Lesson 3　Natural Rubber (NR)

New Words

Notes

[1] The strain-induced crystallization gives natural rubber products high tensile strength and resistance to cutting, tearing, and abrasion. 拉伸诱导结晶可以提高天然橡胶的拉伸强度、抗剪强度、抗撕裂性能和耐磨性。

[2] Rubber is unique in the extent to which it can be distorted, and the rapidity and degree to which it recovers to its original shape and dimensions. 橡胶可以发生形变，并且能够迅速恢复形状和尺寸的特性是独一无二的。

[3] The commercial utility of natural rubber has in fact grown from the ease with which its useful properties can be changed or improved by compounding techniques. 实际上随着配合技术的提高，天然橡胶的性能得到了改善，进而扩大天然橡胶的商业应用。

Exercises

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

2. Put the following words into English.

天然橡胶　　　环氧化天然橡胶　　结晶　　　　耐磨性　　　　　脱水

胶乳　　　　　弹性　　　　　　　永久变形　　拉伸诱导结晶

Properties of NR

Vulcanized products made from NR have high mechanical strength and can be compounded to have excellent elasticity (ability to snap back to their original shape). NR has very good abrasion resistance which, with its low relative cost, makes it a significant choice for slurry pump liners and impellers as well as for tank linings. It has very good dynamic mechanical properties and is therefore used in tires, rubber springs and vibration mounts. It is one of the few elastomers that have high strength. As NR rubber gum vulcanizate has a very high elasticity, thus most of the kinetic energy of an impacting particle is converted into deformation of the vulcanizate which then releases the energy by returning to its original undeformed state.

It also has very good low temperature resistance, down into the region of －57℃ at which its stiffness shows a considerable increase. Its high temperature heat aging resistance limit for continuous use is in the region of 75℃. Inherent weather resistance provided by the raw elastomer is poor. Significant components of weather, from the rubber technologists point of view, are UV light and ozone. Addition of carbon black to a compound gives resistance to UV, antiozonants and waxes, and helps with ozone resistance. Ozone attack is of most concern for thin products and those that are subjected to stretching in service.

Words and Expressions