What is the surface of this performance? Rubber and its products in the process of processing, storage and use, due to the comprehensive role of internal and external factors caused by the gradual deterioration of the physical and chemical properties of rubber and mechanical properties, and finally lost the use value, this change is called rubber aging. On the surface of the performance of cracking, sticky, hardening, softening, powder, discoloration, mildew and so on.

Second, what are the factors that affect the aging of rubber?

　　The factors that cause the aging of rubber are:

(A) oxygen and oxygen in rubber with rubber molecules in the free base chain reaction, molecular chain fracture or excessive cross-linking, resulting in changes in rubber properties. Oxidation is one of the important reasons for rubber aging.

(B) The chemical activity of ozone and ozone is much higher and more destructive than that of oxygen, which also breaks the molecular chain, but the effect of ozone on rubber varies with the deformation of rubber. As rubber used for deformation (mainly unsaturated rubber), there is a crack perpendicular to the direction of stress, that is, the so-called "ozone cracking "; When acting on deformed rubber, only the surface produces an oxide film without cracking.

(C) Heat: Increasing the temperature can cause thermal cracking or thermal crosslinking of rubber. But the basic effect of heat is still the activation effect. It is a common aging phenomenon, thermal oxygen aging, to increase the rate of oxygen diffusion and activate the oxidation reaction, so as to accelerate the oxidation reaction speed of rubber.

(D) Light: the shorter the light wave, the greater the energy. What does damage to rubber is the high energy ultraviolet rays. In addition to directly causing the fracture and crosslinking of rubber molecular chains, rubber produces free radicals due to the absorption of light energy, which triggers and accelerates the oxidation chain reaction process. Ultraviolet light acts as a heating. Another characteristic of light acting (unlike thermal action) is that it is mainly born on the oak surface. The high glue content of the specimen, both sides will appear mesh cracks, that is, the so-called "light outer layer crack ".

(E) Mechanical stress: Under the repeated action of mechanical stress, the rubber molecular chain fracture will produce free radicals, trigger oxidation chain reaction, and form the chemical process of force. Mechanical fracture molecular chain and mechanical activation oxidation process. Which one can prevail depends on the conditions in which it is located. In addition, it is easy to cause ozone cracking under the action of stress.

(F) Moisture: the effect of moisture has two aspects: rubber in wet air rain or soak in water, easy to destroy, this is due to rubber water-soluble substances and water groups and other components are pumped dissolved. Caused by hydrolysis or absorption and other reasons. Especially in the alternating action of water immersion and atmospheric exposure, the damage of rubber will be accelerated. But in some cases, water is not damaging to rubber, and even has the effect of delaying aging.

(G) Other: The factors that act on rubber are chemical media, variable-price metal ions, high-energy radiation, electricity and biology.

Third, rubber aging test methods can be divided into which categories?

　　Can be divided into two broad categories:

(A) test methods for natural ageing.

　　It is divided into atmospheric old test, atmospheric accelerated aging experiment, natural storage aging test, natural medium (including buried land, etc.) and biological aging test.

(B) Manual accelerated Aging test method.

　　For thermal aging, ozone aging, light aging, artificial climate aging, light ozone aging, biological aging, high-energy radiation and electrical aging, as well as chemical media aging.

Four. Thermal Air Aging Test what temperature level should I choose for all kinds of rubber?

For natural rubber, the test temperature is usually 50~100℃, synthetic rubber is usually 50~150℃, and some special rubber test temperatures are higher. Such as Nitrile rubber with 70~150℃, silicone fluoride is generally used 200~300℃. In short, it should be specifically determined on the basis of the experiment.

Butadiene Rubber SBR is the earliest industrialized synthetic rubber. In 1933, the emulsion polymerization Butadiene rubber was first developed by acetylene synthesis route in Germany, and industrial production began in 1937. 1942 the United States used petroleum as raw materials to produce butadiene rubber. Production also began in the former Soviet Union in 1949.

 

These are copolymers at high temperatures (50 ℃), called high-temperature butadiene rubber. In the early 50, low-temperature butadiene rubber with excellent performance appeared. At present, low temperature emulsion polybutadiene rubber accounts for about 80% of the whole butadiene rubber. Production of oil-filled butadiene rubber began in 1951. After the emergence of butadiene rubber carbon black masterbatch rubber, oil-filled butadiene rubber carbon black rubber, high styrene butadiene rubber, hydroxyl butadiene rubber and liquid butadiene rubber.

 

In the middle of the 60, solution polymerization Butadiene Rubber (SSBR) began to come out.

 

At present, the production of butadiene rubber (including latex) accounts for about 55% of the total synthetic rubber production, is the largest production and consumption of synthetic rubber.

 

Advantages and disadvantages of butadiene rubber: Butadiene rubber is an unsaturated hydrocarbon polymer with a solubility parameter of about. Physicochemical reactions occur under the action of light, heat, oxygen and ozone, but their oxidation is slower than that of natural rubber, and the rate of aging reaction is slower even at higher temperatures. The aging effect of light on rubber is not obvious, but ozone resistance is worse than that of natural rubber.

 

The brittle temperature is about minus 450C and the low temperature performance is slightly worse.

 

Compared with general general purpose rubber has the following advantages and disadvantages:

 

1. Advantages

(1) The glue is not easy to scorch and sulfur, the vulcanization flatness is good.

(2) Wear resistance, heat resistance, oil resistance and aging resistance are better than natural rubber. High temperature wear resistance is good, suitable for the use of tires.

(3) The molecular weight in the processing is reduced to a certain extent, so it is not easy to be over, the plasticity is uniform. The hardness of vulcanized adhesive changes little. (4) High filling can be achieved by increasing the molecular weight. The processing performance of oil-filled butadiene rubber is good.

(5) It is easy to use with other unsaturated general rubber, especially with natural rubber and butadiene rubber, by formula adjustment can overcome the shortcomings of butadiene rubber.

 

2. Disadvantages

(1) The strength of pure glue is low, need to add high-activity reinforcing agent can be used. The difficulty of adding mating agent is larger than that of natural rubber, and the dispersion of mating agent is poor in rubber.

(2) The trans structure is many, the structure is not regular, the side base has the benzene ring, thus than the natural rubber lag loss is larger, the heat is high, the elasticity is low, the cold resistance is also slightly worse. But when the oil is filled, it can reduce the heat.

(3) The vulcanized adhesive shrinkage is large, the strength is low, the adhesion performance is not as good as the natural rubber.

(4) The vulcanization speed is slower than the natural glue.

(5) vulcanized adhesive flexural cracking is better than natural glue, but crack propagation speed is fast.

Precautions for daily use of Hydraulic Hose

 

In order to ensure the safety of Hydraulic Hose itself and connected equipment, in the daily operation process, it is necessary to ensure the safety of its operations, then what are the specific matters to be noted?

1, high-pressure steel wire knitting high-pressure rubber tube high-pressure hose bending radius is too hour generally choose right angle joint to avoid high-pressure hose appearance sharp bend misrepresentation.

3, in the usual operation, the trigger of the stem can not be too fierce, must be steep, otherwise it will constitute a high-pressure rubber pipe burst.

4. In order to avoid the damage of high pressure steel wire winding hose and the limitation of flow rate, the bending radius of high pressure rubber pipe should be increased.

5, when in the operation, the hydraulic system appears too high temperature rise, about timely inspection of high-pressure tubing, and in continuous operation, should use the necessary cooling methods.

6, the most important is the choice of hose must be reasonable. In order to avoid improper use, resulting in accelerated aging of high-pressure rubber tubes, it should also be noted that the installation of Hydraulic Hose should be left with a certain amount of space, to avoid the use of high-pressure rubber tubes in the process of causing contact with objects.

Name of various rubber performance usage introduction

 

1, Natural Rubber (NR) Comprehensive performance is more comprehensive, simple processing technology, the disadvantage is oil-resistant, heat-resistant, cold resistance, chemical-resistant, aging resistance and other performance is too poor, far less than other synthetic rubber. Mainly used in tires, hoses, tape, medical supplies, sporting goods and some other industrial supplies.

2, Butadiene Rubber (SBR) Comprehensive performance is comparable to natural rubber, while wear and thermal aging performance is better than natural rubber, with natural rubber and a variety of synthetic rubber, processing performance is good, is a general rubber. The main use of language hose, tires, tape. Rubber shoes, as well as a variety of industrial rubber products.

3, Butadiene Rubber (BR) Good processing performance, with excellent wear resistance and elasticity, less heat, low temperature resistance and good performance. Flexural resistance is also good, the disadvantage is tear strength and anti-skid resistance is not good. Widely used in tires, hoses, tapes, rubber shoes and other rubber products.

4, Neoprene (CR) ozone resistance, climate aging resistance, oil resistance, solvent resistance, flame retardant, insulation and water resistance, air tightness, tensile strength and other aspects of the performance are better. The disadvantage is poor cold resistance, large specific gravity (density). Suitable for hose, tape, conveyor belt, wire and cable, air conditioning rubber products, as well as construction, ships, automobiles and other sealing products.

5, Nitrile Rubber (NBR) can be used for a long time at a temperature of less than 120 degrees, air tightness is good (second only to butyl rubber) oil resistance, wear resistance, tear resistance and other performance functions are excellent (note: This material belongs to semiconductor rubber, therefore not suitable for insulating products) applicable to automobiles, machinery hose, seals, cable sheath, sponge products.

6, hydrogenated nitrile Rubber (HNBR) can be used in the 40-180 degree working environment for a long time, with good processing performance, high strength, excellent abrasion resistance, small permanent deformation, and unique anti-ozone and hydrogen-resistant effects. Suitable for engine sealing products, oil seals, oil fields, drill pipe rubber products, low-temperature tubing, air conditioning pipe, electronic system protection parts.

7,Ethylene Propylene Rubber (EPDM) heat and ozone resistance is the aging of the sky, low temperature resistance, electrical insulation, acid resistance, alkali and other aspects of excellent performance. Widely used in construction, automobiles, ship doors and windows seals, wire and cable, automobiles, motorcycle parts and other industrial products.

8, Silicone Rubber (SR) can be used in the 60-120 degree working environment for a long time, transparent non-toxic tasteless insulation performance, good processing performance. Disadvantages are wear resistance, tear performance and oil resistance, poor chemical media resistance. Widely used in electric electrical appliances, electrical and electronic industry, aviation, defense, machinery, construction and construction, medical, food hygiene, as well as kitchen supplies, household miscellaneous products.

9, Fluorine Rubber (FPM) excellent high temperature resistance (250 degrees) and good dielectric properties, as well as excellent oxidation resistance, oil resistance, chemical corrosion resistance, wear resistance and other excellent properties. The disadvantage is that the processing process is more difficult. Widely used in aerospace missile rockets and other scientific fields as well as industrial equipment in all aspects, such as hose, seals, wires, diaphragms, tape and other products and anti-corrosion lining.

10, Butyl Rubber (IIR) airtight performance in a variety of rubber is the best, excellent heat and aging performance, ozone aging resistance, as well as electrical insulation performance, colleagues have a wide range of temperature use. Widely used in tire inner tube, vulcanization capsules, water tires, wind tires, auto parts, wire and cable, hose, tape, building waterproof sheet, clogging materials (such as bottle cover) door and window seals, as well as chemical equipment anticorrosion.

11, Sulfur Rubber (TR) has good oil resistance, hydrocarbon resistant solvents, resistance to atmospheric aging, water resistance, as well as low temperature flexural properties. At the same time, a variety of materials have very good adhesion, used as automotive sealing materials, non-dry rubber putty and chemical equipment lining, road paint and oil-resistant paint, paint, oil-resistant hose insulating glass seal and so on.

12 Polyacrylate rubber (ACM and ANM) can be used at temperatures up to 175-200 degrees, air tightness, weathering resistance, heat resistance and oil resistance. The disadvantages are water resistance and poor low temperature resistance. The processing performance is difficult to master, and the vulcanization process is corrosive to the mold. Mainly used in the automotive industry, seals and special requirements of hoses, tapes, colleagues also used in the manufacture of wire and cable gloves, adhesives and other contact with high temperature oil.

13 Ethylene Acetate Rubber (EVW) can be used at 175 °C for a long time. It has excellent flame retardant properties and oil resistance. The product has low compression deformation at high temperature. Suitable for subways, high-rise buildings, and marine high-performance halogen-free flame-retardant wire and cable and other sealing products.

14 Chlorinated polyethylene (CPE) is a special synthetic rubber with heat resistance, weather resistance and flame resistance. It has excellent electrical properties and chemical resistance. It also has the advantages of oil resistance, ozone resistance, weather resistance, heat aging resistance and flame resistance. It is widely used in wire and cable with good flame resistance and weather resistance, sealing products and industrial products such as hoses, tapes and rubber rollers that require temperature resistance, acid resistance and flame resistance.

15 Thermoplastic styrene-butadiene rubber (SBS) is the most economical thermoplastic elastomer of the current production (accounting for 7%). Its properties are similar to those of styrene-butadiene rubber. It has more elasticity, feel, color, format and low hardness. The disadvantage is heat resistance and poor oil resistance. Widely used in handles, toys, sports equipment, shoe materials and other fields.

16 Thermoplastic elastomer (SEBS) is a saturated SBS produced by hydrogenation. It is resistant to aging and ozone. It has a large improvement in its original properties and is especially suitable for outdoor use. The disadvantages are heat resistance and poor oil resistance. The operating temperature range is between -60 and 100 degrees. Widely used in handles, toys, sports equipment, medical accessories and other fields.

17 Thermoplastic elastomer (TPV) is a dynamically vulcanized EPDM/PP blend. Cold and heat resistant, excellent elasticity, aging resistance, ozone resistance, tear strength, chemical resistance, excellent coloring performance, can be used at temperatures between -60-135 for a long time. Widely used in automobiles, ships, mechanical parts, hose tapes and various industrial products, often used to extrude various types of sealing strips.

18 Thermoplastic polyurethane rubber (TPU) has outstanding wear resistance, high elasticity, high mechanical strength, excellent oil resistance and excellent flexing resistance. The long-term use temperature can be between -40 and 120 degrees. The disadvantage is that there are very few varieties with low hardness. Widely used in the brake pipe, tubing, interior parts, cables, pipes, shoe materials and sports equipment, and heterogeneous materials for the automotive industry.

19 Polyvinyl chloride (PVC) is one of the most widely used plastics at present. It is economical and has excellent flame retardancy, chemical resistance, high abrasion resistance and good electrical insulation. The disadvantage is that the cold resistance is poor, the winter becomes hard and brittle, and the chlorine is irritating. Widely used in all walks of life, automotive, construction, machinery, daily necessities cable.

Characteristics of EPDM Rubber

(1) Low density and high filling

Ethylene Propylene rubber is a rubber with a lower density, with a density of 0.87. Coupled with a large amount of oil filling and ternary ethylene propylene The addition of filler, thus reducing the cost of rubber products, to make up for the high price of ethylene propylene rubber raw rubber, and for the Gaumenni value of ethylene propylene rubber, high filling after the physical mechanical energy reduction is not significant.

(2) Aging resistance

Ethylene Propylene rubber has excellent weather resistance, ozone resistance, heat, acid and alkali resistance, water vapour, color stability, electrical properties, oil filling and normal temperature fluidity. Ethylene Propylene Rubber products can be used for a long time under 120 ℃ and can be used briefly or intermittently under 150-200 ℃. Adding suitable antiaging agent can increase the temperature of its use. Ternary ethylene propylene rubber crosslinked with peroxides can be used under harsh conditions. EPDM rubber in the ozone concentration of 50pphm, tensile 30% conditions, can reach more than 150h without cracking.

(3) Corrosion resistance

Because of the lack of polarity and low saturation of ethylene propylene rubber, it has good resistance to all kinds of polar chemicals such as alcohols, acids, alkalis, oxidants, refrigerants, detergents, animal and plant oils, ketones and lipids, but the stability of lipids and aromatic solvents (such as gasoline, benzene, etc.) and mineral oils is poor. Performance also decreases under the long-term action of concentrated acids. In ISO/TO 7620, nearly 400 corrosive gaseous and liquid chemicals were compiled to provide information on the properties of various rubber, and 1-4 levels were specified to indicate the extent of their action, and the effects of corrosive chemicals on rubber properties:

Grade Volume Swelling rate/%; Hardness reduction value; Impact on performance 

1                                    <10                              <10                          Minor or non

2                                     10-20                          <20                          Smaller

3                                     30-60                          <30                         Medium

4                                     >60                             >30                          Serious

(4) Resistant to water vapor performance

Ethylene Propylene rubber has excellent water vapor resistance and is better than its heat resistance. In 230 ℃ superheated steam, the appearance of EPDM near 100h has no change.

Fluorine rubber, silicone rubber, fluorine silicone rubber, butyl rubber, nitrile rubber, natural rubber under the same conditions, experienced a short period of appearance of obvious deterioration of the phenomenon.

(5) Resistant to hot water performance Ethylene Propylene rubber has good resistance to hot water, but it is closely related to all vulcanization systems. After 15 months of soaking in 125 ℃ superheated water, the mechanical properties changed little and the volume expansion rate was only 0.3%, with TMTD rubber with two morphine sulfide and the vulcanization system.

(6) Electrical properties

Ethylene Propylene rubber has excellent electrical insulation properties and corona resistance, electrical performance is better than or close to butadiene rubber, chlorosulfonated polyethylene, polyethylene and crosslinked polyethylene.

(7) Elasticity

Because of the cathode substitution base in the molecular structure of ethylene propylene rubber, the molecular cohesive energy is low, and the molecular chain can remain supple in a wide range, second only to natural discussion and butadiene rubber, and can still be maintained at low temperatures.

(8) Adhesion

Ethylene Propylene rubber due to the molecular structure of the lack of active groups, low cohesive energy, coupled with the glue easy to spray frost, self-stickiness and mutual stickiness is very poor.

The cold resistance of rubber refers to the ability to maintain rubber elasticity and normal operation at a specified low temperature. Vulcanized rubber at low temperature, due to the rapid deceleration of relaxation process, hardness, modulus and molecular friction increase, elasticity significantly reduced, resulting in a decrease in the working capacity of rubber products, especially in the dynamic conditions are particularly prominent, when the temperature drops to the elastic limit of the use of temperature, rubber will harden and shrink, resulting in leakage failure of seals. The cold resistance of vulcanized adhesive mainly depends on the two basic characteristics of polymer: vitrification transformation and crystallization.

　　Both will cause the rubber to lose its elasticity at low temperatures. The choice of cold-resistant gelatin is the key to cold resistance, the cold resistance of rubber mainly depends on the variety of rubber. For non-crystalline rubber, the vitrification temperature is low and the cold resistance is better. For crystalline rubber, the cold resistance should take into account the level of vitrification temperature, crystallization situation. Increasing the flexibility of rubber molecular chains, reducing intermolecular forces and spatial resistance, and weakening the regular rubber composition and structural factors of the large molecular chain are beneficial to improve the cold resistance of rubber.

　　Rubber is used as a common method to adjust the cold resistance in rubber formulation design, such as SBR and BR, NBR and NR, CO, ECO, can improve the cold resistance of rubber. The type of cross-linked bond affects the cold resistance of rubber. When natural rubber uses the traditional vulcanization system, with the increase of sulfur dosage, until 30 parts, its shear modulus increases, and the vitrification temperature increases (which can rise to 20~30℃). Choosing an appropriate and effective vulcanization system, the rubber vitrification temperature is 7 ℃ lower than the traditional vulcanization system. Therefore, NR and SBR, DCP vulcanization has the best cold resistance, with autumn lamb vulcanization, cold resistance has been reduced, and sulfur/sub-sulfonyl agent vulcanization of the worst cold resistance. The reason for the above difference is that when sulfur is vulcanized, when the sulfur bond is generated, the cross-linking bond of the molecule is also generated, and the cyclic reaction occurs, so the activity of the chain is reduced, the elastic modulus is increased, and the vitrification temperature rises. When reducing the amount of sulfur, using semi-effective or effective vulcanization system, the number of sulfur bonds decreases, mainly the generation of single sulfur bond and disulfide bond, the possibility of binding sulfur in the molecule is reduced, so the vitrification temperature rises more than the sulfur bond is small. When vulcanized with peroxides and radiation, its cold resistance is better than that of effective vulcanization system and traditional vulcanization system, because the volume expansion coefficient of peroxide vulcanized adhesive is larger. The volume expansion coefficient is large, which can increase the free space of the chain activity, which is beneficial to the reduction of vitrification temperature. In addition, peroxide vulcanization, the formation of a firm, short C-C cross-linked key, and the use of sulfur vulcanization, will form a small firmness, a larger length of the multi-sulfur bond, so in the event of deformation, to overcome the inter-molecular force will be larger, at the same time weak bond distortion, which increases the lag loss, increase the creep rate, The viscous resistance part of the vulcanized adhesive is larger than that of the peroxide vulcanized adhesive.

　　In other words, in the sulfur sulfide rubber, the force between the molecules is much larger, which is the reason why the cold resistance of vulcanized glue is poor. The effect of fillers on the cold resistance of rubber depends on the structure formed by the interaction between the filler and the rubber.

　　Increase the amount of glue, reduce the amount of filler, the addition of fillers will hinder the change of chain configuration, increase the rigidity of fillers, so can not expect to add fillers to improve the cold resistance of rubber. In addition, the reasonable selection of softening plasticizing system is an effective measure to improve the cold resistance of rubber products, adding plasticizer, can make the rubber vitrification temperature drop. The cold resistance of nitrile rubber, neoprene and other polar rubber, mainly by adding appropriate plasticizers to improve its cold resistance. Because plasticizers can increase the flexibility of rubber molecules, reduce the force between molecules, so that the molecular chain is easy to move, so polar rubber to choose its polarity similar to the solubility parameters close to the plasticizer. The type and dosage of softening plasticizer are very important to the cold resistance of rubber.