Flame retardant thermoplastic elastomers

1. An essentially halogen-free thermoplastic elastomer compound, comprising:

(a) styrene-containing thermoplastic elastomer;

(b) an ammonium polyphosphate-containing flame retardant;

(c) expandable graphite filler;

(d) plasticizer; and

(e) polypropylene;

wherein the styrene-containing thermoplastic elastomer is selected from the group consisting of styrene-ethylene-butylene-styrene, styrene-ethylene-propylene-styrene, styrene-ethylene-ethylene/propylene-styrene, styrene-isobutylene-styrene, styrene-butadiene-styrene, styrene-isoprene-styrene, and combinations thereof; and

wherein weight percents of the ingredients comprise

Styrene-containing thermoplastic elastomer

10-35%

Flame retardant containing ammonium polyphosphate

25-60%

Plasticizer

10-40%

Polypropylene(s)

 5-25%

Expandable graphite filler

10-25%

Anti-oxidant

 0-2%

Thermal Stabilizer

 0-2%

Other Optional Additives

 0-10%.

2. The compound of claim 1 , wherein the styrene-containing thermoplastic elastomer has a weight average molecular weight of at least 200,000.

3. The compound of claim 1 , wherein the styrene-containing thermoplastic elastomer is not maleated but has a weight average molecular weight in excess of 75,000.

4. The compound of claim 1 , wherein the plasticizer is a paraffinic oil.

5. The compound of claim 1 , further comprising adhesion promoters; biocides; anti-fogging agents; anti-static agents; bonding, blowing and foaming agents; dispersants; fillers and extenders; fire and flame retardants and smoke suppressants; impact modifiers; initiators; lubricants; micas; pigments, colorants and dyes; plasticizers; additional processing aids; release agents; silanes, titanates and zirconates; slip and anti-blocking agents; stabilizers; stearates; ultraviolet light absorbers; viscosity regulators; waxes; and combinations of them.

6. The compound of claim 1 , wherein the weight percents of the ingredients comprise:

Styrene-containing thermoplastic elastomer

15-25%

Flame retardant containing ammonium polyphosphate

30-50%

Plasticizer

15-30%

Polypropylene(s)

 5-20%

Anti-oxidant

 0-1%

Thermal Stabilizer

 0-1%

Expandable graphite filler

15-20%

Other Optional Additives

 0-5%.

7. A thermoplastic article, comprising the compound of claim 1 .

8. A thermoplastic article, comprising the compound of claim 7 , wherein the article is expandable in the presence of heat.

9. The thermoplastic article of claim 8 , wherein the article is in the shape of a door seal and is expandable in the presence of heat at least 300% over its dimension when not heated.