Performance and structure changes of the aromaticco-polysulfonamide fibers during thermal-oxidative aging process

2016 ◽  
Vol 133 (41) ◽  
Author(s):  
Jinchao Yu ◽  
Kang Chen ◽  
Xiaoyun Li ◽  
Feng Tian ◽  
Shenghui Chen ◽  
...  
Keyword(s):  
Aging Process ◽  
Oxidative Aging ◽  
Structure Changes ◽  
Thermal Oxidative Aging

scholarly journals How Small Molecules Affect the Thermo-Oxidative Aging Mechanism of Polypropylene: A Reactive Molecular Dynamics Study

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1243
Author(s):  
Fan Zhang ◽  
Yufei Cao ◽  
Xuan Liu ◽  
Huan Xu ◽  
Diannan Lu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Acetic Acid ◽  
Small Molecules ◽  
Aging Process ◽  
Experimental Studies ◽  
Hydroxyl Group ◽  
Oxidative Aging ◽  
Reactive Molecular Dynamics ◽  
Aging Mechanism ◽  
Effects Of Temperature

Understanding the aging mechanism of polypropylene (PP) is fundamental for the fabrication and application of PP-based materials. In this paper, we present our study in which we first used reactive molecular dynamics (RMD) simulations to explore the thermo-oxidative aging of PP in the presence of acetic acid or acetone. We studied the effects of temperature and oxygen on the aging process and discussed the formation pathways of typical small molecule products (H2, CO, CO2, CH4, C2H4, and C2H6). The effect of two infection agents, acetic acid and acetone, on the aging reaction was analyzed emphatically. The simulation results showed that acetone has a weak impact on accelerating the aging process, while acetic acid has a significant effect, consistent with previous experimental studies. By tracking the simulation trajectories, both acetic acid and acetone produced small active free radicals to further react with other fragment products, thus accelerating the aging process. The first reaction step of acetic acid is often the shedding of the H atom on the hydroxyl group, while the reaction of acetone is often the shedding of the H atom or the methyl. The latter requires higher energy at lower temperatures. This is why the acceleration effect of acetone for the thermo-oxidative aging of PP was not so significant compared to acetic acid in the experimental temperature (383.15 K).

EV Systems for NR. II. Further Development of Curing Systems and Vulcanizate Properties

1969 ◽  
Vol 42 (2) ◽  
pp. 418-440 ◽  
Author(s):  
R. M. Russell ◽  
T. D. Skinner ◽  
A. A. Watson
Keyword(s):  
Thermal Stability ◽  
Zinc Oxide ◽  
Fatigue Cracking ◽  
Oxide System ◽  
Oxidative Aging ◽  
Thermal Oxidative Aging ◽  
Further Development ◽  
Resistance To Heat ◽  
Thermal Stability Of ◽  
Simple Network

Abstract It was shown in Part I that the use of EV systems in NR provides a simple network in which the crosslinks are mainly monosulfidic. Part II describes in some detail the properties of vulcanizates obtained by the use of EV systems and their relationship to conventional and TMTD-zinc oxide cured vulcanizates. The disadvantages of short scorch time and heavy bloom which accompany the TMTD-zinc oxide system are overcome by the new EV systems. The monosulfidic network obtained by the use of EV systems confers on NR good overall physical properties together with much improved resistance towards thermal and thermal oxidative aging. The thermal stability of this type of network is reflected in the outstanding resistance of the vulcanizates to set and reversion, and their good resistance to heat build-up under dynamic conditions. Vulcanizates derived from EV systems have increased resistance to thermal oxidative aging due to the inherent thermal stability of the networks and good response to antioxidant protection. This increased resistance results in much better retention of tensile properties, tear resistance and fatigue cracking resistance on aging, relative to that of conventionally cured vulcanizates.

scholarly journals Analytical and Chemometric Characterization of Fino and Amontillado Sherries during Aging in Criaderas y Solera System

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 365
Author(s):  
Manuel J. Valcárcel-Muñoz ◽  
María Guerrero-Chanivet ◽  
María del Carmen Rodríguez-Dodero ◽  
María de Valme García-Moreno ◽  
Dominico A. Guillén-Sánchez
Keyword(s):  
Aging Process ◽  
Hierarchical Cluster ◽  
Biological Aging ◽  
Microbiological Activity ◽  
Dry Extract ◽  
Oxidative Aging ◽  
Physical Chemical ◽  
Sherry Wine ◽  
Flor Yeasts

Fino and Amontillado are Sherry wines, produced in Marco de Jerez area (southern Spain), and aged in Criaderas y Solera system. Fino Sherry wine follows a biological aging process, under a veil of flor yeasts, while Amontillado Sherry wine shares the same biological aging firstly, followed by oxidative aging, which gives them special features. Organic acids, esters, higher alcohols, phenolic compounds and total dry extract of Sherries evolve during aging due to evaporation processes, physical-chemical reactions, wood contributions and microbiological activity. During aging, Sherry wines improve their organoleptic profile, as could be proved in the tasting sessions. Hierarchical Cluster Analysis and Factor Analysis with factor extraction using Principal Components of Sherry wines studied were carried out and natural groupings of the wines according to the type of aging and their age were observed. A strong correlation between the parameters analyzed and the aging of each wine has been seen in the Multiple Linear Regression studies, establishing two different models, one for each type of Sherry wine, that, with only four of all the variables studied estimated the wine age with more than 99% of confidence. This constitutes a useful tool to control the age of these Sherry wines in the winery.

Effects of thermal cycling on phenylethynyl-terminated PMDA-type asymmetric polyimide composites

2018 ◽  
Vol 31 (7) ◽  
pp. 861-871
Author(s):  
Yixiang Zhang ◽  
Masahiko Miyauchi ◽  
Steven Nutt
Keyword(s):  
Thermal Cycling ◽  
Mechanical Degradation ◽  
Thermal Cycles ◽  
Oxidative Aging ◽  
Short Beam ◽  
Beam Shear ◽  
Thermally Driven ◽  
The Matrix ◽  
Service Environments ◽  
Thermal Oxidative Aging

The effects of thermal cycling on a polymerized monomeric reactant (PMR) type polyimide (TriA X) reinforced with carbon fibers were investigated. Composite specimens were subjected to 2000 thermal cycles between −54°C and 232°C. At 400-cycle intervals, laminates were inspected for microcracks, and glass transition temperature ( T g) and short-beam shear (SBS) strength were measured. The composites did not exhibit microcracks after thermal cycling, although after 2000 thermal cycles, mechanical properties of the matrix declined slightly. The matrix degradation decreased the resistance to microcracking upon further loading. No effects of thermal oxidative aging were observed from thermal cycling, and thermally driven fatigue and creep were identified as the primary and secondary factors inducing mechanical degradation of the matrix. T g of the composites exhibited no change after 2000 cycles, while the SBS strength decreased slightly (3–9%). The results highlight the potential for use of TriA X composites as long-term structural components in high-temperature service environments.

scholarly journals Wine Aging Technology: Fundamental Role of Wood Barrels

Foods ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1160
Author(s):  
Maria Carpena ◽  
Antia G. Pereira ◽  
Miguel A. Prieto ◽  
Jesus Simal-Gandara
Keyword(s):  
Aging Process ◽  
Storage Time ◽  
Economic Implications ◽  
Oxidative Aging ◽  
General Terms ◽  
Two Phases ◽  
Light Bottle ◽  
Wine Aging ◽  
The Eu

The aging of wines is a process used to preserve wine but also to enhance its properties. It is a process of great interest, mainly because of the additional properties it adds to wines and because of its economic implications. Historically, barrels have been employed for centuries for preserving and aging wine due to their resistance and relative impermeability. In general terms, the wine aging process can be divided into two phases: oxidative and reductive aging. Oxidative aging traditionally takes place in barrels while reductive phase occurs in the bottle. During both processes, oxygen plays a fundamental role as well as other factors, for instance: temperature, light, bottle position, microbial growth or storage time. Likewise, during the aging process, a series of chemical reactions take place influencing the composition and organoleptic profile of wine. At this point, oxidative aging in barrels is a fundamental step. Barrels are directly involved in the produced changes on wine’s composition due to the transference of oxygen and phenolic and aromatic compounds from wood to wine. This way, barrels act as an active vessel capable of releasing compounds that affect and improve wine’s characteristics. Regarding, the importance of barrels during aging process, some attention must be given to the species most used in cooperage. These species are conventionally oak species, either French or American. However, other non-conventional species are currently being studied as possible wood sources for the production of wines, such as chestnut robinia or other oak species. In the last decades, new approaches have been developed for barrel aging to find new alternatives more suitable, affordable and feasible to sanitize the process, such as other materials different from wood or the use of wood chips, which is regulated since 2006 by the EU. However, even though some of them have shown promising data, barrels are currently the most used technology for the oxidative stage of table wines aging.

scholarly journals Thermal Degradation Studies of a Polyurethane Propellant Binder

2000 ◽  
Vol 73 (4) ◽  
pp. 678-693 ◽  
Author(s):  
M. Celina ◽  
A. C. Graham ◽  
K. T. Gillen ◽  
R. A. Assink ◽  
L. M. Minier
Keyword(s):  
Tensile Elongation ◽  
Polymer Network ◽  
Nmr Relaxation ◽  
Oxidative Aging ◽  
Oxidation Rates ◽  
Highly Sensitive ◽  
Arrhenius Diagram ◽  
Network Properties ◽  
Dominant Process ◽  
Thermal Oxidative Aging

Abstract The thermal oxidative aging of a crosslinked hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) based polyurethane rubber, used as a polymeric binder in solid propellant grain, was investigated at temperatures from 25 to 125 °C. The changes in tensile elongation, polymer network properties and chain dynamics, mechanical hardening and density were determined with a range of techniques including modulus profiling, solvent swelling, NMR relaxation and O2 permeability measurements. We critically evaluated the Arrhenius methodology that is commonly used with a linear extrapolation of high temperature aging data using extensive data superposition and highly sensitive oxygen consumption experiments. The effects of other constituents in the propellant formulation on aging were also investigated. We conclude that crosslinking is the dominant process at higher temperatures and that the degradation involves only limited hardening in the bulk of the material. Significant curvature in the Arrhenius diagram of the oxidation rates was observed. This is similar to results for other rubber materials.

Thermal-oxidative aging behavior of nitrile-butadiene rubber/functional LDHs composites

2016 ◽  
Vol 133 ◽  
pp. 219-226 ◽  
Author(s):  
Xianru He ◽  
Tianxiang Li ◽  
Zhengren Shi ◽  
Xin Wang ◽  
Fei Xue ◽  
...  
Keyword(s):  
Butadiene Rubber ◽  
Aging Behavior ◽  
Oxidative Aging ◽  
Nitrile Butadiene Rubber ◽  
Thermal Oxidative Aging

Micro-Mechanical Model for Thermo-Oxidative Aging of Elastomers

2018 ◽  
Author(s):  
Hamid Mohammadi ◽  
Roozbeh Dargazany
Keyword(s):  
Mechanical Model ◽  
Strain Energy ◽  
Aging Process ◽  
Polymer Chains ◽  
Constitutive Behavior ◽  
Network Decomposition ◽  
Oxidative Aging ◽  
The One ◽  
Micro Sphere ◽  
Good Agreement

In this study, a micro-mechanical model for constitutive behavior of elastomers subjected to thermo-oxidative aging is proposed. The model is based on the network decomposition concept and lies within the framework of continuum mechanics. It is assumed that the aging process leads to the formation of a new network with tighter chains. Accordingly, the strain energy of the system is constituted of two independent sources, the energy of the original soft network and the one of the reformed network. These strain energies were computed by integration of entropic energy of polymer chains in each direction of a micro-sphere. The model demonstrates good agreement with different experimental data on relaxation and intermittent tests.

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