Special Safety Considerations When Using Reactive Hmpur Adhesives - ITW Dynatec DYNAMELT D15 Series Technical Documentation Manual

Page 1-4 Safety Precautions
Revised 10/14

Special Safety Considerations When Using Reactive HMPUR Adhesives

Reactive hot melt PUR (HMPUR) adhesives are known for superior adhesion to numerous substrates and their exception-
al heat, cold and moisture-resistance qualities. They are an excellent choice for the difficult-to-bond substrates used in a
wide range of environments. HMPUR adhesives chemically cross-link (i.e., cure or thermal-set) to reach maximum bond
strength, typically over a period of 24 to 48 hours after being exposed to moisture and/or high temperatures.
The advantages of using HMPURs, however, come with special handling requirements. The adhesive must remain sealed
off from the environment and maintained at low temperatures until it is dispensed, otherwise there is a risk that the adhes-
ive will cross-link within the glue application equipment, rendering it impervious to melting when it is re-heated. Most
importantly, when over-heated, many HMPURs release gases that can be hazardous to humans. Therefore, adequate vent-
ilation must be available to prevent injury to personnel in the workspace. ITW Dynatec PN 114367 Vent Hood is re-
quired.
The following is a list of general operational considerations for the use of HMPURs in ITW Dynatec equipment. In addi-
tion, it is important to contact your adhesive manufacturer to discuss and verify precautions that must be implemented to
prevent damage to equipment and injury to personnel who are working with their products.
 Assure the workspace has adequate ventilation.
 Assure the entire adhesive delivery system is sealed from the environment to the greatest extent possible to
prevent moisture-related adhesive cross-linking.
 Assure all air is evacuated from the adhesive delivery system as soon as possible after it has been introduced
(i.e., when changing hoses, replacing filters, changing adhesive supplies, etc.) to prevent moisture-related cross-linking.
 The ITW Dynatec equipment should not be left dormant (sealed at ambient temperature) with PUR inside for
longer than recommended by your adhesive manufacturer. The ITW Dynatec system, especially applicators and nozzles,
should be thoroughly purged of adhesive using a PUR purge material if the system will be left dormant for extended time
periods.
 HMPUR viscosity increases the longer it remains molten within a system and can cross-link due to temperat-
ure exposure. Assure the molten adhesive does not sit within the ITW Dynatec equipment at operating temperature for
more than a cumulative total of 2 to 4 hours. Utilization of the Temperature Standby feature will ensure a temperature
drop occurs automatically.
 Turn off any gear pumps in the system if it will not be used for a period of five minutes or more. Doing so will
reduce potential glue degradation.
 When using spray applicators, the nozzles must be thoroughly cleaned on a regular basis to prevent the adhes-
ive from cross-linking inside or on the surface of the air passageways.
 The adhesive applicators must be either fully sealed or thoroughly cleaned with PUR purge material if the sys-
tem is to be idle for more than two hours. Otherwise, HMPUR adhesive present in the exposed orifices of the applicator
could potentially cross-link, clogging them.
 Recommended adhesive application temperatures should never be exceeded. Higher application temperatures
may result in higher adhesive viscosities and thermal-related cross-linking.
 The use of air dryers such as ITW Dynatec PN 117944 or 117974 are recommended in humid environments.
There are many advantages to using HMPURs. However, the proper handling of these unique adhesives is imperative to
assure success without damage to equipment or injury to personnel. ITW Dynatec equipment has been engineered to min-
imize the effort required to assure safe and proper handling of HMPURs. ALLOWING PUR ADHESIVE TO CURE IN
A UNIT OR ITS COMPONENTS VOIDS ITW DYNATEC'S WARRANTY. Please consult with your ITW Dynatec rep-
resentative to discuss these topics in further detail, if necessary.
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