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. 異戊二烯單體聚合得到的結構單元，即天然橡膠的結構單元，有四種不同的異構體：反-1，4-結構、順-1，4-結構，帶有乙烯基側鏈的1，2結-構和3，4-結構。

[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，聚異戊二烯橡膠更容易加工，表現出重現性很好的硫化特性(盡管比天然橡膠稍慢)，還能與EPDM和溶聚SBR良好地相容，也比天然橡膠的格林強度低。

[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. 這種合成的彈性體具有較小的支化程度，較高的分子量和更窄的分子量分布，這些結構特點使得生熱會比天然橡膠低。

Exercises

1. Translate the first and second paragraphs of the text into Chinese.

2. Put the following words into English.

聚異戊二烯橡膠　　　有規立構的　　　溶液　　　合成的　　　催化劑

純度　　　　　　　　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