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硅胶的品种:硅橡胶主要分为室温硫化硅橡胶,高温硫化硅橡胶。因此,室温硫化硅橡胶按成分、硫化机理和使用工艺不同可分为三大类型,即单组分室温硫化硅橡胶、双组分缩合型室温硫化硅橡胶和双组分加成型室温硫化硅橡胶。这三种系列的室温硫化硅橡胶各有其特点:单组分室温硫化硅橡胶的优点是使用方便,但深部固化速度较困难;双组分室温硫化硅橡胶的优点是固化时不放热,收缩率很小,不膨胀,无内应力,固化可在内部和表面同时进行,可以深部硫化;加成型室温硫化硅橡胶的硫化时间主要决定于温度。
1 v/ s& ?8 V) V( y; H 硅橡胶按其硫化特性可分为热硫化型硅橡胶和室温硫化型硅橡胶两类。按性能和用途的不同可分为通用型、超耐低温型、超耐高温型、高强力型、耐油型、医用型等等。按所用单体的不同,可分为甲基乙烯基硅橡胶,甲基苯基乙烯基硅橡胶、氟硅,腈硅橡胶等。" J7 c( Q! a2 t( e; N# O
: p! g. {" u* l) P1 I5 d* K( \6 V0 uVarieties of silica gel: silicone rubber RTV silicone rubber consists of high temperature vulcanized silicone rubber. Therefore, by component RTV silicone rubber, curing mechanism and the use of technology can be divided into three types, namely, one-component RTV silicone rubber, dual-component condensation RTV silicone rubber and two-component addition cure RTV silicone rubber . These three series of room temperature vulcanized silicone rubber has its own characteristics: one-component RTV silicone rubber has the advantage of easy to use, but the curing rate of the more difficult deep; two-component room temperature vulcanized silicone rubber has the advantage of curing and hold heat, shrinkage is very small, not inflated, no internal stress, curing and surface at the same time internal, you can deep sulfide; plus RTV silicone rubber molding cure time depends mainly on temperature. `2 }: T* K- b0 g I7 i9 c
Curing characteristics of silicone rubber can be divided according to their heat curing silicone rubber and RTV silicone rubber types. According to the different properties and uses can be divided into general-purpose, ultra-low temperature type, ultra high temperature, high strength-based, oil-based, medical-type and so on. Used by the different monomers can be divided into methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber, fluorosilicone, nitrile rubber and so on. / U& o# F% n; q: b/ [, {6 _& \
& w) S+ e# G# S& E- b" O ^5 f) q硅胶吸附有机杂质后的再生方法:
( |# g) u5 V# g! @7 a⒈焙烧法 ; J6 {" R5 D$ H
对于粗孔硅胶,可放在焙烧炉内逐渐升温至500--600℃,约经6—8小时至胶粒呈白色或黄褐色即可。对细孔硅胶,焙烧温度不能超过200℃。
* M8 N w( h ~# e# M ⒉漂洗法 4 `7 j5 D8 r6 u' ?; F
将硅胶在饱和水蒸汽中吸附达到饱和后放热水中浸泡漂洗,并可结合使用洗涤剂以除去废油或其它有机杂质,再经净水洗涤后烘干脱水。 $ r5 Y! ?2 O9 B/ C3 b
⒊溶剂冲洗法 8 }" J3 F6 z8 }( C1 Z. u
根据硅胶吸附有机物种类,选用适当的溶剂将吸附在硅胶内的有机物溶出,然后将硅胶加热以脱除溶剂。 Z7 S3 x# c! s& K* k/ P9 ~
硅胶再生应注意的问题. |# d, [9 T- c: Z2 u/ L
⒈烘干再生时应注意掌握逐渐提高温度,以免剧烈干燥引起胶粒炸裂,降低回收率。
) z0 D$ `& b1 P5 s, a ⒉对硅胶焙烧再生时,温度过高会引起硅胶孔结构的变化而明显降低其吸附效果,影响使用价值。对于蓝胶指示剂或变色 硅胶,脱附再生的温度应不超过120℃,否则会因显色剂逐步氧化而失去显色作用。 ( A( n- h1 t4 g, n& N
⒊经再生后的硅胶一般应过筛除去微细颗粒,以使颗粒均匀。
" p h, W- g, f' fSilica gel adsorption regeneration of organic impurities: ' u- v1 F0 i% x3 l6 p: n- z
⒈calcination 8 d+ v. O E2 ^5 R3 ?
For the coarse silica gel can be placed within the gradually warming up to the roaster 500 - 600 ℃, after about 6-8 hours to rubber can be white or tan. Of pore silica gel, calcination temperature should not exceed 200 ℃. / h+ H* i. [, n4 `8 b2 D7 D8 |
⒉ rinse method
- a* i1 T0 \- R$ ]5 V4 YThe silica gel in saturated water vapor to reach saturation in the adsorption heat water immersion rinse, and combined with detergent to remove oils or other organic impurities and then washed by water drying dehydration.
" R" O; E: M3 Z% t# E7 p1 J; g ⒊ solvent washing method
% [8 y, L+ i+ `Organic compounds based on silica gel, choose the appropriate solvent in the adsorption of organic matter dissolved in the silica gel, silica gel and then heated to removal of solvent. & v' K# r) W6 l$ j* _
Regeneration Problems in silica gel 6 x2 s! z2 d* @5 x# a5 x
⒈ drying should be careful to take the gradual increase in regeneration temperature, so as not to burst particles caused severe drying and reduce the recovery rate.
+ \+ j9 g' Z5 F2 J& `% d; L; w ⒉ regeneration of silica calcination temperature is too high will cause changes in pore structure of silica gel significantly reduced the adsorption effect of use value. For the blue silica gel indicator or discoloration, desorption temperature should not exceed regeneration of 120 ℃, otherwise they will be gradually oxidized reagent lose color effects.
7 ^# \8 G) Z+ Q$ ]* } ⒊ been regenerated silica should generally be sifted to remove fine particles, so that uniform particles. |
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