PEM ✖ Schubert

Background reading music curated for this article is available at the bottom. Click to enjoy

01 How PEM Attracts me

During my tour in Japan, I noticed construction workers spraying concrete-like fluid on to the walls and within seconds the fluids “puffed up” and solidified, filling the gaps of the walls. 

construction workers spraying "fluid" into walls

This phenomenon recalls me of expansions and contractions of solids under the rise or drop in temperature. However, what cannot be explained is the process of solidification of the fluid. The truth may not be that simple.

02 Mechanism

Digging deeper into research, I found myself being wrong from the very start. This material is not undergoing any thermal expansions. 

what I first thought about the process (thermal dynamics expansion)

It is producing gas and the gas is making the fluid solidify. From a material-chemistry way, PEM foam (typically polymeric foams such as polyethylene or polyurethane-based systems) forms through a gas-generation and stabilization process within a polymer matrix. 

raw material for structures

Chemical blowing agents release gases such as CO₂, creating nucleation sites in the reacting polymer. As the polymer chains gain mobility, these gas bubbles expand rapidly, leading to the observed “puffing” effect. At the same time, viscoelastic stabilization and crosslinking or crystallization of the polymer matrix “freeze” these bubbles into a closed-cell or open-cell structure, turning the fluid into a solid foam. The final foam morphology—such as cell size and density—is governed by the balance between gas pressure, surface tension, polymer viscosity, and reaction kinetics. This microcellular structure ultimately gives the material its low density, thermal insulation, and mechanical cushioning properties.

03 Application

In practical applications, PEM foams are valued for their versatility as lightweight, non-structural materials. In construction, they are widely used for gap filling and sealing, especially around doors, windows, and wall joints, where their ability to expand allows them to conform to irregular spaces and prevent air or water leakage. 

PEM making the room "snowy"

Their closed-cell structure also makes them effective for thermal insulation, reducing heat transfer in walls, roofs, and pipelines. In addition, PEM foams provide acoustic damping by absorbing sound waves and mechanical cushioning by dissipating energy under compression, which is useful for vibration control and impact protection. These combined properties make them an efficient solution for improving energy efficiency, durability, and overall performance of modern building systems.

Another application I haven't thought of is PEM as 3D printing material.

PEM-printed structures

These particles have the potential to be easily modified in shape, thus being welcomed in all fields that requires creativity.

Music

PEM foam gives me a feeling of support as well as the soft internal characteristic. I prefer to use Unfinished Symphony No. 8 in B minor composed by Franz Schubert as a coherent music piece at the end.

Franz Schubert – Unfinished Symphony No.8 in B Minor

2:24

Beneath the dark, tender melodies, there lies intricate motivic interplay, strong tonal architecture. It is highly structurally cohesive.