INUMESCENT TECHNOLOGY
FOR THERMOSET RESINS
PHILIP S. RHODES
BROADVIEW TECHNOLOGIES
NOV. 14-15, 2005

INTUMESCENT TECHNOLGY
 Provides fire protection by building a continuous char foam layer on the polymer surface when exposed to heat or flame.

Different types of fire retardants
 Halogenated additives and resins
 Water releasing additives
 Intumescing agents/ char formers
 Activated intumescing agents

Halogenated additives and resins
 PROS  CONS
 Cost effective
 Efficient at low loading levels
 Harmful thermal decomposition products
 Dioxins produced when burned in resource recovery plants

Water releasing additives
 PROS  CONS
 Low cost  High loading levels
 Only provides short term protection

Intumescent agents
 PROS  CONS
 Non hazardous thermal decomposition products
 Long term fire and thermal protection
 High loading levels
 Only work with select resins
 May require synergists

Activated intumescent agents
 PROS  CONS
 Long term thermal protection
 Low-moderate loading levels
 Work with a wide variety of resins
 Moderately expensive
 Still require the right resin-intumescent agent match

Intumescent agents
How do they work?

 Intumescent agents are catalysts for char formation
 They convert to mineral acids when heated but are non acidic at temperatures below 200 C
 Catalyze dehydration reactions
 Work best with organic compounds that can undergo dehydration reactions

Classic dehydration reaction
R-OH + R’OH + ACID = R-O-R’ + HOH
= R-O-R + HOH
=R’-O-R’ + HOH

What types of compounds readily undergo dehydration reactions
 Starches
 Sugars
 Cellulosics
 Pentaerythritol

 Starch  Pentaerythritol
 (C6 H10 O5)n  C5 H10 O4

Can intumescent agents work if the carbons do not contain a oxygen/nitrogen functional group?
The answer is YES.

Two approaches to overcome a low number of functional groups
 The addition of additives that contain a high number of functional groups such as pentaerythritol and melamine
 Use of an activated intumescent agent

What is an activated intumescent agent?
An intumescent agent that will help add functional groups onto hydrocarbons when they do not exist.

When polymers start thermal decomposition what happens?
 Hydrogens are stripped off forming carboncarbon double bonds
 The hydrogen combines with oxygen in the vapor phase to produce water vapor and heat
 The carbon bonds break and low molecular weight alkenes enter the vapor phase
 These alkenes are further split and oxidized to produce CO, COO and HOH

What happens in the presence of an activated intumescent
 Hydrogens are stripped off forming carboncarbon double bonds
 The hydrogen combines with oxygen in the vapor phase to produce water vapor and heat
 The water vapor adds back across the double bonds via a catalytic route
 The hydroxyls formed combine to form thermally stable ether linkages that produce char
 During this dehydration reaction water is released cooling the polymer via a ablative mechanism

 Formulation
Epoxy example
 DER 331 10
 ANC. 350A 4.5
 INTU. AC2BG 1.5
 PROPERTIES
 (5 mil coating)
 Char yield 66%
 Char ht(mil) 1000
 Expansion 200 x
 Protection m
40

Urethane example
 Formulation
 Poly diol 61
 TMP 2.5
 Int AC2hph 36.5
 MDI 22.5
 Properties
 (5 mil coating)
 Char yield 62%


Char ht
Expansion
 Protection m
250
50x
29

 Formulation
Styrene acrylic
 RH TR (50%s) 10
 Intu AC3WM 3
 Properties
 (5 mil dry coating)
 Char yield 76%


Char ht
Expansion
 Protection m
450
90x
36

Polypropylene
 Formulation
 Polpropylene 10
 Plasticizer
1
 Intu AC-3
3
 Properties
 (5 mil film on steel)
 Char yield 70%
 Char ht 60
 Expansion 12x
 Protection 18 m