Viscosity management of automotive and PCB production adhesive and sealant formulations

New high-strength industrial adhesives are currently being used in automotive and other manufacturing operations to replace spot welding, mechanical fasteners and other traditional joining methods. Adhesives offer several key advantages over traditional fastening technologies, including more uniform bond strength over a larger surface area compared to the localized strength typically achieved with mechanical fastening.

Adhesives and sealants are also used to join substrates or seal joints or gaps. They come in a variety of forms, but are usually dispersions containing polymeric materials or hardeners, surfactants and solvents. In the case of reactive adhesives, adhesion can be induced by mixing two or more reactive ingredients such as epoxy resin and hardener, or by external stimuli such as ultraviolet rays, heat, and moisture. In the case of non-reactive adhesives, adhesion is induced by a physical stimulus, for example pressure or solvent evaporation.

Most adhesives and sealants are composed of polymeric materials or contain monomers or oligomers that react to form cross-linked polymer networks. As a result, the molecular weight and molecular structure of these components are very important for the material properties before and after bonding. Many adhesive and sealant formulations are two-phase systems containing emulsions containing dispersed polymers or, in the case of caulk, dispersed solids. In both cases, particle size and droplet size can be critical to product performance. The adhesive or sealant must flow to the substrate surface and then change from a flowable liquid to a structural solid without creating harmful internal stresses in the joint. Many adhesive or sealant problems that occur are not due to poor material selection or joint design, but are often directly related to poor production techniques lacking proper process control.

< Why measuring viscosity is important >

Viscosity (and rheology) is the most important parameter in adhesive production and processing Various solvents, soluble agents, resin powders or inert fillers control the viscosity of the adhesive The viscosity of adhesive systems increases or decreases depending on application and operating environment
It is highly desirable that the viscosity is automatically adjusted to a substantially constant value Essential to improve performance and reduce costs in virtually all formulation and delivery processes Recognize the need for a viscometer to monitor viscosity and temperature
Ensure consistency using temperature-compensated viscosity as key process variable Failures can be reduced

< Why viscosity monitoring and control is important in adhesive and
sealant formulation, testing and delivery >

Adhesion and sealing quality
Joined parts must conform to finished product specifications, and process control is critical to achieving this.
In-line viscosity monitoring and control can help achieve the consistency needed in delivery and formulation systems adhesive and sealant applications.
Defect Reduction
Viscosity control helps mitigate mistakes (air entrapment, moisture build-up) that occur during the preparation, testing and delivery of adhesives and sealants.
Better yield
Ensuring consistency throughout the coating process significantly reduces scrap rates, saving money and time, and supporting continuous processes.
Correct Attribute
Poor mix quality can have a negative impact on the desirable properties of the joint, such as resistance to thermal cycling, chemical resistance, electrical insulation, flexibility, dimensional stability, and low shrinkage.
All of these properties depend on how well the process is controlled, so controlling viscosity is important.
Incorrect viscosity harms more than just quality.
Poor viscosity control increases the use of thickeners, fillers and diluents. Continuous viscosity measurement during the mixing process can ensure homogeneity, optimize energy use and reduce diluent use.
Eliminating the need for manual viscosity control saves operators time and allows them to focus on other tasks.

Jinwoo Hi-Tech’s inline solution for the automobile and PCB industries

Brookfield TT-100

nline rotational viscometer
▶ Viscosity: 10~500,000 cP
▶ Shear Rate: 10~1,000 sec-1
▶ Repeatability: ±0.5% of span
▶ Pressure Range: 200 psig
▶ Max Flow Rate: 5 m3/h
▶ Output Signal: 4-20mA
Rheonics SRV, SRD

In-line vibrating viscosity and density meter
▶ Viscosity: 0.5~50,000 cP
▶ Accuracy: 1% of reading
▶ Repeatability: 1%
▶ Density: 0.4~4.0 g/cc
▶ Accuracy: 0.001 g/cc
▶ Repeatability: 1%
▶ Analog & Digital output
Brookfield TT-100

Inline ultrasonic flow meter
▶ Flow range: 0.01~25 m/s
▶ Accuracy: ±1.0% (±0.3%)
▶ Repeatability: 0.15%
▶ Pipe Size: 6~6,500 mm
▶ Temp range: -40~240 ℃
▶ Analog & Digital output