Why do Cases for Nordic builds prefer copolymer PP?

Answer: Because the brittleness temperatures sit 25 K apart. Homopolymer turns brittle near -10 °C and keeps 2 kJ/m² at -40 °C, where copolymer holds 3.2 kJ/m².

Where does a 1.2 m six-face drop fail first?

Answer: At a corner, where three faces and the weld line meet; weld strength there is 30% of warm, so the first impact splits 40 mm against a 1.5 mm dent warm.

PA66 or POM for the latch?

Answer: Follow the cycles. Under 50 openings a year, toughened PA66 at 4.5 kJ/m² works; daily transit needs die-cast stainless, since a 0.2 mm score ends a POM hook.

How long before opening a case that sat at -40 °C?

Answer: 24 h at 0–5 °C for a 45 L shell, then the warm room, which cuts condensate from 0.8 to 0.1 g/dm²; a 90 L shell needs 30 h.

Cases for Nordic: -40 °C Cold Start

Quick answer: Cases for Nordic projects start at impact strength, not at a cold rating: homopolymer PP drops to 2 kJ/m² at -40 °C, a third of its 23 °C value. Then the latches and the grease go stiff.

The Cold Budget: Impact Strength at -40 °C
Drop at 1.2 m: Six Faces, Corners First
Latch Material: PA66 or POM at -40 °C
Gasket Tg: Silicone Sits 70 K Above EPDM
Cold-Start Torque: Ribs for Handle and Wheels
Frost, Condensation and the Warm-Up Rule
FAQ

1. The Cold Budget: Impact Strength at -40 °C

Cases for Nordic projects open with impact strength, not with a quoted cold rating. Homopolymer PP reads 6 kJ/m² notched at 23 °C, 3 kJ/m² at -20 °C and 2 kJ/m² at -40 °C, one third of the warm value, and 2 kJ/m² means a 1 kg tup from 30 cm starts a crack.

Thickness does not buy that back: embrittlement freezes the chain segments and leaves stress no path to relax. Brittleness temperature is the second line: near -10 °C for homopolymer, -35 °C for copolymer, so -40 °C lands 5 K outside the boundary, and a Nordic build either switches resin or goes from 2.8 mm to 3.4 mm for 12% more weight.

Compound	23 °C	0 °C	-20 °C	-40 °C
PP homopolymer	6 kJ/m²	5 kJ/m²	3 kJ/m²	2 kJ/m²
PP copolymer	8 kJ/m²	7 kJ/m²	4.5 kJ/m²	3.2 kJ/m²
PA66 toughened	9 kJ/m²	8 kJ/m²	6 kJ/m²	4.5 kJ/m²
POM homopolymer	7 kJ/m²	6 kJ/m²	4 kJ/m²	2.8 kJ/m²

State the method with the number: ISO 179 Charpy notched, 80×10×4 mm, 4 h soak at -40 °C, break within 10 s.

2. Drop at 1.2 m: Six Faces, Corners First

A 1.2 m drop is the height Cases for Nordic shells fall from a hand, and it doubles as the flexibility test: six faces, three edges, one corner, one drop per sample, no through-crack, no latch release.

At room temperature the cycle leaves a 1.5 mm dent; after a 4 h soak at -40 °C the same shell splits 40 mm at a corner on the first impact, where three faces and the weld line meet at 30% of warm strength.

Cases for Nordic as a close-up of a white case rim, one grey round gasket seated in the groove, smooth groove wall, textured foam outside

Three fixes: a corner radius from 1 mm to 3 mm cuts stress concentration 25% for almost no weight; moving the weld onto a flat needs a new gate; foam at 25 mm on six corners adds 0.4 kg and is cheapest.

3. Latch Material: PA66 or POM at -40 °C

The latch is the first plastic part to fail on Cases for Nordic shells. Toughened PA66 holds 4.5 kJ/m² notched at -40 °C against 2.8 kJ/m² for homopolymer POM, and the field gap is notch sensitivity: a 0.2 mm score at the hook root ends a POM latch outright.

Dry PA66 is its brittle state: 2.5% moisture restores toughness and swells the part 0.6%, while a dry Nordic winter takes an outdoor latch under 1% in three months for 15% of impact. Under 50 openings a year a toughened PA66 grade is enough; daily transit moves to die-cast stainless at 90 g and 40% more cost.

4. Gasket Tg: Silicone Sits 70 K Above EPDM

A gasket follows its glass transition. Silicone sits near -120 °C, EPDM near -50 °C, and at -40 °C silicone is still elastic while EPDM has entered the transition ahead of the glassy state, losing recovery from 60% to 35%.

Lost recovery is lost sealing: the lid closes short of design compression, a 0.4 mm gap opens at the corner, and opening force climbs from 60 N to 140 N.

Compound	Tg	Recovery at -40 °C	Opening force	Verdict
Silicone	-120 °C	55%	100 N	Outdoor, long term
EPDM	-50 °C	35%	140 N	Indoor rotation
Neoprene	-45 °C	30%	150 N	Not advised

A gasket frozen into its groove fails more often: overnight frost bonds the seal to the land, and forcing the lid pulls it out of the channel. Warm the rim with a palm.

Cases for Nordic as a white case opened flat, two grey latches, grey lid foam, cut foam cavities

5. Cold-Start Torque: Ribs for Handle and Wheels

Drag on cold Cases for Nordic shells begins with grease: penetration falls from 265 to 180 and rail torque climbs to 2–3 times the warm figure. A 45 L trolley measures 1.8 N·m at 20 °C and 5.4 N·m at -40 °C.

Ribs are sized against that torque: handle seats from 2 ribs to 4 at a 1.5 mm root, rib thickness at 60% of wall, wheel housings from 4 mm to 6 mm with a steel insert in the axle bore, where the PP-to-steel gap at -40 °C reads 0.07 mm. An M6 self-tapper loses 20% of its grip in a PP boss, so Nordic builds add 0.8 mm of boss wall.

6. Frost, Condensation and the Warm-Up Rule

Carried from -40 °C into a 20 °C room, a shell frosts and then condenses. At 20 °C and 50% relative humidity the dew point is 9.3 °C, and the wall needs about 50 min to reach it at 1 K/min; open the lid sooner and moist air settles on wall and foam.

Warm up in two stages. Cases for Nordic shells leaving a -40 °C store go to a 0–5 °C ante-room for 24 h before the 20 °C room, cutting condensate from 0.8 to 0.1 g/dm². Past 72 h in the cold, a 45 L shell needs 24 h and a 90 L shell 30 h.

Conclusion

Cases for Nordic cold design compresses into four numbers: homopolymer PP keeps 2 kJ/m² at -40 °C where copolymer holds 3.2 kJ/m² on a -35 °C transition; the 1.2 m drop fails at the corner; the gasket is chosen on Tg, where 70 K decides whether recovery survives; cold-start torque reaches 2–3 times warm, so ribs are sized at 5.4 N·m. The last item is free: 72 h cold, 24 h warm-up, then open.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.