Accelerated aging

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Accelerated aging is testing that uses aggravated conditions of heat, humidity, oxygen, sunlight, vibration, etc. to speed up the normal aging processes of items. It is used to help determine the long-term effects of expected levels of stress within a shorter time, usually in a laboratory by controlled standard test methods. It is used to estimate the useful lifespan of a product or its shelf life when actual lifespan data is unavailable. This occurs with products that have not existed long enough to have gone through their useful lifespan: for example, a new type of car engine or a new polymer for replacement joints.

Contents

Physical testing or chemical testing is carried out by subjecting the product to

Mechanical parts are run at very high speed, far in excess of what they would receive in normal usage. Polymers are often kept at elevated temperatures, in order to accelerate chemical breakdown. Environmental chambers are often used.

Also, the device or material under test can be exposed to rapid (but controlled) changes in temperature, humidity, pressure, strain, etc. For example, cycles of heat and cold can simulate the effect of day and night for a few hours or minutes.

Library and archival preservation science

Accelerated aging is also used in library and archival preservation science. In this context, a material, usually paper, is subjected to extreme conditions in an effort to speed up the natural aging process. Usually, the extreme conditions consist of elevated temperature, but tests making use of concentrated pollutants or intense light also exist. [1] These tests may be used for several purposes.

There is no single recommended set of conditions at which these tests should be performed. In fact, temperatures from 22 to 160 degrees Celsius, relative humidities from 1% to 100%, and test durations from one hour to 180 days have all been used. [1] ISO 5630-3 recommends accelerated aging at 80 degrees Celsius and 65% relative humidity [2] when using a fixed set of conditions.

Besides variations in the conditions to which the papers are subjected, there are also multiple ways in which the test can be set up. For instance, rather than simply placing single sheets in a climate controlled chamber, the Library of Congress recommends sealing samples in an air-tight glass tube and aging the papers in stacks, which more closely resembles the way in which they are likely to age under normal circumstances, rather than in single sheets. [3]

History

The technique of artificially accelerating the deterioration of paper through heat was known by 1899, when it was described by W. Herzberg. [1] Accelerated aging was further refined during the 1920s, with tests using sunlight and elevated temperatures being used to rank the permanence of various papers in the United States and Sweden. In 1929, a frequently used method in which 72 hours at 100 degrees Celsius is considered equivalent to 18–25 years of natural aging was established by R. H. Rasch. [1]

In the 1950s, researchers began to question the validity of accelerated aging tests which relied on dry heat and a single temperature, pointing out that relative humidity affects the chemical processes which produce paper degradation and that the reactions which cause degradation have different activation energies. This led researchers like Baer and Lindström to advocate accelerated aging techniques using the Arrhenius equation and a realistic relative humidity. [1]

Criticism

Accelerated aging techniques, particularly those using the Arrhenius equation, have frequently been criticized in recent decades. While some researchers claim that the Arrhenius equation can be used to quantitatively predict the lifespan of tested papers, [4] other researchers disagree. Many argue that this method cannot predict an exact lifespan for the tested papers, but that it can be used to rank papers by permanence. [5] [6] A few researchers claim that even such rankings can be deceptive, and that these types of accelerated aging tests can only be used to determine whether a particular treatment or paper quality has a positive or negative effect on the paper's permanence. [7]

There are several reasons for this skepticism. One argument is that entirely different chemical processes take place at higher temperatures than at lower temperatures, which means the accelerated aging process and natural aging process are not parallel. [1] [7] [8] Another is that paper is a "complex system" [5] and the Arrhenius equation only applicable to elementary reactions. Other researchers criticize the ways in which deterioration is measured during these experiments. Some point out that there is no standard point at which a paper is considered unusable for library and archival purposes. [8] Others claim that the degree of correlation between macroscopic, mechanical properties of paper and molecular, chemical deterioration has not been convincingly proven. [5] [9] Reservations about the utility of this method in the automotive industry as a method for assessing corrosion performance have been documented [10] [11]

In an effort to improve the quality of accelerated aging tests, some researchers have begun comparing materials which have undergone accelerated aging to materials which have undergone natural aging. [12] The Library of Congress, for instance, began a long-term experiment in 2000 to compare artificially aged materials to materials allowed to undergo natural aging for a hundred years. [13]

See also

Related Research Articles

Mass deacidification is a term used in library and information science as one possible measure against the degradation of paper in old books, the so-called "slow fires". The goal of the process is to increase the pH of acidic paper. Although acid-free paper has become more common, a large body of acidic paper still exists in books made after the 1850s; this is because of its cheaper and simpler production methods. Acidic paper, especially when exposed to light, air pollution, or high relative humidity, yellows and becomes brittle over time. During mass deacidification an alkaline agent is deposited in the paper to neutralize existing acid and prevent further decay. Mass deacidification is intended for objects on acidic paper that will be lost if no action is performed.

In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates. The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 1884 that the van 't Hoff equation for the temperature dependence of equilibrium constants suggests such a formula for the rates of both forward and reverse reactions. This equation has a vast and important application in determining the rate of chemical reactions and for calculation of energy of activation. Arrhenius provided a physical justification and interpretation for the formula. Currently, it is best seen as an empirical relationship. It can be used to model the temperature variation of diffusion coefficients, population of crystal vacancies, creep rates, and many other thermally-induced processes/reactions. The Eyring equation, developed in 1935, also expresses the relationship between rate and energy.

Sizing or size is a substance that is applied to, or incorporated into, other materials—especially papers and textiles—to act as a protective filler or glaze. Sizing is used in papermaking and textile manufacturing to change the absorption and wear characteristics of those materials.

<span class="mw-page-title-main">Acid-free paper</span> Type of paper used for preservation

Acid-free paper is paper that, if infused in water, yields a neutral or basic pH. It can be made from any cellulose fiber as long as the active acid pulp is eliminated during processing. It is also lignin- and sulfur-free. Acid-free paper addresses the problem of preserving documents and preserving artwork for long periods.

Print permanence refers to the longevity of printed material, especially photographs, and preservation issues. Over time, the optical density, color balance, lustre, and other qualities of a print will degrade. The rate at which deterioration occurs depends primarily on two main factors: the print itself, that is, the colorants used to form the image and the medium on which image resides, and the type of environment the print is exposed to.

Preservation of documents, pictures, recordings, digital content, etc., is a major aspect of archival science. It is also an important consideration for people who are creating time capsules, family history, historical documents, scrapbooks and family trees. Common storage media are not permanent, and there are few reliable methods of preserving documents and pictures for the future.

The conservation and restoration of photographs is the study of the physical care and treatment of photographic materials. It covers both efforts undertaken by photograph conservators, librarians, archivists, and museum curators who manage photograph collections at a variety of cultural heritage institutions, as well as steps taken to preserve collections of personal and family photographs. It is an umbrella term that includes both preventative preservation activities such as environmental control and conservation techniques that involve treating individual items. Both preservation and conservation require an in-depth understanding of how photographs are made, and the causes and prevention of deterioration. Conservator-restorers use this knowledge to treat photographic materials, stabilizing them from further deterioration, and sometimes restoring them for aesthetic purposes.

The salt spray test is a standardized and popular corrosion test method, used to check corrosion resistance of materials and surface coatings. Usually, the materials to be tested are metallic and finished with a surface coating which is intended to provide a degree of corrosion protection to the underlying metal.

Forced degradation or accelerated degradation is a process whereby the natural degradation rate of a product or material is increased by the application of an additional stress.

William James Barrow was an American chemist and paper conservator, and a pioneer of library and archives conservation. He introduced the field of conservation to paper deacidification through alkalization.

<span class="mw-page-title-main">Conservation and restoration of parchment</span>

The conservation and restoration of parchment constitutes the care and treatment of parchment materials which have cultural and historical significance. Typically undertaken by professional book and document conservators, this process can include preventive measures which protect against future deterioration as well as specific treatments to alleviate changes already caused by agents of deterioration.

<span class="mw-page-title-main">Cellulose acetate film</span> Base material for photographic emulsions

Cellulose acetate film, or safety film, is used in photography as a base material for photographic emulsions. It was introduced in the early 20th century by film manufacturers and intended as a safe film base replacement for unstable and highly flammable nitrate film.

<span class="mw-page-title-main">Mold control and prevention (library and archive)</span>

Mold control and prevention is a conservation activity that is performed in libraries and archives to protect books, documents and other materials from deterioration caused by mold growth. Mold prevention consists of different methods, such as chemical treatments, careful environmental control, and manual cleaning. Preservationists use one or a combination of these methods to combat mold spores in library and archival collections.

Accelerated photo-ageing of polymers in SEPAP units is the controlled polymer degradation and polymer coating degradation under lab or natural conditions.

Leafcasting is a method of strengthening paper so as to preserve it. Leafcasting fills in parts that may be missing in papers by the design of conservators or by age. The process covers an existing sheet of damaged paper with replacement fiber, thus increasing its future usability. The process must be performed on a perfectly calibrated machine to avoid damaging the paper. There are few institutions around the world that have the capabilities to perform leafcasting treatments. As few institutions have the required equipment, leafcasting is not a popular form of paper strengthening.

Accelerated life testing is the process of testing a product by subjecting it to conditions in excess of its normal service parameters in an effort to uncover faults and potential modes of failure in a short amount of time. By analyzing the product's response to such tests, engineers can make predictions about the service life and maintenance intervals of a product.

<span class="mw-page-title-main">High-temperature operating life</span>

High-temperature operating life (HTOL) is a reliability test applied to integrated circuits (ICs) to determine their intrinsic reliability. This test stresses the IC at an elevated temperature, high voltage and dynamic operation for a predefined period of time. The IC is usually monitored under stress and tested at intermediate intervals. This reliability stress test is sometimes referred to as a "lifetime test", "device life test" or "extended burn in test" and is used to trigger potential failure modes and assess IC lifetime.

The conservation and restoration of film is the physical care and treatment of film-based materials. These include photographic film and motion picture film stock.

<span class="mw-page-title-main">Conservation and restoration of photographic plates</span>

The conservation and restoration of photographic plates is the process of caring for and maintaining photographic plates in order to preserve their materials and content. It covers the necessary measures that can be taken by conservators, curators, collection managers, and other professionals to conserve the material unique to photographic plate processes. This practice includes understanding the composition and agents of deterioration of photographic plates, as well as the preventive conservation and interventive conservation measures that can be taken to increase their longevity.

Kenneth T. Gillen is a retired Sandia National Labs researcher noted for contributions to service life prediction methods for elastomers

References

  1. 1 2 3 4 5 6 7 8 9 "Archived copy". Archived from the original on 29 November 2014. Retrieved 19 November 2014.{{cite web}}: CS1 maint: archived copy as title (link), Porck, H. J. (2000). Rate of paper degradation: The predictive value of artificial aging tests. Amsterdam: European Commission on Preservation and Access.
  2. ↑ Bansa, H. (1992). Accelerated aging tests in conservation research: Some ideas for a future method. Restaurator 13.3, 114-137.
  3. ↑ "Accelerated Aging of Paper: A New Test (Preservation, Library of Congress)". Library of Congress . Archived from the original on 27 July 2009. Retrieved 11 August 2009., Library of Congress (2006). Accelerated aging of paper: A new test. The Library of Congress: Preservation. Retrieved 8 August 2009.
  4. ↑ Zou, X.; Uesaka, T; & Gurnagul, G. (1996). Predication of paper permanence by accelerated aging I. Kinetic analysis of the aging process. Cellulose 3, 243-267.
  5. 1 2 3 Strofer-Hua, E. (1990). Experimental measurement: Interpreting extrapolation and prediction by accelerated aging. Restaurator 11, 254-266.
  6. ↑ Bégin, P. L. & Kaminska, E. (2002). Thermal accelerated ageing test method development. Restaurator 23, 89-105.
  7. 1 2 Bansa, H. (2002). Accelerated aging of paper: Some ideas on its practical benefit. Restaurator 23, 106-117.
  8. 1 2 Bansa, H. (1989). Artificial aging as a predictor of paper’s future useful life. The Abbey Newsletter Monograph Supplement 1.
  9. ↑ Calvini, P. & Gorassini, A. (2006). On the rate of paper degradation: Lessons from the past. Restaurator 27, 275-290.
  10. ↑ Hunt, Gregory (3 April 2018). "New Perspectives on Lubricant Additive Corrosion: Comparison of Methods and Metallurgy". SAE Technical Paper Series. Vol. 1. pp. 2018–01–0656. doi:10.4271/2018-01-0656.
  11. ↑ Hunt, Gregory (4 April 2017). "New Perspectives on the Temperature Dependence of Lubricant Additives on Copper Corrosion". SAE International Journal of Fuels and Lubricants. Vol. 10. pp. 2017–01–0891. doi:10.4271/2017-01-0891.
  12. ↑ Batterham, I & Rai, R. (2008). A comparison of artificial ageing with 27 years of natural ageing. 2008 AICCM Book, Paper and Photographic Materials Symposium, 81-89.
  13. ↑ , Library of Congress (2008). 100-year paper natural aging project. The Library of Congress: Preservation. Retrieved 8 August 2009.
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