Reinforcing effect of nano silica in silicone rubber-Iota

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News > Dynamic industry > Reinforcing effect of nano silica in silicone rubber

Reinforcing effect of nano silica in silicone rubber

Nano silicon dioxide is the best filler of high temperature vulcanized silicone rubber. The effect of nano silica on the properties of silicone rubber was studied. The results show that the nano silica aggregates have good reinforcing effect on the silicone rubber. Nano silica powder is added to the silicon rubber, and the microcrystalline region, which is the core of silicon dioxide, is formed, which increases the physical crosslinking point and is more prone to crystallization.
The mechanical strength of the pure silicone rubber is very low, when mixed with added filler, the tensile strength of the vulcanizate can be increased from 0.35 to 14MPa, reinforcement ratio as high as 40 times, far higher than the other rubber can reach the reinforcement ratio (1.4-10 times), visible filler on the final performance of silicone rubber with decisive role. The results show that the structure of the network structure of the particles increases the effective volume of the filler, and the modulus of the elastic body increases. In this paper, the effect of nano silica on the properties of silicone rubber was studied.
1 part of the experiment
1.1 main raw materials
Methyl vinyl silicone rubber (VMQ), molecular weight 600000, vinyl content 0.17%. Nano silica (equivalent to VK-SR01); M-5; ECUST; hydroxy silicone oil, containing 10% hydroxyl; curing agent bis - two five.
1.2 sample preparation
According to the proportion of formula will be rubber, hydroxyl silicone oil and nano silicon dioxide in twin roll mixing machine and mixed evenly, compound thin film and in 170 DEG C heat treatment 2h after mixing and vulcanizing agent, thin film, the next day on the vulcanizing machine molding. The curing condition was 175 t90. T90 was used for the determination of the normal curing time of LH-90.
1.3 performance test
Hardness according to national standard GB/T531 determination. The tensile and tear properties of the AG-2000A - type SHIMADZU universal testing machine, tensile speed of (500 + 50) mm/min were measured by GB/T528 and GB/T529 respectively. Using LH-90 rubber - type curing apparatus, the vulcanization time and curing temperature of vulcanized rubber were determined. Using the Particle Analysis LS-230 particle size analyzer, the particle size distribution of the powder was analyzed by ultrasonic analysis (2000 ~ 0.04 m).
2 results and discussion
2.1 nano silica in the presence of structural form
As shown in Figure 1, the primary particles of nano silica for 2 - 20 nm spherical particles, spherical particles by chemical bond into 50 to 500 nm pearl on the structure of branched aggregates, the structure of aggregates not by mechanical shearing force dispersed, is covering the base of silicon rubber in this unit, aggregates and by hydrogen bonds formed loose reticulate agglomerates.
Effect of nano silica on the reinforcing effect of 2.2 NM
As shown in Figure 2, the A-200, m-5, ECUST agglomerate after ultrasonic depolymerization, the peak of aggregates formed normal distribution, uniform distribution, particle size 100-200 nm is fill strong silicon rubber particle size. The particle size distribution of the powder is wider, the proportion of the powder is smaller, the performance is decreased. Alpha f said for silica powder agglomerate structures in the presence of difference, it and the filler morphology is closely related to the expressed in existing filler vulcanizate in mixing, mixing and vulcanizing process of structural damage. According to table 1, it can be seen that the higher the peak shape of aggregates, vulcanizates in the presence of packing structure is effective, vulcanizates greater torque, f alpha increased, tensile and tear properties better mechanical properties.
2.3 specific surface area of the effect of reinforcement
Nano silica powder and rigid chain structure is fill the basic skeleton of the strong interactions, as shown in Figure 3, the hardness increases than surface area increases and the linear increase, the tear strength in 250 surface reached the maximum and the tensile strength at 200 specific surface area about the maximum around the area.
Effect of nano silicon dioxide on Crystallization Behavior of silicone rubber
Silicone rubber chain structure is relatively simple, backbone is composed of key -Si-O-. On the Si side chain atoms symmetric contact has two methyl, chain stereoregularity, substituents with smaller steric hindrance, crystallization rate is relatively large. Due to the addition of nano silica powder, powder surface bound hydroxyl silicone rubber and the oxygen atoms with hydrogen combined formed by powder for the nucleation of microcrystalline region, dispersed in the matrix, an increase of physical crosslinking points, so that the crystallization is more likely to occur. From Figure 4, we can see that with the increasing dosage of filling, microcrystalline zone melting decalescence decreases, from raw 27.84J/g, reduced to 35 copies of 16.92 /.
3 conclusions
Chain structure of A. nano silica is filling the basic skeleton of the strong silicon rubber, specific surface area of 200 + 50m2 / g. and the depolymerization of aggregates size distribution in 100-200nm, and uniform distribution of nano silica powder, fill strong silicone rubber of the tensile and tear properties in the best.
DSC B. analysis showed that the addition of the nano silica powder, and the microcrystalline region of the silicon dioxide as the core, increased the physical crosslinking point, which made it more easy to crystallize.

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