Extrusion Welding

There are a number of methods to weld thermoplastics, which include hot gas (air) hand welding, and hot gas (air) extrusion welding. In the following, hot gas (air) hand welding and hot gas (air) extrusion welding are being addressed since they play a major role in the field of custom thermoplastic fabrication. A further application for these techniques is the modification or repair of rotationally molded, blow molded, vacuum formed or injection molded parts.

THE MOST COMMONLY WELDED THERMOPLASTIC MATERIALS ARE:

• Polypropylene
• Polyethylene
• Polyvinylchloride
• Chlorinated Polyvinylchloride
• Polyvinyldenefluoride

Welding means raising the temperature of the materials to their thermoplastic state, applying pressure to allow the molecules to newly position themselves and thus creating a new homogeneous area when cooled down. The thermoplastic state, i.e. the temperature range in which the material is weldable, differs between materials. Compared to PP and PE, PVC and CPVC have a very small thermoplastic state, i.e. the temperature window for welding is relatively narrow.

Compatibility between materials is an important factor. It is recommended to verify that the melt flow rates of HDPE materials to be welded together are the same or neighboring. With PP it is not recommended to use Homopolymer rod with Copolymer parent material.

Hot gas (air) hand welding and hot gas (air) extrusion welding are manual operations and require the use of a filler material. The quality of the weld is highly dependent on the knowledge and skill of the operator. The operator needs to be knowledgeable in both the setup of the equipment and the proper execution of the weld.

HDPE Pipe Grade

HDPE material displays improved performance characteristics in a variety of piping applications. In addition, the material is UV stabilized and ideal for use in demanding outdoor applications. It retains its properties between -220°F and 180°F and resists most chemicals. It is also NSF certified under Standard 61 to be used in potable water piping systems. HDPE Pipe Grade can be used in a variety of applications including manhole lids and bottoms, pipe reducers, trenches, sumps, pipe flanges, pipe end caps, tanks, milled flange adapters and lifting lugs.

PROPERTIES

Physical Properties	Units	ASTM	Results
Density	lb/in^3	ISO 1183	0.959

Mechanical Properties	Units	ASTM	Results
Tensile Stress at Yield	psi	ISO 6259	>3,500
Tensile Strain (Break)	%	ISO 6259	>500
Resistance to Rapid Crack Propagation	psi	ISO 13477	>174
Slow Crack Growth PENT	hrs	ISO 16241	>3000
Tensile Strength – for Butt – Fusion		ISO 13953	Test to Failure Ductile

Thermal Properties	Units	ASTM	Results
Oxidation Induction Time	min	ISO 11357-6	>20

APPLICATIONS:Chemical tank and equipment construction;Piping systems;Power and electrical engineering;Air-conditioning and ventilation systems;Mechanical engineering;Transport, materials handling and storage systems;Mobility;Environmental technology;Tanks and equipment;Chemical process industry;Water purification;Industrial waste water.

ADVANTAGES:UV resistant;Great weldability;High tensile strength;Stiffness for machine parts;RoHS and REACH compliant;Formable;Chemical resistant;Stress crack resistant;NSF 14 and 61 certified for potable water.

PTFE(PolyTetraFluoroEthylene) Tubing

If your temperature requirements range up to 500º F (260º C), PTFE Tubing (PolyTetraFluoroEthylene) is the recommended choice. It resists “melt-off” by soldering irons when making terminations. Because of its excellent dielectric properties, it is widely used in electronics and electrical service. Another key advantage of PTFE Tubing is its non-stick properities that allow the transport of materials with minimal fluid resistance. Please do be aware, however, that PTFE reacts with fluorine, molten sodium hydroxide and molten alkali metals.

PTFE Tubing outperforms glass and graphite by its inherent superior chemical resistivity and low coefficient of friction, making it an ideal material for fluid transfers. PTFE Tubing can be used with virtually all industrial solvents, chemicals, and corrosive materials, and can be used in processes at elevated temperatures. It can be steam sterilized without effecting its physical properties, such as surface hardness, elongation, flex life or deformation under load. PTFE Tubing is normally translucent white in color, however, the degree of whiteness varies from lot to lot, and with dimensional wall thickness. Colored PTFE tubing is also available and is generally used to simplify tube routing during system installations.

PTFE Tubing Advantages:

• Non-stick properties
• Temperature resistance up to 260º C (500º F)
• Aging resistance
• Can be steam or chemically sterilized in-line
• Superior chemical resistivity and low coefficient of friction

PTFE Tubing Applications:
Aerospace &Transportation Technology, Electronics, Components & Insulators, Chemical & Pharmaceutical Manufacturing, Food Processing, Environmental Sciences, Air Sampling, Fluid Transfer Devices and Water Processing Systems.

Thread Seal Tape

Thread seal tape (also known as PTFE tape or plumber's tape) is a polytetrafluoroethylene (PTFE) film for use in sealing pipe threads. The tape is sold cut to specific widths and wound on a spool, making it easy to wind around pipe threads. It is also known by the genericised trade-name Teflon tape; while Teflon is in fact identical to PTFE, Chemours (the trade-mark holders) consider this usage incorrect, especially as they no longer manufacture Teflon in tape form.Thread seal tape lubricates allowing for a deeper seating of the threads, and it helps prevent the threads from seizing when being unscrewed.The tape also works as a deformable filler and thread lubricant, helping to seal the joint without hardening or making it more difficult to tighten, and instead making it easier to tighten.

Typically the tape is wrapped around a pipe's thread three times before it is screwed into place. It is commonly used commercially in applications including pressurized water systems, central heating systems, and air compression equipment.

Types:Thread seal tape used in plumbing applications is most commonly white, but it is also available in various colors. It is often used to correspond to color coded pipelines (US, Canada, Australia and New Zealand: yellow for natural gas, green for oxygen, etc.). These color-codes for thread sealing tape were introduced by Bill Bentley of Unasco Pty Ltd in the 1970s. In the UK, tape is used from coloured reels, e.g. yellow reels for gas, green for potable water.

• White – used on NPT threads up to 3/8 inch
• Yellow – used on NPT threads 1/2 inch to 2 inch, often labeled "gas tape"
• Pink – used on NPT threads 1/2 inch to 2 inch, safe for propane and other hydrocarbon fuels
• Green – oil-free PTFE used on oxygen lines and some specific medical gasses
• Gray – contains nickel, anti-seizing, anti-galling and anti-corrosion, used for stainless pipes
• Copper – contains copper granules and is certified as a thread lubricant but not a sealer

Uses:Thread tape is appropriate for use on tapered threads, where the sealing force is a wedge action. Parallel threads may not seal effectively with or without tape, as they are intended to be sealed by a gasket.

Thread sealing tape is almost entirely applied by hand, although at least one machine is available for production wrapping of fittings.

PTFE tape is also commonly used in the stretching of body piercings, through a process known as taping, because it is inert and safe for this use. The wearer wraps layers of the tape around a plug, slowly increasing the size and thus slowly increasing the size (gauge) of the piercing.

CPVS Pipe Grade

CPVC pipe is produced from a specialty blend of chlorinated polyvinyl chloride material with unique physical properties desirable for piping applications (i.e., improved impact resistance and good fire resistance capabilities). Pipe grade CPVC product line includes schedules 40 and 80 piping from 1/4″ through 24″ diameters. CPVC piping systems can handle more than three-fourths of the temperature/pressure requirements of today’s typical process plants. CPVC pressure pipe has an upper working temperature limit of 200° F (93° C), or approximately 60° F (15° C) above that of Type I Grade I PVC. As with all thermoplastic piping systems, CPVC’s ability to withstand pressure varies with pipe diameter, wall thickness, and temperature. As the pipe diameter and temperature increases, the pressure rating of the product decreases. For example, 1/2″ Schedule 80 CPVC pipe is engineered for continuous service of 850 psi @ 73°F (23°C). The same pipe in service @ 180°F (82°C) carries a maximum working pressure rating of 210 psi at this temperature. 6″ Schedule 80 CPVC pipe is designed for 270 psi @ 73°F, and 54 psi @ 200°F.

PROPERTIES

 

NOTE: The property values presented above are typical values intended for reference and comparison purposes only. They should NOT be used as a basis for design specifications or quality control.

APPLICATIONS:Welded Tanks, liners;Valves, fittings, and piping systems;Ducts;Pumps.

ADVANTAGES:High impact strength;Dimensionally stabile;Easily machined using standard metal working tools;Corrosion resistant;Easily cemented and welded;Lightweight;Excellent electrical properties;Excellent fire rating;Good chemical resistance.