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1 Experiment 11 Major raw materials Guoji Petroleum Jilin Chemical Group Corporation organic chemical plant products; methyl vinyl silicone rubber (MVQ), grade 110-2 Chenguang Chemical Research Institute Second Branch Factory products; fumed silica, Shenyang Chemical Plant products. Precipitation white carbon black, grade S-760, Shanghai Hudong Chemical Factory product; ethylene-vinyl acetate copolymer (EVA), product of Shanghai Research Institute of Chemical Industry; peroxide dicumyl (DCS) Shanghai Gaoqiao Chemical Plant Products; 5-Dimethyl-2S Di-tert-Butyl Peroxide Hexane (Sulfurizer Dual 25), Silicone Center Products of Chenguang Research Institute; Conditioner A (antioxidant) and B (sulfur-containing organic compound) .
12 Instruments and Equipment XK-160 Double-Roll Rubber Mixer, Shanghai Light Industry Machinery Research Institute; YX-50 Pressure Molding Machine, Shanghai Xima Weili Machinery Co., Ltd.; YX-1 Shore A Type Hardness Tester, WS -1 type rubber Vickers plasticity gauge and QP-16 type plastic prototype machine, Shanghai Chemical Machinery Fourth Factory.
13 Production Process The rubber compound is mixed on an open mill. The mixing process is as follows: raw rubber mastication, in order to add white carbon black, engine oil, ethylene glycol, and zinc oxide, mixing for a certain period of time, adding a vulcanizing agent and a foaming agent Smelt evenly and take a piece. After the mixing rubber is parked for 4 ~ 12h, it is trimmed, weighed, loaded, and vulcanized (including one-stage and two-stage vulcanization, and the following non-explained refers to one stage of vulcanization) to obtain EPDM foamed material (plate).
14 Performance Test Hardness test: After testing the surface hardness of the sample with Shore A hardness tester, cut the sample skin and measure the foam hardness of the sample.
Density test: Use a vernier caliper to measure the geometry of the sample and calculate the volume of the sample. V Measure the mass of the sample using an industrial balance m Calculate the density P of the foamed material (P=m/V).
Plasticity test: A plastic sampler was used to make a Y16mmX 10mm sample, and the Vickers plasticity test (test temperature 70X) was used to test the Vickers plasticity of the sample.
Physical property test: The EPDM foam material was cut into thin (1.7 Â± 0.3) mm sheets and the test specimens were cut to test the tensile strength, elongation at break, and permanent tearing properties.
2 Results and Discussion 2 1 Formulation Design 21.1 Main Body Materials In order to facilitate foaming, a Mooney-low-visibility EPDM or EPDM/MVQ (combined with 900) was used as the host material.
21.2 Curing system The vulcanization system of EPDM foaming materials is mainly sulphur yellow and peroxide curing system. When sulfur vulcanization system is adopted for EPDM compound, the foamed material forms a crosslinked structure mainly composed of polysulfide bonds. The tensile strength is high, but the heat resistance and aging resistance are slightly poor; when peroxide cure system is used, The foam material forms a single carbon-carbon cross-linking bond, which is excellent in heat resistance and aging resistance, small in compression set (good in stress relaxation), and elongation at break is comparable to that of the sulfur vulcanization system. Therefore, peroxide curing systems are suitable for the preparation of high-performance foams that are resistant to heat, aging, and small permanent compression.
Since acyl peroxide-containing peroxides are easily decomposed during compounding and the curing effect is poor, we chose the vulcanizing agent DCP and Duo 25 for the vulcanization foaming test of the compound. The results are shown in Tables 1 and 2. It can be seen that the curing agent DCP compound cures faster than the curing agent compound 25 compound. In view of the fact that the decomposition temperature of the foaming agent is in the range of 140-180Â°C, the vulcanizing agent DCP must be used as the main vulcanizing agent in order to obtain a good foaming effect of the rubber compound, so that the vulcanization rate and the foaming rate of the rubber compound can be matched. . After testing, determine the appropriate amount of peroxide cure system for 2 to 3 parts.
1.3 Reinforcing Agent White carbon black is the main white reinforcing agent for EPDM compounds and can impart excellent properties to EPDM products. Precipitated silica is used as a reinforcing agent, and the fluidity of the rubber is good (in favor of foaming). The permanent deformation of the foamed material is small. Vapor-phase white carbon as reinforcing agent Table 1 Curing agent DCP and double 25 vulcanization test Comparison item Vulcanizing agent double 25 vulcanization temperature/Â°C Decomposition activation energy/Vulcanization rate Note: Test formulation: EPDM MVQ10; 2 gas phase French white carbon 30 oil 7; foaming agent AC6 zinc oxide Table 2 vulcanizing agent DCP and double 25 rubber vulcanization foaming test comparison project vulcanizing agent double 25 vulcanization (curing time 10min) foaming effect density 0. bubble The pore size is large and the pores are uniform. The porosity curing effect is fully vulcanized. The elasticity is good. Soft and sticky. No foaming Shore A hardness 28 degree Elastic two-stage vulcanization (vulcanization time 12 min) Foaming effect Density 0. Pore size 0. Vulcanization The effect is good, tearing is more permanent vulcanization, good elasticity, long deformation small surface Shore A hard Note: test formula: conditioner A 1 remaining formula with the table 1. At a vulcanization temperature of 170, diphenylsilyldiol (which reacts with the hydroxyl groups on the silica surface at high temperatures) can be modified to modify the surface morphology of fumed silica and improve the fluidity of the compound. .
The effect of silica on the vulcanization of the rubber foam is shown in Table 3. It can be seen from Table 3 that the vapor-phase silica has a low plasticity value, a large foaming resistance, and a small pore diameter of the foamed material. However, the physical properties of fumed silica foams are better than those of precipitated silica and modified fumed silica.
1.4 Plasticizers 9 Sulfur, 1 Zinc paraffin oil, Dioctyl sebacate and 30 oils have good Table 3 Effect of white carbon on the vulcanization of EPDM compounds Project precipitation White carbon modified 2 gas phase White silica * 2 fumed silica: amount of diphenylsilanol/fraction of foaming agent AC/volume of vulcanizing agent DCP/volumes Weicheng plasticity vulcanization temperature/Â°C vulcanization time/mill surface Shore A Type Hardness/degree Soak A Shore Hardness/degree Foam Aperture Aam Foaming Effect Uniform epidermis Thicker skin Thickness Note: * First treated with diphenylsilanol, processing conditions 160t: X60 min Basic Formula: EPDM100 30 oil 10; glycol 3; vulcanizing agent DCP plasticity, suitable for EPDM foam plasticizer plasticizer f1. To ensure the physical properties of foaming materials, the amount of plasticizer should not be too much, suitable for It is 10~20 copies.
21.5 Foaming System Rubber blowing agents are mostly organic foaming agents, of which the blowing agents AC and H are the most widely used. Foaming agents AC and H use foaming aids zinc oxide and silicone oil, respectively, to adjust the foaming rate and foaming effect. The thermal weight loss curves of blowing agents AC and H in the combination of zinc oxide and silicone oil, respectively, are shown. It can be seen that the blowing agent H starts to be subdivided at a lower temperature. The decomposition temperature range is wider and the decomposition rate is slower; the blowing agent AC decomposes less than 150Â° C., and the decomposition rate exceeds 160Â° C. Faster, suitable for foaming temperature The thermal weight loss curves of foaming agents AC and H 1 - Foaming agent AC (foaming aid is zinc oxide) 2 - Foaming agent H (foaming agent is silicone oil) Foaming system The impact of EPDM rubber foaming effect is shown in Table 4. It can be concluded from Table 4 that the foaming material of foaming agent H/silicone oil foaming system is dense and uniform; but after long-term parking, foaming agent H/silicone oil The density of the foamed material of the foaming system is significantly increased, while the foaming material AC/zinc foamed system has little change in the density of the foamed material. Therefore, the foaming agent AC/zinc oxide foaming table 4 foaming system should be selected to affect the foaming effect of EPDM rubber compound. Project foaming system 1Â° foaming system 22) Surface Shore A hardness/degree foam Type A Hardness/degree Bubble Diameter/mm Foaming Effect Density after storage for 20 days Uniform skin Thickness Note: 1) foaming agent AC 8; zinc oxide 8.2) foaming agent H 100; 2 fumed silica 50; 30 oil 10; B system.
In addition, in order to increase the expansion ratio of the rubber compound, EVA can also be added, but the addition of EVA will cause the elasticity of the foam material to decrease and the permanent deformation of the tearing material to increase. Therefore, it is not suitable to add EVA to a foam material with good physical properties. 21.6 Vulcanized foaming modifier tests found that EPDM rubber with DCP as the vulcanizing agent has a faster vulcanization rate and a slower foaming speed. When the vulcanization is almost completed, foaming reaches its peak. As a result, the amount of blowing agent AC is as high as 8 parts. The density of the foamed material was reduced to about 0.50 MgÂ°m3. For this purpose, vulcanization foaming regulators were used to adjust the vulcanization and foaming speeds so that the vulcanization and foaming processes were matched. The results of the tests are shown in Table 5. It can be seen from Table 5 that the vulcanization of the conditioner A/B combination system was used. The foaming time is longer, the density of the foamed material is small, the homogeneity is good, and the hardness is low, which indicates that the modifier B has the effect of delaying the vulcanization time and reducing the degree of vulcanization, so the vulcanization foaming modifier uses the conditioner A/B combination system.
Table 5 Effect of Vulcanizing Frothing Regulators on the Vulcanization of EPDM Compounds Item Blank Regulator A/B Combination System 2) Vulcanization Time (170C)/Surface Shore A Hardness/Foot Shaul A Type Hardness/degree Foaming effect Thicker epidermis Thicker surface Evenly coated Note: 1) Conditioner A 1.2) Conditioner A 1; Conditioner B 0.5. Basic Formula: EPDM 100; 2 Fumed silica 50; 30 Engine oil 10; Alcohol 3; DCP2; foaming agent AC8; zinc oxide 8. 21.7 Optimization formula to determine EPDM foaming material is optimized: EPDM 100; 2 fumed silica 50; 30 oil 10; ethylene glycol 3; sulfurizing agent DCP 2~3; Zinc Oxide 8; Foaming agent AC8; Conditioning agent A1; Conditioning agent B0.5. 22 Process conditions 22.1 Mixing process: Alcohol 22ç¯† Conditioner Mu16.0-type open-air machine for Jomal ElectrodcPubli without cooling water Device 7/The mixing book1 should therefore be kneaded on an open mill and the roll temperature is (in 23 the size and the roller can only cool naturally. According to the EPDM's poor plasticity and cohesiveness, it is not easy to mix with the compounding agent, the compounding The refining process was determined as follows: EPDM was thin-passed at a roll temperature of (23Â±5)Â°C for 5 to 10 times, and then added at a roll temperature of 60 to 70Â°C. Oil (improved roll effect), followed by the addition of silica, ethylene glycol, zinc oxide, vulcanizing agent and foaming agent, after all the compounding agent mixed with the rubber, the thickness of the pass between 0. 2 ~ 0.5mm 10 to 15 times, to ensure that the rubber compounding evenly, but the compound can not be tempered to avoid excessive plasticity.
Films extruded after mixing should be compact, free of bubbles and impurities, and have a smooth surface. The film used for molding should be complete and uniform in thickness. It is better not to glue the corners with small glue pieces, otherwise it will cause problems such as unevenness of the styrofoam sheet and partial degumming.
2.2 Vulcanization Conditions The effect of vulcanization temperature and time on the vulcanization and foaming properties of EPDM foaming compounds is shown in Tables 6 and 7. It can be seen from Tables 6 and 7 that the vulcanization time is fixed, the higher the vulcanization temperature, the higher the curing rate of the rubber compound. Faster, the greater the density of the foamed material, the higher the hardness; the vulcanization temperature is certain, the longer the vulcanization time, the higher the degree of vulcanization of the rubber, the higher the density of the foamed material and the higher the hardness. From Table 7 it can also be seen that the vulcanization time is 6 min, the rubber material is less than sulfur, and the foaming material is overly dense when the curing time exceeds 10 min. Therefore, to ensure that the EPDM foam material has moderate density and good physical properties, the curing time must be strictly controlled. The suitable vulcanization condition of the EPDM foamed rubber material is to further increase the vulcanization degree. The foaming material should be subjected to the second and second stage vulcanization but the second stage vulcanization time should not be too long to avoid the problem of peeling and blistering of the foamed material. The second-stage vulcanization conditions were determined as: 12min 23 Mechanical properties of the foamed material The physical properties of the foamed material obtained using the optimized formulation and process conditions determined in this study are shown in Table 8. It can be seen from Table 8 that the EPDM and EPDM/MVQ combined system was used The foam material has higher tensile strength and hardness, greater elongation at break, and permanent tearing. Table 6 Vulcanization temperature of EPDM foaming compound - time effect Item Vulcanization time (170C) min Density/Shallow Shore A hardness / Note: The test formula: The reinforcing agent is a modified 2 fumed silica, and the rest is the same as the optimized formula (the main material is EPDM).
Table 7 Vulcanization time effect of EPDM foamed rubber compound Vulcanization time (170C) min Soaking Shore A Hardness/degree Vulcanization Effectiveness of the core is better than sulfur Note: The test formulation is an optimized formulation (the main material is EPDM).
Table 8 Mechanical properties of foamed materials with better formulation Foam Shore A Type Hardness/degree Tensile Strength/MPa Tensile Elongation/% Tensile Permanent Deformation/% Note: One-stage vulcanization condition is 170 second-stage vulcanization The condition is that the shape of 170 is smaller and the overall physical properties are better.
3 Conclusion Thermal performance, good aging resistance, small compression set.
The fumed silica is used as a reinforcing agent. The plasticity of the EPDM compound is small, and the foamed material has fine cells with good physical properties.
Using foaming agent AC/zinc oxide foaming system, EPDM foaming material has a small shrinkage and fine cells.
With the regulator A/B and the system used to adjust the vulcanization and foaming rate, the EPDM compound can obtain good vulcanization and foaming effects.
The suitable curing conditions for EPDM foaming compound are:
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