Конструкциялық материалдар және термоөңдеу Конструкционные материалы и термообработка Constructional materials and heat treatment Учебное пособие для специальности: 5В071200– «Машиностроение»

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Rubber is subdivided on: 
- natural. 
- synthetic. 
Natural rubber is extracted from lacteal juice (latex) of rubber-bearing tree 
Hevea, and also rubber-bearing plants containing latex in roots. 
The molecule of natural rubber consists of links of easily flying hydrocarbon - 
isoprene and has everywhere an identical microstructure. 
Synthetic rubber was received in 1931 on a method developed by academician 
S.V.Lebedev. 
Synthetic rubber is received generally from natural and passing oil gases, and 
also separate hydrocarbonic fractions of oil processing. 
Types of synthetic rubber: 
- sodium butadiene, first-ever industrial synthetic rubber, was produced from 
ethyl alcohol on the basis of food starch-containing products. Release is stopped 
since 1964. 
- butadiene - styrene is the most widespread synthetic rubber which turns out 
butadiene and styrene copolymerization. Possesses the sufficient durability and 
wear resistance, 
- butyl rubber is received by isoprene and isobutylene copolymerization, it is 
characterized by high gas permeability and chemical firmness, 
- polyurethane rubbers differ high wear resistance, 
- polychloroprene rubbers possess high petroloil resistance, 
- silicone (organosilicon) rubber keeps the properties at temperatures from a 
minus 70ºС to +400ºС, surpassing in thermal stability natural rubber, 
- isoprene and divinyl rubbers possess elasticity which came nearer to indicators 
of natural rubber, and in some other properties and surpass the natural. 
Rubber components. 
Except rubber and vulcanizing substance the structure of rubber mix includes 
also other components giving to rubbers certain properties: 
- curing accelerators (altaks, kaptaks, in number of 1-2% from rubber weight) 
reduce time of curing and increase quality of rubber, 
- amplifiers (active fillers) - soot, a kaolin, zinc whitewash in quantity to 50% 
from rubber weight. Serve for improvement of this or that property of rubber, 
- inactive fillers (elutriated chalk, asbestine flour) in number of 30-40% from the 
weight of rubber are entered for rubber reduction in cost without noticeable 
deterioration of its properties, 
- antiagers (santofleks A, neozon D) in number of 0,5-2,5% from the weight of 
rubber are entered for delay of rubber aging under the influence of air oxygen, 
sunshine and other factors, 

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- softeners and plasticizers (stearin acid, fuel oil, vaseline oil, pine pitch, etc.) in 
quantity from 3 to 20% of weight of rubber improve miscibility of rubber mix 
components and do it more plastic and sticky, 
- dyes are used for coloring of light rubber mixes in the corresponding colors. 
Pigments of a mineral and organic origin are applied. 
Properties of rubbers. 
The rubber basis on which their physicomechanical, strength, protective and 
other properties depend has defining impact on properties of rubbers. 
Temperature with which increase their durability and hardness decrease has 
defining impact on mechanical properties of rubbers. Thus the speed of decrease 
in values of mechanical properties is higher at rubbers on the basis of 
nonsaturated rubbers, and for organosilicon rubbers this speed is minimum. 
The most important characteristics of many types of rubbers are their wear 
resistance and friction coefficient. For rubbers, as well as for other firm 
materials, we distinguish types of wear: 
- fatigue, 
- abrasive, 
- corrosion and mechanical, 
- erosive, 
- "rolling" - is a specific type of wear for rubbers when at friction of 
microroughness of rubber surface are deformed in a roll and come off a surface. 
Except above-mentioned properties quality of rubbers is estimated on: 
- frost resistance, 
- thermal stability or resistance to thermal aging, 
- ozone resistances, 
- bioproofnesses, 
- firmness in liquid environments, 
- dielectric properties, 
- fire danger. 

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