Natural latex reclaimed rubber is made from waste natural rubber, waste latex, and their products, featuring high strength, good elasticity, and low specific gravity. It can fully or partially replace natural rubber in producing various rubber products, effectively reducing raw material costs. When using latex reclaimed rubber to produce rubber products, sulfur is the most commonly used vulcanizing agent; So, which accelerators are best to use with sulfur?
When choosing sulfur for latex reclaimed rubber, the choice of accelerator is not the only option; it should be choosen according to the process requirements of the reclaimed rubber product, such as scorch safety, vulcanization speed, and performance requirements like mechanical strength and aging resistance; Sulfur vulcanization systems are divided into three types based on the ratio of accelerator to sulfur dosage: ordinary sulfur vulcanization systems, semi-effective sulfur vulcanization systems, and effective sulfur vulcanization systems.
1. Common accelerators and key points for the vulcanization system of ordinary sulfur reclaimed latex rubber
The ordinary sulfur vulcanization system for latex reclaimed rubber products uses a combination of high sulfur and low accelerators. The cross-linked bonds are mainly polysulfide bonds. Before aging, the compound has good general physical and mechanical properties, characterized by high strength, good elasticity, and high wear resistance. It is cost-effective, but has poor heat and aging resistance, and high reversion during vulcanization. The sulfur dosage is among 1.5-3 parts and the accelerator dosage is 0.5-1.5 parts.
Common accelerators used in the ordinary sulfur vulcanization system for latex reclaimed rubber products include accelerator M (main accelerator 0.5-1.0 parts), DM (main accelerator 0.5-1.5 parts), CZ (main accelerator 0.5-1.5 parts), NOBS (main accelerator 0.5-1.5 parts), TBBS (main accelerator 0.5-1.5 parts), TMTD (main accelerator 1.5-3 parts, auxiliary accelerator 0.2-0.5 parts), D(DPG) (0.1-1.0 parts of auxiliary accelerator), etc. They can be used alone (main accelerator) or in combination (main accelerator/auxiliary accelerator).
2. Common accelerators and key points for effective vulcanization systems of latex reclaimed rubber
When latex reclaimed rubber products use an effective vulcanization system, the crosslinked bonds formed are mainly monosulfur bonds. Vulcanized rubber has excellent heat aging resistance and does not undergo vulcanization reversion after sulfurization. Using TMTD vulcanization alone is unsafe to operate, prone to scorching, and causes severe frosting. When using latex reclaimed rubber to produce rubber products with requirements for high-temperature and aging resistance, an effective sulfur vulcanization system is preferred, mainly in two formulations.
(1) Effective sulfur vulcanization system combining high and low sulfur effects: accelerator dosage among 2-5 parts, sulfur dosage around 0.5 parts (0.3-0.8 parts, mostly below 0.5, most commonly 0.35). Common accelerators used in the high-promotion, low-sulfur formulation system for latex reclaimed rubber products include S/M/TT (0.5/3/0.5), S/DM/TT [0.3/0.7/0.8 (0.25/1.1/1.2)], S/CZ [0.33/3.2(5)], S/DM/M 0.35/1.1/1.2, S/TT/M0.35/0.7/1.4, S/TT/NOBS 0.35/0.66/1.4, and others.
(2) Effective sulfur vulcanization system without sulfur: sulfur is used for sulfur feeding (e.g., 2-3 parts TMTD or 1-2 parts DTDM). Common accelerators include TT(3), DTDM/DM (1.5/2), DTDM/DM/TT (0.75/1.1/1.2), DTDM/M/TT (1.1/1.1), TT/M (2.5/0.5), TT/DTDM/DM (1.2/0.5/1.1), etc.
3. Common accelerators and key points for combining semi-effective vulcanization systems for latex reclaimed rubber
Latex reclaimed rubber products can also use semi-effective vulcanization systems, which fall among ordinary sulfur vulcanization and effective sulfur vulcanization systems, with crosslinking bonds containing both polysulfide bonds and monosulfide bonds E6LYY130; Latex reclaimed rubber vulcanized using a semi-effective sulfur vulcanization system combines heat resistance, fatigue resistance, and resistance to vulcanization and reversion, among other comprehensive properties. The semi-effective vulcanization system consists of medium sulfur dosage (1-1.7 parts) and accelerator dosage (1.2-2.5 parts), commonly used combinations such as S/NS (1.5/1.5), S/NS/DTDM (1.5/0.6/0.6), etc.
When using latex reclaimed rubber to produce rubber products, avoid using only super-accelerators, such as dithiocarbamate compounds (such as ZDC), which are highly active but prone to burning. It is recommended to add small amounts as auxiliary activators and not as main accelerators; When producing light-colored or colored latex reclaimed rubber, avoid using polluting guanidine accelerators (such as D), and choose non-polluting substances such as M, DM, or CZ; The "main accelerator (M/DM/CZ) + auxiliary accelerator (TMTD/TMTM/D)" mode not only shortens vulcanization time but also ensures processing safety
Exclusive original article [commercial authorization] reprint, excerpt and excerpt in any form are prohibited without written authorization. Focus on Hongyun rubber: learn the process formula and raw material technology of producing rubber products from recycled rubber to help you reduce costs and increase profits