Selection Of Raw Materials For Cold-shrink Cable Accessories

Because the cold shrinkage technology utilizes the "elastic memory" characteristic of rubber,
the raw material for Cold Shrink Cable Accessories is silicone rubber. Silicone rubber's molecular structure
contains terminal vinyl groups and is mainly composed of a chain structure
connected by Si-O (silicon-oxygen) bonds. The Si-O bond energy is 443.5 kJ/mol, which is
higher than the C-C bond energy of general rubber (384 kJ/mol) and much higher than
solar energy (398 kJ/mol). This makes silicone rubber have better UV resistance,
heat resistance, electrical insulation, and chemical stability than other ordinary rubbers.
Typical silicone rubber, polydimethylsiloxane, has a helical molecular configuration,
with small intermolecular forces, thus possessing good elasticity. At the same time, the
methyl groups pointing outside the helix can rotate freely, and there is a layer of non-polar
organic groups on the outside of the molecular chain, which has very low solubility in water,
is not miscible with water, and is difficult to absorb moisture. When it comes into contact
with water droplets, it forms small, separate water droplets that only condense and do not
wet the surface. At the same time, it also has hydrophobic migration properties, meaning
that when a large area of ​​dust or impurities accumulates on the material surface, the
hydrophobicity of the material migrates to the contaminated surface after about 8 hours,
making the contaminated surface also hydrophobic. This gives silicone rubber unique
surface properties, namely hydrophobicity, hydrophobic migration, and surface
anti-adhesion.
Silicone rubber can be divided into paste-like and putty-like according to its physical
characteristics. Paste-like silicone rubber includes heat-curing liquid silicone rubber (LSR),
room temperature curing silicone rubber (RTV), and sealant; putty-like silicone rubber is
high-temperature vulcanized silicone rubber (HTV). Because room temperature curing
silicone rubber (RTV) and sealant have poor physical and mechanical strength,
especially very low tear strength, and cannot be expanded and molded 2-3 times, they
cannot be used.