HD-21 Silane
CH2=CHSi(OCH3)3
Introduction
HD-21 silane, vinyltrimethoxysilane, is used as polymer modifier via grafting reactions. The resulting pendant trimethoxysily1 groups can function as moisture-activated crosslinking sites. The Silane grafted polymer is processed as a thermoplastic and crosslinking occurs after fabrication of the finished article upon exposure to moisture.
Typical Physical Properties
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Chemical Name Vinyltrimethoxysilane
Formula C5H12O3Si
Molecular Weight 148.2
Color and Appearance Colorless transparent liquid
Density 25/25℃ 0.960-0.970
Boiling Point 122【760mmHg】
Refractive Index 1.3905+/-0.0005【25℃】
Flash Point 28
CAS No. 2768-02-7
EINECS No. 220-449-8
Purity Min 95.0%
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Applications
● Polymer Modification
HD-21 is used to modify polyethylene and other polymers by grafting its vinyl group to the polymer backbone using a radical initiator, such as peroxide. This peroxide a polymer with pendant trimethoxysily1 groups that may be used as moisture-activated crosslinking sites via hydrolysis of the alkoxy groups followed by condensation of the resulting silanols.
● Crosslinking of Silane-Grafted Polymers.
The reaction of Silane-grafted polyethylene to form a crosslinked or vulcanized polyethylene uses water to form the crosslinks. This technology is widely used around the world for commercial applications in wire and cable insulation, tubing, and other similar uses.
The basic reaction sequence is as follows: polyethylene is reacted (grafted) woth vinyltrimethoxysilane, using a peroxide initiator, in an extruder. The grafted polyethylene is then formed into a finished product, such as cable jacketing, wire insulation, or pipe. The forming step id usually done by a second extrusion, during which a catalyst for the moisture-cure step is added. Finally,the formed article is exposed to moisture or hot water to cause hydrolysis of the Silane and condensation to form crosslinks via Si-O-Si bond formation.
Benefits of Crosslinking
● Higher maximum use temperature
● Reduced deformation under load (creep)
● Improved chemical resistance
● Superior environmental stress crack resistance
● Increased abrasion resistance
● Improved impact strength
● Memory characteristics (shrink film, tubing)
● Improved impact strength
Advantages of Silane Crosslinking over Radiation or Peroxide Crosslinking
● Low capital investment
● Low operating (energy) costs
● Higher productivity
● Processing versatility
● Thick, thin, or variable thicknesses possible
● Complex shaps possible
● Wilder processing latitude (control of premature crosslinking)
● Useful with filled composites
● Applicable to all polyethylene densities and copolymers.
