O-ring butt joint and introduction of NBR formula materials
I. Uses and properties of commonly used rubber:
1051 Acrylonitrile content 41% ML 75 SG 1.00 slightly polluted type
1052Acrylonitrile content 33% ML 50 SG 0.98 non-polluting type
1053 Acrylonitrile content 29% ML 60 SG 0.97 non-polluting type
1052M30 Acrylonitrile content 33% ML 30 SG 0.98 non-polluting type
DN223 Acrylonitrile content 33% ML 35 SG 0.98 non-polluting type
50.75Acrylonitrile content 50% ML 75 SG 0.99 non-polluting type
1965 Acrylonitrile content 19% ML 65 SG 0.95 non-polluting type
DN401 Acrylonitrile content 18% ML 78 SG 0.99 non-polluting type
1043 Acrylonitrile content 29% ML 80 SG 0.97 slightly polluted type
N230SL Acrylonitrile content 35% ML 42 SG 0.98 non-polluting type
N260S Acrylonitrile content 15% ML 62 SG 0.93 non-polluting type
1052M40 Acrylonitrile content 33% ML 40 SG 0.98 non-polluting type
Features:
1. Higher ACN content results in better oil resistance, especially against non-polar or weakly polar mineral oils, vegetable oils, and liquid fuels.
2. The heat resistance is better than that of NR SBR CR, and it can be used for a long time at 120℃.
3. Acts as a semi-conductive material.
4. oil resistance and compression permanent deformation balance, oil resistance and electrical properties balance.
5. Classification of NBR by acrylonitrile content:
ACN > 43%
Extremely high ACN% NBR
36–42%
High
31–35%
Medium-high
25–30%
Medium
<24%
Low
Summary:
The higher the ACN%, the better the oil resistance and the better the heat resistance, but the lower the TG, the better the low temperature resistance, but the oil resistance deviation. And ML will rise, and the compression set is good. Generally, ACN% can pass F17 when it is 29%. If it passes F19, 1965 or DN401 raw rubber must be used.
II. Effect of Copolymer Composition (ACN Content) on NBR:
Characteristics of ACN content in the project：
Items
ACN content
Characteristics
Density
Low → High
Large
Processability (Fluidity)
Low → High
Good
Vulcanization speed
Low → High
Fast
Tensile stress and tensile strength
Low → High
Large
Hardness
Low → High
Large
Wear resistance
Low → High
Good
Permanent deformation
Low → High
Large
Oil resistance
Low → High
Good
Chemical resistance
Low → High
Good
Heat resistance
Low → High
Good
Compatibility with polar polymers
Low → High
Large
Elasticity
Low → High
Small
Cold resistance
Low → High
Poor
Air permeability
Low → High
Poor
Compatibility with plasticizer oils
Low → High
Poor
III. Vulcanization System:
Generally, NBR formulations using semi-effective vulcanization system, for example: TT/CZ 1.5/1.5PHR, this vulcanization system, with better heat resistance, SUL/TS compression distortion and scorching optimal. SUL/DM (CZ) tensile strength is good, with the sulfur-carrying agent can be obtained with excellent permanent deformation of the compression, Cadmium-Magnesium sulfurization of heat-resistant 150 °C, peroxides can be resistant to 150 °C temperature. And compression permanent deformation of the smallest, but poor tearing, activity with ZNO-A/ST-ACD5/1 use, water-resistant formulations with Pb3O4, which can be used without ZNO-A, but the scorch time is short.
IV. Protection System
6C Resistant to flex-cracking.
OD Good heat resistance.
RD Best heat resistance
MB/ZMTI Excellent heat resistance
NBC Good ozone resistance
SUNGUARD Cracking protection wax with good ozone resistance.
AW Very good ozone resistance
Summary:
Pollution has stronger protection effect than non-pollution, and the oil-resistant formula can be selected as an antioxidant that is difficult to extract. Or increase the dosage appropriately.
V.Reinforcing and filling system
1. N550 is a quick press furnace black, generally 2PHR is increased by one degree, N774 is a semi-reinforced furnace black, generally 3PHR is increased by one degree, and N990 is a medium particle thermal cracking carbon black, generally 4PHR is increased by one degree.
Compression set: N990>N550>N774.
2. In the general formula: N77440PHR /N990 30PHR oil 30PHR has a hardness of about 50 degrees.
N55040PHR/N7440 40PHR oil is 15PHR and its hardness is about 70 degrees.
N55080PHR/N990 40 PHR oil is 10PHR and its hardness is about 80 degrees.
Among them, the tensile strength of the compound is N550>N774>N990 under the condition that the remaining amount of the compound is unchanged.
3.White filler, white smoke has the best reinforcement effect, and # 321, Clay and CaCO3 have certain reinforcement effect: 321# has great activity and good reinforcement effect, but the white filler will absorb the accelerator and delay vulcanization, so triethanolamine must be added, generally PEG4000S2PHR is enough, and the white filler has increased white smoke and the hardness of the rubber compound becomes hard. The increase of ML brings difficulties to processing.
4.Formula design of O-ring rubber compound
According to the working conditions of O-ring, such as medium, temperature, pressure and stress state, the rubber compound formula is designed. O-ring used as dynamic seal requires good tear resistance, wear resistance, heat resistance and extrusion resistance besides medium resistance and small compression set.
5.oil seal
Main performance requirements: ① Good chemical stability with the sealing medium, and the rubber compound will not swell and harden in the sealing medium (mainly various oils), otherwise the radial force will be reduced, the interference size will be changed, and the sealing will be invalid. ② It has good heat resistance, wear resistance and low friction coefficient, which is especially important for oil seals with high linear velocity. ③ It has moderate elasticity, can adapt to the changes of shaft roughness and eccentricity, and has good following ability (follow-up) to dynamic eccentricity.
