问题 问答题 论述题

高压聚乙烯分子结构特点是怎么样形成的,对聚合物的加工性能有何影响?

答案

参考答案:

高温状况下,PE分子间的距离缩短,且易与自由基碰撞反应,很容易发生本分子链转移,支链过多,这种PE加工流动性好,.可以采取中空吹塑,注塑,挤出成型等加工方法,具有良好的光学性能,强度,柔顺性,封合性,无毒无味,良好的电绝缘性。

单项选择题

At the ceremony at Yale University in 1983, several honorary degrees were awarded, including one to Mother Teresa. As she and other humanitarians and scholars, each in turn, received their awards, the audience applauded appropriately but with a slight hint of reserve and impatience, for it wished to give its heart to the final recipient who waited shyly in the wings. As the details of her achievements were being recounted, many people left their seats and surged toward the stage to be closer to the great woman. And when the name Meryl Streep was announced, the audience unleashed a sonic boom of affection to wake the New Haven dead. One man who was present when Bob Hope received his honorary doctorate at another institution said that Dr. Streep’s applause surpassed Dr. Hope’s. Knowing how to please a crowd as well as anyone, the intellectual leaders at Yale invited Dick Cavett, the talk-show host, to deliver the commencement address the following year. It is rumored that this year, Don Rickles will receive a Doctorate of Humane Letters and Lola Falana will give the commencement address.

Prior to the 1984 presidential elections, the two candidates confronted each other on television in what were called "debates." These events were not in the least like the Lincoln-Douglas debates or anything else that goes by the name. Each candidate was given five minutes to address such questions as, What is (or would be) your policy in Central America His opposite number was then given one minute for a rebuttal. In such circumstances, complexity, documentation and logic can play no role, and, indeed, on several occasions syntax itself was abandoned entirely. It is no matter. The men were less concerned with giving arguments than with "giving off" impressions, which is what television does best. Post-debate commentary largely avoided any evaluation of the candidates’ ideas, since there were none to evaluate. Instead, the debates were conceived as boxing matches, the relevant question being, Who KO’d whom The answer was determined by the "style" of the men—how they looked, fixed their gaze, smiled, and delivered one-liners. In the second debate, President Reagan got off a swell one-liner when asked a question about his age. The following day, several newspapers indicated that Ron had KO’d Fritz with his joke. Thus, the leader of the free world is chosen by the people in the Age of Television.

What all of this means is that our culture has moved toward a new way of conducting its business, especially its important business. The nature of its discourse is changing as the demarcation line between what is show business and what is not becomes harder to see with each passing day. Our priests and presidents, our surgeons and lawyers, our educators and newscasters need worry less about satisfying the demands of their discipline than the demands of good showmanship. Had Irving Berlin changed one word in the title of his celebrated song, he would have been as prophetic, albeit more terse, as Aldous Huxley. He need only have written, There’s No Business But Show Business.

The text is organized mainly by means of()

A. causal relationship

B. exemplification

C. comparison

D. contrast

选择题