Ask Dr. Dave / Columns

Ask Dr. Dave

January 1, 2007
/ Print / Reprints /
ShareMore
/ Text Size+
January 2007

Question: We want to look at UV adhesives for bonding clear plastic and glass samples but are wary about having high-intensity UV lamps in our plant. Are our concerns valid?

Answer: Fifteen or 20 years ago, some end users became disillusioned with UV systems because of several observed limitations: excessive heat buildup during cure; inability to cure through colored substrates; surface tackiness of the adhesives; and the necessary use of short-wavelength, high-intensity UV lamps for curing. This short-wavelength radiation made it mandatory to have considerable shielding around the equipment, plus skin and eye protection for the operators. Fortunately, several developments over the years have made UV curing much more useful and considerably safer to handle. By using a combination of new monomers, better photoinitiators and new lamp technology, it is now possible to cure these adhesives in seconds using visible light rather than UV. Some of the latest systems even use high-intensity LEDs to cure the adhesives rather than conventional UV-type bulbs. These systems are much safer than the “dinosaur” systems of 20 years ago, they do not generate heat and they cure well through most colored plastics. Although it is still recommended to use eye and skin protection when operating these systems, the possibilities of severe skin or eye damage are minimal when the systems are handled with care.



Question: In an earlier column you mentioned alternatives to fumed silica as thixotropes for epoxy adhesives. Specifications, however, dictate that we continue to use fumed silica even though we find it difficult to handle and it generates huge clouds of irritating dust when poured from its bags. Is there a better way to handle the material?

Answer: There are several ways of handling fumed silica that virtually eliminate dust. Some very large users, such as those making silicone sealants, use completely closed mixing systems, and they can use vacuums to transfer the fumed silicone into tanks. For more common mixing systems using open tanks, fumed silica suppliers offer handling systems that are usually based on using either vacuum or diaphragm pumps to transfer the material directly from large bulk containers, thus avoiding the use of simple paper sacks. Some powder-handling companies also offer specialized systems for fumed silica.

Links

Did you enjoy this article? Click here to subscribe to Adhesives & Sealants Industry Magazine.

Recent Articles by Dave Dunn

You must login or register in order to post a comment.

Multimedia

Videos

Image Galleries

ASI April 2014 Photo Gallery

Our April 2014 issue is now available!

Podcasts

ExxonMobil Tackifier Expansion

Dwight Tozer, vice president of ExxonMobil’s Adhesion Industry business, discusses the company’s latest tackifier expansion project with Editor-in-Chief Susan Sutton.

More Podcasts

Adhesives & Sealants Industry Magazine

ASI July 2014 cover

2014 July

Our annual Distributor Directory helps you locate a distributor that best suits your needs. Check it out today!

Table Of Contents Subscribe

THE ADHESIVES STORE

handbook-sealant-tech.gif
Handbook of Sealant Technology

The Handbook of Sealant Technology provides an in-depth examination of sealants, reviewing their historical developments and fundamentals, adhesion theories and properties, and today’s wide range of applications.

More Products

ASI 2014 Buyers GuideASI's Buyers' Guide

Annual purchasing resource for equipment used in the manufacture/formulation of adhesives, sealants, pressure sensitives, tapes and labels and for application of finished adhesives. 

Clear Seas Research

With access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

STAY CONNECTED

facebook_40px twitter_40  youtube_40pxlinkedin_40 google+ icon ASI 30px