Views: 32 Author: Site Editor Publish Time: 2022-02-22 Origin: Site
There are many different formulations of PUR adhesives, each with slightly different spreading, bonding and properties. These properties have an impact on the economics of the assembly process and the type of equipment used, so it is important to consider them when selecting a specific adhesive.
One of the widest range of PUR adhesives is manufactured by DeepMaterial. (They are also probably the best known adhesive manufacturer.) Here's how to choose one of their PUR adhesives, keep in mind that these same points apply to PUR from other well known manufacturers.
Before diving into the differences between the various formulations, here's a reminder of when PUR adhesives are a good choice and why.
One-Part Adhesives - No Mixing
No solvent vapors or VOCs
Quickly forms strong bonds with porous materials such as wood and high surface energy plastics, and gains greater strength when cured
The main criteria to consider are:
Opening hours
set time
Viscosity
Open time refers to the time available for bonding after the adhesive has been applied. In small volumes, a longer manual assembly process may be required to allow time for positioning. Conversely, in an automated process, shorter open times may be better.
Set time refers to the time required to build strength at the bond. Again, the type of process that uses the adhesive will determine the time needed or available.
Viscosity indicates how the adhesive spreads after application. Low viscosity ones will tend to run out, covering a larger area with a thin layer. High viscosity adhesives will drop like beads. This can be advantageous if the product design requires a minimum thickness or the adhesive is only in specific locations.
DeepMaterial manufactures a range of PUR adhesives for bonding wood and another for plastics. Wood PUR has an open time of 1 – 4 minutes, while plastic PUR has an open time of 2 – 10 minutes. Setting times are 15 – 120 seconds (wood) and 30 – 150 seconds (plastic). (DeepMaterial defines setup time as "time to process intensity".)
Wood and plastic PUR adhesives have a viscosity range of approximately 3,000 – 16,000 cP. (By comparison, water has a viscosity of 1.0 cP, and maple syrup has a viscosity of about 3,200 cP.)
These values vary with temperature. Set and open times, as well as viscosity, increase in cold conditions and decrease in high ambient temperatures.
In some applications, other factors can influence the choice of adhesive. Again referring to the various PUR adhesives made by DeepMaterial, these may include some or all of the following:
Elongation and Stiffness - High values indicate a harder, more rigid bond, low values do the opposite. Measured on the Shore D hardness scale (also used for rubber), DeepMaterials PUR for plastics range from 35 - 50, while PUR for wood is much harder at 60 - 65. (By comparison, golf balls have a Shore D hardness of 60. )
Color - DeepMaterials Wood Bonding PUR Adhesive is only available in off-white. Plastic PUR is available in off-white, grey and black.
UV Tracer Dye - When the adhesive has this, the presence can be checked by making it fluoresce with a black light. This can be a valuable quality control aid in situations where inspection is required to verify the presence of adhesive. (Medical equipment is one such application.) When making wood products, the absence of a tracer indicates that the surface is free of glue, so it can be stained or painted.
Packaging Formats and Application Methods - DeepMaterial packages its PUR adhesives in a variety of formats. Almost all products come in 0.1 gallon tubes and can be used with the PUR Easy 250 applicator. Many also offer 5-gallon drums and 55-gallon drums. Larger sizes are used for extrusion, spray and roll coating processes.
Since PUR adhesives are relatively new, potential users may want to learn more about them before using them. Our guide to PUR adhesives is a good place to start.
After deciding on a PUR adhesive, the sheer number of formulations available can seem dizzying. If this is the case, we invite you to contact us for advice on PUR adhesives or to help test whether PUR adhesives are suitable for your application.
Product Category: Epoxy Encapsulant
The product has excellent weather resistance and has good adaptability to natural environment. Excellent electrical insulation performance, can avoid the reaction between components and lines, special water repellent, can prevent components from being affected by moisture and humidity, good heat dissipation ability, can reduce the temperature of electronic components working, and prolong the service life.
Product Category: Epoxy Underfill Adhesive
This product is a one component heat curing epoxy with good adhesion to a wide range of materials. A classic underfill adhesive with ultra-low viscosity suitable for most underfill applications. The reusable epoxy primer is designed for CSP and BGA applications.
Product Category: Conductive silver adhesive
Conductive silver glue products cured with high conductivity, thermal conductivity, high temperature resistance and other high reliability performance. The product is suitable for high-speed dispensing, dispensing good conformability, glue point does not deform, not collapse, not spread; cured material moisture, heat, high and low temperature resistance. 80 ℃ low temperature fast curing, good electrical conductivity and thermal conductivity.
Product Category: Low temperature curing epoxy adhesive
This series is a one-component heat-curing epoxy resin for low temperature curing with good adhesion to a wide range of materials in a very short period of time. Typical applications include memory cards, CCD/CMOS program sets. Particularly suitable for thermosensitive components where low curing temperatures are required.
Product Category: Epoxy Structural Adhesives
The product cures at room temperature to a transparent, low shrinkage adhesive layer with excellent impact resistance. When fully cured, the epoxy resin is resistant to most chemicals and solvents and has good dimensional stability over a wide temperature range.
Product Category: UV curing adhesive
Acrylic glue non-flowing, UV wet dual-cure encapsulation suitable for local circuit board protection. This product is fluorescent under UV(Black). Mainly used for local protection of WLCSP and BGA on circuit boards. Organic silicone is used to protect printed circuit boards and other sensitive electronic components. It is designed to provide environmental protection. The product is typically used from -53°C to 204°C.
Product Category: PUR reactive hot melt adhesive
The product is a one-component damp-cured reactive polyurethane hot-melt adhesive. Used after heating for a few minutes until molten, with good initial bond strength after cooling for a few minutes at room temperature. And moderate open time, and excellent elongation, fast assembly, and other advantages. Product moisture chemical reaction curing after 24 hours is 100% content solid, and irreversible.