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Chemical Foaming Alternatives to Azodicarbonamide
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• Foaming Agents• What are they and how do you use them?• CFA – Endothermic & Exothermic• Challenges - Regulatory and Technical• Case Study: PP Foam• Cellular Structure• Worldwide Markets
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Foaming Agent(Blowing Agent)
A substance which is capable of producing a cellular structure via a foaming process in a variety of materials that undergo hardening or phase transition, such as polymers and plastics.
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Two technologies:
Physical Blowing Agent
Cellular structure created by injecting gas in a super critical state directly into the barrel through equipment modifications.
For high and medium density foams, gases utilized are usually N2 or CO2.
N2 CO2or
(Gas Injection)
Chemical Blowing Agent
Cellular structure created by a chemical reaction and heat during the plasticating process.
(Chemical Foaming Agent, CFA)
Gas generated is usually CO2, N2, or a combination for high-to-medium density foams.
N2 CO2And/or
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• Reduces CostLess Material Consumption
• Reduces Weight• Eliminates Sink Marks
Improved Printing on Flat Surfaces• Improves Thermal Insulation
• Improves Sound Insulation
• Higher Production EfficiencyLower Processing TemperaturesFaster Cycle TimeReduces Machine Energy
Why Use Foam?
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Why Use Chemical Foam?• Easily Scalable
Stable and RepeatableSimple Process, Easy to Feed
• Easy Startup CostEasy to use AdditiveNo Modifications to Equipment NeededFeeders and extrusion dies optimized for foam are worthwhile upgrades
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• Reduces CostLess Material Consumption
• Reduces Weight• Eliminates Sink Marks
Improved Printing on Flat Surfaces• Improves Thermal Insulation
• Improves Sound Insulation
• Higher Production EfficiencyLower Processing TemperaturesFaster Cycle TimeReduces Machine Energy
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Expectations of Modern CFAEarly CFA Technology:
• 400-500 micron cells were common and acceptable in commodity parts
• High gauge variability and process challenges• Closed-and-Open cells• ADC is most common worldwide; Challenges due to potential
toxicity• No longer acceptable for use in food packaging, children's
products
Modern CFA Technology:• Zero Toxicity• Process Friendly formulations – “Value Added” formulas for
easy processing• Uniform cell structure = more consistent physical properties,
better surfaces• Customers seek 200 microns cells and below, more Closed-
Cell content• Fine Cell structure = better retention of physical properties like
impact strength and elongation at break
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Primary CFA TypesExothermic
Azodicarbonamide (ADC) : Creates Nitrogen and Ammonia, generates heat upon decomposition.
• 50 years of use in rubber and plastics• Slow gas diffusion rate - Positive for some
applications and negative for others• Rapid and Robust gas expansion• N2 is not as soluble in olefins and styrenes as CO2
EndothermicCarbonate / Acid Blends (SAFOAM® Endothermic) : Creates CO2 and water, absorbs heat.
• 30 Years of use in Thermoplastics• Self Nucleating• Rapid gas diffusion rate – Faster crystallization times
due to CO2 being a plasticizer• Slow, controlled gas release (less pressure)• CO2 is more soluble in the polymer melt than N2
Most are FDA, Cool the system, usually make the best structure (small plentiful cells, white).
Typically best for PVC or ABS compounds. Heat up the System. Make Larger cells in Olefins, Styrenics, etc. Best suited for SFM or extruded plastic lumber.
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Under the REACH Regulation(1), azodicarbonamide (ADCA) was identified as a Substance of Very High Concern (SVHC) in December 2012 in a unanimous opinion of the Member State Committee of the European Chemicals Agency (ECHA) considering its hazard classification as a respiratory sensitizer and the view that there is evidence of probable serious effects to human health which give rise to an equivalent level of concern to those of carcinogenic, mutagenic and reprotoxic substances.
(1) Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18.12.2006 concerning the Registration, Evaluation, Authorization and Restriction of Chemicals.
11 February 2015
Harmonized classification H 334 “Respiratory Sensitivity” in EU
Regulatory pressure on ADC per REACH
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Gas Volume:Robust gas evolution rate of ADC may be preferred in free-foaming
applications; such as plastisols and post-foaming applications (soft mats).
Developments are underway to optimize endothermic CFA for these applications
that there are no alternatives to ADC in thermoplastic foams.but it is a myth….
Compounding and processing temperatures:• Typical ADC
Activation of approx. 210°C to 220°C • Typical Carbonate
Activation of approx. 150°C to 180°C• SAFOAM® HT
Activation of approx. 210°C
Challenges
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ZONE 1 ZONE 2 ZONE 3 ZONE 4 CLAMP HEAD DIE400°F 460°F 370°F 370°F 340°F 345°F 350°F
Extrusion profile:
Polypropylene: Exxon PP4712E1, 2.8 MFI1.25” single screw extruder, 30:1 L/D, 3:1 compression ratio.
AZ-130 (ADC - exothermic) powder and Safoam® HT (endothermic) powder were used
Calcium carbonate particle size: 1 micron
Extrusion Case Study 4/10/15
Melt Temp at clamp 380°F (193°C)Melt Pressure:1800 psi
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SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.5% HT 30-140 85 0.750 17.0%
SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.5% AZ-130 40-540 305 0.800 11.5%
0.5% AZ-130 0.5% HT
Melt Temp at clamp 380°F (193°C)Melt Pressure:1800 psi
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SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.5% HT + 0.5% CaCO3
35-130 75 0.685 24.2%
SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.5% AZ-130 + 0.5% CaCO3
45-320 180 0.685 24.2%
0.5% AZ-130 + 0.5% CaCO3
0.5% HT + 0.5% CaCO3
Melt Temp at clamp 380°F (193°C)Melt Pressure:1800 psi
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Why the difference?
ADC HT (Endo)
Head Pressure 1,800 1,800 psi
Temperature 200 200 celsius
Solubility 0.4 2.4 moles of gas / kg of polymerAverage Particle Size 3.0 15.0 microns
Average Cell Size 305 85 microns
CO2 has higher solubility than N2in Polypropylene at comparable temperature. It readily dissolves at lower pressure.
Particle size of the CFA is generally regarded as a prime determinant of cell size. However solubility of the gas must be taken into account when predicting cell size in the finished part.
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Sheet1
ADCHT (Endo)
Head Pressure1,8001,800psi
Temperature200200celsius
Solubility0.42.4moles of gas / kg of polymer
Solubility14.044.0grams per ml
Average Particle Size3.015.0microns
Average Cell Size30585microns
Sheet2
Sheet3
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SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.75% HT 35-180 90 0.529 41.5%
SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.75% AZ-130 100-450 290 0.644 28.8%
0.75% AZ-130 0.75% HT
Melt Temp at clamp 380°F (193°C)Melt Pressure:1800 psi
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SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.75% HT + 0.75% CaCO3
50-230 135 0.495 45.2%
SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.75% AZ-130 + 0.75% CaCO3
125-620 345 0.418 53.8%
0.75% AZ-130 + 0.75% CaCO3
0.75% HT-P + 0.75% CaCO3
Coalescence
Melt Temp at clamp 380°F (193°C)Melt Pressure:1800 psi
Here we may have reached the foamability limit of this particular PP.
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Cell Collapse (Coalescence) Explained
Nucleating agents are used to create a starting point from where a cell can form as gas comes out of solution. A closed-cell structure is crucial in sustaining mechanical properties.
However, in ADC condition 4, poor solubility of the N2 gas has led to cell coalescence creating a closed and open cell structure reducing mechanical properties.
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SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
1% HT 30-220 115 0.623 31.0%
1% HTEndothermic
foaming agents are self nucleating and
self regulating
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SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
1% HT 30-220 115 0.623 31.0%
SAMPLE CELL RANGE (MICRONS) NOMINAL SIZE (MICRONS) DENSITY (G/CC) DENSITY REDUCTION
0.75% HT 35-180 90 0.529 41.5%
Less is More
1% HT0.75% HT
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• High molecular weight, branched, low MFI polymers:
• Good Temperature Control; especially from head, through die• Cool post-head : melt pumps, screen changers, mixers…anything post barrel
head• “Reverse” Temperature profile
• Good Process Pressure• 1800 Psi / 125 bar
• Other tips• L/D 24:1 minimum – 30:1 or greater for better mixing time and gas dispersion• Plug vents• Short Land lengths tightly gapped in center of sheet
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Endothermic CFA Foam Tips
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Endothermic Chemical Foam Facts
• Safe to useFDA/EU food safe additive for thermoplastics
• Safe to shipREACH compliant, not a SVHC
• Easy to processWhite pellets or powdersNo royaltiesScalable
CFA Suppliers
• Reedy Chemical Foam• Clariant Masterbatches• ID Additives• United Color Corp• Tramaco• and others
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Profile extrusion:
Plastic building products are affordable, durable, and safe. Chemical blowing agents are currently utilized in such applications as window profiles, trim molding, siding and decking.
Straighter profiles, increased load-bearing strength and improved insulation accompany lighter weights and faster throughput. Chemical blowing agents have also been used as a special effect colorant for faux wood, as an alternative to lamination.
Worldwide use of Endothermic Chemical Foam
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XPS Nucleation (Extruded Polystyrene):
Chemical blowing agents contribute to environmental responsibility by providing a means to food packaging manufacturers to reduce polymer use, energy and overall costs.
As a nucleating agent for physical gas processes, chemical blowing agents have allowed significant reductions in the use of Hydrofluorocarbons (HFC). The ability of a CBA to create more closed cells results in greater retention of gasses limiting the escape into the atmosphere.
Worldwide use of Endothermic Chemical Foam
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PP hollow profile sheets (twin wall fluted sheet):
• Excellent chemical resistance for building applications• Easy sealing for interlayer pads and food packaging applications• Low thermal conductivity for food packaging applications• Lower density. > 10% weight savings• Improved superficial smoothness for advertising applications• Improved impact strength for packaging and building applications• Higher energy absorption for packaging and building applications
Worldwide use of Endothermic Chemical Foam
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•Internal flow efficiency•Thermal insulation
•Mechanical protection•Negative buoyancy
Sub-Sea Pipe Coatings
Worldwide use of Endothermic Chemical Foam
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AZ-130
HT
Trial Summary• HT activates at 207°C
• AZO-130 activates at 222°C
• HT (endo) generated ½ the gas of ADC
• Same density with ½ the gas, because the
CO2 was fully solubilized
• Self-nucleating HT endo requires no CaCo3.
Although it does help to an extent.
• A smaller uniformly dispersed cell structure
results in a better finished part.
Endothermic CFA is a viable alternative to ADC in most applications but must be optimized.
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Questions? Visit us on the Web!
www.ReedyChemicalFoam.com980-819-6930
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