Science in Plastic Bottle Packaging
Plastic is a kind of polymer material that has a fixed shape and strength at room temperature, but has plasticity at high temperature. It is this plasticity that plastics are made into recycling plastic water bottles of various shapes and properties. Plastic water bottles have become the main liquid packaging containers in the market due to their lightness and low cost. With the widespread use of plastic bottles, the problem of recycling has also arisen. How should we dispose of discarded plastic bottles?
At the bottom of the recycling plastic water bottles, there is a three-arrow pattern connected end to end, which stands for "recyclable", but this does not mean that it can be reused. To use recycled plastic water bottles correctly, we must first figure out the main components of plastic. Each triangle with arrows is marked with a number, and the numbers 1-7 respectively refer to the type of resin used.
"No. 1" PETE: The composition is PET, polyethylene terephthalate, commonly used in mineral water bottles, carbonated beverage bottles, etc. Its heat-resistant temperature is only 70°C. If it comes in contact with high-temperature liquids, harmful substances are easily melted out and deformed. Especially after 10 months of recycling, carcinogens may be released. Plastic bottles marked with 1 PET are best not to be used for soy sauce and rice vinegar, or high temperature water, otherwise it will cause health problems.
"No. 2" HDPE, HDPE stands for high-density polyethylene raw materials, commonly found in white medicine bottles, cleaning supplies, and bath products. Theoretically, it can be reused after careful cleaning, but these containers are usually not easy to clean, and the remaining original cleaning products can easily become a hotbed of bacteria. It is best not to recycle.
"No. 3" PVC stands for polyvinyl chloride and is often used in various building materials. The material has good plasticity, but it is easy to produce harmful substances under high temperature. After the toxic substances enter the human body with food, it may cause diseases such as breast cancer and birth defects of newborns.
"No. 4" LDPE stands for low-density polyethylene, and such marks can be seen on food wrap. Qualified plastic wrap will melt when the temperature exceeds 110℃, leaving some plastic preparations that cannot be decomposed by the human body. Therefore, foods wrapped in plastic wrap cannot be put into the microwave oven together.
"No. 5" PP stands for polypropylene and is often used in microwave lunch boxes. This material has low transparency and can be repeatedly cleaned and used in low-temperature environments. It has a melting point of up to 167°C. It is the only plastic box that can be placed in a microwave oven and can be reused after careful cleaning.
"No. 6" PS stands for polystyrene and is often used in fast food boxes. The chemical stability is better below 100℃. If contact with strong acid or alkali, polystyrene will be produced, which is easy to cause cancer.
"No. 7": Others are collectively referred to as PC other types, often used in space cups and baby bottles. This type of plastic contains bisphenol A, which has always been controversial. Studies have shown that the higher the temperature, the more BPA released and the faster the speed.