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Materials, Logistics, Distribution, Rep Sales

PVC Environmental Considerations


PVC (polyvinyl chloride) is a versatile polymeric plastic used in many industries.
If you are into chemistry, click here for a great, short presentation on the structure of a PVC molecular chain by the Khan Institute.
 
  PVC, commonly called "vinyl", can be made softer and more flexible by the addition of plasticizers, the most widely used being phthalates, thus offering a strong, flexible, weather resistant, and attractive finish for fabrics used in signs, banners, tents, transportation, and many other applications. PVC is a "thermoplastic" which means that it can be repeatedly heated, softened, and rehardened. This property makes the material highly suitable for various methods used to mold, extrude, and shape many products and to weld two PCV-coated surfaces together.

One of the advantages delivered by most PVC products is that their useful life is almost always long and very dependable. For many applications, PVC is not a one-time-use material. Thus, compared to many other products, PVC's longevity is an environmental advantage. Nonetheless, PVC products or their utility does not last forever and some waste (e.g. trimmed pieces) also contributes to the need for recycling.

Recycling:

The Vinyl Institute offers expert materials on the topic of PVC characteristics, environmental considerations and recycling. Please visit their site at http://www.vinylinfo.org/Environment.aspx.

Additionally, new methods for recycling PVC are being developed regularly

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The Vinyloop Process

The relatively new mechanical recycling process known as Vinyloop® technology, developed by Solvay Research & Technology, allows the complete separation of PVC material from the non-PVC materials that are often combined with it, such as: Polyester fibers; glass fibers; natural textiles; polyurethane foam; metals; and rubber. Ferrara PVC Recycling Plant, Italy

  1. Pretreatment: The PVC is physically prepared to be reverted back into a raw material. These steps include cleaning or washing, material size reduction by cutting, grinding or milling and a homogenization step.
  2. Dissolution: The waste is combined with a selective solvent in a closed reactor that releases the PVC compound matrix. Additives and other materials are either dissolved or remain suspended in the liquid.
  3. Separation: Depending upon the insoluble materials, techniques such as centrifuging, decanting and cycloning are used for separation. Following the separation step, the secondary materials are washed with solvent to further remove any remaining dissolved PVC compound.
  4. Precipitation: Steam is injected to completely evaporate the solvent. The PVC compound formulation is recovered as liquid slurry. The PVC resin precipitates into microgranules.
  5. Drying: The slurry from the precipitation, which is a mixture of process water and regenerated PVC compound, is dried and the process water is treated before discharge. The regenerated PVC compound is now ready for use and is packed to await shipment. The solvent used in the process is contained in a closed loop. More than 99.9 percent of the solvent is recovered and separated from the process water, using condensation and density separation.

The production of each component needed for virgin PVC manufacturing consumes more natural resources, uses more energy, creates more air and water pollution and, overall, has a greater environmental effect than the Vinyloop operation itself. Additionally, the end product of the Vinyloop process is of the same quality.

Creative Recycling

Inventors, recycling chemists, and business people are seeking new ways to make next-generation use of vinyl billboard advertising materials that would otherwise go into landfills. Los Angeles Eco-Logical Art Gallery focuses on a green solution to this waste by creating functional art from recovered vinyl billboards.

The vinyl sheets used in billboard advertising are stretched so that the material can be used as canvases. The vinyl canvases are almost impervious to the elements with little signs of fading, flaking or wear. As a result, “eco-logical” artwork appears on billboards around Los Angeles. The gallery has also planned a national “renewable imagery” billboard art tour. The goal is to get the material into public schools and provide free mural walls to inner-city youths.

Welding Methods:

Many industrial fabric companies use welding technology to join panels using overlapped or butt seams. In overlap seams, one sheet of vinyl-coated fabric is welded to another piece, usually of the same type, by laying one sheet on the other along the intended joint with anywhere from a one half to three inch wide contact area. In a butt seam, the two primary sheets are aligned with no overlap and an additional third piece, a narrow strip of a compatible fabric, is welded behind the joint. By thus joining sheets of fabric which are usually woven and coated in sizes no wider than five meters (about 16 feet), fabricators can build many types of industrial barriers, tarps and covers, tents and tensile structures, grand format banners and building wraps, agricultural covers, and other large structures.

To add the strength calculated for properly engineered structures, webbing that is also PVC-coated can be added to seams and edges. Different types of welding equipment can be used for different seaming and edging operations. But the chemical process of marrying two vinyl-coated surfaces is based on having compatible coatings. Thus it is possible to join fabrics with differing internal fabric weaves ("scrims") but with similar outer PVC surfaces. It is always advisable to be certain that surfaces to be joined are clean before welding.

In cases where the scrim of a heavy webbing product is considerably more dense than that of the broad fabric to which it is being welded, it may be necessary to experiment with a variety of intensity and dwell time settings to be sure that the amount of heat needed to weld the webbing is not so great that it could cause damage to the broad fabric.

Because the polyester webbing inside PVC-coated webbing is essentially the same as regular polyester webbing, PVC-coated webbing can also still be sewn using traditional stitching machinery. This method is used in heavy applications such as reinforcing fold-backs behind tent hardware and in lightweight applications such as for smaller signs and banners where the waterproof characteristics of the PVC-coating may be desired but when welding is impractical. Once sewn, PVC-coated webbing offers the advantage that if can be slightly re-melted with a heat gun to seal needle holes.

In small sign shop applications, PVC-coated webbing can also be applied using PVC-specific solvent adhesives or with double-sided banner tape without any welding at all..

Be familiar with four different methods for welding PVC fabrics:
(information collected from various manufacturers)
     
Hot Air Welding    
Two surfaces are pressed together by a roller which follows a hot air nozzle. Air heated to over 400o F is directed through a nozzle precisely into the space between the fabrics. (Not from the outside as in a heat press.) In smaller welding machines and hand-held applications, the nozzle is moved along the welding track. Larger machines can use either a moving nozzle or a stationary nozzle with a carriage system that feeds the fabric layers to be welded.    Hot Air Equipment Suppliers:

Production-Scale Machines:
Miller Weldmaster

Smaller Shop Tools:
Forsthoff  (Abbeon Cal)
Leister
Mini-Hemme
     
Electronic Welding    
Compatible materials are pressed together between a sealing bar and a bed plate. Thermoplastic vinyl molecules are excited (heated) by radio frequency waves or electronic pulses. Electronic controls manage the duration and intensity of generated radio waves. Bars can be stationary or can move along a track delivering a series of similar welds without having to move the positioned fabrics.   High Frequency Equipment Suppliers:
Cosmos/Kabar
Fiab
Forsstrom
Hall Dielectric
JTE Machine Systems
Zemat Technology Group

Impulse Welding
Asco
Novaseal
     
Wedge Welding    
Heated fabrics are pressed together by a trailing roller after passing between spaces above and below a heated metal wedge. In smaller machines and hand-held applications, the wedge is moved along the welding track. Larger machines can use either a moving wedge mechanism or a stationary wedge with a carriage system that feeds the fabric layers to be welded.    Wedge Equipment Suppliers:
Miller Weldmaster
Novaseal
Sinclair Equipment
     
Solvent Welding    
After a brief waiting period during which a chemical solvent has had time to soften the vinyl coatings, two compatible  materials can be joined with pressure at ambient (room) temperature without additional heat. Prior to being pressed, the chemical solvent is spread along the surfaces to be joined. Consult manufacturer for information on period required to be sure that the newly joined surfaces are allowed to achieve a "tacky" consistency and then clamped for sufficient time for molecular bonding to be achieved. This method is useful on many smaller projects such as banner edges and for field repairs of any vinyl structure.    Fabric Adhesive Suppliers:
Adhesive Engineering & Supply
Chemical Concepts
H&H (Snyder Vinyl)
IPS WELD-ON

 

     
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Lighter sizes used for tents and banners:
25mm   1 in   1400 lbs   white
30mm   1-3/16 in   1650 lbs   white
             
Mid-range sizes used for
tents, tarps, and curtainside trucks:
40mm   1-1/2 in   2400lb   white and black
47mm   1-/7/8 in   2900 lb   white & black
    (called "two inch")    
47-50 mm   1-7/8+ in   5200 lb -   white & black
        5900 lb    
 
Other sizes special order, including:
  Heavy tent sizes up to 11,000 and 16,500 lb.
  Custom Colors
  Custom widths and special weaves.
     


 

 

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Tent Renters Association
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