FR-20 Magnesium hydroxide [Mg(OH)2] Application Data Sheet for Ethylene-Vinyl Acetate copolymer (EVA) 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 polyethylene and its copolymers such as EVA. As a result of its chemical nature, high purity and excellent thermal stability (Tables 1 and 2), FR-20 exhibits inherent advantages over other halogen-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 treatments are available to optimize processability and properties of polymers containing FR-20.
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 For high fire safety, high loading (40-65%) of FR-20 is necessary. Thermal stability Thermogravimetric analysis of FR-20 reflects its high thermal stability. Its technological processing window is up to 300 0 C. Its thermal stability combined with excellent resistance to degradation, makes it a product of choice when recycling is an issue. Excellent smoke suppressant FR-20 is also an excellent smoke suppressant and it is one of its main advantages over halogen- and antimony- based FRs. A significant smoke suppression by FR-20 is already observed by addition of 20 to 30% FR-20 in EVA flame retarded by a brominated/antimony trioxide FR system. Surface treatment In order to cope with the high loadings needed to get UL-94 ratings, surface treated grades, for instance FR-20 200 (containing 2% stearic acid coating), are preferred for extrusion and injection moulding applications of EVA.
Coated grades of FR-20 have indeed a good contribution to improve melt flow during extrusion or injection molding (Figure 1). Figure 1: Influence of surface treament on MFI (EVA 28% VA; V-2 with 56% FR-20; 190 C - 5 kg) 10 MFI,g/10 min 5 0 FR-20-200 FR-20-100 The water absorption of EVA containing FR-20 is significantly reduced by its coating. This is illustrated in Figure 2 where grade 100 is not coated. Processing conditions Table 2 provides indicative formulations enabling to get class V-2 (3.2 mm) with EVA copolymers flame retarded by FR-20. It may be advisable to feed FR-20 in two steps: circa 35% in the feeding zone the rest, 20-25%, at the end of the second third of the extruder via a lateral feeder. Typical processing conditions to compound and mold EVA flame retarded with FR-20 are as follows:
Compounding: Compounding in a co-rotating twin-screw extruder (L/D = 24) at about 160ºC. Screw speed, Rpm: 190 Injection molding Temperature profile, 0 C 165 175 185-190 Mold temperature, 0 C 35 Figure 2: Water absorption (EVA 28% VA; 56% FR-20) g/cm² 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time, days 100 200 Properties Properties achievable in EVA are summarized in Table 2 and 3.
Applications The applications for FR-20 in polyethyelene and its copolymers are mainly for the production of wire and cables used in the telecommunication and in the car industries. Table 2: Properties of EVA flame retarded by FR-20 Ref. no FR FR-20 200 FR-20 100 Mg(OH) 2 Compet. 1 COMPOSITION, wt % EVA (ELVAX 3175, DuPont) 100 33.7 33.7 33.7 FR-20 200 (S7 or S10) - 56.3 56.3 FR-20 100 (S7 or S10) 56.3 PROPERTIES Flame retardancy UL-94 class (3.2 mm) NR V-2 V-2 V-2 LOI, % (S7 grade) 26.6 36 41 LOI, % (S10 grade) 33 42 35 MFI, g/10 min (S7 grade) 8 3 3 kg) 5(190 0 C- 33 MFI, g/10 min (S10 grade) kg)5(190 0 C- 7 3 3 Tensile properties (S7 grade) Strength at break, MPa 10.8 11.8 9.3 Elongation at break,% 326 197 337 Tensile properties (S10 grade) Strength at break, MPa 10.7 12.2 11.7 Elongation at break,% 322 184 200 1 - The data are based on equivalent materials commercially available in the market.
Table 3: Properties of EVA flame retarded by FR-20 Influence of the FR-20 loading and its grade Ref. no FR Ref. FR-20 100 Untreated (S-7 grade) FR-20 200 (S-7 or S10 grades) COMPOSITION, wt % EVA (VA content 18%) 100 44 80 60 44 35 FR-20 200-56 20 40 56 65 PROPERTIES Flame retardancy UL-94 class (3.2 mm): Class (S7 grade) NR V-2 NR NR NR NR Class (S10 grade) NR NR V-2 V-2 V-2 LOI, % (S7 grade) 20 31 22 25 28 36 LOI, % (S10 grade) 20 24 25 28 33 Hardness Shore D (S7 grade) 34 50 36 38.5 44 45.5 Shore D (S10 grade) 34 37 40 44.5 44 Tensile properties (S7 grade) Strength at break, MPa 3.7 10.2 4 4.6 5.9 6 Elongation at break,% >460 53 >460 450 340 325 Tensile properties (S10 grade) Strength at break, MPa 3.7 4 4.7 5.4 5.8 Elongation at break,% >460 >460 415 280 335
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