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Bonding and surface carachteristics

AIPI – Milano, 15 May 2014

DELO Industrial Adhesives – Stefano Farina

Stand: 03/12

Introduction

� The quality of the surface decides on the bonding

� Only defined surfaces enable a defined bonding

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Advantages of bonding

� Manifold material combinations

� Constant tension distribution

� Low thermal influencing

� Isolation and corrosion protection

� Method combination with other joining methods

� Production automation

� Miniaturization

� Properties of assembly materials are maintained

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Adhesion and cohesion

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� Alcohols, e.g. ethyl alcohol, isopropanol- excellent for tensiles and salts (polar)- good for fats and oils

� Ketones, e.g. acetone, MEK- good for fats and oils (polar)

� Ester, e.g. ethyl acetate- universal cleaning effect, strong exhalation, relatively long evaporation

� Hydrocarbons, e.g. cleaning agent,DELOTHEN NK1 und NK3- excellent for fats and oils- less suitable for polar impurities

1. Cleaning, degreasing…….

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Residua after cleaning ����

Residua free cleaning ☺☺☺☺

1. …..and removing !!

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2. Sufficient bonding area

m = 1.500 kg

F = G = 15.000 N

A = 10 x 10 cm² = 10.000 mm²

σ = F / A = 15.000 N / 10.000 mm²

Tensile strength: σσσσ = 1,5 N / mm²

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3. Bonding-optimized design

Bonding-optimized design means:

� large bonding areas

� only shear and tensile stresses

� avoid peel and bending stresses

03/2011

Example – sealing of a housing

Tongue and groove connection

Housing

Cover

03/2011

Worst case scenario - example

Subsequent bonding and sealing of an existing tongue and groove

Current design

The customer‘s idea for sealing:

� Adhesive application (red)

� Joining of the components

Problem: During joining, the adhesive (red) is sheared off

Wetting is undefined.

The gap is too small to form a bonding layer.

03/2011

Better case scenario - example

Sealing and bonding of a tongue and groove connection

� Project in the design phase

The customer‘s idea:

� Adhesive application in the grooves

� Joining of the components

Problem:

� Trapped air when joining the components

� Uncontrolled spreading of the adhesive

03/2011

Best case scenario - example

Sealing and bonding of a tongue and groove connection

� Suggestion for improvement in cooperation with the customer

Design:

� Guide groove for centering the connection

� Area which can take up adhesive

� Bead dispensing in the groove

Joining of the components:

� The adhesive spreads evenly in the gap

� No trapped air

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4. Bonding-optimized design

� Provide a constant and sufficient bondline thickness:

Adhesive layer thickness d

Adh

esio

n st

reng

th

Source: Habenicht