English
Views: 0 Author: Site Editor Publish Time: 2026-04-07 Origin: Site
Abstract: With the complete phase-out of HCFC-141b blowing agent production by 2026, HFC 245fa, as the primary alternative blowing agent, has been widely used in the rigid polyurethane foam spraying industry. This paper systematically summarizes common issues in the practical application of the 245fa foamng system, including storage instability, foam defects, poor adhesion, and dimensional instability, conducts an in-depth analysis of their causes, and proposes corresponding technical solutions, providing technical references for enterprises to smoothly transition to the new foaming system.
Keywords: rigid polyurethane foam; spraying; HFC-245fa; blowing agent; technical problems
According to the announcement issued by the Ministry of Ecology and Environment in 2025, starting from January 1, 2026, the production of polyether blend products using HCFC-141b as the blowing agent will be completely banned, and sprayed polyurethane foam products will also be included in the production ban from July 1 of the same year. This means that the spraying industry will completely phase out the HCFC-141b foaming system and fully enter a new stage of application of environmentally friendly blowing agents represented by HFC-245fa. However, the 245fa foaming system faces numerous technical challenges in practical application, calling for systematic research and targeted solutions.
In the 245fa foaming system, performance instability often occurs after the polyether blend has been stored for a period. The main reason is the difference in compatibility between 245fa and polyether polyols compared with 141b, which may cause blowing agent volatilization or phase separation during long-term storage. Studies have shown that storage stability can be significantly improved by selecting appropriate base polyethers and additive systems.
Foam shrinkage is a common problem in the 245fa spraying system, characterized by shrinkage around the formed foam and gaps between the foam and the substrate. The main causes include excessive material viscosity leading to poor flowability, excessively fast curing reaction forming excessive closed-cell structures, and thermal expansion and contraction effects. Brittle foam is usually related to excessive isocyanate component, high moisture content, or excessively low substrate temperature.
Weak bonding between foam and substrate and local delamination are prominent issues affecting construction quality. The causes can be summarized into three aspects: first, oil, moisture or dust on the sprayed surface; second, incomplete reaction under low-temperature conditions resulting in brittle bottom foam; third, improper selection of catalyst system failing to effectively promote interfacial chemical bond formation. Experiments show that the use of a composite catalyst system can increase adhesion strength by more than 35%.
Poor dimensional stability of 245fa sprayed foam under high-temperature and high-humidity environments is a recognized technical difficulty in the industry. This is mainly due to the uneven closed-cell structure of foam in high-water foaming systems, leading to foam expansion or shrinkage under hot and humid conditions. Practices by Huntsman show that the use of low-viscosity polyester polyols promotes uniform dispersion of the foaming system and significantly improves dimensional stability.
The 245fa foaming system often suffers from non-compliant flame retardant performance. The reason is that after the replacement of the blowing agent, the compatibility between the original flame retardant system and the new blowing agent changes, altering the dispersion state of flame retardants in the foam and affecting the overall flame retardant effect.
In view of the fast volatilization and poor compatibility of 245fa, technical difficulties can be solved through raw material selection and formulation optimization. Specific measures include: selecting low-viscosity polyester polyols to ensure uniform dispersion; optimizing the composite catalyst system to balance foaming and gelling reaction rates; precisely controlling the dosage of 245fa. Huntsman has successfully reduced the 245fa dosage to 5 parts, cutting costs at the source.
Catalysts play a key role in the 245fa system. Specialized catalysts can significantly shorten curing time and improve low-temperature construction efficiency; meanwhile, by regulating closed-cell ratio and cell structure, they enhance the thermal insulation and mechanical strength of foam. Experiments show that hybrid catalysts can achieve a closed-cell ratio of 94.5% and a thermal conductivity of 0.017 W/(m·K).
During winter construction, measures such as preheating raw materials and heating the working surface should be adopted; construction in rainy days requires ensuring a dry working surface to prevent moisture interference with the reaction; strictly control the mixing accuracy to avoid foam delamination or embrittlement caused by improper ratio; keep the working surface clean by removing oil and dust.
As the main alternative to HCFC-141b, 245fa has broad application prospects in the rigid polyurethane foam spraying industry. By deeply understanding the causes of common problems and adopting comprehensive measures such as formulation optimization, catalyst regulation and process improvement, issues including storage instability, foam defects and poor adhesion can be effectively solved, ensuring a smooth transition of the foaming system. In the future, with increasingly stringent environmental regulations, foaming systems with lower GWP values such as LBA and all-water systems will also become development trends.
