New ADDHERE Adhesive Tie Layer Bonds Acrylic Cap Layers To Substrates Of Thermoplastic Polyolefin (TPO)
Mansfield, TX - Solvay Engineered Polymers, Inc., has introduced its first adhesive tie-layer material for use in the production of extruded sheet. The new ADDHERE tie layer is designed specifically to bond an acrylic layer onto a substrate of thermoplastic polyolefin (TPO) for use in thermoforming applications.
Effective bonding of dissimilar materials
The ability of the ADDHERE material to bond simultaneously to both an acrylic and an olefinic layer is a major breakthrough in the production of olefinic sheet stock. "Acrylic films are well understood and widely used across many industries for high gloss, depth of image, and surface durability in decorative applications," explains Eric Short, manager of the thermoforming business unit at Solvay Engineered Polymers. "And engineered polyolefins are likewise valued for their impact resistance, dimensional stability, and low- temperature ductility. But until now, there has been no way to effectively bond these two dissimilar materials in an efficient, in-line process."
ADDHERE adhesive tie layer is a pelletized material that can be co- extruded with a TPO substrate, to which acrylic film rollstock can be laminated in-line. Or sheet producers can tri-extrude each of the three materials - acrylic, tie layer, and TPO - from the melt phase to produce a multi-layer sheet.
New ADDHERE tie layer can be colored and recycled
Color can be introduced into an acrylic/TPO sheet in the opaque tie layer. With the acrylic layer free of pigment, it can provide optimum gloss, depth of image, and scratch resistance. At the same time, the absence of pigment from the TPO substrate means its performance properties can be easily and economically controlled.
Both major forms of scrap produced in the process of producing sheet for thermoforming can be recycled back into the TPO substrate - both the line-trim from the sheet extrusion, and the trim removed after the forming of the final shape. Solvay Engineered Polymers provides guidelines for recycling material containing the new ADDHERE™ tie layer, so that the properties of the TPO substrate are maintained.
"Depending on the performance requirements of the final application," says Short, "sheet with this tie layer can be recycled back into the virgin TPO at levels of 20 to 30%. Low-temperature ductility is the main factor in determining the percentage of material that can be recycled."
Benefits to the thermoforming process
Bonding an acrylic cap to a TPO substrate with an ADDHERE tie layer increases the melt strength of the resulting sheet. Compared with that of a monolayer TPO, sheet sag in the thermoforming process is improved by up to 15%, depending on the thickness of the multilayer sheet. This means thermoformers will enjoy a broader process window, making it easier to achieve quality parts and to reduce scrap rates. In addition, the forming process itself actually strengthens the bond provided by the ADDHERE tie layer between the acrylic and the TPO layers.
Performance advantages of TPO/acrylic sheet
ADDHERE adhesive tie layer has been developed to work with three different extrusion-grade TPO and engineered polyolefin materials produced by Solvay Engineered Polymers: DEXFLEX® E118 thermoplastic polyolefin, SEQUEL® E3000 engineered polyolefin, and SEQUEL® E5800 engineered polyolefin. This selection of substrate materials provides a wide range of economical performance alternatives.
Acrylic/polyolefin sheet could provide advantages over the ABS, metal, or fiberglass materials now employed in large, durable and decorative applications. Compared with ABS, polyolefins exhibit superior low-temperature ductility and resistance to stress cracking - particularly in parts that involve movement or vibration.
Sheet of engineered polyolefin laminated or co-extruded with an acrylic cap could replace painted metal in some applications. The need for expensive dies and machinery would be reduced, and the cost of the painting process would be eliminated, along with the volatile organic compounds (VOCs) associated with the painting process.
Compared with fiberglass, the use of multi-extruded polyolefin/acrylic sheet could significantly shorten production cycle times, eliminate expensive labor costs, and reduce the weight of finished parts. Replacing fiberglass in an application would also have the environmental benefit of eliminating the associated VOCs.
SOURCE: Solvay Engineered Polymers, Inc