Know How
The PTL manufacturing technology and know-how of heat shrinkable tubing can be split in 4 major stages:
Compound technology and know-how
The PTL compounds are carefully selected compositions of raw materials to meet the stringent customer demands and international specification requirements. Besides the choice of polymers, also the selection of flame-retardants, synergists, anti-oxidants, UV-stabilizers, accelerators, processing-aids, fillers, modifiers and other additives are of extreme importance.
The compounds of PTL will easily meet the requirements on properties such as:
A wide range of PTL compounds are available to manufacture a complete range of heat-shrinkable products.
Extrusion technology
In the extrusion process the extruder acts essentially as a pump which supplies a continuous stream of molten thermoplastic compound or another material to a forming die. The die shapes the material, or extrudate, into a product, for instance tubing. This (hot) tubing is then delivered to a cooling and calibration system where sufficient heat is removed to solidify the tubing into the right size.
A take-off device removes the tubing from the cooling system and delivers it to a winder, where the tubing is wound on spools.
The extruders, supplied by PTL are all provided with a specially designed screw configuration, for optimal mixing and a homogeneous and consistent tubing.
The special design of the extrusion head allows to changing extrusion tooling in just a few minutes. For excellent concentricity, which is extremely important in the manufacturing process of heat-shrinkable tubing, our designers have developed special provisions in the extrusion head.
In general the following cross-linking technologies are applied commercially in industries, such as cable & wire, foam, pipe, film and heat-shrinkable products:
While the improved maximum operating temperature was one of the initial attractions of crosslinking, there are other important product advantages as a result of crosslinking polymers, such as:
a) Crosslinking by means of moisture.
A flexible and economical process has been commercialized for heat-shrinkable products which utilizes reactive silane-groups, which will crosslink in a humid environment. The moisture crosslinked polyolefins are linked through a C-Si-O-Si-C moiety, rather than a C-C bond. The crosslinking usually takes place around 80 degrees Celsius.
Moisture crosslinking offers a greater processing latitude, as the fabrication does not have to be done below the peroxide decomposition temperature as required in the peroxide crosslinking process. Additionally, the extruded tubing in the moisture crosslinkable process can be cooled quickly during the extrusion process, instead of beginning an increasing thermal cycle to decompose the peroxide.
PTL has been able to develop compounds based on the moisture crosslinking technology, which comply with all international standards and can easily compete with the products, which are sold by global heat-shrink players, controlling this profitable business. This wide range of compounds combined with our reliable equipment makes PTL a unique supplier of heat-shrink technology.
Low investment
Compared to the huge investment in a radiation facility, amounting up to US $ 4 million , the PTL cross-link technology only needs an investment of less than 5% of the amount involved in the set-up of a radiation facility. Besides this low investment, the PTL technology offers the advantage that the total manufacturing system can be easily moved to any place in the world, where electricity and water are available.
Moreover PTL is able to supply a complete heat shrinkable tubing factory, which can easily be moved from one place to another. The plant will be working within 24 hrs after the equipment has been installed, whereas the installation of a radiation facility will consume up to several months....
b) Crosslinking by means of irradiation
The major disadvantage of this crosslinking technique is the investment in a radiation facility. A radiation facility requires:
Electron-beam irradiation also shows a limited penetration depth, resulting in a inhomogeneous crosslinked network.
Chemical reaction: The irradiation process, causes free radical formation, followed by carbon-carbon bond formation, called crosslinking.
In case you have already access to a radiation facility, PTL is able to offer you extrusion and expansion equipment required to manufacture heat-shrinkable tubing.
Many years of experience in the field of radiation crosslinked heat-shrinkable tubing, enables the PTL staff to supply the complete technology and a complete range of compounds.
Heat-shrinkable tubing, manufactured with these compounds, will meet international standards, such as:
and many others in the electronics, military, aerospace, electrical, energy, telecommunications and other markets.
c) Crosslinking by means of peroxides
The principle is that peroxide is incorporated in the polymer and is activated at a high temperature. In order to avoid premature crosslinking, the extrusion temperature should be only slightly above the melting point of the polymer. Immediately after extrusion, the tubing is heated to the decomposition temperature of the peroxide, until the crosslinking is complete. Usually, the heating of the tubing requires a high pressure tank to prevent void formation in the insulation which is caused by gaseous decomposition products from the peroxide reaction.
Sofar, the peroxide crosslinking method, has only been successful in thick wall heat-shrinkable products. The lack of ‘body’ for thin wall heat-shrinkable products results in a failing manufacturing process.
In this thermal process the diameter of the tubing is increased by forces at a temperature slightly above the crystalline melting point of the polymer used. Due to the three dimensional crosslinks which are incorporated by means of the crosslink process, the tubing does not melt and obtains its perfect shape memory.
Immediately after the tubing reaches its required expanded size, the tubing is cooled down far below its crystalline melting point and thus reaches a state in which much radial stretch is incorporated in the tubing. This stage is called the "expanded" state.
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