raw · notes · ingested 2026-07-02
PCM container / sealant / metal compatibility matrix (research note)
confidence: medium
Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC6479576/
Purpose: the material-pairing decisions for a DIY translucent PCM panel, consolidated from several charts + primary sources. Credibility: Medium — mixes peer-reviewed data with manufacturer charts and one maker method.
Containers (translucent options)
- Polycarbonate — best translucent choice; resistant to paraffin oil and saturated CaCl₂/Na₂SO₄ (ePlastics; Covestro Makrolon). Caveat: additives in solvent-cut oils migrate and attack PC; crazes under stress. Sources: eplastics.com Lexan chart; Covestro Makrolon chemical-resistance PDF; Plastics International chart (paraffin rated “A” on all plastics; mineral oils “C” on PC/PET).
- Acrylic (PMMA) — best clarity, resists clean aliphatic paraffin, but highly prone to environmental stress crazing (needs tensile stress + crazing agent + susceptible polymer). Alcohols/ketones/esters/solvent-cut PCM craze it; daily melt-expansion adds stress. Keep stress-free (no over-tight clamps; relieve molded-in stress). Source: industrialspec PMMA chart; DTIC ADA205624 crazing report.
- PVC-U — most inert (<0.1% mass change vs all four PCMs, PMC6479576) but not clear.
- LDPE/PP thin film — avoid with paraffin (6–7% swelling uptake, PMC6479576); OK-ish with salt hydrate (≤1.8%).
Sealants
- Standard clear acetoxy RTV silicone swells in molten paraffin and loses adhesion.
- Prefer a mechanically clamped gasket or an oil-resistant / fluorosilicone RTV.
- Rigid PC/acrylic: solvent/ultrasonic welding gives a monolithic seam — but leave an expansion void (paraffin ~10%/melt).
Metals (salt hydrates corrode)
- Stainless 316/304 = safe (0–1 mg/cm²·yr). Aluminium corrodes. Copper = caution (esp. CaCl₂/MgCl₂). Ferrer/Cabeza corrosion data. Keep salt hydrate off bare metal; use plastic/glass walls.
A concrete maker method (Endless Sphere forum, concept-stage)
Seal both ends of extruded greenhouse multiwall polycarbonate channels with silicone, fill each channel ~90% with liquid paraffin (~50 °C melt) leaving 10% for expansion. Notes PC’s own insulation slows charge/discharge. No measured result. https://endless-sphere.com/sphere/threads/phase-change-material-panel-concept.99442/