Tensile strength characterizes the maximum capacity of rubber to resist tensile failure and is the ratio of the maximum force during the tearing of the rubber to its original area. Natural latex reclaimed rubber, made from waste latex, waste natural rubber, and their products, retains the basic performance characteristics of natural rubber and can replace natural rubber in producing rubber products with high tensile strength requirements. So, what factors affect the tensile strength of products made from reclaimed latex rubber?
1. Tensile Strength of Reclaimed Latex Rubber
The tensile strength of rubber products mainly depends on the structural composition and structural regularity of the rubber. When producing high tensile strength products using reclaimed latex rubber, it is recommended to choose reclaimed latex rubber with high tensile strength (generally, the higher the rubber content of the reclaimed latex rubber, the greater the tensile strength). To further improve the tensile strength of reclaimed rubber products, natural reclaimed rubber can be used in combination with an appropriate amount of natural rubber.
2. Influence of Vulcanization System on the Tensile Strength of Reclaimed Latex Rubber Products
The effect of the vulcanization system on the tensile strength of reclaimed latex rubber mainly includes two aspects: crosslink density and type of crosslink bond.
Tensile strength exhibits a peak as the crosslink density changes; for latex reclaimed rubber products to achieve high tensile strength, the amount of crosslinking agents must be appropriate to ensure a moderate crosslink density. In terms of crosslink type, the early breakage of weak bonds (E5LYY626) is beneficial for the orientation and crystallization of the crystalline rubber main chain, which is favorable for obtaining high tensile strength. The tensile strength of latex reclaimed rubber vulcanizates decreases as the bond energy of the crosslinks increases. The relationship among tensile strength and crosslink type decreases in the following order: ionic bond > polysulfide bond > disulfide bond > monosulfide bond > carbon-carbon bond.
A well-designed vulcanization system can effectively improve the tensile strength of reclaimed latex rubber. It is recommended to use a sulfur-accelerator system, combining thiazole-type and guanidine-type accelerators, and to reasonably increase the amount of sulfur.
3. Influence of Reinforcing Filler System on the Tensile Strength of Reclaimed Latex Rubber Products
Reinforcing fillers are one of the key factors affecting tensile strength. The smaller the particle size of the filler, the larger the specific surface area and the higher the surface activity, leading to better reinforcement. In producing rubber products with reclaimed latex rubber, carbon black is often used for reinforcement (for white and colored rubber products, white carbon black can be used). The smaller the carbon black particle size and the greater its surface activity, the less the amount needed to achieve maximum tensile strength. When the reclaimed latex rubber formulation contains softening agents, the amount of carbon black used is greater than when no softening agents are added.
4. Influence of Softening Agents on the Tensile Strength of Reclaimed Latex Rubber Products
The effect of plasticizing softening agents on the tensile strength of reclaimed latex rubber greatly depends on their type and amount. Generally, adding softening plasticizers reduces the tensile strength of vulcanized reclaimed latex rubber, but it can improve the dispersibility of fillers in the rubber compound. Therefore, when designing formulations for natural reclaimed latex rubber products, a reasonable filler/softening agent ratio allows the vulcanized reclaimed rubber to achieve higher tensile strength.
What other factors affect the tensile strength of reclaimed latex rubber? We will continue discussing related issues with you in the future.
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