Low fogging HR foams (MDI)

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HR foams can significantly contribute to fogging of windshields in cars. The use of low volatility components such as surfactants, catalysts is important to reduce fogging. Either high molecular weight additives or additives with functional groups can be used to achieve no-fogging.
Increase in the crosslinking density of the urea hard segment is important to improvement in recovery and good compression set. Either diethanolamine or polyfunctional isocyanates can be used to increase crosslinking. Increasing the crosslinking density of the soft phase (higher functional polyols) will reduce the elongation. The resulting increase in chain entanglements reduces the mobility and increases the recovery time.
Formulation HR Foam Carbon dioxide blown

Polyether propylene oxide, ethylene oxide 85 % primary OH OH # 28 9003-11-6, 106392-12-5

100

Diethanolamine, CAS # 111-42-2

1.8

Low fogging silicone surfactant

1.0

Water

4.5

Triethylenediamine 33 %, CAS # 280-57-9

0.5

Bis(dimethylamino)ether formic acid, CAS # 51390-19-3

0.15

MDI purified and modified NCO % 25

72.74

Test results of machine prepared foam (test methods) (Conversion factors)

Overall density kg/m ( lb/ft3),  (1 kg/m = 0.0624 lb/ft3 )

53.4(3.34)

Core density kg/m( lb/ft3)

51.6(3.22)

SAG factor

3.1

CLD at 25 %, kPa

3.4

CLD at 40 %, kPa

4.5
CLD at 65 %, kPa 11.3

Tensile strength kPa (PSI)  (1 kPa = 0.145 PSI)

98(14.2)

Fogging

Silicone ppm

20
Besides silicone surfactants amine, antioxidants can contribute to fogging. For hydroxyl or amine reactive amines with low fogging tendency.
The foams can be prepared by hand mix laboratory procedure or with a stirrer of 2" diameter at 2500 rpm. The polyol. diethanolamine, silicone surfactant and amine catalyst were blended for 1 minute and with the isocyanate for 7 seconds.

Last edited on:

November 22, 2006

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