Metal clothes hook is a kind of macromolecule polymer.
Polyethylene is by a lot of ethylene molecules, for example, the product of link together hand in hand;
Polyvinyl chloride (PVC) is made up of a number of vinyl chloride molecule, you pull me, I pulled him, change out together.
Vinyl chloride molecules why join hands?
Speaking, it was interesting, carbon atoms of the acrylonitrile molecules are two hands up each other.
If we add a small amount of catalyst, a hand in them will separate, rather than the other carbon atoms in a molecule of vinyl chloride pull up his hand.
Vinyl chloride is a biting a molecules that are associated with long chain, which is chemically said 'aggregation'.
Vinyl chloride molecules together in this way, then form a chain of large molecules, many of these large molecules together, is what we usually see white PVC resin powder.
Polyvinyl chloride (PVC) is that the matter can be just soft.
It's so just bite molecules of the 'joint', combined with a tight.
If on the 'joint' plus some 'lubricating oil', 'joint' activities, it becomes soft material.
What is 'lubricating oil'?
Some metal clothes plasticizer industry said.
In winter, the weather is very cold, some plasticizers not hardy, its 'lubrication' ability to reduce the 'joint' hangs in metal clothes, so they harden.
The warm weather, plasticizer and restored the nature of 'lubrication', 'joint' activities, metal clothes is soft.
Some of the plasticizer is volatile.
Metal clothing products with long, metal clothes off in the form of 'lubricating oil', in the 'joint' ineffective, will certainly to harden.
Often with soap and water washing clothes products, metal or metal clothing products in contact with oil, also can make plasticizer from loss, metal clothes will harden.
Metal coat hooks products use for a long time, also can become hard.
This in addition to because the plasticizer volatilization, activity between the molecules 'joint' ineffective, but also because of each bite a long-chain molecules, by action of the wind and rain, the sun and other natural forces, will make the long-chain molecules break into short chains of molecules, metal clothes will harden.
On the metallic clothing industry, a phenomenon known as 'ageing'.