HDPE (high density polyethylene) is a synthetic material that has a rather aggressive amount of linear movement during temperature changes. Don’t like it? Sorry, PE (polyethylene) changes for for no-one. Except that is, when the temperature changes, in which case it move in a measured amount (of inches) per degree (of temperature change).
There are several points we need to consider before moving forward, with a finished product or finish cut part in any synthetic material – below is the important factors when assessing the end part needed:
- What is the maximum length the part can be in its final environment?
- If that answer is 73” then the part will need to be cut at ?
- What is the minimum length the part can be in its installed environment?
- Does the environment support the part only up to 72” inches?
- What is the temperate range in the environment?
- Material movement is calculated as inches per degree of temperature change.
Assuming max 73” and minimum 72” with an environment that has a max temperature swing of 35 degree’s the part would be best “finish” cut at 72 ½” :
- Allowing movement amount of 0.3996” total acceptable range
- Minimum length after contraction 72.10”
- Maximum length after contraction 72.8996”
- Resource: using a thermal expansion calculator you can determine the approximate movement of any material – Tangent HDPE falls under the general category of PE in this one: https://goodcalculators.com/thermal-expansion-calculator/
Summary here is that expansion and contraction is a fact of life all synthetic materials and HDPE (PE) is no different. Plan on movement, engineer your product around it and you will be all set for a long term performance product.