Welding Thermoplastics
Welding is the process of uniting surfaces by softening them with heat. When welding thermoplastics, one of the key components is the material itself. For as long as plastic welding has been around many people still do not understand the basics which is critical to a proper weld.
The No. 1 rule of welding thermoplastics is you must weld like-plastic to like-plastic. In order to get a strong, consistent weld, it is necessary to make sure your substrate and your welding rod are identical; for instance, polypropylene to polypropylene, polyurethane to polyurethane or polyethylene to polyethylene.

Welding
Plastics welding techniques have been around for over 50 years; both hot gas welding and spin welding were first reported in the 1930's. The total number of welding techniques for plastics has risen to 20, six of which are still in various stages of development and have yet to find industrial applications. These are laser welding, microwave welding, infrared welding, forced mixed extrusion welding, orbital welding and friction stir welding. More common welding methods are extrusion welding, hot gas welding, butt welding, spin welding and solvent welding.

Bonding
Using adhesives to bond plastics offers many advantages over traditional assembly methods, including reduced weight, assembly costs, cycle times and safety concerns. To gain the full potential of adhesives, designers need an understanding of the performance characteristics of each adhesive, and knowledge of the factors affecting the bondability of plastics.

The wide variety of plastics substrates, an invaluable asset when selecting design materials, becomes a serious limitation when selecting the optimum adhesive. The number of adhesives, coupled with the many grades of plastics, make it difficult to locate bond strength data for specific adhesive/plastic combinations. The designer must first select a plastic and then evaulate different adhesives to identify one which meets the performance requirements of the application. Such screenings typically occur without information on the adhesive's performance characteristics.

Other factors such as cure speed, environmental resistance, thermal resistance and suitability for automation play a role in selecting the best adhesive for an application. Lower performance adhesives include rubber base solvent cements, host melts, two-part epoxies and urethanes, but they are not suitable for high speed automated processes.

For more information, contact Mike at Ultra Acrylics, Inc.

Thermoforming
Thermoforming is the process of creating a form from a flat sheet by combinations of heat and pressure, which first soften the sheet and then form the sheet into some three-dimensional shape. This is one of the simplest, more economical plastic forming processes. There are numerous variations of this process. There are three types of thermoforming: roll-fed, sheet-fed and in-line.

Thermoforming offers many distinct advantages over other shaping methods: lower tool mold cost that is one-tenth that of injection molding, the use of water cooled aluminum tools providing surface temperature control, simplified formation of laminates containing layers of different materials and higher production /throughput capabilities.

Thermoforming provides significant time and labor savings when producing large parts in smaller quanities. Design through final product (art-to-part time) is substantially reduced when using thermoforming. Other important benefits are low machine cost and short delivery time.

Compared to injection molding, thermoforming uses significantly less energy in order to form parts, often using sheets of different color and thickness for each part, resulting in lower mold costs and shorter lead times. The process also produces more stress-free products that resist cracking and is often the most cost-effective method to form large parts.

Thermoforming's disadvantages include the need to use more expensive plastic sheet rather than resins in pellet form, the required trimming operation, and the related problems of scrap storage.

For more information, please contact Mike, at Ultra Acrylics, Inc.

The poor thermal conductivity of plastics requires that care is taken to prevent the area being machined from getting too hot. The type of tool, depth of cut, rate of feed and coolant flow may have to be adjusted. If a coolant is used, make sure it does not chemically attack the plastic.

Check the supplier literature for recommendations on the types of tools and speeds to be used with a specific material.

Tolerances
Many designers will arbitrarily put a +/-.005 in tolerance on a part if it is to be machined. Quiz the designer to determine if the tolerances can be increased. Look at a ruler to visualize the size of the tolerance and think about the tools available to make the cut. Work with the designer to specify the tolerances really needed to make his part work and discuss what can actually be produced with the equipment available.

For more information, contact Mike at Acrylics, Inc.

Annealing is the baking of a material, without melting or distorting the part, to relax the internal stresses. The internal stresses are usually caused by uneven cooling. This means that the outside of the part cools much faster than the inside when the blank is made. This uneven cooling can also cause variations in the properties from the outside to the inside.

In today's challenging marketplace, the fabrication of plastic materials can add value for your customers. Following is an overview of the various fabrication techniques for stock shapes.

Machinability
Plastic stock shapes may be easily machined. However, the tool geometry and speed must be adjusted for optimum performance with a special material. The tolerances for machining plastics usually should be larger than those applied to metals. The tolerances must be larger because of thermal expansion and the shape changing from the relaxation of internal stresses within the material. In critical applications, it may be necesssary to premachine the part slightly oversize and stress relieve or anneal the part before taking the final cuts.

Mirrored Acrylic Sheet
The lightweight, fabrication versatility, increased strength and break resistance are just a few of the advantages acrylic mirror offers over glass mirror. Mirrored acrylic is 10 times more break resistant than glass mirror of equal thickness, allowing it to be used in many applications where glass is not acceptable.

Depositing aluminum on the substrate creates a superior reflective surface. A paint backing is then applied over the aluminum for protection. The quality and durabaility of the paint used in this process is crucial to prevent scratching during shipping, handling and various fabrication techniques.

Additional backings on the substrate include paper masking and vinyl. These backings provide heightened protection in demanding fabrication processes. A pressure sensitive adhesive backing is also available replacing hand applied adhesives that can be difficult to apply and more likely to produce an un-uniformed adhesive coverage. Pressure sensitive adhesive backing is used in those applications where the mirror is mounted to a fixture or in a permanent setting.

Protective coatings
A variety of protective coverings are used on acrylic, polycarbonate and PETG mirror sheet products. These include polyfilm, 3-mil laser polyfilm, papermask and adhesive film.

Mirrored acrylic products
Mirrored acrylic sheet is produced mainly in a thickness range of .060'' to .236''. Generally, sizes are from 36'' x 60'' up to 80'' x 120''. A one-inch overage on both length and width provide a maximum yield in fabrication process such as laser cutting. A variety of colors and textures are available including shades of red, blue, green, gray and bronze, yellow, pink and purple, as well as stipple, prismatic and non-glare patterns.

See-thru mirrored acrylic
See-thru, or two-way mirror allows a percentage of incident light to pass while reflecting the remainder. The illuminated side becomes a mirror and the darkened side becomes transparent. These mirrors are used in monitoring and surveillance devices in institutions, hospitals, casinos and stores. Main thicknesses are available .118'' and .236''.

First surface mirrored acrylic
First surface, or two-sided mirror consists of an opaque film of aluminum protected by a clear coating. Incident light is reflected in either direction making this sheet ideal for applications where the back of the mirror remains exposed, or where a reflection in both directions is desired.

PETG mirror
PETG mirror combines versatile fabrication properties with good impact strength, design flexibility and speed of fabrication. PETG mirror is ideal for children's toys, cosmetic uses and office supplies.

Scratch-resistant coating
A scratch resistant coating that is applied to the substrate is used in more demanding applications requiring abrasion, stain and solvent resistance. A coated sheet can be written upon with erasable pencils making it ideal for scheduling boards and restaurant menus.

Polycarbonate mirror
Polycarbonate mirror offers increased strength, heat and flame resistance. It is also available in see-thru, first surface and with a scratch-resistant coating.

For more information, contact Mike at 763-754-2020.

Insulation value of polycarbonate sheets
Polycarbonate sheets play an important role in today's agricultural market place. From greenhouses to garden centers, polycarbonate is the ideal product of choice. Polycarbonate is light weight, easy to install and allows abundant natural light into interior spaces. In addition, polycarbonate boasts the best fire rating among plastic products and has excellent insulation properties, all leading toward the design and construction of safe, energy-efficient agricultural buildings.

There are two alternatives available for covering greenhouses: a soft cover utilizing polycarbonate. Because most greenhouses not only shelter flora and fauna but also state-of-the-art equipment, a hard polycarbonate cover is most often selected.

Once the decision to utilize a hard cover has been made, then you must again choose between corrugated polycarbonate and twin-wall polycarbonate. Because of better thermal efficiencies and greater diffusion of natural sunlight, twin-wall polycarbonate is likely the product of choice.

Building owners should always keep in mind that utility costs are directly related to the energy efficiencies of any building. For greenhouses the energy cost is equal to the energy lost. As we keep heating, we lose energy through the covering.

Four wall, 8 mm (5/16'') thick polycarbonate sheets offer the perfect solution for today's energy and budget conscious market. With an R value of 2.08, about 15 percent more efficient than comparable two wall sheets, the material will actually pay for itself in less than three years by reducing the heating cost. "Pay more to pay less!"

Now more than ever, it is vitally important that we strive to save as much energy as possible. We have many customers across North America successfully utilizing the four wall, 8 mm thick polycarbonate sheets.

For more information, contact Mike at Ultra Acrylics, Inc.