cling

Plastic wrap, cling film, Saran wrap, cling wrap, Glad wrap or food wrap is a thin plastic film typically used for sealing food items in containers to keep them fresh over a longer period of time. Plastic wrap, typically sold on rolls in boxes with a cutting edge, clings to many smooth surfaces and can thus remain tight over the opening of a container without adhesive. Common plastic wrap is roughly 0.0005 inches (12.7 μm) thick. The trend has been to produce thinner plastic wrap, particularly for household use (where very little stretch is needed), so now the majority of brands on shelves around the world are 8, 9 or 10 μm thick.

Plastic wrap was initially created from polyvinyl chloride (PVC, 聚氯乙烯), which remains the most common component globally. PVC has an acceptably-low permeability to water vapor and oxygen, helping to preserve the freshness of food. There are concerns about the transfer of plasticizers from PVC into food. poly:多。vinyl: 1. 乙烯基塑料; 2. 用1做的唱片。

A common, cheaper alternative to PVC is low-density polyethylene (LDPE =polythene，聚乙烯)。It is less adhesive than PVC, but this can be remedied by adding linear low-density polyethylene (LLDPE), which also increases the film's tensile strength.

In the US and Japan, plastic wrap is sometimes produced using polyvinylidene chloride (PVdC, 聚偏二氯乙烯), though some brands, such as Saran wrap, have switched to other formulations due to environmental concerns.

The accumulation of plastic debris on the Earth threatens both wildlife and the environment. Plastic debris might choke or trap wildlife, and it could also penetrate toxic compounds into ecosystems. This land-originated problem has become a problem in ocean ecosystem as well since streams and rivers which are close to the land have carried the plastic debris into the coast, and currents transfer it to everywhere in the ocean. Plastic debris is a potential danger to all forms of aquatic life. Some marine species, like sea turtles, take plastic as prey items by mistake. Besides, some species might even pick up plastics and feed their offspring, which cause huge problems on growth and even cause mortality. Toxic compounds in plastics can disrupt hormone regulation in the cells of organisms, which can lead to alteration of animals’ mating behavior, reproductive ability, and even cause the development of tumors. Plastic debris could be a big threat to lives in the ocean.

A study shows that using recycled plastic materials can reduce the environmental impacts significantly as a result of minimizing exploration, mining and transportation of natural gas and oil. One of the possible ways to increase the recycling rate is adding fibrous reinforcement into plastics. The environmental impact has been assessed using the life cycle assessment method. The results showed that plastics with fibrous reinforcement added can sharply reduce resource usage and global warming in civil applications.

六级/考研单词: wrap, cling, seal, thereby, brand, component, oxygen, alternate, formulate, accumulate, debris, choke, trap, penetrate, toxic, compound, ecosystem, marine, turtle, prey, besides, offspring, mortal, disrupt, regulate, organism, mate, reproduce, tumor, recycle, fibre, reinforce, evaluate, usage, globe

标签：food,Plastic,PVC,debris,cling,wrap,plastic
来源： https://www.cnblogs.com/funwithwords/p/16463887.html