Volume 9, Number 2
Jul 1996

Update: ASTM/ISR Paper Aging Research Program

by R. Bruce Arnold
Chair, Research Program Sponsor Committee

The American Society for Testing and Materials (ASTM) and its subsidiary division, the Institute for Standards Research (ISR), is fully launched in the first phases of its research program. The purpose of the program is to conduct credible studies of the physical, chemical, and optical aspects of printing and writing paper aging in a way that will lead to accelerated aging test methods that define the life expectancy of the papers. The purpose is to use the results to move from standards that specify composition requirements, to standards that are based only on the performance requirements of end users.

This program is currently sponsored by 25 organizations in the U.S., Canada, and Australia. They include pulp and paper companies; libraries, archives, and other cultural conservation organizations; government groups; and suppliers to the pulp and paper industry. The program has a budget of $4.0 million. This includes both direct cash contributions and various types of in-kind support. To date the program is approximately $1.3 million short of its goal. Fund-raising efforts continue to be actively pursued.

The program began with manufacture of 15 very fully characterized papers, for which most of the pulp was donated by sponsor companies. Of these, 13 were made at the Herty Foundation in Savannah, Georgia, and the other two were made and contributed by Crane & Co., Inc., of Dalton, MA. These papers include both acid and alkaline papers. They range from a pure long-staple cotton furnish to a mix of 20% bleached northern softwood kraft and 80% slush stone groundwood pulp. Other furnishes include those of pure northern softwood kraft pulp, pure softwood bleached chemithermomechanical (BCTMP) pulp, mixtures of softwood and hardwood kraft, and mixtures of softwood kraft and hardwood BCTMP.

For each of the 15 sets of paper, more than 30,000 sheets of 8-1/2 x 11-inch size were produced. Each of these papers were fully randomized within their type so than when boxed into 500-sheet reams, all contained some of all parts of the production of that type. The randomized papers were then shrink-wrapped in polyethylene film, boxed in alkaline cartons, and packed into corrugated containers. Each type of paper was then stored on its own pallet for shipment to a cold storage facility.

Prior to shipment to the research organizations for scientific evaluation or to libraries and archives for long-term storage, these papers are being kept in cold storage to minimize the amount of aging that can take place. They are held just above the freezing mark, and because of their packaging, they are stored in the dark to prevent unwanted light aging.

There are basically four areas of research focus in the program. They include three specific efforts to develop accelerated aging test methods. The other focus is on basic, fundamental issues of physics and chemistry associated with paper aging that are not fully understood. Work is in progress toward development of all test methods.

The first program currently underway to develop an accelerated aging test method utilizes elevated concentrations of pollutant gases as the aging accelerant. This work is being conducted by the Image Permanence Institute at Rochester Institute of Technology. Mr. James Reilly is the principal investigator. In this program, sulfur dioxide, nitrogen dioxide, and ozone are utilized separately and in combinations to age the papers. Gas concentrations that approximate 10, 100, and 1000 times the normal amount found in a well-managed office space or library are used to accelerate the aging. The exposure times range from one to six months, with longer exposures assigned to the lowest gas concentrations. Both chemical and physical evaluations of the exposed papers are undertaken at equal intervals. Six such evaluations are done for each condition, so as to develop curves of the paper degradation.

The Forest Products Laboratory (FPL) of the U.S. Department of Agriculture is conducting a two-part study of light aging. Dr. Rajai Atalla is the principal investigator. In the first part, a three-year study of natural aging is underway. In this work, in three separate chambers, natural daylight through a north-facing window, fluorescent light, and halogen light are utilized to expose all 15 of the specially made papers. In early findings, natural daylight is found to cause more rapid yellowing of the papers than artificial illumination.

The second part of the FPL studies involves exposure of the papers to high photon flux levels in a specially prepared chamber. Studies of the papers are being conducted to evaluate the nature of photochemical changes taking place. Physical tests of the papers are also conducted to determine if physical properties are affected by the exposures. The marriage of the natural and accelerated aging studies is intended to lead to a light aging test method that will predict life expectancy of papers in terms of their brightness and color properties.

The U.S. Library of Congress is involved in an ongoing research program. They are providing their findings to the ASTM/ISR research effort. Dr. Chandru Shahani is the principal investigator. Their focus is on development of a test method utilizing elevated temperature in the presence of a reasonable level of relative humidity as the means to accelerate the aging. To study the relationships between accelerated and natural aging, the Library is utilizing specially developed techniques to measure the products of paper degradation caused by aging. The principal technique is the use of high-performance liquid chromatography (HPLC). Dr. Peng Song has been contracted by the ISR to assist the Library in the development and use of these techniques. Aging of papers is done over a range of temperatures from 70° to 90°C and through a range of relative humidities from 40 to 90%. Six of the specially made papers of the ASTM/ISR program will be evaluated. They represent the full range of composition variables of these papers. Additionally, four commercial papers, selected by the Library, are already under investigation. Single sheets, stacks of sheets, and sheets enclosed in sealed glass tubes are all included in the study.

While not yet funded, some of the fundamental studies desired include evaluations of acidity and basicity at the molecular level. The work is also aimed at oxidation and autoxidation studies. Such considerations as oxidation by peroxy radicals, alkaline "peeling" reactions at mildly alkaline pH, and measurements of the volatile products of paper aging are included. Arrhenius studies of various variables are an intended part of the overall program.

In order to optimize available funding, first priority is being given to those elements of the work that must be completed to develop scientifically credible test methods that can be used to predict the life expectancy of these papers.

The program is intended to be a three-year effort. The first key phase, already underway, is expected to be complete by the end of 1998. If additional fundraising efforts are successful, the remaining work should be complete by the end of 1999.