NEW CHALLENGE for INCORPORATION of EXPANDABLE GRAPHITE as FLAME-RETARDANT in VARIOUS POLYMERS VIJAY J. BHAGAT

Transcription

1 NEW CHALLENGE for INCORPORATION of EXPANDABLE GRAPHITE as FLAME-RETARDANT in VARIOUS POLYMERS VIJAY J. BHAGAT RESEARCH & DEVELOPMENT CENTRE CLEANLINE PRODUCTS Pvt. Ltd., PUNE, INDIA PRESENTED AT FIRE & MATERIALS TH INTERNATIONAL CONFERENCE & EXHIBITION SAN FRANCISCO, USA. ABSTRACT: Expandable Graphite is well accepted as a flame retardant in most of the foam system. Incorporation of expandable graphite in foam system makes it easier due to its lower operating temperature but it becomes difficult task to incorporate expandable graphite into higher processing temperature of polymer. This paper demonstrates about the incorporation of expandable graphite into high processing temperature of polymer. It also helps to identify the growth areas of expandable graphite to meet future demand of the market. INTRODUCTION: For safety and environmental reasons, flame retardancy has become a critical issue, particularly in the area of construction, transportation, and electronic/electrical application. Although halogenated Flame-Retardants are highly effective in reducing flammability at commodity products, their future use is not precisely defined; this is due its potential unacceptable risk to the human health and the environment. This is the driving force for the development of non-halogenated Flame- Retardants.

2 R&D centre of Cleanline Products Pvt. Ltd., is constantly working on new technique and future oriented NON HALOGENATED PRODUCTS. In last three years CPPL scientists have studied the market demands and aggressively moved to broaden their product range of Non Halogenated Flame Retardant - Expandable Graphite under the brand name of CARBOFOIL which is : - ENVIRONMENT FRIENDLY. ECONOMICAL. MAINTAIN FLAME RETARDANT PERFORMANCE AT LOWER LOADING. IMPROVING & PRESERVING MECHANICAL PROPERTIES OF POLYMERS. COMPATIBLE WITH PROCESSING CONDITION OF VARIOUS POLYMERS. CARBOFOIL FLAME RETARDANT EXPANDABLE GRAPHITE Expandable graphite consist of black flakes and characteristically exhibits expansion along C axis of the crystal structure by about more than hundred times, when it rapidly heated above C. The mechanism of expansion lies in the vaporization of Intercalent present into the layer of graphite flakes 1. Oxidation of graphite is necessary for expansion and flame retardancy of expandable graphite. Expandable graphite is manufactured by oxidation of graphite in sulfuric acid 2 ; oxidized graphite when exposed to heat it expands. Expansion of graphite depends upon 1. Size of flake. 2. Purity of graphite. 3. Intercalent present into the layer of graphite flake. Flame retardant properties of expandable graphite depends up on activation of expandable graphite at temperature lower than the critical temperature (CT) where polymer start to melt, decompose or ignite 3.

3 Figure of Expanded Graphite. Expandable graphite is well accepted as a flame retardant in most of the foam system (Ref. 4,5 & 6) and resins (Ref.7). The work reported into the paper seems to have limitation to use E.G at higher processing temperature. Our work demonstrates that by selection of Expansion Activation Temperature (E.A.T.) of E.G it is easier to incorporate into various polymer during processing. EXPANSION IN CC/ 1 GM / 2 MINUTES EXPANSION ACTIVATION TEMPERATURE OF DIFFERENT EXPANDABLE GRAPHITE (CARBOFOIL GRADES) EAT EAT EAT EAT EAT EAT TEMPERATURE IN DEGREE CENTIGRADE

4 Selection of expandable graphite on the basis of E.A.T. with various polymers processing temperature. EXPANDABLE GRAPHITE CARBOFOIL PROCESSING TEMPERATURE OF POLYMER Grade E.A.T < 150ºC < 220ºC < 240ºC < 270ºC EAT ºC X X X EAT ºC X X X EAT ºC X X X EAT ºC X X EAT ºC X EAT ºC Easy incorporation X Expandable Graphite expands during processing Work carried out by Fumio Okisaki shows that expandable graphite has limitation for the flame-retardant properties and it works excellent in combination with other chemical. However, our work revealed that by selecting the expansion of EG from 300ºC to 500ºC, limitation of expandable graphite for flame retardant properties can be overcome. We have selected four grades of polymers (i.e. EVA, PP, LLDPE & PC.) for the evolution of flame retardancy with the different expandable graphite grades.

5 Flame retardation of polymer with various expandable graphite EXPANDABLE GRAPHITE HOST CARBOFOIL POLYMER Grade E.A.T EAT ºC EVA EAT ºC EVA EAT ºC EVA EAT ºC PP EAT ºC PP EAT ºC PP EAT ºC LLDPE EAT ºC LLDPE EAT ºC PC EG (phr) UL 94 RATING at 3.2 mm 0 N.R.. 20 V1 30 V0 20 V1 30 V0 30 N.R 0 N.R.. 30 V1 40 V0 20 V1 30 V0 30 N.R 30 N.R. 40 V0 30 N.R 10 V1 15 V0

6 Identified Growth Areas : To mask black colour of the graphite. To make smaller particle size of expandable graphite with higher expansion for higher processing temperature of polymers. Lower loading to improve physical and mechanical properties of various polymers. CONCLUSION : Hereby it is demonstrated that expandable graphite grades CARBOFOIL EAT 220, CARBOFOIL EAT 240 & CARBOFOIL EAT 270 make easy incorporation at processing temperature 220ºC, 240ºC & 270ºC respectively. By selection of expansion properties at 300ºC to 500ºC improve the flame retardancy performance of polymer without addition of other flame retardant. REFERENCES : 1. Carbon & graphite hand book by Charles L Mentel. 2. Zhong Patent cn A 29 October Vijay J. Bhagat, Behavior of Expandable Graphite as a flame retardant in flexible PU foam presented at Polyurethane Foam Association, Arlington Virginia, USA, May 10, R.W.H Bell Flexible polyurethane foam. UK patent application 2,168,706 A. 5. MIKIO Fire- Resistance styrene resin foam and their manufacture. JP A219 July R.W.H Bell Manufacture of Flame retardant rubber latex foam. EUR.PAL.APL EP A1. November 19, Daniel W Krassowski & Brain M Ford. Expandable Graphite flake as an intumescent flame retardant additive.