Medical-grade silicone is not a marketing word. It is a test result. Here is what that result actually means — in the lab and on your wrist.
What "medical-grade" actually means
To be called medical-grade, a silicone must pass ISO 10993, the international biocompatibility standard. The test panel checks for cytotoxicity, sensitization, irritation, and systemic effects on skin contact. Materials that pass can legally touch human skin (and in some grades, be implanted). It is the same grade used in catheters, baby pacifiers, and surgical seals.
Platinum-cured vs peroxide-cured
Silicone needs to cure (cross-link) to become solid. Two catalyst systems exist:
- Peroxide curing. Older, cheaper. Leaves byproducts. Smells when fresh. Yellows over years.
- Platinum curing. Modern, cleaner, more expensive. Zero residual byproducts. Stable color and feel for 5+ years.
POPSTRAP uses platinum-cured. The cost difference is significant; the longevity difference is more significant.
The molecular backbone
Silicone is built on silicon-oxygen (Si-O) bonds, not the carbon-carbon (C-C) bonds of rubber. Si-O bonds are stronger and far more UV-resistant. That is why silicone does not crack under sun while rubber turns brittle in 18 months.
Shore A hardness and skin comfort
Shore A is the scale for soft polymer hardness. POPSTRAP uses Shore A 50 — the sweet spot:
- Shore A 40: too soft, stretches over time, loses shape
- Shore A 50: skin-soft but structurally stable
- Shore A 60-70: starts feeling stiff in cold weather
Tear strength and elongation at break
Two lab specs that predict real-world durability:
- Tear strength — resistance to ripping. Medical silicone: 25-40 N/mm. Cheap silicone: 8-15 N/mm.
- Elongation at break — how far it stretches before snapping. Medical: 400-600%. Cheap: 150-250%.
The difference shows up at year 3, not week 1.
Hypoallergenic by design
Zero nickel, zero latex proteins, zero phthalates, zero BPA. The same reason it works in pacifiers is why it works on sensitive wrists. More in our silicone guide.
How it ages over 5 years
UV testing: medical-grade silicone retains 90%+ of its original tensile strength after 2,000 hours of UV exposure (equivalent to ~3 years of daily wear). Cheap silicone loses 50% in the same window.
From catheter to wrist
The same exact material grade in implantable medical devices is what we mold into your strap. Not a marketing borrowing — a specification borrowing. See our workshop • Shop Drop 01.