Description
Introduction:
KH***1 silane,
vinyltrimethoxysiane, is used as a polymer modifier via grafting
reactions. The resulting pendant trimethoxysilyl 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:
CAS
No.:
********7
Molecular
Weight:
**8.2
Boiling
Point<**0mmHg>: **2
Flash
Point:
*8
Color and
Appearance: Colorless
transparent liquid
Density<*5/*5>:
0.****0.**0
Refractive
Index<*5>:
1.***5+0.***5
Min.
Purity:
*8.0%
Applications:
*- Polymer Modification:
KH***1 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 provides a polymer with pendant
trimethoxysilyl 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) with
vinyltimethoxysilane, 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
is 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:
a)
Higher maximum use temperature
b)
Reduced deformation under load (creep)
c)
Improved chemical resistance
d)
Increased abrasion resistance
e)
Improved impact strength
f)
Memory characteristics (shrink film, tubing)
g)
Improved impact strength
*- Advantages of Silane
Crosslinking over Radiation or Peroxide Crosslinking
a)
Low capital investment
b)
Low operating (energy) costs
c)
Higher productivity
d)
Processing versatility
e)
Thick, thin, or variable thicknesses possible
f)
Complex shapes possible
g)
Wilder processing latitude (control of premature
crosslinking)
h)
Useful with filled composites
i)
Applicable to all polyethylene densities and
copolymers.
