayer Fibrous Membrane for Sustained Drug Release

Building on the success of the many earlier studies on electrospun nanofibers technique which provide a non woven web to the order of nanometers introducing superior properties such as large surface area, superior mechanical properties and ease of implementation in many fields of applications, elctrospun nanofibers became an important issue for many researchers in various fields. Using elctrospun fibers as a drug carrier, is showing a huge promising potential for the future of biomedical application. Our work in this research is focusing on engineering a system to control the drug release profile rate especially for wound dressing. Nanocomposite multilayer fibrous membranes, using electrospinning method, have been developed for drug release in form of sandwich structure of three layers. Inner layer which is kept Polycaprolactane (PCL) loaded with drug. The two outer layers have been changed with different blend ratios between Chitosan (Cs) and PCL as follow [0%:100% Cs:PCL, 30%:70% Cs:PCL, 50%:50% Cs:PCL, 70%:30% Cs:PCL]. The results showed that the release rate has been affected dramatically by the outer layer composition. SEM images showed changing in the morphology due to the different in the composition of outer layer.

Thermal insulation properties of hybrid textile reinforced biocomposites from food packaging waste

Due to the significant and harmful effect of the global warming on our communities, health, and climate, the usage of thermal insulation material in building is must to decrease the energy consumption and to improve energy efficiency. On the other hand, the utilization of waste and biomass resources for developing new bio-based composite materials is attracting much attention for the environmental and socioeconomics. Therefore, in this study, thermal insulation bio-based composite panels from Tetra Pak® waste and wool fiber waste with different ratios were manufactured. Likewise, other sandwich bio-based composite panels were manufactured using Tetra Pak waste as a core material with glass woven fabric and jute wove fabric as skin materials. Thermal conductivity and thermal resistance results showed a significant improvement on thermal insulation properties of the developed biocomposite panels compared to the control samples made of plain Tetra Pak®.

Developing Biocomposites Panels from Food Packaging and Textiles Wastes: Physical and Biological Performance

The urban solid waste problem has been one of the biggest environmental challenges these days. In this context, developing biocomposites with improved performance by using various sources and wastes has been intensified in the last decades for economic and environmental points of view. In this study, physical behavior, fungal decay and termite attack tests were conducted in laboratory conditions to investigate the performance of composites developed from TetraPak and textile wastes. All the results were compared to standard wood products. The water swelling properties strongly decreased in the manufactured TetraPak composites when compared with the conventional particleboard panels. The fungal decay resistance tests revealed that the stand alone TetraPak based composites were not completely resistant to wood-decaying fungi. A significant amelioration in the decay durability was observed for the manufactured TetraPak composites compared to the standard wood samples. Durability classes were determined according to the criteria given in the European standard (CEN/TS15083-1). Interestingly, the data indicated that the increment of the wool waste proportion in the produced boards lead to a significant enhancement counter the test fungi. The results of termite screening test showed further considerable resistance for whole TetraPak based composites against termites when compared to traditional wood samples. Such panels could be an available alternative without any additives for wood based composite structures and it can be used in a wide range of applications.

A novel technique for producing conductive polyurethane nanofibrous membrane for flexible electronics applications

A novel technique for producing stretchable and flexible conductive polyurethane nanofibrous membrane for flexible electronics applications has been developed. One of the most important challenges in fabricating polymeric membranes for flexible electronics is to enhance its sensitivity and conductivity maintaining its flexibility and stertchability. Wet electrospinning technique was used to fabricate thermoplastic polyurethane (TPU) nanofibers through a coagulant bath of a conductive grade co-polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT: PSS). A Kapton sheet was used as a substrate to load TPU/PEDOT: PSS nanofibers on it. The morphology and stability of the as-spun TPU/PEDOT: PSS nanofibers has been investigated. The fabricated TPU/PEDOT: PSS nanofibrous membrane has showed a well stabilized ohmic behaviour under a wide range of different temperatures up to 90 °C as well as different values of tensile strain up to 4.43 %, which makes it suitable for high temperature strain sensing applications.

Novel Bio-Based Composites Panels from TetraPak Waste

Due to the significant and harmful effect of the global warming on our communities, health, and climate, the usage of sustainable, bio-based and green materials became an imperative. On the other hand, the utilization of waste and biomass resources for developing new bio based composite materials is attracting much attention for the environmental and socio economics. Therefore, in this study, bio based composite panels from TetraPack® waste were developed. To enhance the mechanical and physical performances of TetraPak panels, sandwich structures were constructed. Mechanical and physical tests results showed significant improvements due to using sandwich structure in compare to No-skin structure. By comparing the developed TetraPak sandwich panels with the standard commercial particleboard, significant improvements in both mechanical and physical performances have been clearly observed. Consequently, the developed biocomposite TetraPak panels can be used in a wide variety of applications. Finely, this can be contributing in reducing environment contaminating, meanwhile introduce cheap and suitable product for different technical fields.

AN UNUSUAL CAUSE OF CHEST PAIN AFTER CORONARY ARTERY BYPASS GRAFTING

Iatrogenic aortocoronary arteriovenous fistula (ACAVF) resulting from grafting of an arterial graft to a cardiac vein is an unusual complication of coronary artery bypass grafting (CABG), it has been only reported in 37 cases. A 35-year-old female patient with history of diabetes mellitus and

Development of UV Protective Polymeric Layer for High Performance Fibers

High performance fibers are characterized by their high strength to weight ratio, high thermal resistance and high chemical stability, which make them suitable materials for composite structures in planetary Venus balloons, competitive sail fabrics, soft and hard body armor, bulletproof vests, as well as, tendons for super pressure scientific balloons. High performance fibers, however, degrade upon exposure to Ultraviolet-Visible (UV-VIS) radiations. The objective of this research is to develop a polymeric protective layer to improve the UV-VIS resistance of high performance fibers. Polymeric sheath from Linear Low Density Polyethylene (LDPE) matrix compounded with (a) Rutile TiO2 nano-particles, and (b) Polyone, Inc white pigment with product code CC00012837X1 were developed to protect a braid made of poly(p-phenylene-2,6-benzobisoxazole) (PBO) yarns from UVVIS radiation. The compounded LDPE with the selective UV absorber was extruded around the PBO braid. The effectiveness of shielding the PBO tendon braid from radiation effects were investigated using commercial chambers, as well as, flight tests. The results showed that LDPE compounded with 10% TiO2 as well as LDPE compounded with the white pigment achieved very good blockage for the UV-VIS light. The results of commercial exposure, as well as, flight exposure on the BLAST and CREAM missions will be presented in this paper.