2010’ International Symposium on Flame-Retardant Materials & T echnologies, Sichuan University, Chengdu, China, Sept.17-20, 2010 Polymeric Flame Retardants
Sergei V. Levchik*∗1,Pierre Georlette2, Yoav Bar-Yaakov2, Ita Finberg2, Yaniv Hirschsohn2
1: ICL-IP America, 430 Saw Mill River Rd, Ardsley, NY, 10502
2: ICL-IP, P. O. Box 180, Beer Sheva 84101, Israel
Keywords:polymeric flame retardants; bromine; phosphorus; Polyquel TM; Fyrol®PMP
Introduction
Polymeric flame retardants are large molecules (M w > 1000) and they are unlikely to penetrate through the cell membranes of living tissue. Furthermore, polymeric FRs typically have low solubility in water, which means that once incorporated into the end-product plastic matrix, they become integrated with the plastic and leaching is unlikely to occur. Because of negligible vapor pressure they do not migrate to the surface of the plastic during aging, thus eliminating any potential blooming in the finished product. Extensive testing has also shown that polymeric brominated FRs pose no risk of polybrominated p-dibenzodioxins and dibenzofurans, either in manufacturing or end-life incineration of the plastic product. I
t was also found that thermoplastics containing polymeric brominated FRs show good stability in recycling operations, a very important consideration from an environmental viewpoint. In this paper we will review existing and new polymeric phosphorus and bromine flame
example of a new development where polymeric and reactive flame retardant features are combined in one molecule.
Polypropylene and its co-polymers
ICL-IP has a range of polymeric FRs applicable for PP and its co-polymers. FR-1025, polypentabromobenzyl acrylate, is the top performer. Apart of very high efficiency, FR-1025 shows excellent resin flow, non-blooming performance and high HDT in PP and PP copolymers. Recently it was found than combinations of FR-1025 and magnesium hydroxide allow a significant decrease of the loading of antimony trioxide and achieve advantages in some physical properties. Table 1 shows flame retardant compositions and physical properties of PP block copolymer flame retarded with FR-1025 and FR-20-120 (magnesium hydroxide). Because FR-1025 is a compatible polymeric flame retardant it helps to increase HDT of PP copolymer from 75 to 127°C and further addition of an impact modifier helps improve impact strength to the level even higher than non-flame-retarded PP copolymer.
∗ To whom correspondence should be addressed.
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Table 1. Flame retardant compositions and physical properties of PP block copolymer
based on FR-1025 and FR-20 120
FR type No FR, Ref.FR-1025 Ref.FR-1025 + FR-20-120
Composition, wt %
PP block copolymer 100 49.1 44.8 39.8
Impact modifier 10    5 10
26.2
26.2
-
react to the recent
FR-20-120 -
21.4
21.4
30
FR-1025 -
Antimony trioxide - 10.9    2.6    2.6
Properties
UL-94 class (1.6 and 3.2 mm) NR V-0 V-0 V-0
Izod notched impact, J/m 146 168 192 401
HDT (450 kPa), °C 75 127 115 108
Nylons
The most common flame retardant for glass-filled nylon 6 and nylon 6.6 is brominated polystyrene.
ICL-IP offers it under the trade name FR-803P with average degree of bromination of aromatic rings
2.7 and molecular weight of 600,000. ICL-IP also offers a series of brominated epoxy polymers either
non-end-capped (F-2000 series) or end-capped with tribromophenol (F-3000 series) for glass-filled
nylons. Interestingly, it has been found that F-2400 of molecular weight of 50,000 and F-3100 of
molecular weight of 15,000, and FR-1025 provide similar or better performance compared to the
brominated polystyrene. Brominated epoxies and brominated polyacrylate also show very high oxygen
index in the glass reinforced nylon 6.6. At 10 wt. % Br it can be as high as 46.
Polyesters (PBT)
Table 2 shows physical properties of glass-filled PBT formulated with different polymeric FRs at
the level of passing UL-94 V-0 rating (0.8 mm). FR-1025 gives the best overall performance. Izod
impact strength is higher than non-flame retardant resin, because FR-1025 enhances adhesion of PBT
to the glass-fibers. FR-1025 is also beneficial as a flow promoter. Medium molecular weight
brominated epoxies F 3100 (M w = 15,000) and F 2100 (M w = 20,000) are also good flow promoters,
whereas brominated polycarbonate, often used as a flame retardant in PBT, has poor flow properties.
New polymeric FRs for polyolefins and styrenics
Recently ICL-IP introduced new family of polymeric flame retardants under the trade name
Polyquel TM. Polyquel TM is being supplied in the form of dust free pellets, which significantly improves
dosing, mixing, compounding and other usual downstream operations of the plastic industry. Bags and
other packaging containers are easily and completely emptied and this minimizes loss of the material
and potential release into the environment. Polyquel TM is targeting wide range of thermoplastics.
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Table 2. Physical properties of 30% glass filled PBT flame retarded with polymeric FRs (V-0 at 0.8 mm)
FR type No FR FR-1025 F-3100 F-2100 F-2400 Br-PC
Composition, w%
PBT 70 55.3 52.3 51.7 52.1 53.2
Glass
fiber 30 30 30 30 30 30
13.2
13.6
12.1
13
FR
10
trioxide    4.5    4.5 4.5 4.5 4.5
Antimony
(antidrip) 0.2 0.2 0.2 0.2 0.2
PTFE
Properties
MFI, g/10min (250°C, 2.16kg) 53 58 66 56 42 38
J/m 92 114 88 83 58 76
IZOD
notched,
HDT (1820 kPa), °C (annealed) 200 204 202 200 200
Tensile:
Strength, MPa 121 122 123 116 121 110
Elongation at break, %    3.4    2.3    2.1    2.2    2.3    2.3
Modulus, MPa  9,300 10,600 10,400 10,500 10,000 10,300 V 250-300 200 200 200 200
CTI,
Table 3. Physical properties and appearance of Polyquel TM 145.
Type Polyquel TM 145 Appearance
Appearance Free flowing off-white
granules
Specific gravity, g/cc    1.9
Bromine content, wt% 53.8
Softening range, ºC 105-220
TGA, 10% wt. loss, ºC 355
Recommended applications HDPE Injection molding
Polyquel TM 100 series is tailor made for polyolefins, more specifically for UL-94 HB and V-2 rated
high density polyethylene (HDPE). Physical properties of Polyquel TM 145 are shown in Table 3. The
main advantage of Polyquel TM 145 over low molecular weight FRs is its permanency in the polymer
matrix (non blooming).
Polyquel TM 200 series is designed for styrenic polymers (HIPS and ABS) and their alloys like
PC/ABS or PPE/HIPS. Polyquel TM 200 has build-in antidripping properties and it allows significant
reduction in the FR loading. Polyquel TM 240 and Polyquel TM 241 are tailored for extrusion and
injection molding applications respectively. Both provide good impact and tensile strengths and
exceptional UV stability.
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Epoxy resin
Recently ICL-IP introduced a new flame retardant curing agent for epoxy resins, Fyrol® PMP. It is a polymeric organophosphorus product (see structure below) which reacts with epoxy by insertion of phosphate ester bond into epoxy group. This flame retardant is very safe to use because it transforms from one polymeric form to another and therefore it has minimal risk of exposure to humans and to the environment. Due to special curing mechanism, cross-linked epoxy has a low concentration of secondary aliphatic alcohol groups, which are the thermally “weak links” of any cured epoxy. Because of this Fyrol® PMP is especially beneficial for lead free soldering applications. Epoxy cured with Fyrol® PMP shows 5 % weight loss at 365-375ºC, whereas 330º is barely achievable with a traditional dicyan
diamide curing system.
(HO)n
O
P
O
CH 3
O
O
P
O O CH 3
(OH)m p
m,n = 0 or 1
Conclusions
Bromine based and phosphorus based polymeric flame retardants are safe to use because they have very low mobility and therefore do not migrate to the surface of the polymer. The use of polymeric FRs is very versatile with examples shown in polyolefins, engineering thermoplastics and thermosets. Recent addition of Polyquel TM  family to the polymeric FRs significantly improves handling of brominated FRs and therefore eliminates spread in the environment. Oligomeric polyphosphonate, Fyrol® PMP, shows unique properties because, during the curing reaction, it transforms from linear polymeric form into cross-linked thermoset resin.
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