Clearing the fog about fogging effects of liquid fire retardants in flexible foam.

To build up knowledge of fogging behavior of different flame retardants (FR) a study of two non-reactive oligomers, a reactive oligomer and two monomers was conducted. Test conditions followed automobile manufacturer specifications. This article clarifies the difference in the fogging tests specified by some of the worlds auto companies. The data here show the relative fogging performance of some of the most common FR-additives used in flexible foams and two experimental additives. Testing is on foam samples, not raw materials. Foams were prepared containing no flame retardant, 5.0 parts of FR and 15 parts of FR, at a density of 1.8 lbs./cu. ft. The fogging test conditions shown (with resulting product classification) include those required by Ford, General Motors, Mercedes and Toyota.

Clarification

In recent years, competent scientists have reported contradictory data on the effect of FR additives on fogging performance. This article will clarify both the performance to be expected and the reason for the confusion, which is widespread. Comparisons are made on flexible foam samples. The following are some of the primary assumptions leading to the confusion.

* The effect on fogging performance by different chlorinated phosphate esters is similar (not true). Example: comparison data between tris chloro propyl phosphate (TCPP) and tris di chloro propyl phosphate (TDCP) is shown.

* There is only one "fogging" test (not true); or

* All fogging tests lead to the same conclusion (not true). Various tests are described showing some of the differences in conclusions based on test selection.

* Oligomers are good and monomers are bad (not true). Data will be shown that some monomers perform better than many oligomers (part of this is due to the presence of the parent monomer in polymers).

* Reactive FR additives are good, non-reactive are bad (not true). Although true in theory, data will show that in many reactive products their fogging performance is dominated by non-reactive additives that are included with the product. Comparison of two similar products with good fogging performance but much different reactivity will clarify this point.

* Fogging tests on raw materials are an adequate measure of performance in flexible urethane foams (not true).

* General knowledge is generally misleading.

* All people who undertake the task of clarifying misunderstandings in fogging are sorry they did (true).

In Europe and Japan the gravimetric method is preferred. Our study supports this choice. [Gravimetric at 100 [degrees] C*/16 hrs.**/21 [degrees] F***(* = bath temperature,** = time in bath, *** = temperature of cooling plates) and 110 [degrees] C/3 hrs./21 [degrees] F]

In the United States, the Photometric is the standard test procedure, however, GM and Ford have their own test specifications. Their conditions are as follows: GM-85 [degrees] C/ 6 hrs./38 [degrees] F, 95 [degrees C/6 hrs./38 [degrees] F and 110 [degrees] C/6 hrs./38 [degrees] F and Ford: 90 [degrees] C/3 hrs./21 [degrees] F and 100 [degrees] C/3 hrs./21 [degrees] F. (At least seven tests to choose from [table 1]).

Table 1 - fogging tests

       Temp.           Time             Temp.
bath ([degrees] C)     hrs.      plate ([degrees] C)

       100             16                21
       110              3                21
       110              6                38
       100              3                21
        95              6                38
        90              6                21
        85              6                38

       Temp.              Country        Method
bath ([degrees] C)

       100                Europe      Gravimetric
       110                Europe      Gravimetric
       110                U.S.A.      Photometric
       100                U.S.A.      Photometric
        95                U.S.A.      Photometric
        90                U.S.A.      Photometric
        85                U.S.A.      Photometric

Data evaluation

Foams were prepared with all the FRs mentioned above. Foams also were prepared without any flame retardant, as a blank used for control purposes.

Relation airflow versus fogging behavior

Foams with different air flows were prepared by changing the stannous octoate levels, giving air flow levels of 2.5, 5.5 and 8.0 CFM. No significant differences in amount of fog between the different foams were found. Openness of the control foam did not influence the amount of fog (confirmation ref #1).

Figure 1 and table 3 show the relative performance of the fire retardants tested in both of the gravimetric tests and at two different FR levels.

[Figure 1 ILLUSTRATION OMITTED]

Table 3 - fogging data-gravametric/grams

Conditions       Non    O-NR1     O-R1     TDCP     O-NR2     TCPP
Gravametric      FR

100/16/21/     0.0003   0.0007   0.0009   0.0010   0.0017   0.0132
FR @ 5.0

100/16/21      0.0002   0.0022   0.0029   0.0032   0.0061   0.0367
FR @ 15.0

110/3/21       0.0015   0.0010   0.0013   0.0021   0.0023   0.0079
FR @ 5.0

110/3/21       0.0014   0.0027   0.0031   0.0035   0.0039   0.0169
FR @ 15.0

The data confirm comments in refs. 1 and 2 that fogging increases with increased concentration of the FR additive.

Comparing TDCP and TCPP it is clear that:

* Some FRs contribute significantly to fogging.

* Not all monomers are bad (comment from Japan).

* Some monomers are as good as some oligomers.

Comparing oligomer O-NR1 with oligomer O-R1 it is clear that reactivity does not guarantee a better performance. These two oligomers have the same basic structure differing by the hydroxyl content in O-R1.

Figure 2 and table 4 show the performance of these products in the photometric or reflectance test. For the products chosen all the tests give similar results relative to rating the different Fits. This may not always be the case. In the gravimetric method the test plate is placed in a desiccator before weighing, eliminating the likelihood that water will be a major contributor to the fogging. This is not done in the photometric test, therefore moisture retained in the test sample will contribute to fog test results. Figure 3 compares a data set performed in the standard photometric test with the same test run after drying the samples for only one hour in a desiccator.

[Figures 2-3 ILLUSTRATION OMITTED]

Table 4 - fogging data-photometric/fog index

Conditions      Non FR    O-NR1    O-R-1    TDCP    O-NR2    TCPP
Photometric

110/6/38        96.85     84.67    83.34    82.10    81.72    25.82
FR @ 5.0

110/6/38        96.86     83.99    82.22    81.16    80.19    23.16
FR @ 15.0

95/6/38         96.32     87.87    87.03    84.98    84.03    28.15
FR @ 5.0

95/6/38         97.11     86.72    85.67    83.98    83.10    27.18
FR @ 15.0

90/6/21         97.70     88.90    88.30    87.40    86.16    32.50
FR @ 5.0

90/6/21         97.60     88.18    87.80    86.20    85.40    31.60
FR @ 15.0

85/6/38         96.11     95.36    94.56    93.39    89.81    35.80
FR @ 5.0

85/6/38         98.99     94.73    93.94    91.32    88.25    34.50
FR @ 15.0

100/3/21        97.90     85.78    84.60    83.82    83.08    26.70
FR @ 5.0

100/3/21        97.80     84.88    84.08    82.88    82.20    25.90
FR @ 15.0

Conclusions

Non reactive oligomers can be good FRs for fogging behavior in the automotive foams, either in gravimetric or photometric methods. [Ref. oligomer 1 (experimental) and oligomer 2 (Fyrol 99)].

Reactive oligomers should also give good fogging behavior in both methods. [Ref. oligomer 2 - reactive analog of oligomer 1].

TDCP (Fyrol FR-2) also gives good results in the photometric method, and slightly better results in the gravimetric methods.

Oligomer 2 (Fyrol 99) gave a slightly worse performance than TDCP (Fyrol FR-2).

TCPP (Fyrol PCF) gave the worst results in either gravimetric or photometric methods. TCPP should not be used if fogging is a major concern in the final application.

The reproducibility for the gravimetric method is good.

The reproducibility for the photometric method is poor (confirmation ref. 3).

The presence of humidity, either before the test or after removal from the test unit can have a great effect on the final results - (compare tables 2 and 3). Careful attention must be given when determining reflectance on exposed glass plates.

Table 2 - foam preparation

3,000 mw Polyol     100.0    100.0   100.0   100.0  100.0   100.0

Flame retardant     Non-FR   O-NR1   O-R-1   TDCP   O-NR2   TCPP
Level                  ---   5/15    5/15    5/15   5/15    5/15
H2O                   3.55   3.55    3.55    3.55   3.55    3.55
Niax A-1              0.10   0.10    0.10    0.10   0.10    0.10
Niax L620              1.0   1.0      1.0     1.0    1.0     1.0
Stannous octoate      0.20   0.20    0.20    0.20   0.20    0.20
TDI 80/20            47.50  47.50   47.50   47.50  47.50   47.50
TDI index              110    110     110     110    110     110

O-NR1 = Non-reactive oligomer O-R = Reactive oligomer TDCP = Tris dichloro propyl phosphate/Fyrol FR-2 TCPP = Tris chloro propyl phosphate/Fyrol PCF O-NR2 = Non-reactive oligomer/Fyrol 99

References

(1.) Blundell, Dr. C. and Wuestenenk, J. 1992. "The fogging performance of flame retardants in flexible polyurethane foam," Utech 1992.

(2.) Grillo, D.J., Hansel, T.L. and Landis F.A. "Reduction of volatiles in polyester based flexible foams," PFA October 1994.

(3.) Duncan, C.B. and Chiasson, P.J. 1991. "Variations occurring in the light scattering film test," Journal of Vinyl Rheology, Sept. 1991.

(4.) Hill, R.A. "New antioxidant package for polyether polyols with reduced fogging behavior," SPI Polyurethane Technical Marketing Conference, 1992.