CHEMISTRY

and start over. All these cases can be solved with

the help of cyanoacrylate adhesive removers.

Simply applying this liquid to the glued joint

will, over a few dozen seconds, help to separate

wrongly adhered parts, but it is always better to

take an active approach to cleaning and ungluing

parts and removing the glue using a debonder.

Probably the most suitable tool for cleaning parts

from cyanoacrylate glue is the use of cotton

swabs dipped in the remover. Traces of the glue

are removed by gently rubbing

the area with a moistened swab

until we are satisfied with the

appearance of the fixed area.

Since the glue dissolves under

the cotton swab and clogs the

cotton tip, depending on the

extent and amount of glue to be

removed, it is advisable to use

several applications with clean

swabs, as required. For areas

that are difficult to access or

areas with a broken surface, it is

appropriate to use fine brushes,

that have been relegated

specifically for this purpose after

serving out their usefulness as

paint applicators. Inexpensive

brushes from art supply stores

or hobby shops will suffice for

these needs. When choosing a cyanoacrylate

adhesive remover, or debonder, it is good to

check to make sure that the type doesn’t etch the

plastic of the model, as some will.

EPOXY TYPE ADHESIVES

Epoxy glues, which consist of two components,

are also included among the glues that

are commonly found in plastic modelling.

The principle and application of this class of

adhesive is very simple. After mixing both

components in the specified ratio, usually

one to one, a chemical reaction occurs, the

observable start of which begins after a few

dozen seconds. Subsequently, the mixed

components harden very quickly. Epoxy glues

are especially suitable for hard materials, which

underlines the suitability of their use in plastic

modelling. Their biggest advantage is that after

curing, they do not leave visible traces in the

form of fume production in their local vicinity,

as in the case of instant glues, and are thus

a big help when gluing larger models, especially

if they are made of a polyurethane or laminate.

Such types of models cannot be glued with

solvent type glues, which we detailed in the first

part of this article, and epoxy two-part glues are

a suitable alternative for gluing together large

surfaces and eliminating the shortcomings of

cyanoacrylate glues. Another good use of these

types of adhesives is joint reinforcement along

invisible join lines, allowing any required thinning

of plastic parts in preparation for the installation

April 2023

of aftermarket accessory sets. A general

shortcoming is their apparent softness compared

to hard cyanoacrylate joints, and therefore they

are sand poorly. Currently, there are already

special two-component epoxy adhesives with

additional additives on the market that can

minimize these shortcomings.

DISPERSION TYPE ADHESIVES

As in the previous cases, we will explain what

dispersion adhesives are and what they are

suitable for in plastic modelling. A common

mistake in the definition of dispersion adhesives

is that they are a solution consisting of a polymer

in water. In fact, it is a mixture of polymer with

water, whereby the aforementioned polymer is

not dissolved, but only perfectly dispersed in the

resulting emulsion. Dispersion adhesives have

a milky white color that gradually fades to clear as

it hardens. The white color is therefore not caused

by any pigment, but by small polymer particles that

scatter light and create that ‘milky effect’. Many

dispersion adhesives can be diluted as needed

with water (non-waterproof dispersion adhesives

such as those produced by Herkules) and thus

create a liquid that can be embedded into porous

surfaces to attach individual details. A typical

example is the simulation of natural surfaces in

the creation of dioramas. The opposite is the case

of dispersion water-resistant adhesives, which

have a substantially higher dry matter content

of the polymer and are therefore not as thin as

adhesives that can be diluted with water. Dilution

of these adhesives is only possible to a small

amount, to some 5% and always only with distilled

cold water; otherwise precipitates will form. At the

same time, if we let such diluted glue stand, the

water will begin to separate. A higher dry matter

content of the polymer then means a higher

strength of the joints, and the adhesives thus have

up to 3 times greater strength (as in the case of,

for example, Herkules vs. PERFECT G Express).

Another difference compared to glues with

a lower dry matter content is their hardness and

the possibility of sanding the hardened glue. If we

use glues with a lower content of polymer solids,

when trying to sand, the glue starts to chew up

because it is soft. On the other hand, dispersion

adhesives with a higher proportion of polymer

solids are significantly harder after curing and

can be sanded. Here, however, it is important

to note that it is better to use coarser/sharper

sandpapers and to minimize friction, because

high friction creates a higher temperature, which

causes the glue to soften after setting, despite

its high percentage of polymer solids (i.e. D3/D4based glue).

PERFECT G Express glue

An example of dispersion PVAC glues is Bolt

Perfect G Express. The specific properties of this

glue make it suitable for porous materials such as

wood or paper, and it is therefore useful mainly for

the needs of creating dioramas or for attaching

accessories to models of combat equipment. The

benefit of this type of glue is mainly the shortened

curing time compared to classic dispersion glues

(for example Herkules, Tamiya Craft Bond, etc.),

which enables accelerated creation and thus

saves invested time. Specifically, the complete

drying time is between 5-15 minutes, depending

on the amount of glue and the extent of the glued

joint. As with other dispersions, the glue is white

in its liquid state and clear after curing. The high

dry matter polymer content of the in this type of

glue means above all the ability of the glued joint

to be stronger. Such a property is suitable for the

use of gluing clear parts on aircraft models. The

glue is thus a good compromise for those who

are afraid of damaging clear parts when gluing

them with solvent glues or, on the other hand,

are afraid of the fumes that are released from

cyanoacrylate glues. Gluing with a dispersion

adhesive is not as strong as compared to the

mentioned types of adhesives, but if we choose

a suitable dispersion adhesive with a higher

polymer dry matter content, we will also achieve

good bond strength.

SUMMARY

In the first two parts of our series focusing on

modelling chemistry and tips for beginners and

advanced modellers alike, we presented the

basic, readily available and commonly used types

of glues that can be used for plastic modelling.

All the mentioned types described in the first and

second parts of our series have their strengths

and weaknesses, and the use of all the mentioned

types of glues gives the plastic modeller the

ability to deal with constructing all conceivable

assemblies from various materials that they

might come up against. In the next part, we will

focus on tools and aids suitable for applying and

working with the types of glue presented thus far.

INFO Eduard

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