New standards for particleboard & MDF.

Voluntary industry standards for these two important engineered wood products have been the subject of a new round of revisions by the American National Standards Institute, reflecting evolutionary changes in both the panels and the markets they serve.

Furniture and cabinet manufacturers, builders and other users of engineered wood products understand the importance of knowing their suppliers and their raw materials. The manufacturer-supplier relationship has become a central element in the new thrust toward "total quality." A key component of this relationship is the product standard.

Product standards provide a common language to facilitate communication between buyer and seller. While product transactions may include discussions about property specifications not included in a product standard, the standard frequently provides a base line -- something to be referenced as a minimally acceptable measure of quality.

The American National Standards Institute is the most widely recognized source of industry performance and safety standards. In addition to helping develop new standards, ANSI is involved with revising standards to reflect changes in the products and markets they serve.

GENERAL USES & GRADES OF PARTICLEBOARD

Grade                         General Use

M-2, M-3                      Industrial: For furniture and cabinet
applications                               that require demanding surface and
strength                               characteristics. These are the most
common                               grades produced.

M-1, M-S                      Commercial: For applications not as demanding
                              as typical industrial.

H-1, H-2, H-3                 High Density Industrial: For demanding
                              industrial applications that require higher than
                              normal strength.

LD-1, LD-2                    Door Core: Low density panels, usually 1 1/8 in.
                              or more thick.

M-1, M-2, M-3 Exterior Glue   Exterior Construction and Exterior Industrial

H-1, H-2, H-3 Exterior Glue   High Density Exterior Industrial

PBU                           Underlayment: A non-structural top layer for
                              two-layer floor systems.

D-2, D-3                      Manufactured Home Decking: For one-layer
                              structural floors in manufactured homes.

LEGEND:

LD Low density -- Generally less than 640 kg/|m.sup.3~ (40 lb/|ft.sup.3~)

M Medium density -- Generally between 640 and 800 kg/|m.sup.3~ (40 to 50
lb/|ft.sup.3~)

H High density -- Generally above 800 kg/|m.sup.3~ (50 lb/|ft.sup.3~)

1,S,2,3 Relative level of dimensional tolerances and physical properties
within a density or product grade (1 is low, 3 his high)

For example, the particleboard (PB) industry recently completed work on a major revision of the American National Standard (ANSI A208.1-1993) and the medium density fiberboard (MDF) industry has completed work on a major revision of its standard, ANSI A208.2.

There were several driving forces behind the revision of these two standards. In 1992 the PB industry committed to the U.S. Environmental Protection Agency and Consumer Product Safety Commission to incorporate lower formaldehyde emission levels for specific products into the ANSI Standard. In addition, the increasingly global nature of the PB and MDF markets suggested that it was time to metricate the standards and assure that they conform with international standards development criteria. And finally, the previous PB ANSI standard contained several outdated products while the 1986 ANSI MDF standard was long overdue for revision.

This article provides an overview of the major changes in these two revised standards.

Particleboard -- ANSI A208.1-1993

ANSI A208.1-1993 (effective July 29, 1993) is a revision of the standard, ANSI A208.1-1989.

It represents the seventh version of the PB standard since the original Department of Commerce standard CS236-61 was developed 32 years ago. When a committee of PB manufacturers met during the summer of 1992 to revise the standard, it quickly became clear that the new standard needed to be more than just an "update" of the existing standard. Major goals for revision included streamlining the confusing number of products identified by the standard, providing new, lower formaldehyde limits for certain grades and converting the standard to metric units.

Grades: One of the more interesting aspects of the PB standard's historic evolution is the number of product grades specified. The original standard, CS236-61, had just two grades. Each successive revision of the standard added more until ANSI A208.1-1989 topped out at 19 different specified grades. Appreciating that many of the existing grades were seldom, if ever used, ANSI A208.1-1993 reverses this grade proliferation by reducing the number of grades to 12.

These 12 grades are specified in the standard's two tables. Table A specifies properties for nine "industrial" products for applications such as furniture, cabinets and door cores. Table B specifies properties for the three flooring products -- underlayment (PBU) and manufactured home decking (D-2) and (D-3). Product grades eliminated include waferboard (2-M-W) and six Type 2 (exterior) grades.

Gone from the new standard are the old "Type 1" and "Type 2" designations for interior and exterior grades. However, grade identification labels are designed to be familiar to experienced PB users. Grades are identified by a letter designation (H, M, LD for "industrial" density ranges, PBU for underlayment, and D for decking), followed by a hyphen and a digit or letter (S, 1-3 for the physical property levels). Special performance characteristics are identified by the use of a letter, number or term (such as "Exterior Glue") located immediately following the grade designation.

Physical properties for the remaining grades have not changed appreciably, except to accommodate the change to metric units.

Formaldehyde: The allowable formaldehyde emission limits from all PB flooring products covered in the new standard's Table B (PBU, D-2 and D-3) has been reduced by 33 percent to 0.2 parts per million. The National Particleboard Assn. estimates that products complying with the new limit will be comparable in emissions to products complying with the German E1 formaldehyde standard. Since these lower levels are now incorporated in the national standard, the industry's interim "Voluntary Standard for Urea-Formaldehyde Bonded Particleboard Flooring Products," NPA 10-92, will be withdrawn March 1, 1994.

The industrial products in Table A are limited to formaldehyde emissions of no more than 0.3 ppm, the same level as the 1989 standard. Producers of industrial panels may use the lower Table B emission limits on an optional basis. Metrication: The new standard has been "hard" converted to metric units with equivalent inch-pound units in provided parenthesis. The process for developing hard metric units follows.

First, the original inch-pound unit was precisely converted to its metric equivalent. The metric unit was then "rationalized" or rounded to an appropriate degree of precision. The new rounded metric unit was then precisely converted back to an inch-pound unit for reference. For example, the modulus of rupture (MOR) of M-2 (the old 1-M-2) used to be 2,100 psi. When precisely converted to metric, the value became 14.479 N/mm2. This new metric value was then rounded to 14.5 N/mm2 and the precise inch-pound equivalent is calculated and printed next to metric for reference purposes as (2,103 psi). Conversion to metric dimensions is a relatively simple process for the panel manufacturer. A 4-foot by 8-foot panel simply becomes 1,200mm by 2,400mm (47.24 inches by 94.49 inches). Incorporation of metric values by the material specifiers and users may be more of a challenge. From a practical perspective, the conversion to metric by the entire distribution chain may take several years. Metrication of the national standard was a necessary first step. MDF -- ANSI A208.2-199X

ANSI Standard A208.2-199X for Medium Density Fiberboard is in the final review process for acceptance as an American National Standard and represents the third version of this MDF industry standard. ANSI Standard A208.2-1980, "Medium Density Fiberboard for Interior Use," was the first MDF standard published in 1980 under combined sponsorship by the NPA. The original standard and its 1986 revision were specific to MDF for interior applications and described two classifications of MDF-based on product thickness.

Like the particleboard standard, the current revision represents some significant changes to the original standard. The new standard includes specifications for low and high density products, exterior products and formaldehyde emission limits, and provides a metric format. These represent changes made in response to changing market needs. Further, the new standard increases the physical property -- modulus of rupture (MOR) and modulus of elasticity (MOE) -- requirements of the existing standard.

Grades: The new standard provides the buyer with a choice of MDF products which is much more representative of today's MDF manufacturing technology. Three density grades -- high density (HD), medium density (MD) and low density (LD) -- with unique mechanical properties suitable for a variety of applications, are specified. In the format of the 1986 standard, the medium density (MD) grade is further subdivided into products up to 21mm in thickness and those greater than 21mm. The new standard also includes specifications for exterior grade MDF with its own unique property requirements. Formaldehyde: One important reason for revising the MDF standard was to incorporate formaldehyde emission limits into the ANSI standard. The formaldehyde emission limits in the new standard incorporate the provisions of NPA 9-87, "Voluntary Standard for Formaldehyde Emission from Medium Density Fiberboard," with its 0.3 ppm limit and applies to all product guides. Inclusion of formaldehyde limits in the standard is an important means of informing the consumer and providing guidance to the manufacturers about this important product characteristic.

Metrication: Although metric property values were calculated in a manner similar to the particleboard standard, there is a distinct difference in the presentation of the inch-pound units. After determining the "rationalized" metric value, the corresponding inch-pound unit, shown in parentheses, is precisely calculated and then similarly "rationalized" or rounded to a similar degree of precision. Metric property values are the primary values used in determining product performance requirements.

Copies available

Copies of the new ANSI particleboard standard are available for $6 each from the National Particleboard Assn., 18928 Premiere Court, Gaithersburg, MD 20879; [phone]. The MDF standard is undergoing procedural review at ANSI -- the step prior to final approval -- and is expected to be available by March. Rich Margosian is general manager of the National Particleboard Assn. based in Gaithersburg, Md.