Contents
- 1. What "flexible foam" actually is — and why selection matters
- 2. The four parameters that drive every specification
- 3. Selection by application — furniture, mattress, automotive, packaging, medical
- 4. Slabstock vs moulded — how the production method shapes properties
- 5. Certifications and regulatory expectations
1. What "flexible foam" actually is — and why selection matters
In Turkish industry, the word sünger covers a broad family of flexible polyurethane foams — open-cell, low-to-moderate-density materials that compress under load and recover their shape when the load is removed. The term sünger hammaddesi (flexible foam raw material) typically refers to the bulk material that converters cut, shape or laminate into the finished article: a mattress core, a sofa cushion, an automotive seat pad, packaging insert, medical positioner, acoustic panel.
The reason selection matters is that two flexible foams that look identical at the cutting table can behave entirely differently in service. One sofa cushion sags after eighteen months; another stays firm for ten years. One mattress core breathes; another traps heat. One packaging foam absorbs an impact cleanly; another bottoms out. Each of those outcomes traces back to four foam parameters that the buyer can see on a Technical Data Sheet (TDS) — and to two regulatory parameters that the market enforces. Understanding both sets is what separates a good purchase from a costly one.
2. The four parameters that drive every specification
1. Density (kg/m³). Density is the mass of foam per unit volume, and it is the single best proxy for how long the material will last under repeated use. A higher-density foam holds its shape, resists fatigue and ages slowly; a lower-density foam costs less but breaks down faster. Most furniture seat foams sit between 22–35 kg/m³; mattress cores commonly run 28–45 kg/m³; premium automotive and medical foams routinely exceed 45 kg/m³. Density is the first number a buyer should read on a TDS and the first one to align with the expected service life.
2. Hardness (ILD or CLD). Hardness is how much load the foam carries at a given compression. The two common units are Indentation Load Deflection (ILD), which presses a flat disc into the foam to a defined depth (usually 25% or 40% of the original height), and Compression Load Deflection (CLD), which compresses the whole sample. Hardness is the "feel" the end user notices: too soft, the cushion bottoms out; too firm, it doesn't conform to the body. Hardness is independent of density — a high-density foam can be soft, and a low-density foam can be firm — and choosing them together is the core formulation choice for any seating or mattress application.
3. Compression set. Compression set measures how much permanent deformation remains after the foam has been held under load for a defined time. It is the parameter that predicts whether a cushion or mattress will keep its shape over years of daily use. A foam with low compression set returns close to its original thickness; a foam with high compression set takes a permanent dent. For mattresses and high-use seating this is often more decisive than density itself, because it directly governs the perceived loss of support over the product's life.
4. Tensile strength, elongation and tear. These three mechanical properties together describe how the foam handles handling — being pulled, stretched, cut and stitched on the converter's line, and being twisted and folded by the end user. They matter most where the foam is exposed (furniture, automotive seating) or repeatedly flexed (packaging inserts that are reused). Higher values give more margin against premature tearing during use.
Two regulatory parameters typically run alongside these: the fire class required for the target market (e.g. BS 5852 for UK furniture, B1/B2 for parts of European construction, FMVSS 302 for US automotive interiors, EN 597 for mattresses) and the chemical compliance (CertiPUR-US, Oeko-Tex Standard 100, REACH in Europe, KKDIK in Türkiye). Both can be deal-breakers if the foam doesn't match the certification the end customer expects.
3. Selection by application
Furniture cushions and upholstery. Mid-range density (22–35 kg/m³) with medium ILD is the workhorse for sofa seats and backs in the domestic market. Premium furniture pushes density higher (35–45 kg/m³) for longer life and better recovery, and may layer a softer top foam over a firmer support foam. In Türkiye the most common fire test for residential furniture is the TS-EN 1021 cigarette/match test; export to the UK pushes the bar up to BS 5852.
Mattress cores and toppers. The mattress core typically sits at 28–45 kg/m³ with a tuned ILD profile (different firmness at head and foot in some designs). Compression set becomes the dominant parameter — a mattress that loses 5 mm of thickness in two years is a market failure, even if every other parameter is within spec. Premium tier layers viscoelastic (memory foam) on top of a high-density support foam, in which case selection follows the dedicated viscoelastic curve rather than a standard flexible foam.
Automotive seating. Automotive applications run high-density (45–60+ kg/m³), moulded rather than slabstock, with strict fire performance to FMVSS 302 and demanding compression set and ageing requirements. Hardness is tuned by zone (firmer in the bolster, softer in the cushion centre), often within a single moulded part. This is the most specification-heavy segment of the flexible foam market and the closest to a customer-specific formulation.
Packaging and protective foam. Low density (14–22 kg/m³) for cost-driven cushioning where the foam compresses once or a few times. Anti-static variants for electronics, conductive variants for sensitive components, ester-based foams for thermal stability where the package may see elevated temperatures. Tensile and tear performance matters most where the insert is removed and replaced repeatedly.
Medical and acoustic. Medical positioners and pressure-relief cushions tend to use higher densities, hypoallergenic formulations and tightly controlled cell structures. Acoustic foam — for studios, audio enclosures and HVAC ducting — selects on cell openness and tortuosity rather than mechanical strength, and is often supplied in profiled or convoluted form. Both are smaller-volume applications where the formulation work tends to dominate the supplier choice.
4. Slabstock vs moulded — how production method shapes the product
Slabstock is the continuous block process: the polyol-isocyanate mix is poured onto a moving conveyor under controlled temperature, rises freely into a long loaf and cures as it travels. The cured block is then cut into sheets, blocks or shaped parts. Slabstock is the most economical route to flexible foam and is dominant for furniture, mattress, packaging and acoustic foam. The trade-off is that properties are tuned at the line level — the same line typically produces a range of densities and hardnesses by changing formulation, not geometry.
Moulded foam pours the mix directly into a closed mould shaped like the finished part. The mould defines geometry and surface, and the formulation is tuned for higher density, controlled skin formation and a fast demould cycle. Moulded foam is the dominant route for automotive seating, certain office-chair components, headrests and bolsters. The capital cost per part is higher, the unit cost per kilogram is higher, but the finished part can be ready to ship straight off the line — no cutting, no upholstery underbody work.
For most buyers outside automotive and high-volume mass seating, slabstock will be the right answer; the question becomes which slabstock grade. For moulded applications, the conversation typically starts with the part geometry, the line cycle time and the fire/ageing requirement — and the system house formulates against those.
5. Certifications and regulatory expectations
The certifications expected on a flexible foam depend on where the finished product is sold. CertiPUR-US covers heavy-metal, ozone-depleter and emission limits on the foam itself and is increasingly requested by furniture and mattress brands selling into North America. Oeko-Tex Standard 100 covers harmful-substance limits and is common in the European mattress trade. EUROPUR (the European bedding foam association) publishes voluntary technical guidance that many converters reference.
Fire performance certifications are typically market-specific: BS 5852 (UK furniture filling test), FMVSS 302 (US automotive interior), EN 597-1/2 (mattress cigarette and match test) and the B1/B2 classes under DIN 4102 / EN 13501 for parts of the construction stack. Knowing in advance which test the foam needs to pass is the difference between a system that just works and a re-formulation cycle after a failed batch.
On the chemical-regulatory side, the European REACH framework governs ingredient registration and SVHC declarations, and the August 2023 diisocyanate restriction requires documented user training where applicable. Türkiye's parallel KKDIK regulation enforces equivalent registration and Turkish-language safety data sheets for domestic distribution. Exporters into the EU should expect to demonstrate compliance with both.