The curing speed of the rubber is a very important characteristic parameter.The speed of curing directly determines the time it takes for the rubber product to be removed from the mold, and the shorter the time spent in the mold, the lower the cost of production.
The following experimental scheme may increase the curing speed of the rubber compound. Readers should study and read the relevant literature sources in the book, including those cited later, by themselves. Note: These general experimental plans may not be applicable to every specific situation. Any variable that can increase the curing speed is bound to affect other properties, for better or worse. However, this book does not elaborate on the changes in other properties. This book does not explain safety and health issues either.
1. The selection of accelerators
Consider choosing a curing system containing the following accelerators:
1 ) Aldehyde-amine accelerators: Slow sulfation rate.
2 ) Guanidine enhancers: Moderate sulfation rate.
3 ) Thiazole accelerators: The sulfation rate is moderately fast.
4 ) Hyposulfonamides: Rapid rate of sulfation - delayed action.
5 ) Hyposulfonylimines: Rapid rate of sulfation - delayed action.
6 ) Dithiophosphates: Rapidly sulphurizing.
7 ) Thurams: Rapidly sulphurizing.
8 ) Dithiocarbamates: Rapidly sulphurizing.
2.TBBS Promoter
Among the subsulfonamides, TBBS has the fastest sulfation rate.
3.Auxiliary accelerator
When secondary sulfonamides (e.g. TBBS, MBS, CBS, etc.) are used as the main accelerant, DPG, TATM, TBZTD, TMITD, TMTM, TETD, ZDMC, ZDEC, ZDBC, and DOTG, etc. are used as the coaccelerants to enhance the speed of curing effectively.In a sulfide system using only TBBS as an accelerator, TMTM can be added as a coaccelerator to increase the rate of sulfidation of the adhesive. For example, the amount of TBBS can be reduced from 1.2 to 0.2 mass. For example, the amount of TBBS can be reduced from 1.2 parts by mass to 0.6 parts by mass. For example, by reducing the amount of TBBS from 1.2 to 0.6 parts by mass, and the amount of TMTM is 35% of TBBS, i.e., 0.2 parts by mass, the speed of curing can be increased by 25%. Although the curing speed is increased by 25%, the modulus does not change much, of course, the results vary when the rubber material is different.
4. ISB Promoter
A laboratory-grade accelerator, 2-isopropylthionylbenzothiazole, in combination with coaccelerators such as tetraethylthiuram disulfide (TETD) or the less environmentally friendly tetramethylthiuram sulfide, results in a safe coking period and a very rapid sulfidation rate.
5. Increase the amount of zinc oxide
If the amount of accelerator in the stock is high and the amount of stearic acid is sufficient, the rate of curing can be increased by increasing the amount of zinc oxide.
6.Avoid speed bumps
When using conventional thiazole accelerators in the vulcanization system for dienophiles, other organic acid reducers such as salicylic acid, benzoic acid or phthalic anhydride should be avoided as they reduce the speed of curing.
7.Peroxide curing
The use of high performance HP peroxide formulations results in faster curing of the compound.Higher quantities of DCP can result in faster curing of the compound compared to BBPIB.Peroxidized ketone peroxides are faster to vulcanize than dialkyl peroxides.
8. Co-sulfurizing agent for peroxides
In the peroxide curing system, trimethanol ethane (TMPTA), trimethanol propane triacrylate (TMPTMA) and N,N'm- hyphenyldimaleimide (HVA-2) can be used to increase the curing rate effectively.The effects of 1,2 polybutadiene (PB), hexadienyl phthalate (DAP), triallyl isocyanurate (TAIC) and triallyl cyanurate (TAC) on the curing rate were small.The use of small amounts of low molecular weight liquid high vinyl 1,2 polybutadiene resins (e.g., Ricon) as a co-curing agent for peroxide vulcanized silicone rubbers improves the rate of curing.
9. Platinum curing of silicone rubber
Curing of silicone rubber with platinum metal catalysts provides 70% faster cure rates than peroxide curing of silicone rubber.
10.IR
High cis or trans structures are faster to vulcanize than high 3,4 structures of polyisoprene rubber for sulfur yellow curing IR.
11.BR
For vulcanized BR, high cis or trans structures curing faster than polybutadiene materials with high 1,2 structures.Similarly, when styrene or SBR is added to high cis or trans BR, the rate of curing decreases.Solution polymerized BRs vulcanize faster than emulsion polymerized BRs because the presence of fatty acids in the emulsion polymerized BRs slows the rate of curing.Polyisoprene 3,4 and polybutadiene 1,2 have higher vulcanization rates when peroxide is used as the curing agent.Increasing the content of 1,2-structured polybutadiene during microwave curing of BR increases the rate of curing.
12.SBR
When curing SBR with sulfur yellow, if the styrene content is high, the curing rate will be low.For example, E-SBR1013 with 40% (by mass) styrene has a lower curing rate than E-SBR1006 with 23.5% (by mass) styrene. E-SBR1013 with 40% (by mass) styrene, for example, has a lower curing rate than E-SBR1006 with 23.5% (by mass) Styrene S-SBR (e.g., 71) has a faster curing rate than high temperature polymerized E-SBR (e.g., 1006), and high temperature polymerized E-SBR1006 has a faster curing rate than low temperature polymerized E-SBR1500.This is due to the use of fatty acids and rosin acids in the emulsion polymerization process, which inhibit the curing reaction.
13.NR,BR and SBR
Typically, NR vulcanizes faster than cis-polybutadiene, while cis-BR vulcanizes slightly faster than SBR.
14.ENR
Typically, epoxidized natural rubber vulcanizes faster than natural rubber because the epoxy groups can also be chemically crosslinked through non-sulfur bonds.
15.Halogenated butyl rubber
Bromobutyls curing faster than chlorobutyls.In contrast to the general unsaturated rubber curing system, acid additives promote the curing of halobutyl rubber, while alkali additives inhibit the curing rate.In halobutyl compounds, when the magnesium oxide content exceeds 0 . In the case of halobutyl compounds, the rate of curing starts to decrease when the magnesium oxide content exceeds 0.5 parts by mass.
16.EPDM
A third monomer, non-randomly distributed EPDM, allows for a faster rate of sulfation.EPDM adhesives containing ethylene norbornene ENB have the fastest curing rates, followed by EPDM containing 1,4-hexadiene (HD), and finally EPDM containing dicyclopentadiene (DCPD.) EPDM with a high content of dienophthalic tertiary monomers will vulcanize more rapidly.
17.NBR
When sulfur yellow sulfurizes NBR, the higher the ACN content, the faster the speed of curing.For peroxide sulfurized NBR, the lower the ACN content, the faster the curing speed.NBR containing fatty acid emulsion polymerization can be vulcanized faster than those containing rosinic acid or a mixture of fatty acid and rosinic acid.NBR emulsion polymerized with calcium chloride as the coagulant has a faster curing rate.
18.ACM
In polyacrylate elastomers, alkaline non-carbon black fillers are often selected.This is because acidic fillers inhibit sulfation.
19.Neoprene
W-type neoprene can be vulcanized very fast by choosing symmetric diphenylthiourea (A-1) as accelerator.The fastest curing rate can be obtained by choosing the best specific surface area and the best dosage of magnesium oxide.Reducing the usual 4-mass magnesium oxide content may increase the rate of curing, but it will also shorten the burn-in safety period.
In neoprene curing systems, MBTS can be used in conjunction with ETUs to obtain faster curing speeds and longer burnout safety periods.
20.AEM
For terpolymer vinyl acrylate rubber AEM (DuPont's trade name Vamae), the curing system is conventional diamines such as hexamethylenetetetramethylene diamine carbamate (HMDC) and DPG, but the addition of diisopropylphenyl peroxide (DCP) and 1,2-polybutadiene (Ricon,152) increases the curing speed by 160%.
21. Thiadiazine promoters for HIIR and CR
A thiadiazole derivative from Vanderbilt under the trade name Vanax 189 is an accelerator for the curing of CR or halobutyl adhesives, which not only provides a safer burn-in period for the rubber, but also improves the speed of curing compared to many other accelerators.
22.Carbon Black
Increasing the filling amount of carbon black can enhance the curing speed, but the extent of the increase will vary depending on the type of elastomer.
23.The curing rate of thick products
For thick product adhesives, it is often necessary to add some metal powders to increase the rate of thermal conductivity.Typical metal powders to choose from are silver, copper and aluminum.Silver is too expensive, copper is an oxidizing and degrading agent for natural gums, and aluminum usually improves both electrical and thermal conductivity, but it increases the fire hazard of the adhesive.In fact, the addition of metal powders, such as aluminum powder, greatly increases the flammability of the rubber.If the thermal conductivity of the rubber can be improved, the curing time of thick products will be greatly reduced.Normally, rubber products are poor conductors of heat, and the center part of thick rubber products has less heat history. A thickness of more than 6mm rubber parts vulcanized at 150 ℃, generally need to vulcanize more than 5min, in order to achieve complete curing, improve the thermal conductivity, will greatly shorten the curing time.
