Lesson 4 Polyisoprene Rubber (IR)
New Words
Notes
[1] The isoprene monomer, the structural unit of the natural rubber polymer, can polymerize in four isomeric forms: trans-1，4-addition, cis-1，4-addition, 1，2-addition, leaving a pendant vinyl group, and 3，4-addition. 异戊二烯单体聚合得到的结构单元，即天然橡胶的结构单元，有四种不同的异构体：反-1，4-结构、顺-1，4-结构，带有乙烯基侧链的1，2结-构和3，4-结构。
[2] Polyisoprene is therefore easier to process, gives a less variable (although generally slower) cure, is more compatible in blends with EPDM and solution SBR, and provides less green strength (pre-cure) than natural rubber. 因此，聚异戊二烯橡胶更容易加工，表现出重现性很好的硫化特性(尽管比天然橡胶稍慢)，还能与EPDM和溶聚SBR良好地相容，也比天然橡胶的格林强度低。
[3] The synthetic elastomer can be produced with the very low level of branching, high molecular weight, and relatively narrower molecular weight distribution that contributes to lower heat buildup compared to natural rubber. 这种合成的弹性体具有较小的支化程度，较高的分子量和更窄的分子量分布，这些结构特点使得生热会比天然橡胶低。
Exercises
1. Translate the first and second paragraphs of the text into Chinese.
2. Put the following words into English.
聚异戊二烯橡胶 有规立构的 溶液 合成的 催化剂
纯度 分子量分布
Application of IR
Polyisoprene elastomers (IR) are synthetic, predominantly stereoregular polymers that closely resemble natural rubber in molecular structure as well as in properties. Polyisoprene elastomers are currently being used in a variety of applications requiring good resilience, low water swell, high gum tensile strength, good tack and high hot tensile strength. The largest end use for polyisoprene by far is in tires. Black-loaded polyisoprene finds uses in tires, motor mounts, pipe gaskets, shock absorber bushings, and many other molded and mechanical goods. Gum polyisoprene compounds are used in rubber bands, cut thread, baby bottle nipples, and extruded hoses, and other such items. Mineral-filled polyisoprene finds applications in footwear, sponges, and sporting goods. Other important uses include medical applications and adhesives and sealants. Of all the applications, medical applications have seen the fastest growth.
Words and Expressions
