Tham khảo tài liệu 'handbook of materials for product design part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Elastomeric Materials and Processes Natural Rubber NR Natural rubber the original elastomer still plays an important role among elastomers. Worldwide consumption of NR in 2000 is expected to be about 7 million metric tons y based on earlier reporting by the International Rubber Study Group. Chemically natural rubber is cis1 4-polyisoprene and occurs in Hevea rubber trees. NR tapped from other rubber trees gutta-percha and balata is the trans isomer of NR s principal uses are automotive tires tire tread and mechanical goods. Automotive applications are always compounded with carbon black to impart UV resistance and to increase mechanical Latex concentrate is used for dipped goods adhesives and latex Latex concentrate is produced by centrifuge-concentrating field latex tapped from rubber trees. The dry rubber content is subsequently increased from 30 to 40 to 60 mini-23 mum. Vulcanization is the most important NR chemical Most applications require cross-linking via vulcanization to increase resiliency and strength. Exceptions are crepe rubber shoe soles and rubber There are a number of methods for sulfur vulcanization with certain methods producing polysulfidic cross-linking and other methods producing more monosulfidic NR is imported from areas such as Southeast Asia to the world s most industrial regions North America Europe and Japan since it is not indigenous to these regions. The huge rubber trees require about 80 to 100 in y 200 to 250 cm y rainfall and they flourish at an altitude of about 1000 ft 300 m .23 As long as NH is needed for tires industrial regions will be import dependent. NR has good resilience high tensile strength low compression set resistance to wear and tear cut-through and cold flow and good Resilience is the principal property advantage compared with synthetic For this reason NH is usually used for engine mounts .
