PU foam (Polyurethane Foam) and PE foam (Polyethylene Foam) are two common polymer foam materials. Due to their distinct chemical structures, they differ significantly in physical properties, application scenarios, and other aspects. The specific differences are as follows:
Material Nature and Production Process
PU foam: It is produced through a chemical reaction between isocyanate and polyol, belonging to "reactive foam". During the foaming process, gases (such as carbon dioxide) are generated, forming either closed-cell or open-cell structures. Its hardness and density can be controlled by adjusting the proportion of raw materials, enabling the production of both soft and hard varieties.
PE foam: It is based on polyethylene resin as the raw material. After adding a foaming agent (such as butane), it is formed through high-temperature extrusion and expansion, classed as a "physical foaming material". The foaming process relies on changes in physical state (gas expansion), with a mainly closed-cell structure. The range of adjustment for density and hardness is relatively limited, and it is mostly of medium to low hardness.
Differences in Core Physical Properties
Density and Hardness
PU foam: It has an extremely large density range (0.02–0.5g/cm³). Soft PU (such as sofa cushions) is soft with high resilience and can recover quickly after being pressed. Hard PU (such as refrigerator insulation layers) is hard and dense, with strong load-bearing capacity.
PE foam: It has a relatively low density (usually 0.03–0.1g/cm³). It is overall soft yet has "toughness" and rebounds slowly when pressed. Its hardness is generally lower than that of hard PU, being closer to soft materials but with more stable support (not prone to collapsing).
Heat Resistance and Chemical Stability
PU foam: It has moderate temperature resistance, with a long-term service temperature generally ranging from -30℃ to 80℃. It tends to soften and deform when the temperature exceeds 100℃. Its chemical stability is poor, as it is easily corroded by organic solvents (such as alcohol and gasoline) and may swell or crack upon contact.
PE foam: It has better temperature resistance and can be used stably within the range of -60℃ to 100℃. It is not easily deformed even when exposed to a high temperature of 120℃ for a short time. It has strong chemical stability, being resistant to acids, alkalis, and most organic solvents, and is not easily corroded by daily liquids (such as water and detergents).
Water Absorption and Breathability
PU foam: PU with an open-cell structure (such as a sponge) has strong water absorption and good breathability (commonly used for cleaning sponges and filter materials). PU with a closed-cell structure has low water absorption, but its breathability is still weaker than that of PE.
PE foam: Due to its mainly closed-cell structure, it has extremely poor water absorption (almost no water absorption) and low breathability (gases can hardly penetrate it), making it suitable for scenarios that require moisture protection and sealing.
Elasticity and Impact Resistance
PU foam: Soft PU has excellent elasticity and high tensile and compression recovery rates, but it is prone to "fatigue deformation" (such as the collapse of old sofa cushions) under long-term pressure. Hard PU has strong impact resistance and can absorb energy through deformation (such as the buffer layer of car bumpers).
PE foam: Its elasticity tends to be "slow rebound", and its impact resistance is more stable. When impacted, it disperses force through slow deformation and is not prone to permanent deformation after long-term pressure (for example, the PE foam pads used in express packaging can still maintain their shape after repeated use).
Differences in Application Scenarios
PU foam:
Soft PU: Used as the filling layer in sofas and mattresses (utilizing high elasticity to enhance comfort), makeup sponges (with an open-cell structure for water absorption and breathability), and sound insulation cotton (with a porous structure to absorb sound waves).
Hard PU: Applied as the insulation layer in refrigerators and cold storages (the closed-cell structure reduces heat transfer), insulation boards for building exterior walls (combining load-bearing and insulation functions), and automotive interiors (such as instrument panel buffer layers).
PE foam:
Packaging field: Used for shockproof packaging of electronic products and precision instruments (offering impact resistance and moisture protection), and as the lining of insulation boxes in the fresh cold chain (with low water absorption and low-temperature resistance).
Daily necessities: Employed in yoga mats (providing anti-slip and flexible support), buffer layers of children's toys (non-toxic and wear-resistant), and pipe insulation sleeves (suitable for water resistance and temperature resistance).
Industrial field: Utilized as water floats (with low density and non-water absorption) and linings of sports protective gear (impact-resistant and lightweight).
Environmental Protection and Recyclability
PU foam: Recycling is relatively difficult. In particular, soft PU has a loose structure and degrades slowly. It may release harmful gases when incinerated and requires professional treatment. Some new types of PU foam use bio-based raw materials, which can improve their environmental performance.
PE foam: It is a recyclable plastic (marked as "PE" or "04") and can be re-melted and processed after recycling. Moreover, some PE foams can achieve environmentally friendly degradation by adding degradants, making them relatively more environmentally friendly.