The Use of Solstice® Gas Blowing Agent (GBA) in Low 

Pressure Spray Polyurethane Foam Applications

MOJEE CLINE

Fomo Products, Inc.

 2775 Barber Rd.

 Norton, OH 44203

MARY BOGDAN

 Honeywell

 20 Peabody St.

 Buffalo, NY 14210

ABSTRACT

 Low Pressure polyurethane one component foam systems (OCF) and two component foams systems collectively 

“LP SPF” are primarily used to stop air infiltration by sealing or adding insulation to the building envelope. The use

of these products includes but is not limited to, insulation, adhesives, gap fillers, air sealants, and patching products. 

Currently, HFC-134a is used extensively as a propellant and blowing agent in these products. One consideration can 

be the global warming potential (GWP). Solstice GBA (HFO-1234ze(E)), an alternative to HFC-134a, has a GWP 

of less than 1 and can be a replacement for HFC-134a. The transition from HFC-134a to Solstice GBA will 

represent a 99.9% reduction in the GWP of these products. The focus of this paper will be the inclusion of Solstice 

GBA into these products via shelf life, product quality and product field performance evaluations.

DISCLAIMER

Although all statements and information contained herein are believed to be accurate and reliable, they are presented 

without guarantee or warranty of any kind, expressed or implied. Information provided herein does not relieve the 

user from the responsibility of carrying out its own tests and experiments, and the user assumes all risks and liability 

for use of the information and results obtained. Statements or suggestions concerning the use of materials and 

processes are made without representation or warranty that any such use is free of patent infringement and are not 

recommendations to infringe on any patents. The user should not assume that all toxicity data and safety measures 

are indicated herein or that other measures may not be required.

INTRODUCTION

 

A wealth of literature exists on the modification of high pressure spray foam systems and their applications using 

hydrofluorooelfin (HFO) as a blowing agent (1, 2, 3, 4). It is important to understand the differences between low 

pressure and high pressure spray foam applications. Although both applications use similar classes of chemicals and 

produce polyurethane foam, there are significant differences between the products and how they are applied. The 

designation “Low Pressure” describes a class of polyurethane foams that are delivered in kits and refillable systems 

that are maintained at pressures less than 250 psi. The key differences between low (LP SPF) and high pressure 

spray polyurethane foam (HP SPF) systems are identified in Figure 1.
*Note recommended use is provided by product suppliers

www.spraypolyurethane.org/PPE

Figure 1. Key Differences of Low Pressure vs. High Pressure SPF

Low pressure SPF’s are designed to fill and insulate large voids and surfaces. Residential applications include 

insulating and sealing rim/band joists, crawl spaces and walls. In doing this air infiltration is reduced, which is 

critical in building insulation. Other applications include sealing spent mine shaft to maintain proper ventilation in 

active areas, acoustic barriers, pipeline fortifications, and protective undercarriage coatings.

The composition of low pressure SPF’s have changed since their implementation. In the early 2000’s the spray 

polyurethane foam industry experinced a change in blowing agents/propellants with the transition from 

hydrochlororfluorocarbon (HCFC) to hydrofluorocarbon (HFC) technology due to the high Ozone Depletion 

Potential (ODP) of HCFC’s. HFC-134a became the non-flammable blowing agent/propellant of choice for many LP 

SPF companies due in part to an ODP value of zero. Today, there is a growing focus on the global warming impact 

of building products. The LP SPF industry is now transitioning away from high GWP HFC’s. A wealth of literature 

exits on the modification of high pressure spray foam systems and their application using hydrofluorooelfins(HFO) 

as a blowing agent (1,2,3,4). HFO’s have low GWP values and ODP values of zero.

One such HFO is the commercially available Solstice Gas Blowing agent (GBA, HFO-1234ze(E), trans 1,3,3,3 

tetrafluoropropene) produced by Honeywell. This paper will begin with a discussion of what physical, chemical and 

environmental properties a blowing agent propellant requires for this application. It will include a discussion on how 

the properties of Solstice GBA compare to those of the currently used blowing agent/propellant HFC-134a. 

The paper will continue with a discussion of the development process for Solstice GBA LP SPF and conclude with a 

discussion of how products made with Solstice GBA meet the required industry quality standards for both OCF and 

LP SPF products.
BLOWING AGENT/PROPELLANT

In one component foam (OCF) and two component low pressure polyurethane foam systems collectively “LP SPF”,

the fluorocarbon blowing agent/propellant used is traditionally a gas. Therefore, the gaseous blowing agent must 

have certain properties and must maintain these properties over the shelf life of the product. The characteristics that 

are particularly important to customersare summarized in Table 1. They cover the necessary environmental 

properties such as ODP and GWP and the chemical properties necessary for both foam processing and final foam 

properties. 

Table 1. Characteristics of A Blowing Agent/ Propellant to Meet Customer Needs

Category Characteristics

Environmental & Health Acceptable Environmental Properties ( ODP, GWP)

Odor Free

Low Toxicity

Polyol Blend Good Polyol Miscibility

Compatible with Other Raw Materials

Non- Corrosive

Appropriate Vapor Pressure

Compatible with Packaging, Hoses and Guns

Foam Processing Appropriate Vapor Pressure

Non- Flammable

Foam Properties Low Thermal Conductivity

No Effect on Polymer

Provides Small Size Cells

The environmental and physical properties of Solstice GBA are compared with those of HFC-134a which is 

currently used in the industry, in Table 2. Both materials are volatile organic carbon (VOC) exempt in the U.S. and 

are non-ozone-depleting. As stated earlier, the primary reason for the transition from HFC technology is to reduce 

the environmental footprint of the product. There is a 99.9% reduction in GWP when transitioning from HFC-134a 

to Solstice GBA technology.

Flammability of a blowing agent/ propellant has an impact on the LP SPF and OCF formulation and the application 

of the products. HFC-134a and Solstice GBA are non-flammable gases confirmed by both ASTM E-681, and EU 

Test method A-11. It should be noted that flammability characterization and flammability regulations for gaseous 

materials are evaluated at 21°C. Solstice GBA exhibits narrow vapor flame limits at temperatures above 28°C. At 

30°C, it exhibits flame limits LEL/UEL at 7.0/9.5 volume percent in air. 

Since the LP SPF and OCF products are installed in a variety of applications and may require respiratory protection 

during installation, it is important to confirm that the WEEL workplace environmental exposure level (WEEL) value 

for Solstice GBA is similar to that for HFC-134a. The American Industrial Hygiene Association has assigned a 

WEEL of 800 PPM (8-hour time weighted average) to Solstice GBA.
Table 2 Comparison of Environmental and Physical Properties of Solstice GBA and HFC-134a

Property Solstice GBA HFC-134a

Environmental Properties

Ozone Depletion Potential (ODP) ~0 ~0

Global Warming Potential (GWP) (100 yr) <1 1300*

VOC ( Volatile Organic Compound) US- Exempt US- Exempt

Physical Properties

Molecular Weight 114 102

Boiling point, °C (°F) -19 

(-2.2)

-26 

(-14.8)

Flammability

Flashpoint, °C (°F) None None

LFL/UFL, ( Vol % in air)@ 21C None None

Health & Safety

Exposure Level 

(AIHA WEEL– 8 hr TWA), ppm 800 1000

*IPCC,2013: Climate Change 2013: The Physical Science Basis, Contributions of Working Group 1 to the Fifthe Assessment Report

of the Intergovermmental Panel on Climate Change[ Stocker,T.F.,D. Qin, G-K. Plattmer, M. Tignor, S.K. Allen, J. Boschung, A. 

Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)}. Cambridge University Press, Cambridge, United Kingdom and New York, NY, 

USA,1535 pp.

OCF and LP SPF manufacturer product literature generally states that the products have a shelf life of 12-18 month

depending on the specific application. It is important that during this storage time the propellant/blowing agent does 

not react with the product containers. Solstice GBA is non-reactive and non-corrosive toward all commonly used 

metals in polyurethane processing and both one-component and low pressure two component foams package and 

filling equipment. This includes carbon steel, stainless steel, copper and brass. This assessment was performed by 

immersing metal coupons in neat Solstice GBA in a sealed tube, and held at elevated temperatures (400°F [200°C] 

and 600°F [315°C]) for two weeks. In addition, Honeywell investigated compatibility of plastics and elastomers by 

immersing test coupons in neat Solstice GBA in a sealed tube at room temperature for a period of two weeks. The 

sealed tubes, under pressure, exposed the substrate to the liquid and gas phases of Solstice GBA. It should be noted, 

however, that other components such as polyurethane pre-polymer were not evaluated, as formulations vary by 

manufacturer. The results of this compatibility study are summarized in Tables 3 and 4. In addition, Fomo has 

confirmed that there are no compatibility issues with the materials used in the containers, tubing and guns used in 

OCF and LP SPF applications.
Table 3. Plastics Compatibility Solstice GBA

Average Percentage Change

Polymer Weight Volume

HDPE +0.8 -3.7

Polypropylene + 0.8 0.0

PET 0.0 0.0

Nylon 6,6 -0.3 0.0

PVC-Type 1 0.0 -0.4

PVDF + 0.2 0.0

PTFE + 2.0 + 2.4

Polyetherimde 0.0 0.0

Table 4. Elastomer Compatibility Solstice GBA

Average Percentage Change

Elastomer Hardness Weight Volume

Fluoroelastomer -11.3 +4.4 +5.7

EPDM -1.5 +2.0 -2.5

Butyl Rubber -1.1 +1.3 +0.9

Neoprene +7.3 -7.7 -11.5

Since the fluorocarbon acts as both a propellant and a blowing agent in this application, the vapor pressure of the gas 

and the solubility of it in the polyol blend are important criteria. The propellant pushes the product from the 

container; if the vapor pressure is not high enough, sufficient material will not be dispensed from the container. The 

vapor pressure of Solstice GBA is compared to that of HFC-134a in Graph 1. Although the vapor pressure of 

Solstice GBA is lower than HFC-134a it is still acceptable for this application.

Graph 1. Key Comparison of Vapor Pressure of Genetron 134a and Solstice GBA
Solubility of a blowing agent is critical to both the foam processing and the foam quality. There is a fine balance 

between solubility in the polyol blend yielding fine foam structure and sufficient pressure in the container for 

dispensing the product. Table 5 reports the miscibility of Solstice GBA in various polyols and diisocyanates.

Table 5 Miscible of Solstice GBA in 75°F (24°C) of Various Polyols and Diisocyantes 

Weight % 5% 10% 15% 20%

Polyols

Polyether- Sucrose 

Glycerine initiated, 

OH-360

Miscible Miscible Miscible Miscible

Polyether- Phenol 

Initiated( Mannich) 

OH- 520-540

Multiple layers Multiple layers Multiple layers Multiple layers

Polyether- Nonyl 

Initiated( Mannich) 

OH- 470

Miscible Miscible Miscible Miscible

Aromatic polyesterOH-232

Multiple layers Multiple layers Multiple layers Multiple layers

Polymeric MDI

Mid 

Functionality(2.7) 

% NCO 31.5

Miscible Miscible Multiple layers Multiple layers

High 

Functionality(2.8) 

% NCO 31.0

Multiple layers Multiple layers Multiple layers Multiple layers

In summary, Table 1 lists the characteristics of a blowing agent/propellant in OCF and LP SPF applications. The 

data presented in this section demonstrates that Solstice GBA meets the environmental and health requirements by 

being a non-ozone depleting, ultra- low GWP, and a VOC exempt material. In addition, a WEEL has been 

established for the material. From a polyol blend perspective, Solstice GBA is compatible with many construction 

materials used in both the processing of polyol blends and packaging used for the final product. The boiling point 

and vapor pressure are appropriate for the applications noted earlier. However, the ultimate viability of a blowing 

agent/propellant is determined in application testing. Formulation modification and application testing for OCF and 

LP SPF are discussed in the following sections.

LOW PRESSURE SPRAY POLYURETHANE FOAM (LP SPF) 

LP SPF’s are classified as closed or open cell depending upon the morphology of the cellular structure of the foams, 

i.e. open cells, allowed for fluid penetration into the foam specimens. The physical differences of open and closed 

cell foams are significant, but both offer various advantages depending on the requirements of the specific 

application. Closed cell foams are used where insulation is critical. Table 6 lists typical differences between the two 

types.
Table 6. Typical differences between Closed and Open Cell SPF

Property Closed Cell Open Cell

Aged R-Value 6.0 per inch 4.3 per inch

Strength & Rigidity High Low

Vapor Permeability Low High

Density Medium (1.75 – 2.25 lbs/ft3) Low (<1.0 lbs/ft3)

Sound Absorption Fair Excellent

Air Barrier Properties Yes Yes, at higher thickness

Water Resistance Yes No

 

 Critical properties of LP SPF’s are application specific, and many of these properties are required for building 

codes such as flame and smoke ratings (e.g., ASTM E-84 or ASTM E-162.) Other important properties include Rvalue, closed cell content, bulk density, compressive strength, tensile strength, dimensional stability, cell structure, 

and foam appearance. In addition, product shelf life of at least 6 months ideally 12 months or more is expected. 

 Fomo’s initial work to replace HFC-134a with Solstice GBA focused on maintaining all key properties of a closed 

cell, Class I ASTM E-84 formulation. It was apparent after the first prototype completed a 3-month accelerated 

aging protocol (aged for 12 days at 50°C to simulate a 3 month shelf life at room temperature) that this would not be 

a “drop-in” change. The result was foam with poor cell structure, delayed cure profile, poor foam rise and 

inhomogeneous yet smooth surface. Figure 2 highlights the physical appearance of this attempt.

Figure 2. Initial attempt with direct replacement of HFC-134a with Solstice GBA. Three month aged sample.

 The formulation was then optimized. Subsequent prototypes, while shelf-life stable, did not provide the required 

properties listed in Table 6, particularly density. After several designed experiments with varying polyol, surfactant,

water content and catalyst packages, a stable B-side formulation with acceptable physical properties, including 12-

month shelf life was developed. Table 7 contains a general overview of the B-side formulations.
Table 7. Composition of LP SPF ASTM E-84 Insulation (HFC and HFO)

B-Side Components Approximate Concentration (Weight %)

HFC Formulation HFO Formulation

Polyol(s) 52 51

Flame Retardant 40 41

Surfactant 2 2

Catalyst 5 5

Water 1 1

 Although the weight percentages of the different classes of ingredients remained relatively unchanged, the specific 

chemicals used in the new HFO formula differ from those used in the current HFC formula. Physical properties of 

the new HFO formula are listed in Table 8. 

Table 8. Physical Properties of HFO-LP-SPF

Properties Target Results 

Shelf Life 12+ months 12 months

Tack Free Time 30 – 60 sec 30 – 60 sec

Cuttable 2 – 5 minutes 2 – 5 minutes

Initial R-Value at 1” ASTM C518 @ 75 F Mean Temp ~ 7.0 6.0 – 6.5

Compression Strength ASTM D1621 

Parallel 26 lbf/in2 18.5 lbf/in2

Medium Density ASTM D1622, Free Rise 1.75 – 2.25 lb/ft3 1.9 – 2.25 lb/ft3

Closed Cell Content ASTM D2856 >90 % >90 %

Dimensional Stability ASTM D2126 ±5% (Volume) ±5% (Volume)

Fire Rating ASTM E84, Tested at 2” Thickness PASS – Class I PASS – Class I

Fire Rating (Mining Applications) ASTM E-162 PASS PASS

Cold Temperature Performance Good Excellent

 Cross section images are shown in Figure 3. There is a shift in cell structure after aging of the polyol premix, as 

well as a slightly slower cure profile. Work is underway to further enhance these properties prior to extended field 

tests in residential applications. Demonstrations in niche markets, such as mining, confirmed superior cold weather 

performance of this formulation. 
Figure 3. Current prototype with Solstice GBA. Twelve month aged sample.

Figure 4. Spray outs outside a West Virginia mine in February 2015.

ONE COMPONENT FOAM (OCF)

 Low pressure one-component polyurethane foam sealants and adhesives are pre-reacted in a single can or cylinder 

to form a pre-polymer. This pre-polymer then reacts with ambient moisture at the time of application to produce 

foam. The tack-free condition, which identifies surface cure time, is within five to 10 minutes (depending on the 

amount of moisture in the air), and the overall cure time is typically 12 to 24 hours. 

 

OCF’s are generally used for smaller bead applications such as around door and window frames, pipes, and other 

openings. They may also be used as fire block materials. OCF adhesives are used in construction for roofing and 

architectural structures. Physical properties for OCF’s are application specific and include shelf life stability 

between 9 and 18 months, density, tensile strength, dimensional stability, cell structure, and foam appearance.

 

The initial work to replace HFC-134a with Solstice® GBA (HFO-1234ze (E) focused on maintaining all key 

properties of an adhesive formulation. Unlike the efforts with the LP SPF formulation, Solstice GBA proved to be a 

“drop in “ and resulted in foam with good shelf-life stability and maintaining most physical properties. An 

overview of the formulation is shown in Table 9 with corresponding physical testing results shown in Table 10. 

Figure 5 contains pictures of the same formulation sprayed with HFC and HFO versions. 
Table 9. Composition of HFO-OCF Adhesive

Components Approximate Concentration (Weight %)

Polyol Blend (Includes FR, Surfactant, Catalyst) 30 - 40

Isocyanate (pMDI) 45 - 55

Blowing Agent/Propellant <20

Table 10. Physical Properties and other attributes of HFO-OCF

Properties Target Range HFO Results

Flow Rate Consistent- minimal sputtering Consistent- no sputtering

Tack Free Time 4-8 minutes 4-8 minutes

Cell Structure Free of large voids Free of large voids

Foam Appearance Holds shape to adhere to tiles Holds shape to adhere to tiles

Curing in Foam Center Good Good

Tensile Strength 15 psi minimum >15 psi

Density >1.5 pcf >1.5 pcf

Dimensional Stability +/- 5% +/- 5%

Compressive Strength >8 psi >8 psi

Water absorption <10% <10%

Shelf life 12 months 12 months

Closed cell content >50% >50%

Figure 5: LP OCF samples blown with HFC-134a (left) and Solstice GBA (right)

CONCLUSION

Solstice GBA meets the specified environmental and health requirements for a blowing agent/propellant in both 

OCF and LP SPF applications. Honeywell Solstice GBA (HFO-1234ze(E), trans-1,3,3,3-tetrafluoropropene) is a 

non-flammable, gaseous low GWP fluoroolefin, which has been developed as a blowing agent/ propellant for rigid 

insulating foams. It is a potential alternative to HFC-134a and other gaseous blowing agents used in foam 

production. In addition, Solstice GBA has a GWP of less than 1, offering improved environmental properties. 

Solstice GBA has PMN and SNAP listing for use in spray foam applications. It is non-ozone depleting and is listed 

as VOC exempt at the federal level in the U.S. and the State of California.

Solstice GBA has proven to be a replacement for HFC-134a. In OCF formulations, Solstice GBA proved to be a

near drop in replacement. The product has the necessary shelf life, foam processing and foam product qualities. In

fact it is being in sold commercially in this application today. 

 
Solstice GBA was not a drop-in into LP SPF systems. With modifications of the polyol, surfactant, and catalyst 

packages, a stable B-side formulation with acceptable physical properties, including 12-month shelf life was 

developed. Initial field testing results are positive.

Overall the evaluations proved that Solstice GBA meets the environmental and field requirements of a next 

generation blowing agent/ propellant for OCF and LP SPF applications. 

REFERENCES

1. Mary Bogdan, Michael Ross, Clifford Gittere. “Honeywell’s Next Generation (LGWP) of Blowing Agents

for Global Spray Foam Applications” in CPI Polyurethanes 20121Technical Conference Proceedings.

2011. 

2. Bogdan, M.; Ling, J.; Williams, D.; Next Generation (LGWP) of Blowing Agents for Spray Foam

Applications; CPI Polyurethanes Proceedings’ 2009

3. Bogdan, M.; Ross, M.; Williams, D. ; Continuing the Study of Next Generation (LGWP) of Blowing

Agents for Spray Foam Applications; CPI Polyurethanes Proceedings’ 2010

4. Bogdan, M.; Grossman,R.; Pascual,X.; Yu, B.; Discussion of Solstice TM Liquid Blowing Agent Spray

Foam Field evaluations; SPI Polyurethanes Proceedings’ 2014.

5. Honeywell Solstice GBA technical data sheet.

BIOGRAPHIES

Mary Bogdan

Mary Bogdan is a Sr. Principal Scientist for Honeywell. She earned a Bachelor’s degree in Chemistry/Biochemistry 

and an MBA from Canisius College. Since joining Honeywell in 1989, Mary has held numerous positions in 

research and development. She currently supports the fluorine products blowing agent business leading application 

research projects and providing technical service to the global spray foam industry. She is a Six Sigma Black belt. 

She has more than 20 U.S. patents and has numerous published technical articles on the development and use of 

fluorocarbons as foam blowing agents. She is currently a member of the SPFA Board of Directors and has received 

industry recognition for leadership and excellence in presentation of technical papers. 

Mojee Cline

Mojee Cline is Vice President, Technology for Fomo Products, Inc. She earned a Bachelor’s degree in Chemistry 

from the University of Akron and a PhD in Physical Chemistry from Virginia Tech. She had over 15 years’ 

experience in product development in the personal care and pharmaceutical industries before joining Fomo Products 

in 2011. Since then, Mojee held the position of Technical Department Manager before her promotion to VP, 

Technology in 2015. She currently manages Research & Development activities as well as the Quality Control, 

Process Management, and Product Compliance Departments.