【Popular Science Tips on Polymers and Materials】--013 Popular Science Tips on the Everyday Uses of Plastic Bags + ljtjbx

“Plastic bags are generally divided into two types: one is made from polyethylene, and the other is made from polyvinyl chloride. Food-grade plastic bags are required to be made from polyethylene ； Polyvinyl chloride is mostly used for wire insulation, fiber optic coatings, packaging paper, and so on. ” Fun facts about plastic bags and whether they are toxic: Ultra-thin bags (on the right in the flame image) emit yellow-green smoke along with black fumes; they are toxic. ◎ Principle of the experiment: Polyethylene can burn continuously, and during combustion, continuous droplet-like substances are produced, just as with a burning candle; the smell is similar to that of wax. Polyvinyl chloride is not flammable; when it burns, it produces black smoke, an unpleasant odor, and the flame appears green. ◎Experimental procedure: An eco-friendly bag purchased from a supermarket was ignited with a lighter; the flame was yellow in color, and droplets were continuously formed, with a smell very similar to that of burning candles. Ultra-thin plastic bags obtained from the market do not burn continuously when ignited; the edge of the flame is green, accompanied by black smoke, and the smell is also very pungent. ◎Experimental conclusion: It is highly likely that the ultra-thin bags contain chlorine; the use of color masterbatches and recycled materials cannot be ruled out either, and they are toxic.

As a child, I used fire to light plastic bags for fun, and it emitted a pungent smell. What are those biodegradable plastic bags? Please spread the word about them!

Plastic bags that can decompose naturally in the environment are known as biodegradable plastic bags; those that cannot do so are not. Currently, almost all plastic bags on the market are non-biodegradable! ! Biodegradable plastics are mainly produced from natural polymers such as starch, cellulose, and chitin, or from agricultural by-products, through microbial fermentation or synthesis to create polymers with biodegradability. Plastics such as thermoplastic starch plastics, aliphatic polyesters, polylactic acid, and starch/polyvinyl alcohol all fall into this category. It’s impossible to tell the difference by looking at the appearance; one has to check the specifications. Additionally, there is a significant price difference between biodegradable and non-biodegradable versions. Biodegradable plastics are materials made from things such as plant straw that are friendly to both humans and the environment. Unlike the three major types of synthetic plastics, they can decompose on their own under biological conditions after being discarded, posing no harm to either humans or the environment; thus, they belong to the category of green packaging. Biodegradable plastic bags are disposable shopping bags that are capable of degradation. Depending on the raw materials used and the factors involved in their decomposition, biodegradable plastic bags can be divided into two types: • One type is made primarily from polyethylene plastic, with biodegradable agents such as starch added; these are also known as biodegradable plastic bags. Such bags decompose mainly through the action of microorganisms. • The other type is also made primarily from polyethylene plastic, but with photodegradable agents and mineral powders such as calcium carbonate added; these are known as photodegradable plastic bags. These bags decompose under the influence of sunlight.

So, what if a biodegradable plastic bag is swallowed by an animal? Will anything happen? I remember when I was young, the cows, dogs, and pigs at home would swallow things, and some of them almost choked to death.

It should not be possible. Two biodegradable methods: microbial degradation; it is estimated to be difficult to achieve degradation within the body ； Another type of photodegradation is even more difficult to achieve within the body. Unless a packaging similar to the soft shell of the candies we eat is created, one that melts in the mouth would also be good. Hehe, but can it still hold things? Is the strength sufficient? It’s worth studying

I came across a case where a certain person rented an apartment in Shenzhen; he had a mistress and a child. For some reason, he argued with them, killed the mother and child, then wrapped them in plastic bags and evacuated the air from them. The landlord found out when someone was sent to clean the place because the rent hadn’t been paid for several months (although it used to be paid regularly). Then this kind of plastic is definitely not biodegradable, right?

1. Place fresh chives in a plastic bag and store them in a cool, dry place, which will keep them fresh for up to three days. ------What is the principle behind this? Does it prevent oxidation by keeping air out? 　　2. Put rice into the composite plastic food bag, squeeze out the air from the bag, and tie the opening of the bag tightly with a rope where it meets the rice; this will prevent the rice from getting damp and moldy.------ Without humid air, mold growth is definitely avoided. 3. At the end of spring, take the red dates that have been exposed to sunlight for several days, heat them with salt and then let them cool down. Place the red dates and salt in layers inside plastic bags or jars, seal them, and this way the red dates can survive the summer safely. -------Table salt absorbs moisture and kills bacteria; sealing it properly prevents dampness. I remember that in the past they were stored in lime containers. 4. Use shopping bags or plastic bags in Shenzhen to store sea cucumbers. After drying, the sea cucumbers are placed in double-layered non-toxic plastic bags, the openings of the bags are sealed tightly, and they are hung in a well-ventilated and dry place. During summer, they should be taken out and exposed to direct sunlight several times; this method helps to keep the sea cucumbers from spoiling over an extended period of time. -------Isolate from air to prevent moisture, and kill bacteria. 5. Thread the fully dried chilies together, use a plastic bag of appropriate size, pass the string holding the chilies through the bottom of the bag, and hang it under the eaves. Every 1–2 months, remove the plastic bag and expose the chilies to sunlight. This prevents the peppers from getting infested with insects and also stops them from accumulating dust. ------This works in the northwestern region, but try it in the Yangtze River basin or Sichuan – it will definitely get moldy. 6. In winter, cabbage can be stored in plastic bags. If you buy too much cabbage in winter and are worried it might spoil, when the temperature is too low, wrap the entire cabbage in a plastic bag and tie it up; if the temperature is above 0°C, simply cover the cabbage with a plastic bag from the top without tying it, and plant it in the ground with its roots facing down. ---------Keep it dry by isolating it from air? ? ? 　　7. When washing clothes in summer, first rinse the white tank tops to be washed with clean water, and then gently clean and rinse them with soap or laundry detergent. Then apply soap, scrub gently, place it in a plastic bag and tie it tightly; leave the shopping bag in the sun for an hour before cleaning it. T-shirts and tank tops that are difficult to clean and have turned yellow can be made as white as new. --------What principle? Is it the accelerated bleaching effect caused by sunlight? ? ? ? 　　8. Store chestnuts in plastic bags. Chestnuts are placed in plastic bags and kept in an area with good ventilation and stable temperatures indoors. When the temperature is below 10°C, seal the opening of the plastic bag tightly; when the temperature is above 10°C, leave the opening of the plastic bag open for storage. In the initial stage, turn them over every 7–10 days; after 1 month, the frequency of turning them over can be reduced appropriately. This method helps to preserve chestnuts for a longer period of time. -------It’s usually kept in the fridge, right?

Vacuum bags, also known as moisture-proof bags, aluminum foil bags, or aluminum-plastic composite bags, are typically made of PET/AL/CPE or PET/NY/AL/CPE materials. Among these, PET provides good printing quality, NY offers low oxygen permeability, AL provides strong barrier properties and is light-proof, while CPE serves as the inner layer of the packaging. Adhesive: Water-soluble adhesive (more hygienic, environmentally friendly, with no solvent residues). This product offers excellent anti-static, oxygen-barrier, shielding, moisture-proof, and light-blocking properties, as well as good heat-sealing characteristics.

That’s really scary of you – to think of such horrible things even from a plastic bag.

Life tips – it’s probably just that different people use them in different ways, but they can still achieve certain results. If another person does the same thing, inconsistent steps and requirements may lead to different outcomes. Plastic bags can actually be put to good use.