How can you tell the difference between high-temperature PET and low-temperature PET? This is a question many people are curious about. Today, we’ve gathered expert insights from China Packaging Bottle Network in a Q&A format to help you understand better.
Q: For recycled materials, can they be identified with the naked eye or simple methods?
A: If you have a melting point tester, it’s very easy. By the way, these devices typically cost around 20,000 yuan and are portable like a briefcase. Without one, you’re at a disadvantage when evaluating PET bottles.
When burning, pull the wire and observe its elongation. If the broken fiber can be wound into several loops, it suggests a normal melting point. The more loops, the higher the melting point. However, due to my limited experience, I can’t define exactly how many loops qualify as “good.â€
Additionally, if the material melts quickly during ignition, that indicates a lower melting point. Darkened bottle flakes after burning also suggest a lower melting point. A sweet smell during burning may also indicate a lower melting point—this is what older workers used to say.
Here are some practical tips:
1. **Smell test**: PET has a distinct aroma compared to regular plastic. When burned, it gives off a pleasant, aromatic scent. If other ingredients are present, the smell becomes pungent. For example, bottles containing SEBS may not be suitable for PET use.
2. **Observe the burnt area**: If black spots or oil droplets appear rapidly, it often means the melting point is not normal. This is commonly seen in PET film.
3. **Pulling the wire**: When burning, pull the molten thread and check its length. If it doesn’t stretch much, and the broken end isn’t curled into a small ball, it may indicate a higher melting point. Generally, for bottles, this isn’t a major issue. However, the most important thing is to check whether PVC is present, as it’s harmful to PET.
Other observations: When ignited, pull the wire and see if it stretches before breaking. If the broken wire can be rolled into multiple loops, it suggests a normal melting point. Again, I can’t specify an exact number of loops that qualify. Also, if the material melts quickly and the bottle flakes become dark, it likely has a low melting point. A sweet smell during burning could also be a sign of lower melting point.
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