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Fabricating and Assembly: Adhesive-curing technology provides lasting bonds

Issue: Oct. 2017

Adhesives — a standby for quick household repairs and children’s art projects — work in the plastics factory, too. Applying the compound that is appropriate to the substrate is key; so are the devices that allow precise dosing and complete drying to ensure a bond that lasts.

Henkel

Henkel, a maker of adhesives and adhesive-curing technologies, serves myriad industries, but Karl Gabrielson, director of global equipment, said some of its light-curing products work especially well with plastics. Since the summer, it’s expanded its Loctite brand, which includes a number of the devices.

Henkel’s EQ CL28 CureJet LED-curing system

“They’re really suited for plastics, because there’s a low level of heat generation,” Gabrielson said. “They’re really friendly toward plastics.”

Some of the devices that Henkel’s products glue together include medical needles and catheters. Big products also sport glue: According to Gabrielson, there are Henkel adhesives in appliances and automobiles.

The company’s newest products include its Loctite EQ CL28 CureJet LED Spot, Loctite CL30 LED Flood and Loctite CL32 LED Spot systems, which perform LED curing. The systems use ultraviolet (UV) light to catalyze a chemical reaction that converts liquids into solids, forming a powerful bond between substrates. It’s a fast-acting assembly strategy that requires no clamping, Gabrielson said.

“When you shine the light on this, it is basically secured within seconds,” he said.

Users of LED-curing technologies choose the adhesive type that suits their needs and calibrate the equipment to the proper wavelength for that adhesive. If the job is to assemble flexible medical devices, for example, users might choose Henkel’s Loctite 4902, a clear, highly flexible cyanoacrylate adhesive suitable for use with plastic, rubber and metals.

According to Henkel, LED curing requires little energy and produces no infrared emissions, which can cause part warping. Another benefit: The LED bulbs can last up to 20,000 hours.

Consisting of a light source, controller for setting light-exposure time and related cable, the Loctite EQ CL28 CureJet LED Spot system can be machine-mounted or used as part of an automation system.

With intensities of up to 27 watts per square centimeter, the system delivers extremely high power and fast curing, and can flash-cure plastics to a wide variety of substrates. For maximum performance, the innovative design combines both high intensity with a significantly wider cure area than most spot systems. It can cure an area with a 16mm diameter. The company offers wavelengths of 380 nanometers (nm), and 405 nm, along with single- or quad-controller options.

By comparison, the Loctite CL30 LED Flood system, offering a choice of wavelengths, including 365 nm, 380 nm and 405 nm, cures a bigger area, maxing out at about 4 inches by 4 inches. It can be integrated easily into either stationary applications or fully automated processes. It has a compact footprint and integrated air cooling.

For curing smaller components, the company offers its Loctite CL32 LED Spot, a portable, flexible LED light source that can be mounted or used as a hand-held device. Its lightweight, compact design helps minimize operator fatigue, and its small size and long focal length are suitable for use in crowded and hard-to-reach areas. The CL32 comes with 365 nm and 405 nm heads. It can be line-powered or run off a battery with a three-hour battery life. It is suitable for prototyping, scale-up or full production environments.

“It’s meant to be a hand-held unit that people could use pretty much as people use a pencil,” Gabrielson said.

Nordson Adhesive Dispensing

Superior bonding isn’t all about chemistry. Making sure the adhesive is handled correctly and applied appropriately are two other sticking points.

Nordson’s Vulcan Jet dispensing system with a touch-screen controller

Nordson, which supplies equipment for extrusion, injection molding and compounding, recently released products addressing these concerns. Last month, it expanded on its Unity line of dispensing systems with its introduction of the Vulcan Jet adhesive-dispensing system. Equipped with 30-milliliter applicators, the system precisely applies discrete dots of adhesives into hard-to-reach surfaces, such as grooves.

The system, which features a 7-inch touch-screen controller with flow-monitoring capabilities, can apply adhesives with accuracy and precision at high speeds at a maximum distance of 6mm from the substrate. According to global marketing manager Cory Strunk, the Vulcan Jet is ideal for use by makers of products such as electronic sensors and automotive components.

Made for a wide range of hot-melt materials, including PU, the Vulcan Jet features automatic pressure compensation that adjusts for changes in adhesive viscosity. With this feature, the system can maintain consistency over the dots it dispenses.

The system can be used in combination with another new product, Nordson’s PureFlow adhesive-
delivering hoses. Compatible with most heated fluids, the hoses are appropriate for use with standard hot-melt adhesives and reactive hot-melt adhesives.

“These products were specifically engineered for the plastic bonding/adhesive applications,” Strunk said.

Unlike other hoses, the PureFlow hoses are designed to protect the adhesives within them. According to Nordson, when adhesive sits inside of a typical heated hose, it begins to degrade. The effects of this degradation include discoloration, curing and odors. For example, reactive PU adhesives tend to cure within heated hoses and restrict flow, requiring frequent hose replacements. Adhesive degradation also can lead to nozzle-clogging char and can affect the rheology of the compound. Ultimately, contaminated and deteriorated adhesives fail to perform appropriately when applied.  

By reducing degradation, the PureFlow technology, along with the Vulcan Jet system, enables customers to enjoy greater operation efficiency by vastly extending their preventive maintenance schedules for hoses.

“When used together, utilizing a low-pressure melter and PureFlow hose reduce the effects of char on the entire system,” Strunk said.

To further protect the life of the hoses, Nordson has equipped the PureFlow hoses with loops that fit around them called RediFlex II hangers. The hangers give users an easy way to install and move the hoses without crimping them; they also improve the temperature consistency of bundled hoses.

Magnum Venus Products (MVP)

A supplier of equipment for composites manufacturing, MVP has a large portfolio of products, including pumping systems, spray guns and filament winding systems. In mid-September, it unveiled a filling station for adhesive cartridges. The station handles cartridges that can be refilled from containers ranging in size from 5 gallons to 55 gallons.

According to MVP, the filling station features an easy-to-learn control panel that ensures accurate dispensing. It uses pneumatic pressure sensors and can fill two components into the cartridge independently.

MVP’s filling station

The filling station works in conjunction with two of MVP’s adhesive-metering systems, the Patriot 1:1 Adhesive & Sealants Chop Check and Patriot 10:1 55-gallon adhesive systems, which can dispense epoxies, urethanes, methacrylate, silicone and other materials to bond composites and plastics.

The filling station poses numerous advantages to users, the company says.

“This new product allows the adhesive user to have the convenience of cartridge autonomy while also receiving the benefit of buying adhesives in bulk. It allows the user to refill cartridges, which will save on waste and decrease production times,” said Peter Hedger, MVP’s director of marketing. The new product also offers “a simple, easier user interface to control a large, rather complicated machine.”

The filling station streamlines the dispensing process and reduces the potential for waste. According to Hedger, the station could cut users’ adhesives cost by 75 percent, because it will allow them to buy the materials in bulk.

The Patriot 1:1 Adhesive & Sealants Chop Check system delivers a fixed 1-to-1 material mixing ratio without the need for gears or transfer pumps, which improves reliability and reduces maintenance costs. Equipped with an MVP stainless-steel UltraBond gun, the Patriot 10:1 55-gallon adhesives system accurately meters methacrylate adhesive bonding materials. Furthermore, the system is equipped with an MVP stainless-steel Ultrabond gun and catalyst pumps for a rugged, yet easily maintained unit.  

Phillip Britt, correspondent

pbritt@plasticsmachinerymagazine.com

For more information

Henkel Corp.,
Westlake, Ohio, 800-562-8483,  www.loctiteproducts.com

Magnum Venus Products,
Kent, Wash., 253-854-2660, www.mvpind.com

Nordson Adhesive Dispensing,
Duluth, Ga., 770-497-3700, www.nordsonadhesive.com