问题 问答题 简答题

选用溶剂的原则有什么?了解常用的溶剂?

答案

参考答案:溶剂的选择原则:"相似者相溶"和溶度参数。

常用的溶剂

1)甲苯,C6H5CH3:使用于空气干燥乙烯,氯化橡胶涂料以及稀释剂硝化棉涂料中的一种芳香烃用混合溶剂

2)二甲苯C6H4(CH3)2:广泛使用在短油醇酸树脂,乙烯,氯化橡胶,聚氨酯中的一种芳香烃溶剂,有良好的溶解能力和适中的蒸发速度,经常用来喷雾凹陷涂层,以及烘焙固化型涂料。

3)丁醇C4H9OH:一种挥发率比较底的溶剂,应用于各种油类及树脂特别是氨基酸及丙烯酸树脂;并可以作为溶剂来组合硝化棉树脂。

4)甲基异丁基酮,快挥发性强溶剂,在混合溶剂中添加量少,快挥发速率及强溶解性将有易于液态涂料和成膜特性。

阅读理解

The search for life in the universe took a step forward last month with the opening of the Allen Telescope Array(艾伦望远镜阵列) in Hat Creek, California. The telescopes were partly made possible by a gift of twenty-five million dollars from Paul Allen. The total cost of the project is already fifty million dollars.

At present, there are 42 radio telescopes working at the Hat Creek observatory. The signals they receive are combined to create what is equal to a single, very large telescope. The telescope will be used to observe objects like exploding stars, black holes and other objects that are predicted but have not yet been observed. Seth Shostak of the SETI Institute says this is the first telescope whose main purpose is to search for signals from intelligent life in space. The SETI Institute is based in Mountain View, California. The organization supports the search for other life forms in the universe.

What makes the Allen Telescope Array unusual is that it can collect and study information from a wide area of the sky. In addition, the 42 telescopes can study information about several projects at the same time. That means studies of large areas of the sky can be made faster than ever before.

Some officials think the Allen Telescope Array will be completed in three more years. 350 individual radio telescopes are planned. The new abilities of the Allen Telescope Array will make searching for stars similar to the sun much faster.

An earlier search by SETI, Project Phoenix, studied about 800 stars to a distance of 240 light years. The project ended in 2004. With the Allen Telescope Array, astronomers hope to gather thousands of times more information in the search for life beyond our planet.

小题1:The main purpose of the Allen Telescope Array is          .

A.to serve for the research of weather predication

B.to prepare for the wars against life from the universe

C.to search for signals from intelligent life in space

D.to observe exploding stars, black holes and other objects小题2:From this passage we know that         .

A.the 42 radio telescopes at Hat Creek observatory can work together

B.the total cost of the project came from Paul Allen

C.Hat Creek observatory can receive signals from all parts of the worm

D.Hat Creek observatory is operated by an American named Paul Allen小题3:Which of the following is TRUE according to this passage?

A.The Allen Telescope Array takes much more room than former telescopes.

B.The Allen Telescope Array is still being built at present in the United States.

C.Another 42 radio telescopes will be fixed in the Allen Telescope Array.

D.The SETI Institute is against the search for other life forms in the universes.小题4:With the help of the Allen Telescope Array,         .

A.astronomers can gather more information than before from other planets

B.humans will have more chances to live on other planets than before

C.humans will be able to find more natural resources on other planets

D.scientists will be able to find more natural resources from other planets

单项选择题