Optimization of Flame Retarded PP-Copolymer Compounds

1. Optimization of Flame RetardedPP-Copolymer Compounds By: Or Kariv Advisors: Dr. Fabian Rios Yoav Bar-Yaakov, Bromine Compounds LTD.

2. Objectives • Finding an optimal formulation of PP copolymer with bromine based FR. • Studying the influence of the FR on the compound’s properties. • Studying the influence of IM processing conditions on the compound.

3. Introduction • PP is known for its good mechanical and processing properties, but also for its high flammability. Bromine FRs • C-Br present low bonding energy and therefore Br can readily be released. • FR molecular structure depends on the thermal stability required for the polymer. Aromatic compounds high thermal stability Aliphatic compounds high flame retardant efficiency

4. FRproperties FR-370 Tris- tribromoneopentyl phosphate • Thermal stability fits polymer processing temperature • Good synergy with the matrix • Good dispersion within the matrix • Non “blooming” • Good flame retardancy • Chemical flame inhibiting mechanism

5. Mechanism Chain Scission & Flame poisoning: a competing reaction of HBr, with the radicals to create a less reactive radicals.

6. Experimental • Materials: • PP copolymer- grade SE- 50E ex by Carmel Olefins • FR-370- Tris- tribromoneopentyl phosphate by Bromine Compounds Ltd. • Free radical source (C-C initiator) • Equipment: • Injection molding machine, Arburg 500-150 • Twin-screw extruder, Berstroff L/D=32

7. Methodology • Studying the influence of additives. • Optimized formulation: • UL-94: V-0 rating • Minimum additives content • Optimal balance of properties • Studying the effect of IM conditions. Stage one- Stage two-

8. Stage one: Selecting the optimal formulation Reference formulations:

9. Results: Flammability Properties LOI- limited oxygen index • Significant increase in the presence of FR • C-C influence insignificant.

10. Results: Thermal Properties HDT- heat deflection temperature • FR exhibits a significant increase of HDT • C-C has inverse effect by causing the crystallinity degree to decrease

11. Results: Rheological Properties MFI- melt flow index • FR exhibits a plasticizing effect in high temperature • C-C causes MW reduction

12. Results: Mechanical Properties Izod impact test • The FR causes a significant decrease of impact strength Particles locate at amorphous phase and cause stress concentration

13. Results: Mechanical Properties Tensile modulus • FR causes a stiffening effect at room temperature • C-C causes MW reduction

14. Formulation costs

15. Finally… Choosing optimal formulation Balance between additives concentrations and properties Minimum costs Formulation Hcc14: 14% Br, 1.6% C-C

16. Stage two:DOE for injection molding conditions • Formulations: Hcc14 and 0cc20. Independent variables: • A- Screw RPM • B- Back pressure • C- Injection speed • D- Melt temperature • E- Mold temperature • F- Holding pressure Dependant variables: • Tensile strength • Tensile modulus • Impact strength • DSC: melting temperature melting enthalpy A six variables, two level screening design

17. Results • No reliable results were obtained from the experiment. The reason • Experimental error larger than variables effects. • Little control over formulations processing. Explanation • Plasticizing effect of the FR on polymer causing difficult processing.

18. DOE results Smaller than experimental error → 0 Marginal → 0

19. Conclusions • FR content affects polymer properties significantly. • FR content can be reduced by adding free radical source while maintaining flammability level. • Mechanical and rheological properties decrease. • Thermal properties increase. • An optimal formulation for flame retardant PP copolymer contains 14% Bromine (20% FR-370) and 1.6% C-C initiator. • While these compounds exhibit good FR properties, they are extremely difficult to process, limiting their commercial applications. • DOE analysis can be performed only on fully controllable processes.

20. Further Research • More extensive research on the rheological properties of PP copolymer- FR compounds is required, using capillary and dynamic rheometers. • A capillary rheometer will show how viscosity changes with higher shearing rates similar to IM process, as opposed to MFI. • The processing problems of these compounds should be addressed, researched and improved to obtain compounds which are more commercially usable.

21. For all the help and support… Ita Finberg, Yaniv Hirschsohn, Izik, Meir & Smadar Dr Iftah Nir, Dr Amos Ofir & Dr Anna Dotan And especially to Dr Fabian Rios from Shenkar Yoav Bar- Yaakov and Racheli Rotem from ICL-IP THANK YOU!

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