SB: Re: Ask Dr. ZB

["Trkstr" <trkstr@hotmail.com>]

I prompted Dr ZB for more info on borax fireproofing and this is the
response:
----- Original Message -----
From: "Mu, Jacob (USBORAX)" <Jacob.Mu@borax.com>
To: "Trkstr" <trkstr@hotmail.com>
Sent: Monday, July 29, 2002 6:17 AM
Subject: RE: Ask Dr. ZB


Dear
I cannot recommend any borate products for homeowners to use for fire
proofing due to the strict building code requirements.  Since there are no
established ASTM standards for fire proofing papercrete or straw, it would
be inappropriate to suggest the types or amount of borate to use.  However,
I can send you a Service Bulletin describing various cellulose insulation
materials which are using borates for fire retardancy (see attached file).



=======================================

     Service Bulletin

Borates for Fire Retardancy in Cellulosic Materials


Contents

1. Introduction
 1.1 Fire Retardant Mechanisms
2. Cellulose Insulation
 2.1 Manufacturing Process
 2.2 Installation
 2.3 Fire Retardant Treatment
 2.4 Common Problems Associated with Fire Retardants
 2.5 Permanency of Fire Retardants
 2.6 National Standard for Cellulose Insulation
3. Wood Products
 3.1 Dimensional Lumber/Plywood
 3.2 Wood Composites
4. Mattresses/Futons
 4.1 Cotton Batting/Garnetting Applications
 4.2 Regulatory Requirements
5. Fabrics
 5.1 Formulations
 5.2 Treatment Techniques
6. Paper









1. Introduction


The burning of cellulosic materials occurs by two alternative mechanisms
(References 1 and 2).  Temperatures of 300oF (149oC) or above cause thermal
degradation of cellulose into gaseous, liquid, tarry, and solid products.
The volatile, flammable gases ignite and provide additional heat to further
pyrolyze the liquids and tars into more flammable vapors, and also to form
residues, mainly carbonaceous char and a gas mixture containing water and
carbon dioxide.  This process continues until only the carbonaceous residues
are left.  The second pathway operates at lower temperatures with the
carbonaceous char from pyrolysis.  The oxidation of the resulting char is a
slow and localized process called glowing or smoldering combustion.
Smoldering combustion may occur in the charred area or consume the entire
specimen, proceeding as a front in the solid state rather than a flame in
the gas phase.  Fire retardants are broadly classified as either flame
retardants or smoldering retardants.  Flame retardants refer to chemicals
added so that the treated material will not support flaming combustion after
the igniting flame is removed.  Smoldering retardants refer to chemicals
which effectively prevent smoldering combustion, the flameless combustion of
materials which occurs after the igniting flame is removed.  Smoldering
combustion is the heart of the fire hazard problem due to its potential for
transition to flaming combustion.

Four different theories have been developed for describing the action of
fire retardants.  They are identified as the chemical, thermal, coating, and
gas theories.  For the purposes of this report we will be discussing
chemical fire retardants.  Chemical fire retardants commonly used are boric
acid, Neoborâ Borax 5 Mol or Borax, ammonium sulfate, ammonium phosphates,
aluminum sulfate, aluminum trihydrate and gypsum.  These chemicals are
generally used in combinations of two or three different chemicals.  The
most common combination is boric acid, Neobor or Borax, and ammonium
sulfate.  To better understand the subject of fire retardancy it is
necessary to comprehend the various fire retardant mechanisms exhibited by
the aforementioned fire retardants.  This can apply to most cellulosic
applications.

1.1 Fire Retardant Mechanism

Combustion of cellulosic materials can occur in a primary mode, where
visible flames are present, or in a secondary mode, where flames are absent.
In the latter case, the combustion is referred to as glowing or smoldering,
depending on whether or not light is emitted.

 Borate-based compounds

Borates act primarily in the solid phase, where they promote the formation
of char and inhibits the release of combustible gases from the burning
materials.  The release of chemically bonded water in boric acid, Neobor or
Borax also reduces flame combustion.  The formation of protective coating on
the char from the melted boric acid is believed to be responsible for
reduced air oxidation.  This might explain why boric acid is effective in
preventing smoldering combustion.  Both Neobor and Borax are very effective
at preventing flaming combustion but relative ineffective in the suppression
of smoldering.

Ammonium-based compounds

Ammonium phosphates are believed to act as fire retardants by their ability
to increase markedly the conversion of organic matter to char during burning
and thus to decrease the formation of flammable carbon containing gases.
Combustion is inhibited because the char does not burn readily and the
amount of combustible gases is greatly reduced.  Both of these compounds
contain no chemically bonded water.  These chemicals decompose and release
ammonia with rapid weight loss beginning in the temperature range of 200 to
300oF (93 to 149oC).  Ammonium sulfate (like aluminum sulfate) acting as a
fire retardant is probably due to an increase in the production of char.
Ammonium sulfate decomposes in the temperature range of 400 to 5000F (204 to
2600C) with an associated odor of released ammonia.

 Aluminum-based compounds

The reason aluminum sulfate act as fire retardants is probably due to the
increased production of char.  Aluminum sulfate starts to lose its
chemically bonded water in the temperature range of 200 to 300oF (93 to
149oC).  When heat is applied to materials containing aluminum trihydrate
the temperature rise is slowed down because this material absorbs heat and
releases water.  The water vapor dilutes and cools the combustible gases and
retards their burning.

Gypsum compounds

Like aluminum trihydrate, when heat is applied to gypsum, the temperature
rise is slowed down as well because this material absorbs heat and releases
water.  The water vapor dilutes and cools the combustible gases and retards
their burring.


2. Cellulose Insulation

During the energy crisis of the 1970's, the public became much more
concerned about the energy efficiency of their homes.  One of the simplest
ways to increase energy efficiency of a house is to lower the heat loss to
the surroundings by increasing thermal insulation in the house.

Because of its high insulating value, ease of application, especially for
existing homes, and relative low cost, cellulose loose-fill insulation was a
frequently utilized insulating material.  For example, a layer of cellulose
5 inches deep is used for an approximately R-value of 19, where R-value is a
measurement of  resistance to heat transfer through the material; the higher
the R-value, the better the insulation.

2.1 Manufacturing Process

Cellulose insulation is produced by passing shredded newsprint through a
hammer mill which converts it to a fibrous consistency with a high thermal
insulation value.  Loose-fill and spray-on cellulosic insulation are used
extensively in the walls and attics of residential and commercial buildings.
The oldest and simplest use is loose-fill cellulose in attics.  The
insulation is blown or poured into the attic space.  Dry-blown cellulose is
also installed in walls as a retrofit insulation material.  The loose-fill
cellulose insulation has an apparent thermal resistance of 3.2 to 3.7 ft2 hr
oF/Btu per inch of thickness at a density of 2.2 to 3.5 lb/ft3.  The
properties of cellulose insulation are summarized in Table 1 (Reference 3).

There are two major processes for the preparation of loose fill cellulose:
dry process and wet process.  The dry process is the more widely used in the
industry and it generally follows the scheme shown below.  The first mill
breaks the paper into approximately 1-2 inch size pieces through the use of
swinging hammer or rotary cutters.  The flame retardant chemicals are
usually introduced simultaneously with the ground paper at the second mill.
This is the most critical stage of the manufacturing process to maintain a
consistent quality of product.  Introduction of chemicals may be by
pneumatic means, gravity feed, or auger feed.  In many processes, the
chemicals are pre-blended, and then ground in a mill to the consistency of
fine four.  The finely ground material is dispersed more readily and easily
blended into cellulosic material.  A newly designed mill to produce long
cellulose fibers of a lower density and higher R-value was pioneered by
several producers.

The wet process involves introduction of an aqueous fire retardant solution
which is sprayed onto the shredded paper leaving the first mill and prior to
entering the second mill.  This method relies on the evaporative ability of
the air stream and the sort duration heat buildup in the final milling
process to remove excess moisture.  Wet processes offer a potentially
improved product with better chemical dispersion and fire retardant
characteristics with less chemicals.  The disadvantage of needing a drying
operation with the associated energy requirements should be balanced against
the benefits of the process.


2.2 Installation

There are a number of ways to install cellulose insulation.  The simplest
use is loose-fill cellulose in attics.  The insulation is blown or poured
into the attic space.  Dry-blown cellulose is also installed in walls as a
retrofit insulation material.

Spray-on cellulose has water and/or binder added during installation to make
it stick when  blown into wall cavities.  Spray insulation can provide
insulation and sound control of exterior cavity walls in residence,
apartments, hotels and offices.  Adhesive concentrate can be pre-mixed with
water and sprayed into the product as a fine mist or added to the product
during manufacture which is activated by a water spray at the nozzle during
its installation.  A major advantage of spray insulation over other types is
its ability to provide a completely homogeneous coverage for thermal and/or
acoustical treatment that is free of voids or cracks.

Another relatively new formulation of cellulose insulation (stabilized
cellulose) is used in attics.  This product has a binder (a polyvinyl
acetate or an acrylic adhesive) in it and is applied with a small quantity
of water.  The binder prevents settling, which may otherwise reduce the
installed thickness of loose-fill cellulose insulation by as much as 25%.
One of several manufacturers producing stabilized cellulose achieves a 1.3
lb/ft3 density with its stabilized attic insulation.  Two other approaches
used for walls do not require water.  In the dense-pack process, cellulose
is blown into closed wall cavities at a relatively high density of 3 to 3.5
lbs/ft3.  Because of the high density, settling does not occur.  With the
other approach, installers use forms to blow dry cellulose into open wall
cavities.  The forms, which are propped against the inner side of stud bays,
hold the insulation in place as it is installed, and the insulation stays in
place after forms are removed and until the inner wall surface is installed.

 2.3 Fire Retardant Treatment

Cellulose insulation is flammable and particularly prone to smoldering
combustion so it is necessary to incorporate flame retardants.  In 1981 the
State of California began requiring all cellulose insulation sold in the
state to be flame retardant and smolder resistant.  Flame retardant means
the material resists the spread of an open flame.  Smoldering combustion is
a non-flaming combustion; the most common example being a burning cigarette.
Cellulose can be treated by a number of different chemicals to achieve flame
retardancy and smolder resistance.  Boric acid is the primary chemical
applied for smolder resistance and NeoborâBorax 5 Mol the primary chemical
for retarding flame spread, although other chemicals such as ammonium
sulfate, ammonium phosphates, aluminum sulfate and aluminum phosphate are
also used (Reference 4).

The concentrations of chemicals commonly added in commercial cellulosic
insulation normally range from 10 to 40% by weight (Reference 5).  Chemicals
commonly used are boric acid, sodium borate, ammonium sulfate, aluminum
sulfate, aluminum trihydrate, mono- or di-ammonium phosphate.  These
chemicals are generally used in combinations of two or three different
chemicals.  The most common combination is boric acid mixed with sodium
borate such as Borax or Neobor.  Most effective flame retardants increase
the quantity of carbon formed at the expense of flammable tars, lower the
decomposition temperature of cellulose, and raise the temperature at which
exothermic pyrolysis occurs (Reference 6).

2.4 Common Problems Associated with Fire Retardants

Ammonium sulfate is deleterious since it combines with moisture to form
acidic byproducts which have been found to cause corrosive damage to
electrical wiring, etc.  Moisture in the heavily moisture-laden air from a
bathroom or range hood tends to condense on the exposed insulation on cold
days.  This condensation has been found to form the acidic byproducts from
ammonium sulfate.  There have been anecdotal reports of copper pipes and
steel truss fasteners in attics corroding when in contact with cellulose
insulation that has gotten wet.  With the rising popularity of wet-spray
cellulose for wall applications, the issue of corrosion is particularly
significant.  Many wet-spray cellulose installers specify material treated
only with boric acid and Borax to eliminate concern about corrosion.
Additionally, ammonium sulfate is very soluble in water.  Under the effect
of moisture, ammonium sulfate will migrate due to the periodic
solubilization upon moisture condensation followed by re-crystallization
upon subsequent moisture evaporation so that the solubilized compounds are
removed from portions of the cellulose.  The exposed cellulose is thereby
deprived of its fire-retardant protection with a resulting, potentially
dangerous condition.  Accordingly, some governmental regulations have
required the discontinuance of cellulose insulation products incorporating
ammonium sulfate as the fire-retardant material.  In addition to becoming
very corrosive when getting wet, ammonium sulfate will react with strong
oxidizers, decompose under heat or in alkalis. It reacts violently with
bases to give off noxious ammonium vapor.  Thermal decomposition of ammonium
sulfate produces gaseous ammonia and oxides of sulfur.  It may also produce
toxic oxides of nitrogen.

The acidic monoammonium phosphate exhibits corrosive properties which must
be neutralized.  Borax constitutes neutralizing agent which inhibit
corrosion thereby rendering the insulation non-corrosive.  The pH of the
agent should be above 7.5, more desirably between about 7.9 and about 8.3.
A maximum amount of Borax is desired because of its flame retardant
properties.  Ammonium phosphates as well as ammonium sulfate are effective
smoke suppressants.

Aluminum sulfate is rarely used due to corrosion concern.  Aluminum
trihydrate is also seldom used because it is too abrasive to grind.

Today, most manufacturers use a mixture of borates and ammonium sulfate, and
some add small quantities of ammonium phosphates.  The Boric Acid/Borax 5
Mol combination yields reliable fire and corrosion test performances.
Ammonia-based compounds are cheaper but they are known to give off ammonia
(especially in the presence of Borax 5 Mol).  In addition, ammonia-based
compounds can cause corrosion problems in the field. There is a trend in the
industry to replace some of the borate with ammonium sulfate, because the
latter is less expensive.

2.5 Permanency of Fire Retardants

Fire retardants used in cellulose insulation are expected to be effective
not only at the time of manufacture but also for the life of the structure
in which they are installed.  Thus, the permanency of the fire retardants
becomes an important consideration.  Unfortunately, an accepted test for
determining retardant permanence does not exist and this has caused the
cellulose industry to be confronted with a confusing issue.

A lack of permanence means either that fire retardant has been transported
away from the insulation or that redistribution of the chemical has left
regions in the insulation with insufficient fire retardant.  Several
possible loss mechanisms for borates have been identified: vibration,
sublimation, leaching as well as separation during shipping and
installation.  Studies by researchers at Tennessee Technological University
and Allied Signal Corporation provide evidence that the fire-retardant
chemicals do not disappear from cellulose insulation except at much higher
temperatures than would commonly be found in attics (Reference 7).   Enough
vibration to simulate 672 years of use in an attic was found to cause no
measurable settling of boric acid or borax in test samples.  As for
evaporation (sublimation) of boric acid from cellulose, the study found that
at very high temperature (90oC or 194oF) and 100% relative humidity, the
loss of boric acid was significant, but the loss was negligible when the
temperature is lower than 70oC (158oF), even at 100% humidity and air
exchange rates of 2.0 attic changes per hour.  It appears that it would take
300 years or more to lose enough boric acid under these conditions to
significantly affect the combustion tests.  Separate studies of ammonium
sulfate by David Yarbrough and Allied Signal Corporation reached similar
conclusions: that loss was not significant except at very high temperatures.

The potential loss of fire-retardant chemicals is believed to be the most
significant concern relating to cellulose insulation.  Further research on
this concern is clearly needed, but the apparent lack of building fires in
which cellulose insulation has been implicated gives us confidence that
cellulose insulation is safe enough for use.

2.6 National Standard for Cellulose Insulation

As a result of a large increase in sales of insulation sales of all types,
especially cellulose insulation, and the appearance of a large number of
unsophisticated newcomers in both the manufacturing and installation aspects
of the business, the Consumer Product Safety Commission of the Federal
Government adopted a national standard for cellulose insulation in 1978.
The Federal Specification HH-I-515-D, currently in effect, (largely based on
the ASTM C-177, -236, -518 and -739), consists of a series of tests such as
design density, starch content, thermal resistance, moisture vapor
absorption, odor emission.

In addition to corrosiveness, fungi resistance, critical radiant flux, and
smoldering combustion are performed.  The design density controls how much
insulation should be used to achieve the required thermal resistance
(R-value) in the attic of a building.  Thermal resistance (R-value) is
determined by measuring the apparent thermal conductivity of a 4 inch or
greater thickness of insulation.  The R-value is the reciprocal of thermal
conductivity.  To get R-value per inch the R-value is divided by the
thickness of the test specimen. The fire retardant chemicals used with the
wrong ratio of chemical or if not buffered may be corrosive.  The Federal
Specification calls for tests with the insulation to determine its
corrosiveness to steel, aluminum, and copper.  Once a mix of fire retardant
chemicals is found to be non-corrosive by the tests, the pH of the
insulation is determined.  As a control of the corrosiveness of the
insulation in production the pH is determined.  If it falls within proper
limits the insulation is considered non-corrosive.

Fire Tests: Radiant Panel, Smolder Combustion, Flame Spread

Fire resistance of the insulation is defined by two tests: critical radiant
panel and smoldering combustion.  The first test shows the resistance of the
insulation to fire traveling on the surface of the insulation.  The radiant
panel test involves a horizontal sample, exposed to the radiation from a
ceramic panel at about 1000oF (538oC) as in ASTM E-162 except the panel is
tilted forward until it makes an angle of 30o with the horizontal.  The
sample is ignited with a pilot flame at the end receiving the most intense
radiation.  The distance the flame front advances front he ignition point
(during a five-minute period) is determined.  From a previously determined
calibration, the incident radiant flux at that point is established and is
termed the "critical radiant flux" (CRF).  In order to meet the standard,
the critical radiant flux must be greater than or equal to 0.12 watts/cm2.
The sample of insulation to be tested is contained in a horizontal,
stainless steel tray; it has been conditioned at 69.8oF (21oC)  and 50%
relative humidity for a minimum of 48 hours before testing..

The second shows its resistance to smoldering inside the insulation. The
smolder test uses a sample of preconditioned cellulose insulation contained
at its "settled density" in a stainless steel box 8" x 8" x 4".  A hole is
punched in the center of the sample with a sharp rod, and a lighted
cigarette dropped into the hole.
The weight loss is determined after two hours, and must not exceed 15% for
the sample to meet the standard.

Although it is not part of the Federal Specification, there is a test used
by testing laboratories called flame spread.  This compares the surface
burning of insulation to red oak.  Red oak's flame spread is 100.  Cellulose
insulation's flame spread is 25 or less.

3. Wood Products

Building codes requiring the use of fire-retardant treated wood have been in
existence for nearly 50 years.

3.1 Dimensional Lumber/Plywood

Flame retardant-treated lumber and plywood have often been successfully used
in structures exposed to temperatures less than 100oF (38oC).  The usual
method of treatment of dimensional lumber and plywood is by vacuum/pressure
impregnation with aqueous solutions of flame retardants.  Flame retardant
plywood can also be produced by impregnation of individual veneers, often
just by soaking, prior to assembly and gluing into plywood.  It is necessary
to ensure compatibility between the flame retardant additives and the
adhesive system to obtain strong bonding.

Boron compounds by themselves are effective flame retardants in lumber or
plywood (Reference 8). They can be used in conjunction with other flame
retardant chemicals including ammonium sulfate, diammonium phosphate or zinc
chloride (Reference 9).  Several theories have been proposed for the
mechanism of flame retardant chemicals.  The most widely accepted mechanism
is referred to as the chemical theory.  This theory suggests that the
retardant chemicals directly alter the pyrolysis of wood, increasing the
amount of char and reducing the amount of volatile, combustible vapors.

Borate-based treatments also inhibit or reduce the rate of thermal
degradation in wood exposed to elevated temperatures.  It is of particular
concern for roof-truss lumber and plywood roof sheathing due to the typical
roof temperatures induced by solar radiation (References 10 and 11).  The
borate-treated wood showed no significant decrease in modulus of rupture
values for all temperature exposures.  The phosphoric acid treatment had the
most deleterious initial and thermal induced effects on module of rupture.
Although not as severe as the effects of phosphoric acid treatment, the
monoammonium phosphate treatment also had deleterious initial and thermal
induced effects on modulus of rupture.

Currently, flame retardant chemicals commonly used for treating lumber and
plywood include boron compounds (e.g., Borax, Boric Acid and NeoborâBorax 5
Mol) and phosphorus compounds (e.g., phosphoric acid, monoammonium
phosphate, guanylruea phosphate and diethyl-N,N-bis(2-hydroxyethyl)
aminomethyl phosphate).  Dicyandiamide is also used in the Dricon process
for flame retardant treatment of wood products (Reference 12).

Borax-boric acid provides pH control.  When used together with other
chemicals, borates can neutralize some acidic commercial fire retardant
chemicals and maintain a neutral pH.  Phosphoric acid is not used as a sole
ingredient in commercial formulations.  However, it is a good fire
retardant.
Monoammonium phosphate and guanylurea phosphate are commonly used in some
commercial formulations.  Diethyl-N,N-bis aminomethyl phosphate, a phosphate
ester, is a good flame retardant because of its neutral pH.

Generally, in commercial practice, flame retardant compositions comprise a
mixture of the above-mentioned additives.  Four compositions detailed in the
American Wood Preservers' Association (AWPA) Specification  P10 were
commonly used prior to 1975.  The concern over hygroscopic properties,
corrosion and strength loss in the flame retardant-treated wood resulted in
the change from chemical specification to performance standard by the AWPA.
Under AWPA Standard C20-96, structural lumber shall be treated for
fire-retardance in accordance with the requirements of the AWPA Standard C1.
The flame retardant system used shall be listed in AWPA Standard PX.
Subsequent to treatment, the lumber shall be air or kiln dried to a maximum
moisture content of 19%.  When tested in accordance with ASTM E-84 tunnel
test (the 25-foot tunnel test:  This test method involves the use of
20-inch by 25-foot specimen exposed horizontally to a furnace operating
under forced draft conditions).  The two results of this test are the flame
spread index and smoke developed index.), the lumber shall have a flame
spread index of 25 or less.  In addition, the lumber shall show no evidence
of significant progressive combustion when the test is continued for an
additional 20 minute period.  Furthermore, the flame front shall not
progress more than 10.5 feet beyond the centerline of the burner at any time
during the test.


For both Interior Type A Low Temperature (LT) and High Temperature (HT)
lumber, material shall have an equilibrium moisture content of not over 28%
when tested in accordance with the ASTM D3201 procedures at 92±2% relative
humidity.

However, fire retardant treated lumber which will be used in high
temperature applications such as roof trusses and framing shall be tested
for strength in accordance with ASTM Standard D-5664 or by an equivalent
methodology.  At least one sample set shall be exposed for a minimum of 105
days.

Since fire retardant treated wood has the potential for further strength
loss when exposed to elevated temperatures and humidity in case, users and
specifiers should obtain appropriate design modification factors for initial
effects on strength or for strength when end use is in extended high
temperature and high humidity environments from the chemical supplier.
Also, fire retardant treatments may change the corrosion potential of the
fire retardant treated product compared to the untreated product.  Users and
specifiers should obtain fastener recommendations from the chemical
supplier.

Flame retardant treated plywood composed of veneers shall be treated in
accordance with the requirements of AWPA Standard C1.
The performance standard, flame retardant formulations as well as effects of
fire retardant treatments are similar for flame retardant treated lumber
(see AWPA Standard C27-96).  For fire retardant treated plywood which will
be used in high temperature applications such as roof sheathing shall be
strength tested in accordance with ASTM Standard D-5516 or by an equivalent
methodology.  At least one sample set shall be exposed for a minimum of 75
days.

It was found that post-treatment redrying at >160oF (71oC) significantly
reduced the strength of flame retardant-treated products.  Mechanical
properties of lumber and plywood were most degraded by chromated zinc
chloride treatment.  The effect of the other flame retardant treatments are
comparable when re-dried at temperature <160oF (Reference 13).

Flame retardant treatment drastically reduced the rate at which flames
travel across the wood surface and reduced the amount of potential heat.
However, some flame retardant treatments may produce unwanted secondary side
effects, such as increased moisture content, reduced strength, and increased
potential to corrode metal connectors.  The magnitude of the side effects
depends on the particular flame retardant chemicals used, and the relative
importance of these side effects depends on the intended application of the
product (Reference 14).  Borax and boric acid are known to have the least
secondary side effects.

The magnitude of wood degradation depends on the flame retardant
formulation, exposure temperature and relative humidity.  Once degrade has
begun at 150oF (66oC), the flame retardant chemicals had a similar rate of
strength loss (Reference 15).  The implication of these findings is that
once an elevated temperature has imparted sufficient energy to cause a flame
retardant chemical to dissociate into its acidic functional form, the
strength degrade rate in any flame retardant treated wood is similar.
The essential difference between most flame retardant chemical systems is
the time and energy required for each chemical to dissociate at a given
temperature into its acidic functional form.

3.2 Wood Composites

This covers the various types of resin-bonded composite board where the
particles are either wood shavings, flakes, chips or fibers bonded together
with thermosetting adhesives such as urea formaldehyde, melamine
formaldehyde, or phenol formaldehyde.  Production of wood chipboard has been
very substantially greater than the other types of board though, in recent
years, world manufacturing capacity for medium density fiberboard has been
rapidly increasing.

Currently, only a small fraction of this production is treated with flame
retardants and demand for flame retardant versions is very dependent on
regulations and hence, localized.

Most particle board production utilize urea-formaldehyde binders and these
are acid setting.  Sodium borates, which are alkaline, can interfere with
this setting action and, as a result, boric acid has become the principal
boron compound used as the flame retardant in such board (References 16 and
17).  Typically, a boric acid loading of around 15% by weight of dry board
is necessary to satisfy required performance levels in most national fire
test standards.  The most widely used method of incorporation is to feed the
boric acid into the flow of particles, usually before the adhesive
application stage.  If sodium borate is used as the flame retardant, phenol
formaldehyde binder is commonly used due to its compatibility with alkaline
chemicals.

Fiberboard is made by a process analogous to that of paper making and large
quantities of water are involved.  Incorporation of soluble flame retardants
can pose a problem due to the necessity of recycling this water to avoid
loss of the flame retardant in the effluent.  The problem was resolved by
applying a solution of Polyborâ Disodium Octaborate Tetrahydrate to the
surface of the formed wet-lap on the machine just prior to it passing over
the vacuum boxes (Reference 18).  In pulling water from the wet-lap, Polybor
solution is drawn into it.
If necessary, the system can be closed at this point to recycle any of the
borate solution which may be pulled through the wet-lap.  For adequate flame
retardancy in fiberboard, loadings of Polybor around 15% by weight of board
are required.

There has been a substantial world-wide growth in the production and
utilization of a resin-bonded fiberboard, known commercially as medium
density fiberboard or MDF.  The bulk of MDF production employs
formaldehyde-based adhesives and where flame retardant grades are required,
it is necessary to use boric acid for compatibility reasons.  However, there
has been some compatible with such adhesives and, hence can be utilized as
the flame retardant.

4. Mattresses/Futons

In December 1973, the U.S. Department of Commerce Flammability Standard
FF4-72 was adopted.  This Act, which requires all mattresses to pass a
cigarette test for smoldering combustion, inspired a frantic search for
materials which would pass the test.  It was found that boric acid addition
to cotton batting was the most effective chemical treatment.  This
conclusion is still valid.

However, a large percentage of mattress suppliers now produce polyurethane
foam-filled mattresses which also pass the current standard but are
significantly more expensive than boric acid-treated cotton.  Mixed
polyester-cotton mattresses have also captured part of this market.

The reason that boric acid-treated cotton is now only a poor third in total
usage, even though it is less expensive and also more flame retardant than
the synthetics, is apparently the resistance of the manufacturers to adapt
their processes to allow chemical addition.  Most boric acid is applied dry,
although wet applications have been developed by USDA and commercialized by
Virginia Chemical.  Laboratory work has confirmed that boric acid is the
most effective chemical additive in cotton mattresses.  It has also been
shown previously that crude boric acid produced by simply adding sulfuric
acid to sodium borates is as effective as technical grade boric acid.

4.1 Cotton Batting/Garnetting Applications

Boric acid may be added at various points along the cotton batting line at
the discretion of the user.  Some add powder immediately after garnetting
directly on the web and in this fashion each layer of the batting will
contain boric acid.  Others add boric acid to a second stage willow.

Since dry additions may cause some loss through dusting, add-on requirements
up to about 12% by weight may be necessary to assure that the treated
product will contain the minimum boric acid necessary to assure the
cigarette test.

Boric acid dusting can be minimized and better adhesion to the fiber can be
achieved by first spraying the cotton with a suitable dust control oil.  The
amount of oil will vary from 1%, or more, depending on the setup and
operation of the individual plant.

4.2  Regulatory Requirements

Futons or soft furnishings used in automobiles and airplanes must be flame
retardant treated according to current U.S. Department of Transportation
codes, but there is no Federal law in the U.S. which requires cotton used in
furniture to be flame retardant treated.  However, the State of California
has adopted a standard in March 1977 which requires furniture to pass both a
cigarette ignition test, similar to that used for mattresses and a vertical
flame test (on the filling only).  In addition, synthetic filling also must
pass a vertical flame test after heat aging at 150oF (66oC).  Treated cotton
is excluded from this requirement apparently because the state believes that
it could not pass the test.  Boric acid-treated cotton may also pass the
heat aging test due to vapor phase diffusion.

The law requires that anyone who manufactures, wholesales, or retails
upholstered furniture or bedding products that are offered for sales in
individual state must hold a valid license.  Approximately 40 states have
some licensing or registration requirements for certain home furnishing
products including mattresses and futons.  The Bureau of Home Furnishings
and Thermal Insulation is an agency within the state Department of Consumer
Affairs with responsibility by law to license or regulate businesses
involved in the home furnishings industry as well as thermal insulation in
California.  Every article of upholstered furniture must have one of four
possible types of flammability labels attached.  The International Sleep
Products Association (ISPA) publishes the home furnishings requirements in
all 50 states.  They also provide the name, address, and telephone number of
the person or agency to contact in each state.

Under the California Administrative Code Title 4, Chapter 3, Section 1371 or
Federal Standard 16 CFR 1632 (FF -72), flame retardant properties shall be
retained by the mattresses under all normal conditions of temperature,
humidity and use and shall be able to meet the test requirements of these
regulations at any time during their useful life.  The mattresses should
pass the cigarette test described in the Technical Service Bulletin 106 -
Cigarette Test of Mattresses and Mattress Pads.  The upholstered furniture
such as futons should pass the cigarette test described in the Technical
Service Bulletin 116 - Cigarette Test of Upholstered Furniture.

The filling materials used in upholstered furniture can also be subjected to
the flame retardancy test under Technical Bulletin 117 - Flame and Smolder
Resistance Test of Furniture Components.


5. Fabrics

Recommendations of fire retardant treatments for fabrics are made basically
for cotton or other cellulosic materials, but may be applicable to certain
synthetics, particularly rayon.  Examples of materials requiring fire
retardancy include some clothing, drapes, rugs, ironing board covers, fabric
heat deflectors for stoves and fireplaces, canvas fire-smothering blankets,
and Christmas tree decorations.


5.1 Typical Formulations

The ratio of Borax and boric acid (5:3 or 3:2), and latterly Polybor became
recommended materials for imparting so called "temporary" flame retardancy
to cotton-based textiles (References 19).  The work "temporary" is used in
the context that, being water soluble, the borates are removed during
laundering and hence the treatment needs to be re-applied.  Consequently,
the treatment has tended to be restricted to fabrics where laundering is
infrequent.  Formulations containing Borax/boric acid, or boric
acid/ammonium phosphate, or Borax/boric acid/sodium phosphate were
recommended for such fire-retardant treatments (Reference 20).

One simple formula suggested contains 7 parts of Borax, 3 parts of boric
acid and 60 parts of water.  For this composition, approximately 15%
solution strength is recommended.  Other formulas include 7 parts of Borax,
3 parts of boric acid, 5 parts of magnesium chloride hexahydrate (or urea)
and 60 parts of water.  For this composition, approximate 25% solution
strength is recommended.  In the case of magnesium chloride, water
temperature should be lower than 100oF (38oC).

The recommendation of salt solution concentrations is based on the past
experience that in treating fabric, on an average, water retention is about
75% of the weight of the fabric.  A sample weighed before and after wetting
will determine the accuracy of this fact for the material under
consideration.  If deemed necessary, compensations in salt concentrations
may be made based on these findings.

Mixtures containing both urea and magnesium chloride are not recommended
because tests show loss of tensile strength of the textile.  Formulations
using magnesium instead of urea is considered superior with respect to
retention of strength of the treated fabric.

5.2 Treatment Techniques

Application of the fire retardant to the fabric by direct spraying or by
dipping the fabric into warm, fire retardant solution is acceptable.
Sprinkling the solution on the fabric is satisfactory but the material must
be completely wet.  Obviously only water fast colors may be treated.
Fabrics containing sizing may be more easily treated by adding small amounts
of soap or a wetting agent to the treating solution.

Ironing of treated fabric will not alter the effectiveness of the treatment
nor harm materials that may be ironed without a fire retardant treatment.
Best results are obtained by allowing the fabric to dry before ironing.


6. Paper

PolyborâDisodium Octaborate Tetrahydrate, combinations of Borax, boric acid
and borates mixed with other chemicals are used to treat paper products
where fire retardant properties are required.  The high levels of flame
retardants necessary (15-20% by weight) for paper do result in a stiffening
effect which can be overcome by inclusion of softening agents such as urea
in the treated solution.  The compositions given below have been tested and
found to impart satisfactory fire retardant properties and to minimize
embrittlement characteristics.

A mixture of Borax, boric acid and magnesium chloride hexahydrate in a ratio
of 7-3-5 has been proven to offer good fire retardancy.  A solution strength
of 12% is recommended.  This concentration may be formulated by dissolving
5.6% Borax, 2.4% boric acid and 4.0% magnesium chloride hexahydrate in
water.

A second composition which offers satisfactory results is Borax, boric acid
and urea in a ratio of 7-3-4.  A solution strength of 10% is recommended.
This concentration may be prepared by dissolving 5.0% Borax, 2.1% boric acid
and 2.9% urea in water.

Good fire retardant results are obtained with solutions containing all of
the components - Borax, boric acid, urea and magnesium chloride.  One
advantage of the four component mixture over that containing magnesium
chloride and not urea, is that solutions have less tendency to precipitate
magnesium borate.  A solution strength of 12% concentration is recommended.
This solution may be obtained by dissolving 5.6% Borax, 2.4% boric acid,
2.4% urea and 1.6% magnesium chloride hexahydrate.

The precipitation of magnesium chloride is very slight in the first three of
these formulations, but certain precautions should be taken.  Polybor, or
Borax/boric acid can be dissolved in the water at any temperature, but
magnesium chloride should not be added at a temperature above 100oF (38oC).
Likewise, the final fire retardant solution should not be heated
continuously above 100oF.



REFERENCES


1. Bikales, N.M., "Encyclopedia of Polymer Science and Technology," Volume
7,  Fire  Retardant, John Wiley, 1967.

2. Shafizadeh, F., "State of the Art on Smoldering Combustion," Wood
Chemistry  Laboratory, University of Montana, Paper presented at ASTM/DOE
Conference  on  Cellulosic Insulation, 1978.

3. Siddiqui, S.A., "A Handbook on Cellulose Insulation", Robert E. Krieger
Publishing  Company, Malabar, Florida, 1989.

4. Chiou, N., and D. W. Yarbrough, "A Review of the Literature: Fire
Retardants in  Cellulose Insulation", J. Therm. Insul., 10, p. 219-224,
1987.

5. McElroy, D.L., "Cellulose Insulation Progress Report," ORNL/TN-6433,
Metal  and  Ceramics Division, Oak Ridge National Laboratory.

6. Sanders, H.J., "Flame Retardants," Chemical and Engineering News, April
24,  1978.

7. Chiou, N., and D. W. Yarbrough, Energy and Buildings, 14, pp. 351, 1990.

8. Middleton, J.C., Draganov, S.M., and F. T. Winters, Forest Productions J.
XV,
 12, December 1965.

9. Technical Service Bulletin 102, Borax Consolidated Limited.

10. Winandy, J. E., and E. L. Schmidt, Forest Prod. J., 45(2), 1995.

11. LeVan, S.L., Ross, R.J., and J. E. Winandy, Res. Pap. FRL-498, USDA
Forest  Serv.,  Forest Prod. Lab., Madison, WI, 1990.

12. Oberley, W.J., Koppers Co., Inc., US Patent 4,373,010, February 8, 1983.

13. Winandy, J. E., et al., Research paper FPL-RP-485, USDA Forest Serv.,
Forest  Prod.  Lab., Madison, WI, 1988.

14. LeVan, S.L., and J.E. Winandy, Wood and Fiber Science, 2(1), 1990.

15. Winandy, J.E., Research Note FPL-RN-0264, USDA Forest Serv., Forest
Prod.  Lab.,  Madison, WI, 1995.


16. R. D. Warnes and F. Bird, British Patent 818,574.

17. J. Dulat, British Patent 1,435,519.

18. F. C. Smith and J. Thornton, British Patent 994,988.

19. British Launderers' Research Association Bulletin, 4(12), January, 1948.

20. Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, 10, 424.



Further advice is available from Technical Service Departments at:

  U.S. Borax Inc.    Borax Consolidated Limited
  President's Plaza I   170 Priestley Road
  8600 W. Bryn Mawr, #710N  Guildford
  Chicago, IL  60631   Surrey, GU2 5RQ
  USA     United Kingdom
  Tel:  1 800 729 2672   Tel:  44 1483 73 4000
  Fax: 1 800 258 4872   Fax: 44 1483 45 7676



The recommendations in this bulletin are based upon information believed to
be reliable.  As the use of our products is beyond the control of the
manufacturer, no guarantee, expressed or implied is made as to the effects
of such or the results to be obtained if not used in accordance with
directions of established safe practice.  Nor is there any warranty of
fitness for a particular purpose which extends beyond the described uses in
this bulletin.  Furthermore, nothing herein shall be construed as permission
or recommendation to practice a patented invention without authorization of
the patentee.



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