Comprehensive List of Additives in Rubber Manufacturing
Terminology
Fillers
- Carbon Black: One of the most widely used fillers, carbon black is added to rubber compounds to improve strength, durability, and abrasion resistance. It also enhances the rubber’s UV resistance and gives it its characteristic black colour.
- Silica: Used as a reinforcing filler, silica improves the tensile strength, tear resistance, and abrasion resistance of rubber. It also reduces rolling resistance in tyres, which can improve fuel efficiency.
- Calcium Carbonate: This non-reinforcing filler reduces the cost of rubber compounds. It also improves processability and can provide a smoother surface finish.
Accelerators
MBT (Mercaptobenzothiazole):
An accelerator used in the vulcanisation process, MBT speeds up the cross-linking of rubber molecules with sulfur, improving the elasticity and strength of the final product.
MBTS (Dibenzothiazyl Disulfide):
A widely used general-purpose accelerator, MBTS provides a moderate curing rate and is often used with other accelerators to optimise the vulcanisation process.
ZDBC (Zinc Dibutyldithiocarbamate):
A fast-curing accelerator, ZDBC is used in latex compounds and for producing transparent and light-coloured rubber products.
CBS (N-Cyclohexyl-2-benzothiazolesulfenamide):
CBS is a delayed-action accelerator that provides a long scorch time (delay before vulcanisation begins) and a fast cure rate, making it ideal for thick rubber articles like tyres.
TBBS (N-tert-Butyl-2-benzothiazolesulfenamide):
TBBS is similar to CBS but provides an even longer scorch time and a faster curing rate. It’s known for its good processing safety and balanced performance.
ZDEC (Zinc Diethyl Dithiocarbamate):
ZDEC is a swift primary or secondary accelerator, for natural and synthetic rubber, often used with other accelerators to fine-tune the vulcanisation process.
ZDBC (Zinc Dibutyl Dithiocarbamate):
ZDBC is a swift accelerator with excellent processing safety, often used in transparent, light-coloured, and non-staining rubber products.
ZBEC (Zinc Dibenzyl Dithiocarbamate):
ZBEC is a non-nitrosamine generating accelerator with similar properties to ZDBC but has improved resistance to blooming (migration of additives to the rubber surface).
TMTD (Tetramethylthiuram Disulfide):
TMTD acts as both; an ultra-accelerator and a sulfur donor in the vulcanisation process, providing fast curing rates. It is often used in combination with other accelerators to modify cure times.
TBzTD (Tetrabenzylthiuram Disulfide):
TBzTD is a safer alternative to TMTD, as it does not generate carcinogenic nitrosamines during the curing. It offers a fast curing rate and is a good sulfur donor.
DPG (Diphenyl Guanidine):
DPG is a secondary accelerator, often used with primary accelerators like thiazoles (e.g., MBT, MBTS). It provides moderate cure rates and enhances the overall efficiency of the vulcanisation process.
Activators
Zinc Oxide:
Commonly used as an activator in the vulcanisation process, zinc oxide helps to improve the cross-linking efficiency between rubber and sulfur. It also contributes to the overall durability and resistance to rubber degradation.
Anti-degradants
Antioxidants:
Chemicals like phenolic compounds, amines, and phosphites are added to rubber to protect it from oxidation, which can lead to cracking and hardening over time.
Antiozonants:
These chemicals, such as para-phenylenediamine (PPD / 6PPD) derivatives, protect the rubber from ozone attacks, which can cause surface cracking and deterioration.
Plasticisers and Softening Agents
Phthalates:
They increase the flexibility, elongation, and softness of rubber. Some common examples include dioctyl phthalate (DOP) and dibutyl phthalate (DBP).
Stearic Acid:
Often used as a lubricant and softener in rubber compounding. Stearic acid also acts as a dispersing agent for fillers and other compounding ingredients.
Curing Agents
Sulfur:
The most common curing agent used in rubber vulcanisation, sulfur creates cross-links between polymer chains, giving rubber its elasticity and resilience.
Peroxides:
Used as an alternative to sulfur curing, especially for heat-resistant and transparent rubber, peroxides provide a different type of cross-linking that enhances heat stability.
Processing Aids
Paraffinic Oils:
It improves the processability of rubber compounds. Paraffinic oils reduce viscosity and improve the flow of rubber during moulding.
Waxes:
Waxes like microcrystalline and paraffin waxes protect rubber surfaces from ozone and oxygen, preventing cracking during storage.
Disclaimers:
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