Why Crosslinked Polymer Foams?
Crosslinked polymer foams (XPE = crosslinked polyethylene; XPP = crosslinked polypropylene) offer superior strength-to-weight ratio, thermal insulation, chemical resistance, and durability compared to non-crosslinked foams. The crosslinked matrix prevents cell collapse during foaming and provides excellent dimensional stability over a wide temperature range.
Organic peroxides serve two critical roles in foam production:
- Crosslinking agent: Creates the polymer network that stabilizes foam cells.
- (Optional) Partial degradation agent: In some processes, a controlled amount of peroxide induces chain scission to reduce melt viscosity, improving foam expandability.
Crosslinked Foam Production Process (Two-Stage Oven)
| Stage | Temperature | Function |
|---|---|---|
| Compounding | 120–180°C | Peroxide + blowing agent mixed into polymer |
| Crosslinking (1st oven) | 150–200°C | Peroxide decomposes, crosslinks form |
| Foaming (2nd oven) | 180–220°C | Blowing agent decomposes, cells expand |
| Cooling & calibrating | 20–60°C | Foam structure set |
Peroxide Selection for Crosslinked Foams
1. Dicumyl Peroxide (Perodox DCP)
The standard crosslinking peroxide for XPE and XPP foams. Its decomposition temperature range aligns well with typical two-stage oven processes.
- Dosage: 0.5–1.5 phr
- Blowing agent pairing: ADC (azo), hydrocarbon (butane/isopropanol)
- Applications: XPE foam for insulation, sports mats, automotive interior
2. Lauroyl Peroxide (Perodox LUNA)
A diacyl peroxide that decomposes at lower temperatures (60–100°C). Often used in EVA foam production for footwear midsoles, where the blowing agent (typically ADC) also decomposes at relatively low temperatures.
- Dosage: 0.3–1.0 phr
- Applications: EVA foam midsoles, flip-flop soles, sports equipment
3. 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane (Perodox 101)
Provides better scorch safety than DCP, making it suitable for fine-cell XPE foams where uniform cell structure is critical.
Foam Density vs. Peroxide Dosage
| Peroxide (phr) | Blowing Agent (phr) | Typical Density (kg/m³) | Application |
|---|---|---|---|
| 0.5 | 5–8 (ADC) | 80–120 | Insulation, packaging |
| 0.8 | 8–12 (ADC) | 50–80 | Automotive interior |
| 1.2 | 10–15 (ADC/hydrocarbon) | 30–60 | Sports mats, high-end packaging |
Frequently Asked Questions
Q: Can I produce crosslinked foam without a blowing agent?
A: No. The peroxide provides crosslinking; a separate blowing agent (chemical or physical) generates the gas cells. The two must be carefully balanced—too much crosslinking before blowing causes high foam density; too little crosslinking causes cell collapse.
Q: What is the difference between XPE foam and non-crosslinked PE foam?
A: XPE foam has a crosslinked polymer matrix, giving it higher strength, better thermal insulation, and superior aging resistance. Non-crosslinked PE foam (e.g., LDPE foam made with physical blowing only) is cheaper but has lower temperature resistance and poorer dimensional stability.
Q: How do I achieve fine-cell foam structure?
A: Use a fine-particle blowing agent (micronized ADC), ensure uniform dispersion in the compound, and use a peroxide with good scorch safety (Perodox 101) to prevent premature crosslinking before the blowing agent decomposes. Cell nucleating agents (e.g., talc, zinc oxide) also help.
Do Sender Foam Solutions
Shandong Do Sender Chemicals Co., Ltd. provides Perodox® organic peroxides for the full range of crosslinked foam applications—from XPE/XPP insulation foams to EVA footwear foams. Our technical team assists with peroxide/blowing-agent ratio optimization, cell-structure analysis, and foam density targeting. All products meet REACH and ISO 9001 standards.
Contact us to discuss your foam application and receive a tailored peroxide recommendation.