development of a wire and cable extrusion line for processing polyolefins containing novel flame...
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BACKGROUNDHalogenated flame retardants have been commercially utilized in the plastics industry since the early 1970’s. They are highly effective in decreasing flammability. When developed, very little information was known regarding the environmental persistence and toxicity of brominated additives. These compounds were elected for study by the National Institute of Environmental Health Sciences in 1995 for hazard evaluation1. Since then, extensive research has been conducted
Development of a Wire and Cable Extrusion Line for Processing Polyolefins Containing Novel* Flame Retardants
Andrew Fothergill, Liam Driscoll, Sethumadhavan Ravichandran,Prof. Stephen Johnston, Prof. Jayant Kumar, Prof. Ramaswamy Nagarajan
University of Massachusetts Lowell
Special Thanks To: The International Wire and Cable Symposium, Professor Stephen Driscoll, and Mayur Kumbhani
ABSTRACT
Due to concerted environmental regulations, some of the halogenated flame retardants such as decabromodiphenyl ether are being phased out. The focus of this project is to complete an investigation into the effectiveness of a bio-derived non-halogenated flame retardant material. Ultimately, the proprietary flame retardant could be compounded into a polyethylene resin to accommodate wire and cable grade products. The successful qualification of the flame retardant will serve as an alternative to current halogenated additives. Extensive testing has shown the ability to reduce the rate of thermal degradation, and has indicated the ability to be melt processed with the base resin. Processability was found to be effected only slightly by increasing loading levels as well.
current grades is now well-known to cause bodily harm through various degenerative diseases4,5 including cancers3. Dioxins and furans are both carcinogenic in very low amounts, and remedial measures and cost-effective reduction to exposure is nearly non-existent. Influenced by sustainability trends, specific studies to understand the root contaminants were initiated. Two specific chemicals were identified to have an impact on the wire and cable industry: polybrominated diphenyl ethers and polybrominated biphenyls. On July 1, 2006, the European Union enacted the RoHS Directive, which initiated the phase-out of poly(vinyl chloride) and halogenated flame retardants6. The directive only restricts the use of these substances. However, companies are phasing out these chemicals to ensure sustainability, safety, and recyclability7. This presents a market potential for non-halogenated flame retardants. This research is focused on exploring the use of a novel alternative material.
REFERENCES1. United States of America. Department of Health and Human Services. National Toxicology Program. Report on
Carcinogens. 11th ed. Vol. 70. Print. Ser. 25.
2. International Chemical Secrateriat. Bromine and Chlorine - Human Health and Environmental Concerns. ChemSec. Clean Production Action, Nov. 2009. Web. 28 Oct. 2010. <http://www.chemsec.org/rohs/reports-and-documents>.
3. Report on Carcinogens, Eleventh Edition; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program.
4. Lebel, G. “Organochlorine Exposure and the Risk of Endometriosis.” Fertility and Sterility, vol. 69 (1998): 221-228.
5. Bertazzi P.A. et al. “The Seveso studies on early and long term effects of dioxin exposure: a review.” Environmental Health Perspectives, vol. 106 (suppl 2, 1998): 625-631.
6. "What Is the RoHS Directive?" EBFRIP - European Brominated Flame Retardants Industry Panel. European Brominated Flame Retardant Industry Panel, 2008. Web. 25 Oct. 2010. <http://www.ebfrip.org/main-nav/european-regulatory-centre/rohs-directive-restriction-of-the-use-of-certain-hazardous-substances-in-electrical-and-electronic-equipment/what-is-the-rohs-directive>.
7. International Chemical Secretariat. Electronics Without Brominated Flame Retardants and PVC. May 2010. Web. 29 Oct. 2010. <http://www.chemsec.org/rohs/reports-and-documents>.3
8. TN 48, “Polymer Heats of Fusion”, TA Instruments, New Castle, DE
9. TA123, “Determination of Polymer Crystallinity by DSC”, TA Instruments, New Castle, DE.
* “Non-Halogenated Flame retardant materials” J. Kumar, R. Nagarajan, S. Ravichandran et al. Patent Pending
regarding the ability of halogenated organics to act as precursors to dioxin and furan generation2. This includes brominated and chlorinated flame retardants. The toxicity of
Figure 4: DSC Comparison Base vs. PVP
Figure 3: DSC Comparison Base vs. Novel
Reduction of crystallinity by 20% for Novel FR Reduction of crystallinity by 30% for PVP FR Minimal variation noticed in TM for blend
Figure 2: TGA Comparison Base vs. PVP
Figure 1: TGA Comparison Base vs. Novel
Novel FR shows a 9% maximum reduction in mass loss rate at 5% loading PVP FR shows minimal effect for various loadings
of additive on degradation characteristics The Novel FR produced twice the amount of
char at 2%
DSC results show a reduced crystalline phase due to the addition of FR
Low loading levels for Novel FR additive
reduced dynamic viscosity up to 15% 15% Novel FR increased viscosity by 20% compared to 51% for the 15% PVP FR PVP FR showed a 20-51% increase in
dynamic viscosity relative to the base resin
All samples passed the UL94-HB test Flame retarded samples swelled upon
burning, which reduced the drip count Results inconclusive as to which loading
level provided best flame retardancy
Figure 5: Dynamic viscosity results
FUTURE WORK Blend higher loadings of FR by mass Potentially blend with nanoclays Scale-up to extrusion/injection molding Additional industry standard testing X-Ray crystallography for crystal size and type
CONCLUSIONS Thermal degradation of the polymer-FR blends
fall within the range of 375oC- 500oC Novel FR had a lower mass loss rate than PVP FR DSC results indicate ability to extrude blend at
similar conditions to base resin• Matching exothermal peaks at 110oC and
endothermal peaks at 125oC• Inhibited crystallinity for both blends
Processability not compromised at low loading levels of Novel FR, slightly effected at 15%
10% loading level underperformed in UL94-HB test due to possible phase separation
Table 2: UL94-HB Burn Test Results
Table 1: Percent Crystallinity from DSC
MATERIALS Medium Density Polyethylene [MDPE]
• Manufacturer: Dow Chemical Company• Grade: DHDB-6549 NT
Flame Retardants [FR]• Bio-derived and non-halogenated
proprietary additive• Poly(4-vinylphenol) [PVP]
COMPOUNDING Blend MDPE with non-halogenated flame
retardants at 5%, 10%, and 15% FR by mass Procedure
• MDPE processed at 185oC – 5 minutesPVP processed at 165oC – 5 minutes
• FR added to melt and blended for 5 additional minutes
CHARACTERIZATION Thermogravimetric analysis [TGA]
• Degradation of samples through thermal exposure to 1000oC
Differential scanning calorimeter [DSC]• Cycle: Heat – Cool – Heat • Rate: 10oC/min
Rheological analysis• Study the non-Newtonian characteristics
based on storage/loss modulus and viscosity Flammability - UL 94-HB
• Determine the burn rate of the base resin and blends
• Burn less than 1.5” per minute to pass
RHEOLOGICAL PROPERTIES
THERMAL PROPERTIES BURN CHARACTERISTICS
Base Resin(Flaming Drips)
5% Novel FR(Hanging Glob)
5% PVP FR(Drip Forming)
THERMAL PROPERTIES