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Most of the low-speed, high-load work sites are non-paved roads, withstand transient impacts, and the operating conditions of the load uncertainty, determine that the framework materials used in construction machinery tires must have high strength to bear and disperse all kinds of stress. Ensure the safe operation of construction machinery. At the same time, the number of carcass cords for construction machinery tires is generally more, and some high-rise giant tires have high carcass capacity of more than 30 layers in order to achieve high load carrying capacity. Because nylon 66 cord single breaking strength under the same fineness is 5 20 kN higher than nylon 6 cord, nylon 66 tire body has high strength, small deformation under load, low heat generation and long life in tire use.
The heat transfer performance of rubber is poor. The thicker the carcass of tires, the greater the heat generation, the more difficult it is to dissipate heat. As the temperature of tires increases during driving, heat accumulates, and the temperature of the shoulder parts is sometimes as high as 120 or more. The physical properties of the vulcanizate and the skeleton material are continuously reduced; when the bonding strength at the weakest part is not enough to resist the shear stress caused by the external force, the tire will be thermally exfoliated. At this time, the tire continues to run, which may cause the tire to burst. . Nylon 66's strength and heat resistance is better than nylon 6 (especially at the critical point), so the strength of the tire carcass made of nylon 66 cords is reduced relatively, and the tire's safety performance is improved.
The dimensional stability of finished tires made of a skeleton material with a low dry heat shrinkage ratio is good, so the smaller the dry heat shrinkage rate of the tire frame material, the better. The smaller the swell of the outer edge of the tire in the later period of use, the better. This is due to the poor wear resistance of the tread rubber in the stretched state, the accelerated wear, and the reduced service life of the tire.
Tire structure design takes a large crown cord angle, which can limit the extension of the outer diameter of the tire: take the buffer layer cord angle larger than the carcass cord angle 1 2? The buffer layer acts as a belt layer to limit the expansion of the outer diameter after the tire is inflated, so that the tread rubber runs in a contracted state or a relatively small stretch state, thereby obtaining better wear resistance. The wear resistance of all-steel or semi-steel radial tires is better than diagonal ones. One of the main reasons is that steel cords are used for the carcass and belt frame materials of all-steel or semi-steel radial tires. The outer diameter of pneumatic tires in practical use is There is little change in the size of the model or the free state. It can be seen that the wear resistance of tires made of polyamide 66 cords with low dry heat shrinkage ratio is better than that of nylon cords made of nylon 6 cords with high dry heat shrinkage.
Tire quality By improving the production technology and process, and adjusting the processes of polymerization, stretching, twisting, and dipping, the strength and elongation properties of nylon 66 can be further improved. At the same denier, the breaking strength of nylon 66 has been steadily increased to 88 cN tex -1 or more, so nylon 66 has a lower denier at the same breaking strength. The comparison and calibration test results for 1870dtex/ 2 nylon 66 and nylon 6 under the same process conditions show that after the same quality of nylon 66 and polyamide 6 cords are coated, the nylon 66 cord can obtain a larger area of ​​the rubber cord and can produce more. The tires contribute to the lightweighting of the tires, and this effect is more pronounced in the production of large engineering machine tires with a larger number of skeleton materials.
The renovation rate is an important indicator of the quality of tires. The service life of retreaded tires can generally reach more than 80% of the new tires (the refurbishment rate is mainly related to the technical level of the refurbishers and the rubber compound formula). The tire carcass made of nylon 66 cords is relatively strong, the size is relatively stable, and the renovation rate is relatively high. The tires made of nylon 6 cords are prone to swell of the carcass due to late use, and it is difficult to fit them back into the model after retreading tire treads.
In actual use of the Chuanshan ore (limestone) mine in Zhenjiang, Jiangsu, the average number of renovations for the 14. 00- 24 24PR dump truck tires made of nylon 66 cords was three, and individual tires were refurbished up to five times.
The production cost of nylon 66 and nylon 6 cords is compared with the actual production cost. It can be seen that the use of nylon 66 cords has a certain cost advantage over nylon 6 cords.
5 Practical application of 2100dtex/2 and 1400dtex/ 3 nylon 66 dipped cord 1400dtex/ 3 nylon 66 dipped cord is a new specification in the nylon cord fabric, which changes the traditional fiber weave structure, ie, the traditional two-fold twisting The line was changed to three shares of twisted-line stocks according to different twist-ups. The tensile strength of 1400dtex/3 nylon 66 cords is the same as 2100dtex/2. Due to the increased specific surface area, the amount of adhesive after dipping is higher than that of 2 strands, and the adhesive strength with rubber is better than that of 2 strands. . The strength retention and adhesive strength retention after 1400 dtex / 3 nylon 66 dipped cords were more than 20% higher than 2100 dtex / 2 nylon 66 dipped cords. In recent years, the actual use of 1400dtex/3 nylon 66 cords in construction machinery tires is good.
Most of the construction machinery tires are high-level, and the carcass consists of multi-layer plies. Bold reduction can reduce the number of carcass plies, help reduce the temperature rise of the carcass, and increase the service life of the tire. The direct consequence of the increase in diameter of the cord is that the fatigue performance of the tire is significantly reduced. The use of 1400dtex/3 nylon 66 new structure cords can effectively solve this type of problem, so it will be more widely used in the production of construction machinery tires. .
2 shows the actual test results of 2100 dtex/2 and 1400 dtex/3 nylon 66 dipped cords. Shows the finished anatomical results of a certain specification of construction machinery tires produced using 1400dtex/3 nylon 66 cords.
100dtex / 2 and 1400dtex / 3 nylon 66 dipped cord actual test results
Application of 1400dtex / 3 Nylon 66 cord fabric of a certain specification 100 N set load elongation / % 9. 5 Tread rubber physical properties Shore A type hardness / degree 69 55 tensile strength / MPa 21. 6 16. 5 pull off Elongation / % 544 350 Akron abrasion loss / cm 3 0. 20 0. 5 bond strength / (kN m - 1) tread rubber (buffer) buffer layer can not open 8. 0 buffer ply 14 0 7. 0 cushion ply carcass ply 11. 9 6. 0 carcass ply 7.3 9. 5
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