scholarly journals Toughness Enhancement of PHBV/TPU/Cellulose Compounds with Reactive Additives for Compostable Injected Parts in Industrial Applications

2018 ◽  
Vol 19 (7) ◽  
pp. 2102 ◽  
Author(s):  
Estefanía Sánchez-Safont ◽  
Alex Arrillaga ◽  
Jon Anakabe ◽  
Luis Cabedo ◽  
Jose Gamez-Perez

Poly(3-hydroxybutyrate-co-3-valerate), PHBV, is a bacterial thermoplastic biopolyester that possesses interesting thermal and mechanical properties. As it is fully biodegradable, it could be an alternative to the use of commodities in single-use applications or in those intended for composting at their end of life. Two big drawbacks of PHBV are its low impact toughness and its high cost, which limit its potential applications. In this work, we proposed the use of a PHBV-based compound with purified α-cellulose fibres and a thermoplastic polyurethane (TPU), with the purpose of improving the performance of PHBV in terms of balanced heat resistance, stiffness, and toughness. Three reactive agents with different functionalities have been tested in these compounds: hexametylene diisocianate (HMDI), a commercial multi-epoxy-functionalized styrene-co-glycidyl methacrylate oligomer (Joncryl® ADR-4368), and triglycidyl isocyanurate (TGIC). The results indicate that the reactive agents play a main role of compatibilizers among the phases of the PHBV/TPU/cellulose compounds. HMDI showed the highest ability to compatibilize the cellulose and the PHBV in the compounds, with the topmost values of deformation at break, static toughness, and impact strength. Joncryl® and TGIC, on the other hand, seemed to enhance the compatibility between the fibres and the polymer matrix as well as the TPU within the PHBV.

2021 ◽  
Vol 11 (18) ◽  
pp. 8778
Author(s):  
Antoniya Toncheva ◽  
Loïc Brison ◽  
Philippe Dubois ◽  
Fouad Laoutid

Natural and synthetic rubber is gaining increased interest in various industrial applications and daily life sectors (automotive industry, acoustic and electrical isolators, adhesives, impermeable surfaces, and others) due to its remarkable physicomechanical properties, excellent durability, and abrasive resistance. These great characteristics are accompanied by some recycling difficulties of the final products, particularly originated from the tire waste rubber industry. In this study, recycled tire rubber was incorporated in polymer matrices using selective laser sintering as 3D printing technology. Two polymers were used-polyamide and thermoplastic polyurethane, for their rigid and elastomeric properties, respectively. Polymer composites containing various tire powder amounts, up to 40 wt.%, were prepared by physical blending. The final materials’ morphological characteristics, mechanical properties, and thermal stability were evaluated. The proposed ambitious additive manufacturing approach looked over also some of the major aspects to be considered during the 3D printing procedure. In addition, examples of printed prototypes with potential applications were also proposed revealing the potential of the recycled tire rubber-loaded composites.


Author(s):  
Luiza В. Atlukhanova ◽  
Igor V. Dolbin ◽  
Georgii V. Kozlov

Целью настоящей работы является раздельное определение модуля упругос-ти компонент нанокомпозитов полидициклопентандиен/многослойные углеродные на-нотрубки, а именно, нанонаполнителя и межфазных областей. Для достижения этой целииспользована микромеханическая модель.Выполненные оценки продемонстрировали, что модуль упругости углеродных нанотрубокв полимерной матрице нанокомпозита, т. е., их агрегатов, приблизительно на два поряд-ка меньше номинальной величины этого параметра для отдельной углеродной нанотруб-ки, тогда как модуль упругости межфазных областей примерно в два раза выше модуляупругости матричного полимера. Эти данные ясно демонстрируют некорректность при-менения номинальных характеристик нанонаполнителя, в частности, его модуля упру-гости, для определения соответствующих показателей нанокомпозита. Однако использо-вание реальных величин модуля упругости агрегатов углеродных нанотрубок в рамкахпростого правила смесей позволяет достаточно точное описание этого параметра в случаенанокомпозитов. Важно отметить, что модуль упругости углеродных нанотрубок в элас-томерной матрице существенно меньше этого параметра в стеклообразной матрице дляодного и того же нанокомпозита. Это означает, что указанный параметр определяется нетолько размерами и структурой агрегатов нанонаполнителя, но также и другими факто-рами, в частности, жесткостью окружающей агрегат полимерной матрицы, эффективнос-тью переноса приложенного к образцу механического напряжения от полимерной мат-рицы к нанонаполнителю и т. п.Применение модифицированного правила смесей для описания модуля упругости нано-композитов показало, что включенный в него, так называемый, фактор эффективностидлины в случае анизотропного нанонаполнителя существенно меньше (на несколькопорядков) рассчитанного теоретически для углеродных нанотрубок, что особенно очевид-но выражено в случае нанокомпозитов с эластомерной матрицей.В качестве вывода укажем, что модуль упругости компонент нанокомпозита являетсясильной функцией их фазового состояния, а определение реальных характеристик этихкомпонент позволяет корректное применение простого правила смесей.       ЛИТЕРАТУРА1. Moniruzzaman M., Winey K.I. Polymer nanocomposites containing carbon nanotubes // Macromolecules,2006, v. 39(16), p. 5194. DOI: https://doi.org/10.1021/ma060733p2. Schaefer D. W., Justice R. S. How nano are nanocomposites? // Macromolecules, 2007, v. 40(24), p. 8501.DOI: https://doi.org10.1021/ma070326w3. Coleman J. N., Cadek M., Ryan K. P., Fonseca A., Nady J. B., Blau W. J., Ferreira M. S. Reinforcement ofpolymers with carbon nanotubes. The role of an ordered polymer intwrfacial region. Experimental andmodeling // Polymer, 2006, v. 47(23), pp. 8556–8561. DOI: https://doi.org/10/1016/j.polymer.2006.10.0144. Kozlov G. V., Yanovskii Yu. G., Zaikov G. E. Particulate-Filled Polymer Nanocomposites. Structure,Properties, Perspectives. New York, Nova Science Publishers, Inc., 2014. DOI: https://doi.org/10.1002/9783527644346.ch35. Mikitaev A. K., Kozlov G. V., Zaikov G. E. Polymer Nanocomposites: Variety of Structural Forms and Applications.New York, Nova Science Publishers, Inc., 2008.6. Jeong W., Kessler M.R. Toughness enhancement in ROMP functionalized carbon nanotube/polydicyclopentadienecomposites. Chem. Mater., 2008. v. 20(22), р. 7060. DOI: https://doi.org/10.1021/cm80209477. Koerner H., Liu W., Alexander M., Mirau P., Dowty H., Vaia R. A. Deformation – morphology correlationsin electrically conductive carbon nanotube – thermoplastic polyurethane nanocomposites // Polymer, 2005, v. 46(12), р. 4405. DOI: https://doi.org/10.1016/j.polymer.2005.02.0258. Ahmed S., Jones F. R. A review of particulate reinforcement theories of polymer composites // J.Mater. Sci., 1990, v. 25(12), pp. 4933–4942. DOI: https://doi.org/10.1007/bf005801109. Aygubova A. Ch., Kozlov G. V., Magomedov G. M., Zaikov G. E. The elastic modulus of carbon nanotubeaggregates in polymer nanocomposites. J. Characterization and Development of Novel Mater., 2016, v. 8(3), p. 227.10. Khan U., May P., O’Neill A., Bell A.P., Boussac E., Martin A., Semple J., Coleman J. N. Polymer reinforcementusing liquid-exfoliated boron nitride nanosheets // Nanoscale, 2013, v. 5(3), pp. 581-587. DOI: https://doi.org/10.1039/c2nr33049k


Author(s):  
Hideo Hayashi ◽  
Yoshikazu Hirai ◽  
John T. Penniston

Spectrin is a membrane associated protein most of which properties have been tentatively elucidated. A main role of the protein has been assumed to give a supporting structure to inside of the membrane. As reported previously, however, the isolated spectrin molecule underwent self assemble to form such as fibrous, meshwork, dispersed or aggregated arrangements depending upon the buffer suspended and was suggested to play an active role in the membrane conformational changes. In this study, the role of spectrin and actin was examined in terms of the molecular arrangements on the erythrocyte membrane surface with correlation to the functional states of the ghosts.Human erythrocyte ghosts were prepared from either freshly drawn or stocked bank blood by the method of Dodge et al with a slight modification as described before. Anti-spectrin antibody was raised against rabbit by injection of purified spectrin and partially purified.


2020 ◽  
Vol 48 (2) ◽  
pp. 429-439 ◽  
Author(s):  
Jorge Gago ◽  
Danilo M. Daloso ◽  
Marc Carriquí ◽  
Miquel Nadal ◽  
Melanie Morales ◽  
...  

Besides stomata, the photosynthetic CO2 pathway also involves the transport of CO2 from the sub-stomatal air spaces inside to the carboxylation sites in the chloroplast stroma, where Rubisco is located. This pathway is far to be a simple and direct way, formed by series of consecutive barriers that the CO2 should cross to be finally assimilated in photosynthesis, known as the mesophyll conductance (gm). Therefore, the gm reflects the pathway through different air, water and biophysical barriers within the leaf tissues and cell structures. Currently, it is known that gm can impose the same level of limitation (or even higher depending of the conditions) to photosynthesis than the wider known stomata or biochemistry. In this mini-review, we are focused on each of the gm determinants to summarize the current knowledge on the mechanisms driving gm from anatomical to metabolic and biochemical perspectives. Special attention deserve the latest studies demonstrating the importance of the molecular mechanisms driving anatomical traits as cell wall and the chloroplast surface exposed to the mesophyll airspaces (Sc/S) that significantly constrain gm. However, even considering these recent discoveries, still is poorly understood the mechanisms about signaling pathways linking the environment a/biotic stressors with gm responses. Thus, considering the main role of gm as a major driver of the CO2 availability at the carboxylation sites, future studies into these aspects will help us to understand photosynthesis responses in a global change framework.


2018 ◽  
Vol 5 (1) ◽  
pp. 93-115
Author(s):  
Miloš Stamenković

SummarySports photography undoubtedly has a significant place in sports press and publicism. It’s main and primary role is to present sports to the readers as art, which it is. Sport is characterized by dynamic and varied movements, and the main role of sports photography is reflected in the fact that it is in this way that sport shows its essence. Having in mind that photography tells more than a thousand words it sends a clear message to the reader as well to people who are informed about events via sports portals. Sports photography is a multidimensional art for many reasons. When we say “multi”, it primarily refers to a wider range that sports photography has to offer, which means sports photography is not only directed at presenting athletes on the move and the main actors who contribute to achieving the results by their engagement – it also has the role of sports “psychophotography” which is an analysis and capture of the emotional reaction of an athlete after winning or losing from the opposing team.


2020 ◽  
Vol 26 (6) ◽  
pp. 1283-1296
Author(s):  
K.A. Omarieva ◽  
P.G. Isaeva

Subject. The article addresses problems and prospects for the banking supervision development in the Russian Federation under modern conditions. Objectives. We review the essence and methods of organization of the banking supervision, and identify the main problems and prospects for its development. Methods. To provide valid, reliable and reasoned recommendations, we apply normative and integrated approaches to the study of the banking supervision effectiveness in the current circumstances. Results. The paper investigates main problems and development prospects for the Russian banking supervision. The essential importance of supervision comes from the main role of the banking system in maintaining accounts of economic entities and making settlements. Even minor failures or delays in operations can lead to negative outcomes and disastrous consequences for the entire monetary system and the national economy. Therefore, we highlight issues that require attention, and make proposals for further development of the banking supervision. Conclusions. In the context of dynamically developing economy, the banking practice is becoming more complex. As a result, there is a need for new financial instruments that can reduce risks, increase the speed and efficiency of operations and document flow, and help achieve the world levels of introduced standards.


Author(s):  
Shamim Mushtaq

Uninhibited proliferation and abnormal cell cycle regulation are the hallmarks of cancer. The main role of cyclin dependent kinases is to regulate the cell cycle and cell proliferation. These protein kinases are frequently down regulated or up regulated in various cancers. Two CDK family members, CDK 11 and 12, have contradicting views about their roles in different cancers. For example, one study suggests that the CDK 11 isoforms, p58, inhibits growth of breast cancer whereas, the CDK 11 isoform, p110, is highly expressed in breast tumor. Studies regarding CDK 12 show variation of opinion towards different parts of the body, however there is a consensus that upregulation of cdk12 increases the risk of breast cancer. Hence, CDK 11 and CDK 12 need to be analyzed to confirm their mechanism and their role regarding therapeutics, prognostic value, and ethnicity in cancer. This article gives an outline on both CDKs of information known up to date from Medline, PubMed, Google Scholar and Web of Science search engines, which were explored and thirty relevant researches were finalized.


2020 ◽  
Vol 20 ◽  
Author(s):  
Qionghui Wu ◽  
Haidong Wei ◽  
Wenbo Meng ◽  
Xiaodong Xie ◽  
Zhenchang Zhang ◽  
...  

: Annexin, a calcium-dependent phospholipid binding protein, can affect tumor cell adhesion, proliferation, apoptosis, invasion and metastasis, as well as tumor neovascularization in different ways. Recent studies have shown that annexin exists not only as an intracellular protein in tumor cells, but also in different ways to be secret outside the cell as a “crosstalk” tool for tumor cells and tumor microenvironment, thus playing an important role in the development of tumors, such as participating in epithelial-mesenchymal transition, regulating immune cell behavior, promoting neovascularization and so on. The mechanism of annexin secretion in the form of extracellular vesicles and its specific role is still unclear. This paper summarizes the main role of annexin secreted into the extracellular space in the form of extracellular vesicles in tumorigenesis and drug resistance and analyzes its possible mechanism.


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