M. Celina's research while affiliated with Sandia National Laboratories and other places
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Publications (109)
The use of self‐assembling, pre‐polymer materials in 3D printing is rare, due to difficulties of facilitating printing with low molecular weight species and preserving their reactivity and/or functions on the macroscale. Akin to 3D printing of small molecules, examples of extrusion‐based printing of pre‐polymer thermosets are uncommon, arising from...
Previous observation of EPDM and FEPM materials aged in thermo-oxidative and thermo-oxidative plus hydrolytic environments revealed an unusual trend: the degradation and disintegration of these polymers in the former case but the ability to maintain mechanical performance and shape in the latter [1]. No abnormalities were observed in the chemical (...
Physical stress relaxation in rubbery, thermoset polymers is limited by cross-links, which impede segmental motion and restrict relaxation to network defects, such as chain ends. In parallel, the cure shrinkage associated with thermoset polymerizations leads to the development of internal residual stress that cannot be effectively relaxed. Recent s...
When diethanolamine (DEA) is used as a curative for a DGEBA epoxy, a rapid “adduct-forming” reaction of epoxide with the secondary amine of DEA is followed by a slow “gelation” reaction of epoxide with hydroxyl and with other epoxide. Through an extensive review of previous investigations of simpler, but chemically similar, reactions, it is deduced...
Elastomers are often degraded when exposed to air or high humidity for extended time periods (years to decades). Lifetime estimates normally involve extrapolating accelerated aging results made at higher than ambient environments. Several potential problems associated with such studies are reviewed and experimental/theoretical methods to address th...
Elastomers are often degraded when exposed to air or high humidity for extended time periods (years to decades). Lifetime estimates normally involve extrapolating accelerated aging results made at higher than ambient environments. Several potential problems associated with such studies are reviewed and experimental/theoretical methods to address th...
We report a new assay for breakdown of high molecular weight, insoluble lignin based on lignin films. In this method, decrease in film thickness is detected upon solubilization of mass through either chemical alteration of the lignin or molecular weight reduction. The assay was performed with organosolv lignin, the only chemical modification being...
The degradation in electrical contact resistance of a contact pair sliding while submerged in silicone fluid has been investigated. While the contamination of electrical contacts by silicone vapors or migrating species at elevated temperature due to decomposition in electric arcs is well known, the present degradation mechanism appears to arise fro...
Elastomers are often degraded when exposed to air or high humidity for extended times (years to decades). Lifetime estimates normally involve extrapolating accelerated aging results made at higher than ambient environments. Several potential problems associated with such studies are reviewed, and experimental and theoretical methods to address them...
A cyanate ester resin mixture with at least one cyanate ester resin, an isocyanate foaming resin, other co-curatives such as polyol or epoxy compounds, a surfactant, and a catalyst/water can react to form a foaming resin that can be cured at a temperature greater than 50° C. to form a cyanate ester foam. The cyanate ester foam can be heated to a te...
All polymers are intrinsically susceptible to oxidation, which is the underlying process for thermally driven materials degradation and of concern in various applications. There are many approaches for predicting oxidative polymer degradation. Aging studies usually are meant to accelerate oxidation chemistry for predictive purposes. Kinetic models...
Ageing of elastomeric materials is an important subject in product development concerning lifetime prediction. Because of environmental influences like temperature, oxygen, radiation and similar conditions rubber and elastomers will change their material properties and hence affect the lifetime. The reason for this material change is the modificati...
Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. In fire environments, foams, such as polyurethanes and epoxies, can liquefy and flow during thermal decomposition, and evolved gases can cause pressurization and failure of sealed containers. In systems safety and hazard analyses, heat transfer an...
More confident lifetime prediction of the performance of polymeric materials requires a better understanding of how temperature may not only accelerate aging but also introduce mechanistic variation in the degradation process itself. Such effects may occur in any high stress level environments that contain a thermal reaction component, i.e., therma...
The thermal oxidation of hydroxy telechelic polybutadiene stabilised with 2,2′-methylene-bis(4-methyl-6-tert-butylphenol) was studied at 100°C using weight changes and stabiliser quantification by liquid chromatography. The extended induction time relative to the unstabilised sample and the initial rate of stabiliser depletion were found to be prop...
The Wear-out approach for lifetime prediction, based on cumulative damage concepts, is applied to several ethylene propylene rubber (EPR) cable insulation materials. EPR materials typically follow “induction-time” behavior in which their material properties change very slowly until just before failure, precluding the use of such time-dependent prop...
Chemiluminescence (CL) has been applied as a condition monitoring technique to assess aging related changes in a hydroxyl-terminated-polybutadiene based polyurethane elastomer. Initial thermal aging of this polymer was conducted between 110 and 50 °C. Two CL methods were applied to examine the degradative changes that had occurred in these aged sam...
Long-term accelerated aging studies (up to 7 years of aging) were conducted on four typical EPR materials used as cable insulation in nuclear power plant safety applications with the goal of establishing lifetime estimates at typical aging conditions of ∼50 °C. The four materials showed slow to moderate changes in mechanical properties (tensile elo...
Thermal degradation studies of a stabilized HTPB based elastomer were conducted at temperatures from 50°C to 110°C. The concentration of extractable antioxidant (AO2246) in the polymer was quantified via AO extraction and a gas chromatography-based method using internal standards. The decrease in extractable AO levels as a function of time and temp...
Poly(vinylidene fluoride) and copolymers of vinylidene fluoride with hexafluoropropylene, trifluoroethylene and chlorotrifluoroethylene have been exposed to gamma irradiation in vacuum, up to doses of 1MGy under identical conditions, to obtain a ranking of radiation sensitivities. Changes in the tensile properties, crystalline melting points, heats...
Lifetime prediction of polymeric materials often requires extrapolation of accelerated aging data with the suitability and confidence in such approaches being subject to ongoing discussions. This paper reviews the evidence of non-Arrhenius behaviour (curvature) instead of linear extrapolations in polymer degradation studies. Several studies have em...
Relaxation nuclear magnetic resonance imaging (R-NMRI) was employed to investigate the effects of thermooxidative aging in a hydroxy-terminated polybutadiene (HTPB)-based elastomer. A series of three-dimensional (3D) Hahn-echo-weighted single-point images (SPI) of the elastomer were utilized to generate a 3D parameter map of the aged material. NMR...
Polymer degradation has been explored on the basis of synergistic infectious and inhibitive interaction between separate materials. A dual stage chemiluminescence detection system with individually controlled hot stages was applied to probe for interaction effects during polymer degradation in an oxidizing environment. Experimental confirmation was...
Smart polymeric materials, such as piezoelectric polymers which deform by application of an electric field, are of interest for use in controllable mirrors as large, lightweight space optics. An important consideration when using any organic material in a space application is their extreme vulnerability to the space environment. In LEO the presence...
Oxygen permeability data, vital parameters for understanding and modeling the thermooxidative degradation of polymers, have been determined for various elastomers. Using a novel experimental setup, oxygen permeability through sheet materials was measured for elevated temperatures up to 225 °C. Under these conditions oxygen can react with the polyme...
A novel dual stage chemiluminescence detection system incorporating individually controlled hot stages has been developed and applied to probe for material interaction effects during polymer degradation. Utilization of this system has resulted in experimental confirmation for the first time that in an oxidizing environment a degrading polymer A (in...
An aged polybutadiene-based elastomer was reacted with trifluoroacetic anhydride (TFAA) and subsequently analyzed via 19F NMR spectroscopy. Derivatization between the TFAA and hydroxyl functionalities produced during thermo-oxidative aging was achieved, resulting in the formation of trifluoroester groups on the polymer. Primary and secondary alcoho...
The optimization of piezo-electric PVDF polymers for adaptive optics in space environments was discussed. The fundamental correlation between chemical and physical features of various PVDF copolymers and piezoelectric properties was analyzed. Using LEO solar ultraviolet data, total UV energy depositions were estimated as equivalent radiation doses...
Predicting polymer lifetimes in air is often based on unconfirmed extrapolations of elevated-temperature Arrhenius behavior. To improve confidence in such extrapolations, we describe an ultrasensitive oxygen consumption approach. Measurements are made at elevated temperatures to confirm correlation between activation energies (E a) for consumption...
The use of d 33 and D-E hysteresis loops to examine the influence of temperature on the piezoelectric properties of three PVDF-based polymers was discussed. The d 33 piezoelectric coefficients and electric displacement-electric field (D-E) hysteresis loops were measured up to 160°C for the d 3 measurements. It was observed that the room temperature...
The theory and application of mid-IR emission spectroscopy to the study of the oxidation of single reactor particles of unstabilized polypropylene (0.4 to 40μg) is described. The rate of formation of carbonyl and γ-lactone oxidation products is followed by FT-IR emission at 150°C and is interpreted within a heterogeneous model of solid state oxidat...
Nuclear magnetic resonance (NMR) relaxation measurements are a microscopic probe of the dynamical behavior of a polymer chain. Various NMR relaxation measurements have been tested to determine their effectiveness for monitoring the condition of thermally aged polymers. The most convenient and promising approach utilizes 1H NMR T2 relaxation times o...
NMR spectroscopy experiments on thermally aged cross-linked hydroxyl-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) based polyurethane rubber indicated only a slight temperature dependence for the degradation products distribution but revealed the presence of chemical and dynamic heterogeneities. The samples were aged in sealed ampu...
Polymeric materials used for cable/wire insulation, electrical connectors, O-rings, seals, and in critical components such as motors, level switches and resistive thermo-devices were evaluated under accelerated degradation conditions in combined radiation-oxidative elevated-temperature acidic-vapor (nitric/oxalic) environments relevant to condition...
Failure models based on the Palmgren–Miner concept that material damage is cumulative have been derived and used mainly for fatigue life predictions for metals and composite materials. We review the principles underlying such models and suggest ways in which they may be best applied to polymeric materials in temperature environments. We first outli...
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 C to 125 C. The changes in tensile elongation, polymer network properties and chain dynamics, mechanical hardeni...
A hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer is commonly used as propellant binder material. The thermal degradation of the binder is believed to be an important parameter governing the performance of the propellant. The aging of these binders can be monitored by mechanical property measurements such as modulus...
The authors have shown that the hydroperoxide species in {gamma}-irradiated {sup 13}C-polyethylene can be directly observed by {sup 13}C MAS NMR spectroscopy. The experiment was performed without the need for special sample preparation such as chemical derivatization or dissolution. Annealing experiments were employed to study the thermal decomposi...
Over the past two decades, Sandia has developed a variety of specialized analytical techniques for evaluating the long-term aging and stability of cable insulation and other related materials. These techniques have been applied to cable reliability studies involving numerous insulation types and environmental factors. This work has allowed the moni...
We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress-relaxation (CSR) techniques in combination with conve...
The thermal degradation of a commercial, stabilized, unfilled neoprene (chloroprene) rubber was investigated at temperatures up to 140°C. The degradation of this material is dominated by oxidation rather than dehydrochlorination. Important heterogeneous oxidation effects were observed at the various temperatures investigated using infrared micro-sp...
Monitoring changes in material density has been suggested as a potentially useful condition monitoring (CM) method for following the aging of cable jacket and insulation materials in nuclear power plants. In this study, we compare density measurements and ultimate tensile elongation results versus aging time for most of the important generic types...
The oxidative thermal aging of a crosslinked hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) polyurethane rubber, commonly used as the polymeric binder matrix in solid rocket propellants, was studied at temperatures of RT to 125 C. We investigate changes in tensile elongation, mechanical hardening, polymer network properties,...
This review explores the feasibility of using high resolution solution 17O nuclear magnetic resonance (NMR) spectroscopy to investigate the oxidation of polymers. The identification of species produced directly during the reaction of polymers with 17O2 (or any other 17O containing reagent) is a novel and promising approach to study detailed aspects...
The radiation-thermal degradation of several types of commercial cable insulation materials (semi-crystalline crosslinked polyolefins) was investigated as a function of temperature in the range of 22–120 °C. Mechanical property deterioration surprisingly occurred most rapidly at the lowest temperatures. This unusual phenomenon was corroborated by f...
The thermal degradation of a commercial, stabilized, unfilled nitrile (Buna-N) rubber material was investigated at temperatures in the range 85–140 °C. The resulting heterogeneous oxidation, due to diffusion limitations in oxygen availability, was studied using infrared microscopy and modulus profiling. Degradation-related spectral changes were obs...
Polymethylmethacrylate and polyimide samples were irradiated with 500 keV carbon and hydrogen ions generated by a high intensity pulsed power ion beam source. Ion penetration was limited to a few microns at an energy deposition in the range of 0.1-5 J cm-2 and a dose rate of approx. 1012 Gy s-1 during each pulse. Rapid energy deposition (< 500 ns)...
Various polymers were irradiated with high energy ( keV) carbon and hydrogen ion beams obtained from a high intensity pulsed power source. Energy deposition was in the range of 0.1–5 J/cm2 during each pulse, and ion penetration was limited to a few microns. The rapid energy deposition (<500 ns) corresponded to a dose rate of approximately 1012 Gy/s...
The thermal degradation of some common polymers was investigated using infrared emission spectroscopy. The potential of the technique to contribute to polymer degradation studies is demonstrated by measuring the spectroscopic changes that occur during thermal degradation, oxidation or decomposition of polymers under air at temperatures ranging from...
A model for the heterogeneous oxidation of polypropylene (PP) is proposed in which it is considered that there is a small initial fraction, po, of oxidizing centres which have a high local rate of oxidation. Within these zones there is a free radical chain reaction producing secondary oxidation products, volatiles and chemiluminescence (CL) from pe...
Alanine dosimeters were irradiated at 3 × 1010 Gy/s using a pulsed electron beam. The response measured by ESR showed good agreement with dosimetry by radiochromic film dosimeters, which are reliable at that absorbed dose rate. The results indicate that alanine dosimeters may be used at very high dose rate, within their nominal-usable dose range up...
Linear Energy Transfer (LET) effects in radiation chemistry are ascribed to the high density of active species in the track structure, resulting in overlapping of spurs. We studied the possibility of spur overlapping in electron beam irradiation at extremely high dose rate, both theoretically and experimentally. Considering differences in overlap m...
The radiation-thermal degradation of a commercial crosslinked polyolefin (XLPO) cable insulation material was investigated as a function of dose rate and temperature in the range of 22–120°C. Degradative changes in the material were monitored by ultimate elongation, density, gel content, O2 consumption, infrared spectroscopy, and differential scann...
The oxidation of solid polypropylene measured by chemiluminescence (CL) has been interpreted as involving heterogeneous initiation that leads to high oxidation rates in localized zones and is followed by the physical spreading of oxidation. Evidence of the high activity of oxidizing centers to promote further oxidation of even physically separated...
The evidence from chemiluminescence analysis for the heterogeneous model for the oxidation of polypropylene powder and film is re-examined. In this model, the polymer contains a small number of localized zones in which oxidation occurs at a high rate and from which it then spreads. Stabilizer, if present, prevents the spreading for a period of time...
A commercial high-sensitivity CCD camera has been applied to image the weak chemiluminescence from the oxidative degradation of polypropylene. Images of powder and film samples were obtained after various oxidation times and showed the heterogeneous characteristics of oxidation. The results are consistent with a model for oxidative spreading from z...
Crosslinked polyethylene (XLPE) used as an insulation material is increasingly employed in aerial bundle cable systems for domestic power supply. This has resulted in the need to investigate the long term performance and properties of the polymer under thermal and UV ageing conditions. In the current study it has been attempted to characterise vari...
Quantitative FTIR-emission spectroscopy was applied to investigate the real-time thermal oxidation of polyolefin samples and shown to be a useful method for studying polymer degradation. The high sensitivity of the technique was demonstrated by studying the oxidation of individual pressed polypropylene (PP) and high-density polyethylene (HDPE) reac...
Cables have been identified as critical components requiring detailed technical evaluation for extending the lifetime of Light Water Reactors beyond 40 years. This paper highlights some of the DOE-sponsored cable aging studies currently underway at Sandia. These studies are focused on two important issues: the validity of the often-used Arrhenius t...
The relationship between mechanical strength of aerial bundle conductor cables of the type used in Australia, and properties of the XPLE cable insulation has been examined. It is found that the overall cable strength does not appear to be closely influenced by the material properties, but possibly is a function of the manufacturing process. Ingress...
Aerial bundle cable (ABC) systems are increasingly employed for domestic power supply resulting in the need to investigate the long term performance and properties of the overall system. In this study it has been attempted to characterise different XLPE materials, particularly various silane and peroxide crosslinked low density polyethylene samples...
Highly sensitive chemiluminescence equipment was applied to study the oxidative behaviour at 125–150°C of individual polypropylene powder particles (10–500 μm) and film sections pressed from the powder. The chemiluminescence curves from the oxidation of single isolated powder particles revealed a range of induction periods equivalent to different i...
From an analysis of chemiluminescence (CL) curves from the isothermal oxidation of polypropylene powder and film, it is proposed that the usual homogeneous kinetic analysis of the sigmoidal increase in apparent oxidation rate with time is inappropriate and should be considered instead as a statistical accumulation of rapidly oxidizing centres. Over...
Aerial bundle cable (ABC) systems were introduced in Australia in
1985 for low voltage reticulation. Although ABC systems had been
reported to have been operated successfully for many years in Europe and
Scandinavia, potential degradation problems could be caused in Australia
by extreme climatic conditions and the use of insulating materials that
a...
Several 1H and 13C NMR techniques have been applied to study the morphology and chemical structure of thermally degraded polyurethane rubber and irradiated polyethylene cable insulation. The combination of heat and presence of air results in oxidation of the hydroxyl-terminated polybutadiene/isophorone diisocyanate polyurethane and the gel content...
The Arrhenius methodology has been utilized for many years to NOV 171998 predict polymer lifetimes in various applications. Unfortunately, there are numerous potential limitations associated with this methodology, o ST I many of which can lead to non-Arrhenius behavior. This paper will review several of these limitations, including a brief mention...
We have been working for many years to develop better methods for predicting the lifetimes of polymer materials. Because of the recent interest in extending the lifetimes of nuclear weapons and the importance of environmental seals (o-rings, gaskets) for protecting weapon interiors against oxygen and water vapor, we have recently turned our attenti...
Hydrolytic degradation has been shown to be a significant problem for poly(ester urethane) elastomers exposed to high humidity environments. The ester group in the soft segment is particularly susceptible to hydrolysis. One of the products of this reaction is a carboxylic acid group that catalyses further hydrolysis. The resulting reduction in mole...
Because of the need to significantly extend the lifetimes of weapons, and because of potential implications of environmental O-ring failure on degradation of critical internal weapon components, the authors have been working on improved methods of predicting and verifying O-ring lifetimes. In this report, they highlight the successful testing of a...
Many weapons components (e.g. firing sets) are encapsulated with blown foams. Foam is a strong lightweight material--good compromise between conflicting needs of structural stability and electronic function. Current foaming processes can lead to unacceptable voids, property variations, cracking, and slipped schedules which is a long-standing issue....
The U.S. is addicted to petroleum--a dependency that periodically shocks the economy, compromises national security, and adversely affects the environment. If liquid fuels remain the main energy source for U.S. transportation for the foreseeable future, the system solution is the production of new liquid fuels that can directly displace diesel and...
Citations
... These polymers can be used as sensors or actuators. Hence, with the aid of these properties, it is possible to develop polymers with unique properties such as self-healing, shape memory effect, reversible crosslinking, and multiresponsiveness [19][20][21][22]. ...
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... This model is used to accurately represent the relevant changes in the mechanical behavior of materials under different strain rates and different aging states. In aging experiments, two frequently employed methods are hot air aging [17][18][19]and aging in a marine environment [20,21]. Indeed, hot air aging experiments are employed to subject EPDM rubber samples to controlled aging conditions. ...
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... 20 However, in this work, the relaxation modulus of lignin-PDMS polyimines is released slowly first and significantly later (Figure 5c,d), indicating that they are adaptable thermoset-like networks mainly due to the dynamic imine covalent networks that are responsible for their stress−relaxation behavior. 43 In other words, the occurrence of imine exchange and metathesis is likely the reason for their network rearrangement and stress− relaxation behavior. 24,44 Comparing lignin-PDMS and lignin-OAm polyimines, the latter exhibits much faster relaxation rates under the same temperatures and applied strain ( Figure 5), as well as a lower E a (Table 3), which can be explained by the fact that the covalent cross-linking network of lignin-PDMS polyimines is more complex and rigid than the core-branchshaped lignin-OAm polyimines, leading to a more difficulty in chain mobility and rearrangement and a reduced capability to dissipate stress over time. ...
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... This aging process affects not only the material performance but also its service life. Therefore, there is a high theoretical relevance and practical engineering benefit in studying the prediction of mechanical quality degradation [2,3]. ...
... Diglycidyl ether of bisphenol A (DGEBA) cured with diethanolamine (DEA) has been a staple engineering epoxy in national defense applications since the mid-twentieth century (see history in [3]) and has a number of advantages even amongst the wide selection of specialty epoxies available today. These include [3,4]: (1) a curative (DEA) of low toxicity, (2) a rapid adduct reaction binding the DEA to the epoxy and restricting DEA's vaporization during cure, (3) a slow crosslinking reaction resulting in an extended pot life and limiting exothermic heating in large samples, (4) a tolerance for small variations in mix ratio without large effects on final properties, (5) a living polymerization nature which gives it a degree of self-healing ability, and (6) a ceiling temperature which inhibits thermal run-away. ...
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... The temperature-dependence on the rate of resistance change allows numerical and graphics-based analysis of this dependence for use as a thermal age sensor. For example, time-temperature superposition (TTS) may be used to determine Arrhenius behavior and activation energy (Ea) of the aging processes as suggested by Gillen, Bernstein and Celina (2017). TTS can also be used to determine Arrhenius behavior of the resistance decrease phenomenon of a conductive composite sensor. ...
... The common oxidation products observed in the case of poly(isoprene) (IR) thermo-oxidation were investigated in detail in the work of Alam et al. 54 They showed that the major oxidation products in IR thermo-oxidated under an 17 O atmosphere were alcohols and ethers and then unsaturated ethers and ketones. In this list, only ethers are susceptible to generate new permanent covalent bonds within the network and thus to lead to the formation of rigid domains. ...
... In this study, we assume sufficiently thin samples for which oxygen is homogeneously distributed and adopt the term thermo-chemical aging instead of "thermo-oxidation" to distinguish between the two scenarios mentioned above. See Shaw et al. (2005) and Steinke et al. (2011) for examples when specimen thickness is large enough such that oxygen diffusion becomes the limiting factor and its implementation must be considered. ...
... After being initiated, the surrounding can be gradually affected with time and the degradation will spread from these initiated spots through the rest of the material. Spreading of the degradation from a point where the oxidation started has been observed by many researchers [47,55,56,57,58,59]. Using polarized optical microscopy Nakatani et al. [60] nicely showed initiation and spreading in the amorphous phase of PP to which a small amount of already oxidized PP was added. ...
... Due to the well-known sensitivity of polybutadiene to oxidative degradation and the utilization of these materials in defence related applications, considerable efforts have been devoted to better understand the long term aging and degradation mechanisms of these materials [21 25]. Thermal aging of HTPB/IPDI materials has been studied in great detail with an emphasis on oxidation sensitivity and chemical-mechanical property correlations [26] , degradation chemistry [27], NMR polymer chain mobility relaxation experiments [28,29] chemical derivatization approaches [30] [and the development of more suitable techniques for lifetime prediction purposes [31,32], As a brief summary, these materials are surprisingly sensitive to oxidation despite the addition of significant stabilization, and undergo thermal crosslinking, densification, hardening and display a general loss of their required elastomeric properties during aging. ...
