FR-20 Magnesium hydroxide [Mg(OH)2] Application Data Sheet for Polypropylene (PP) FR-20, a series of high purity grades magnesium hydroxide, is offered by ICL-IP as inorganic halogen free flame retardants (FR) recommended where use of halogenated products is limited or prohibited. FR-20 is particularly suitable for use with PP. As a result of its chemical nature, high purity and excellent thermal stability (Table 1 and 2), FR-20 exhibits inherent advantages over other halogenated free FR additives currently used for the same applications. Table 1: Properties of FR-20 FR-20 grade S5 S7 S10 CAS Number 1309-42-8 Assay, w% 99.6 Specific gravity 2.36 Molecular weight 58.3 Bulk density, g/ml 0.5-0.7 Particle size, µm: (Malvern Mastersizer 2000) D 50 1.8-2.2 1.45 1.8 1.1 1.4 D 90 < 6 Surface area (BET), m 2 /g 4-6 6-8 8.5-11 Grades with special surface treatments to optimize processability and properties are recommended with PP applications.
The use of FR-20 is advantageous when the following properties are required: halogen-free flame retardancy low and non-toxic smoke high thermal and long term heat aging stabilities dimensional stability after injection molding acid scavenger and heat stabilizer reinforcing filler improving tracking index Thermal stability FR-20 has a high thermal stability up till 340 0 C and its use is recommended where alumina trihydrate (ATH) is not sufficiently stable. Thermogravimetric analysis of FR-20 (Table 2) reflects its high thermal stability allowing high processing temperatures typical to PP. Its thermal stability combined with excellent resistance to degradation, makes it a product of choice when recycling is an issue. Table 2: Thermo gravimetric analysis (TGA-10 0 C/min in air) Weight loss, % Temperature, 0 C 2 370 5 385 10 402
Excellent smoke suppressant FR-20 is also a powerful smoke suppressant and it is one of its main advantages over halogen- and antimony- based FRs. Halogen based PP compounds burn with intense black smoke leading quickly to high values of smoke density in a NBS chamber (Figure 1). On the contrary, PP compounds flame retarded by FR-20 are generating very little quantities of smoke. 1000 Figure 1: Smoke optical density of V-0 PP (NBS smoke chamber - ASTM E 662-94 - Flaming mode) Br FR + Sb2O3 (no FR-20) Optical density, DM 750 500 250 Ref no FR 0 62% FR-20 (no Br FR) 0 2.5 5 7.5 10 12.5 15 Time, min Surface treatment In order to cope with the high loadings needed to get class V-1 or V-0, surface treated grade FR-20 200 is preferred for extrusion and injection moulding applications of PP. FR-20 200 has indeed a good contribution to improve melt flow during injection molding (Figure 2).
100 75 Figure 2: Influence of surface treament on MFI (PP homo V-0 with 62% FR-20; 230 C - 2.16 kg) MFI, % 50 25 0 PP ref. PP + FR-20 200 PP + FR-20 untreated Processing conditions Tables 3 provides indicative formulations enabling to get class V-0 (1.6mm) with PP homo- and block copolymers flame retarded by FR-20 200 and their properties. It may be advisable to feed FR-20 200 in two steps: Circa 40% in the feeding zone The rest, 20-25%, at the end of the second third of the extruder via a sidefeeder. Typical processing conditions to compound and mold PP flame retarded with FR-20 200 are as follow: Compounding: Compounding in a co-rotating twin-screw extruder (L/D = 32) Temperature profile, 0 C: 120-170-170-170-180-190-200-210-220 Screw speed, Rpm: 430
Injection molding Temperature profile, 0 C 220-220-230-230-230 Mold temperature, 0 C 80 Properties Properties achievable in PP homo- and block copolymers are summarized in Table 3. Applications The range of applications for FR-20 200 in PP is very wide: E & E: switches, wire and cables, connectors Automotive: under the hood electrical parts, wire and cables, trimmings and cover panels Building: thermal insulation foam, panels, sheets, ceiling parts and films
Table 3: Properties of PP flame retarded by FR-20 200 S-7 Type of PP PP Homo PP Block copo Ref. no FR FR-20 200 Ref. no FR FR-20 200 Composition, w%: PP 100 38 100 36 FR - 62-64 Properties: Flame retardancy: UL 94 (3.2mm), class NR V-0 NR V-0 LOI 19 30 18 29 MFI, g/10 min (230 0 C; 2.16kg) 3 2.4 7 5 Tensile: Max. strength, MPa 36 17 25 15 Elongation at break, % 158 20 74 1 Modulus, MPa 1600 5700 1500 4300 Impact IZOD notched, J/m 25 38 120 52
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