scholarly journals Rheology in the Presence of Carbon Dioxide (CO2) to Study the Melt Behavior of Chemically Modified Polylactide (PLA)

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1108
Author(s):  
Dominik Dörr ◽  
Tobias Standau ◽  
Svenja Murillo Castellón ◽  
Christian Bonten ◽  
Volker Altstädt
Keyword(s):  
Carbon Dioxide ◽  
Molecular Weight ◽  
Reactive Extrusion ◽  
Elevated Pressure ◽  
Organic Peroxide ◽  
Recrystallization Temperature ◽  
Chemical Modifier ◽  
Rheological Measurements ◽  
Blowing Agent ◽  
Carbon Dioxide Co2

For the preparation of polylactide (PLA)-based foams, it is commonly necessary to increase the melt strength of the polymer. Additives such as chain extenders (CE) or peroxides are often used to build up the molecular weight by branching or even crosslinking during reactive extrusion. Furthermore, a blowing agent with a low molecular weight, such as carbon dioxide (CO2), is introduced in the foaming process, which might affect the reactivity during extrusion. Offline rheological tests can help to measure and better understand the kinetics of the reaction, especially the reaction between the polymer and the chemical modifier. However, rheological measurements are mostly done in an inert nitrogen atmosphere without an equivalent gas loading of the polymer melt, like during the corresponding reactive extrusion process. Therefore, the influence of the blowing agent itself is not considered within these standard rheological measurements. Thus, in this study, a rheometer equipped with a pressure cell is used to conduct rheological measurements of neat and chemical-modified polymers in the presence of CO2 at pressures up to 40 bar. The specific effects of CO2 at elevated pressure on the reactivity between the polymer and the chemical modifiers (an organic peroxide and as second choice, an epoxy-based CE) were investigated and compared. It could be shown in the rheological experiments that the reactivity of the chain extender is reduced in the presence of CO2, while the peroxide is less affected. Finally, it was possible to detect the recrystallization temperature Trc of the unmodified and unbranched sample by the torque maximum in the rheometer, representing the tear off of the stamp from the sample. Trc was about 13 K lower in the CO2-loaded sample. Furthermore, it was possible to detect the influences of branching and gas loading simultaneously. Here the influence of the branching on Trc was much higher in comparison to a gas loading.

Autoclave foaming of chemically modified polylactide

2016 ◽  
Vol 53 (5) ◽  
pp. 481-489 ◽  
Author(s):  
Tobias Standau ◽  
Svenja Goettermann ◽  
Sandra Weinmann ◽  
Christian Bonten ◽  
Volker Altstädt
Keyword(s):  
Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Reactive Extrusion ◽  
Organic Peroxide ◽  
Chain Extension ◽  
Production Volume ◽  
Chemically Modified ◽  
Foaming Process ◽  
Viscosity Increase ◽  
Almost All

Polylactide has emerged as one of the most promising biopolymers due to its good mechanical properties, as reflected by the continual increase in its production volume per year. However, one of the main drawbacks of polylactide is its low melt strength, which is disadvantageous in terms of foaming. To overcome this issue, in this study, several chemical modifiers that induce crosslinking, chain extension or grafting were incorporated by reactive extrusion, which greatly affected the foaming process by increasing the molecular weight and thereby the melt properties of polylactide. By means of gel permeation chromatography, an increase in the molecular weight was observed in the modified polylactides. Elongational viscosity measurements indicate a dramatic viscosity increase for polylactide modified with a multifunctional epoxide and an organic peroxide. With pressure-induced batch foaming, almost all modifications, with the exception of styrene maleic anhydride, led to a decrease in foam density compared to the neat polylactide.

PERANCANGAN PROTEKSI KEBAKARAN OTOMATIS PADA KAPAL BERBASIS ARDUINO

2018 ◽  
Vol 1 (2) ◽  
pp. 1-8
Author(s):  
Dody Hidayat
Keyword(s):  
Carbon Dioxide ◽  
Fire Extinguisher ◽  
Carbon Dioxide Co2

Kebakaran dapat terjadi dimana saja salah satunya dapat terjadi di alat transportasi air yakni kapal. Kebakaran selalu menyebabkan hal-hal yang tidak diinginkan baik kerugian material maupun ancaman keselamatan jiwa manusia. Seiring dari kejadian tersebut musibah kecelakaan kapal yang disebabkan oleh bahaya kebakaran sangatlah mungkin terjadi. Salah satu yang dapat mencegah kejadian kebakaran pada kapal haruslah dapat mendeteksi dini kebakaran tersebut. Untuk mendeteksi dini terjadinya kebakaran dikapal maka dirancanglah sebuah alat proteksi kebakaran otomatisberbasis adruino. Dimana Arduino merupakan board yang memiliki sebuah mikrokontroller sebagai  otak kendali sistem. Sistem otomatisasi atau controller tidak akan terlepas dengan apa yang disebut  dengan ‘sensor’. Sensor adalah sebuah alat untuk mendeteksi atau mengukut sesuatu yang digunakan untuk mengubah variasi mekanis, magnetis, panas, sinar dan kimia menjadi tegangan dan arus listrik. sistem yang dirancang ini dilengkapi dengan beberapa sensor diantaranya adalah sensor apiUV-Tron R2868, sensor asap MQ-2 dan kemudian sensor suhuDS18B20. Mikrokontroller sebagai pengendali akan merespon input yang berupa sensor tersebut ketika data yang dibaca oleh sensor mendeteksikebakaran diantaranya mendeteksi adanya asap, kemudian api dan suhu. Sebagai output dari sistem berupa racun api (fire extinguisher)dimana kandungan yang ada pada racun api tersebut berupa Dry Chemical Powder dan Carbon Dioxide (CO2) yang fungsinya digunakan untuk memadamkan api serta dilengkapi buzzer sebagai alarm peringatan jika terjadi kebakaran. 

The Prenatal Development Effects of Carbon Dioxide (CO2) Exposure in Rats (Rattus Norvegicus)

2012 ◽  
Author(s):  
William R. Howard ◽  
Brian Wong ◽  
Michelle Okolica ◽  
Kimberly S. Bynum ◽  
R. A. James
Keyword(s):  
Carbon Dioxide ◽  
Rattus Norvegicus ◽  
Prenatal Development ◽  
Carbon Dioxide Co2

Physiology of Intraluminal Administration of Carbon Dioxide as a Contrast Medium

2020 ◽  
Vol 25 (44) ◽  
pp. 4656-4661 ◽  
Author(s):  
Nikolaos Patelis ◽  
Mikes Doulaptsis ◽  
Stylianos Kykalos ◽  
Eleftherios Spartalis ◽  
Anastasios Maskanakis ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Contrast Agent ◽  
20Th Century ◽  
English Literature ◽  
Human Organism ◽  
Digital Subtraction ◽  
Extensive Search ◽  
Iodinated Contrast ◽  
Iodinated Contrast Agent ◽  
Carbon Dioxide Co2

Background: Carbon dioxide (CO2) exists in nature around us. In the middle of the 20th century, the intraluminal injection of CO2 demonstrated similar results to those of Digital Subtraction Angiography (DSA) with an iodinated contrast agent (ICA). Since then, the technology behind CO2 DSA has developed significantly. Objective: The aim of this study is to inform physicians about the unique properties of CO2 and its physiology after intraluminal injection. Methods: An extensive search for English literature on the properties of CO2 and the physiology of intraluminal administration was conducted using Pubmed. Results: There is sufficient literature on the properties of CO2 and the physiology of CO2 DSA. A review of this literature explains what happens to the human organism after the injection of CO2. Conclusions: There is enough evidence that CO2 DSA is both effective, diagnostic and safe, but the properties of CO2 should be taken under consideration as complications occur, although rarely.

scholarly journals Carbon Dioxide Laser Vulvovaginal Rejuvenation: A Systematic Review

Cosmetics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 56
Author(s):  
Tassahil Messas ◽  
Achraf Messas ◽  
George Kroumpouzos
Keyword(s):  
Carbon Dioxide ◽  
Systematic Review ◽  
Laser Therapy ◽  
Carbon Dioxide Laser ◽  
Invasive Treatment ◽  
Erbium:Yag Laser ◽  
Non Invasive ◽  
Level I ◽  
Carbon Dioxide Co2

Genitourinary syndrome of menopause (GSM) causes significant symptomatic aggravation that affects the quality of life (QoL). Vulvovaginal atrophy (VVA), the hallmark of GSM, is managed with topical non-hormonal therapy, including moisturizers and lubricants, and topical estrogen application. Patients not responding/being unsatisfied with previous local estrogen therapies are candidates for a noninvasive modality. Carbon dioxide (CO2) laser therapy, especially the fractionated type (FrCO2), has drawn considerable attention over the past two decades as a non-invasive treatment for GSM. This systematic review describes the accumulated evidence from 40 FrCO2 laser studies (3466 participants) in GSM/VVA. MEDLINE, Scopus and Cochrane databases were searched through April 2021. We analyze the effects of FrCO2 laser therapy on symptoms, sexual function, and QoL of patients with GSM/VVA. As shown in this review, FrCO2 laser therapy for GSM shows good efficacy and safety. This modality has the potential to advance female sexual wellness. Patient satisfaction was high in the studies included in this systematic review. However, there is a lack of level I evidence, and more randomized sham-controlled trials are required. Furthermore, several clinical questions, such as the number of sessions required that determine cost-effectiveness, should be addressed. Also, whether FrCO2 laser therapy may exert a synergistic effect with systemic and/or local hormonal/non-hormonal treatments, energy-based devices, and other modalities to treat GMS requires further investigation. Lastly, studies are required to compare FrCO2 laser therapy with other energy-based devices such as erbium:YAG laser and radiofrequency.

scholarly journals Unveiling Carbon Dioxide and Ethanol Diffusion in Carbonated Water-Ethanol Mixtures by Molecular Dynamics Simulations

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1711
Author(s):  
Mohamed Ahmed Khaireh ◽  
Marie Angot ◽  
Clara Cilindre ◽  
Gérard Liger-Belair ◽  
David A. Bonhommeau
Keyword(s):  
Carbon Dioxide ◽  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Hydrodynamic Radius ◽  
Md Simulations ◽  
Molecular Models ◽  
Experimental Values ◽  
Carbon Dioxide Co2 ◽  
Dynamics Simulations ◽  
Apparent Disagreement

The diffusion of carbon dioxide (CO2) and ethanol (EtOH) is a fundamental transport process behind the formation and growth of CO2 bubbles in sparkling beverages and the release of organoleptic compounds at the liquid free surface. In the present study, CO2 and EtOH diffusion coefficients are computed from molecular dynamics (MD) simulations and compared with experimental values derived from the Stokes-Einstein (SE) relation on the basis of viscometry experiments and hydrodynamic radii deduced from former nuclear magnetic resonance (NMR) measurements. These diffusion coefficients steadily increase with temperature and decrease as the concentration of ethanol rises. The agreement between theory and experiment is suitable for CO2. Theoretical EtOH diffusion coefficients tend to overestimate slightly experimental values, although the agreement can be improved by changing the hydrodynamic radius used to evaluate experimental diffusion coefficients. This apparent disagreement should not rely on limitations of the MD simulations nor on the approximations made to evaluate theoretical diffusion coefficients. Improvement of the molecular models, as well as additional NMR measurements on sparkling beverages at several temperatures and ethanol concentrations, would help solve this issue.

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