问题 问答题 简答题

简述覆膜及覆膜的基本要求?

答案

参考答案:

腹膜就是将塑料膜涂上粘合剂,将其与纸为承印物的印刷品,经橡皮滚筒和加热滚筒加压粘合在一起,形成纸塑合一的产品。

基本要求:

1、厚度-薄膜的厚度直接关系到透光度、折光度、腹膜牢度、机械强度等方面。根据薄膜自负性能和使用目的,薄膜厚度在0.01mm~~0.02mm之间比较合适。

2、表面张力--用于覆膜的薄腹须经过电晕处理,或采用其他方法处理,使其表面张力大到4pa,以便有较好的湿润性和和粘合性能。

3、透明度--为了保证被薄膜的印刷品具有最佳清晰度,薄膜的透明度越高越好

4、耐光性--耐光性指塑料薄膜在光线长时间照射下变色的程度,用于覆膜的薄膜应具有良好的耐光性。

5、机械性能--塑料薄膜在覆膜工艺操作中要经受机械力的作用,因此必须使薄膜具备一定的机械强度和柔韧特性。

6、几何尺寸稳定性--塑料薄膜的几何尺寸不稳定,伸缩率过大,不但在覆膜操作时会出现麻烦,而且还会使产品产生皱纹、卷曲等严重质量问题。几何尺寸稳定,表明吸湿蹦胀系数、热膨胀系数、热变形系数、抗寒性等技术指标也比较稳定。

7、化学稳定性-塑料薄膜在工艺操作中要和一些溶剂、粘合剂以及印刷品的油墨接触,因此要求它必须不受化学物质的影响,具有一定的化学稳定性。

8、外观--应膜面平整,无凹凸不平及皱纹,无气泡、针孔及麻点,膜面应无灰尘、无杂质、无油斑等杂物,而且必须厚薄均匀。作为覆膜的主要原料,还要成本低。

阅读理解

Now more and more people may experience excessive (more than normal) hair loss(掉发). Hair loss of this type can affect men ,women and Children. But what causes excessive hair loss?

A number of things can cause excessive hair loss.For example,about 3 or 4 months after an illness,you may suddenly lose a large amount of hair ,This hair loss is related(与……有关)to the stress of the illness and it won’t last long.

For example,many women notice hair loss about 3 months after they’ve had a baby .This loss is also related to hormones (激素). During they have babies,high levels of certain hormones cause hair loss. When the hormone return to normal levels.The normal cycle of growth and loss starts again.

Another way of hair loss is the improper care of your hair .If you wear pigtails(辫子)or use tight (紧的)hair rollers, the pull(拉)on your hair can cause a type of hair loss.

Some medicine can cause hair loss.This type of hair loss improves when you stop taking the medicine.Medicine that can cause hair loss includes blood thinners,medicine used to treat cancer ,Vitamin A(if too much is taken),birth control pills and so on.

But how to stop hair loss ? Perhaps your doctor can help you.He will probably ask you some questions about your diet,any medicine you’re taking,whether you’ve had a recent illness and how you take care of your hair.

Medicine may also help slow or prevent(阻止)the development of hair loss Some medicine is helpful.but you had better ask for doctors’ advice .

任务:请阅读上面短文,根据短文内容完成下面表格中的有关信息。

What causes hair loss?How to stop hair loss?
Hair loss is related to小题1:Doctors can help you
The 小题2:    may cause hair 1oss, such as wearing pigtails ,using tight hair rollers and so on.小题3:        may help prevent hair loss if doctors permit.
小题4:       can cause hair loss.

名词解释