FR-20 Magnesium hydroxide [Mg(OH)2] Application Data Sheet for Polypropylene (PP) F-37 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 S7 S10 CAS Number Assay, w% Specific gravity Molecular weight Bulk density, g/ml 1309-42-8 99.4 2.3 58.3 0.55 Particle size, µm (Malvern Mastersizer 2000) D 50 1.45 1.80 1.10 1.60 D 90 < 6 < 6 Surface area (BET), m 2 /g 7±1 10±1 Grades with special surface treatments to optimize processability and properties are recommended with PP application. 1
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 improves tracking index FR-20, designed for high levels of fire retardancy (UL-94 class V-1 and V-0), is usually efficient at loadings between 40 and 65%. 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 2
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-20 120 is preferred for extrusion and injection moulding applications of PP. FR-20 120 has indeed a good contribution to improve melt flow during injection molding (Figure 2). 3
Figure 2: Influence of surface treament on MFI (PP homo V-0 with 62% FR-20; 230 C - 2.16 kg) 100 75 MFI, % 50 25 0 PP ref. PP + FR-20 120 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-20 120 and their properties. It may be advisable to feed FR-20 120 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- 20 120 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 4
Properties Properties achievable in PP homo- and block copolymers are summarized in Table 3. Table 3: Properties of PP flame retarded by FR-20 120 Type of PP PP Homo PP Block copo Ref. no FR FR-20 120 Ref. no FR FR-20 120 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 3 3 7 7 (230 0 C; 2.16kg) 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 Applications The range of applications for FR-20 120 in PP is very wide (Figures 3 & 4): 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 5
Figure 3: Under the hood electrical parts Figure 4: Insulating foams 6
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