Columns

Dr. Dave

February 27, 2006
/ Print / Reprints /
ShareMore
/ Text Size+

QUESTION: I am somewhat confused by the terms thermoplastic and thermoset as they concern adhesives. Can you explain the difference?

ANSWER: Adhesives can be classified in several ways, including their material origin (natural or synthetic) or their type of cure (physical or chemical). The terms thermoset, thermoplastic, structural or non-structural are also used in the industry.

The term "thermoset" historically meant adhesives that cured, or "set," on heating. The oldest types of this adhesive are the so-called PF, UF and MF resins (phenol formaldehyde, urea formaldehyde and melamine formaldehyde, respectively), which are commonly used to make plywood and are cured using heat and pressure. However, many thermoset adhesives cure at room temperature (e.g., two-part epoxies, moisture-curing polyurethanes, anaerobics and reactive acrylics). What thermosetting really means today is that the polymer chains are chemically crosslinked and do not soften on heating after curing. This makes them very suitable for structural applications where they have to support heavy loads. In contrast, thermoplastic adhesives like polyvinyl acetate (white glue), cyanoacrylates or hot melts also tend to "creep" over time when loaded. In general, thermoset adhesives have better thermal, fluid and environmental resistance than thermoplastics.



QUESTION: We want to market a water-based consumer adhesive to bond various lightweight materials, particularly paper materials. However, we want the adhesive to be totally clear, not white like the PVA adhesives typically sold in this market. What technology would you recommend?

ANSWER: There are several possible adhesive technologies that you might consider, but I would recommend formulating an adhesive based on polyvinyl alcohol. Polyvinyl alcohol is a polymer that is made by the controlled hydrolysis of polyvinyl acetate and is available in several grades, differing in molecular weight and degree of hydrolysis. It is a totally water-soluble polymer, although the typical manufacturing procedure is to disperse it in cold water and then heat to about 90°C. Its solution in water is totally clear and provides adhesives with high wet-tack and paper-tearing bonds. The only negative over conventional white glues is a slightly higher cost and some sensitivity to moisture and water, although this is not usually a serious issue for most applications.

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

In-Depth Features

These articles detail advantages and innovations for multiple end uses.

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

THE MAGAZINE

Adhesives & Sealants Industry Magazine

ASI April 2014 cover

2014 April

Our April issue focuses on pressure-sensitive adhesives, including a preview of PSTC's 2014 Tape Summit, as well as converting/packaging and composites!

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

asi1211p_Cover-DE.gifASI'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