ASTM E2015-99

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
Designation:E2015–99
Standard Guide for
Preparation of Plastics and Polymeric Specimens for
Microstructural Examination
This standard is issued under the fixed designation E 2015; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.3 plastic(s)—a material that contains as an essential
ingredient one or more organic polymeric substances of large
1.1 This guide covers recommended procedures and guide-
molecular weight; is solid in its finished state; and at some
linesforthepreparationofplasticandpolymericspecimensfor
stageinitsmanufactureorprocessingintofinishedarticles,can
microstructural examination by light and electron microscopy.
be shaped by flow.
1.2 This guide is applicable to most semi-rigid and rigid
3.1.4 polymer(s)—asubstanceconsistingofmoleculeschar-
plastics, including engineering plastics. This guide is also
acterized by the repetition (neglecting ends, branch junctions,
applicable to some non-rigid plastics.
and other minor irregularities) of one or more types of
1.3 The procedures and guidelines presented in this guide
monomeric units.
are those which generally produce satisfactory specimens.This
guide does not describe the variations in techniques required to
4. Significance and Use
solve individual problems.
4.1 One of the fundamental objectives of microstructural
1.4 Many detailed descriptions of grinding and polishing of
2 examination of manufactured materials, especially plastics and
plastics and polymers are available (1-7).
polymers, is to gain a more complete understanding of the
1.5 This standard does not purport to address all of the
relationships between the manufacturing processes, the micro-
safety concerns, if any, associated with its use. It is the
structure and texture of the material, and the product’s perfor-
responsibility of the user of this standard to establish appro-
mance (that is, physical, optical, or mechanical properties, or
priate safety and health practices and determine the applica-
combination thereof). Under nearly all conditions, the proper
bility of regulatory limitations prior to use.
selection and preparation of the specimen are of major impor-
2. Referenced Documents tance.
4.2 Because of the wide range of available equipment;
2.1 ASTM Standards:
3 physical,chemical,andmechanicalpropertiesofmaterials;and
D 883 Terminology Relating to Plastics
the personal element, specimen preparation is an art based
E 3 Methods of Preparation of Metallographic Specimens
4 upon scientific principles. However, like metallographic speci-
E 7 Terminology Relating to Metallography
men preparation, certain methods, practices, and procedures
3. Terminology can be used to routinely produce acceptable quality plastic and
polymeric specimens for microstructural examination.Accept-
3.1 Definitions:
able quality means:
3.1.1 For definitions used in this guide of terms directly
4.2.1 The observed microstructure is free of thermal, me-
related to metallography, refer to TerminologyE7.
chanical,andchemicalalterations,artifacts,damage,ordefects
3.1.2 For definitions used in this guide of terms directly
resulting from the specimen preparation process.
related to plastics and polymers, refer to Engineering Materials
4.2.2 A surface finish appropriate for the microscopical
Handbook, Vol 2 (8) and Terminology D 883.
techniques to be used.
4.2.3 The microstructure is reproducibly displayed for a
given specimen.
This test method is under the jurisdiction of ASTM Committee E-4 on
4.3 The mounting, sectioning, grinding, and polishing pro-
Metallography and is the direct responsibility of Subcommittee E04.01 on Sam-
cedures in this guide may introduce thermal, mechanical, and
pling, Specimen Preparation, and Photography.
Current edition approved May 10, 1999. Published July 1999.
chemical stresses on the material being prepared for micro-
The boldface numbers in parentheses refer to the list of references at the end of
structural examination. Thus, knowledge of the material’s
this standard.
physical, mechanical, and chemical properties is of importance
Annual Book of ASTM Standards, Vol 08.01.
Annual Book of ASTM Standards, Vol 03.01. in selecting the most appropriate technique(s) to reveal its true
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
E2015–99
microstructure and to minimize the total number of steps 8. Preliminary Sectioning and Mounting of Specimens
needed to produce high quality polished specimens.
8.1 Contrary to traditional metallographic procedures, small
4.4 The general guidelines presented below will need to be
specimens or parts, or both, with the plane of interest not
modified for each type of plastic or polymer to be prepared.
parallel to a flat surface may require mounting prior to
Table X1.1 presents general procedures for preparing plastics
sectioning to facilitate sectioning of the specimen parallel to
and polymers. Tables X1.2-X1.5 present procedures for pre-
the desired plane to be polished. Also, laminated, friable, or
paring four polymers with very different mechanical proper-
very ductile materials may be mounted prior to section to
ties.
minimize damage during sectioning.
8.2 In general, specimens should be mounted for sectioning,
5. Selection of Specimens
grinding, and polishing. Mounted specimens are typically
5.1 The selection of test specimens is extremely important
easier to handle and less susceptible to damage. Specimens are
and dependent upon the purpose of the examination, the
usually mounted in castable resins but may also be mechani-
material, and the microscopical technique to be used. The
cally mounted. For very soft, flexible materials, it is often
principles of specimen selection presented in Methods E3
necessary to use a combination of mechanical mounting and
should be used as a primary guide for the selection of a plastic
mounting in a castable resin. Compression mounting in ther-
or polymeric test specimen.
moplastic or thermosetting plastic is generally not recom-
5.2 The selection criteria must include the following con-
mended but may be suitable for high temperature engineering
siderations:
plastics.
5.2.1 The size or scale of homogeneity/heterogeneity of all
8.3 Preliminary sectioning may be necessary prior to
structures, textures, and other features within the material
mounting.Thisisusuallyaccomplishedbycuttingorsawingof
being studied;
the unmounted part (see Section 9).These cuts should be made
5.2.2 The size or scale and distribution of the structures to
sufficiently far from the area of interest to minimize damage
be studied;
due to sectioning yet close enough to minimize the next
5.2.3 The microscopical technique(s) to be used; and
material removal step.
5.2.4 The need for control/reference specimens.
8.4 The pre-sectioned specimen must be thoroughly cleaned
5.3 Once the specimen locations have been selected, these
and dried to remove any debris and oils from the suface that
locations should be well documented. Macrographs or micro-
might inhibit the wetting and adhesion of the mounting
graphs, or both, of the specimen locations along with brief
medium to the specimen surface.
specimen location descriptions accompanying the written re-
8.5 Inmanycases,theremaybesomereactivitybetweenthe
sults are usually sufficient.
mounting medium and the specimen. Coating the specimen
with a 20 to 60-nm thick metal film of gold or gold/palladium
6. Size of Specimens
provides an excellent barrier between the mounting medium
6.1 The grinding and polishing procedures presented in this
and the specimen. This metal coating also acts as an interface
guide require the use of automated grinding and polishing
that will improve the adhesion of the mounting medium to the
equipment. Therefore, the specimen size will be limited by the
specimen. The sputter coaters and vapor deposition coaters
holders available for the equipment to be used.
used to prepare conductive coatings for electron microscopy
7. Cleaning of Specimens specimens work very well for this application. In some cases,
electrolessplatingcanbeusedtoproducemetalcoatingsonthe
7.1 Most plastics and polymers are very soft and subject to
plastics and polymers.
abrasionfromdebrisproducedduringsectioning,grinding,and
8.6 Room temperature-cured, castable resins are generally
polishing. In addition, oils and other surface films inhibit
used to encapsulate plastic and polymeric specimens.
uniform coating and adhesion of the mounting resin to the
8.6.1 It is critical that the manufacturer’s recommended
specimen surface. Therefore, it is essential that the specimen
mixing proportions be followed precisely and that mixing of
and all specimen preparation surfaces be kept as clean as
the components be thorough so that uniform and reproducible
possible. Thorough cleaning after each grinding and polishing
results will be achieved.
step will minimize contamination from the carry-over of
8.6.2 Moldsforcastableresinscanbeeasilyproducedinthe
coarser abrasives and debris that may cause damage during the
laboratory and a wide variety of shapes and compositions are
next preparation step.
available from various manufacturers. The molds may be
7.2 The least aggressive solution, which effectively cleans
reusable or not; the choice is a matter of convenience and cost.
the specimen surface, should be used.This requires knowledge
Handling of these resins requires care. They all can cause
of the specimen’s reactivity in potential cleaning solutions. For
dermatitis as well as other problems.
many plastic and polymeric materials, cleaning with an aque-
8.6.3 Styrene, latex, or other plastic spheres or particles can
ous solution of dish soap is very effective. However, some
be mixed into the mounting resin to modify the mechanical
plastics and polymers are subject to physical and chemical
properties of the cured resin to more closely match those of the
changes when placed in contact with aqueous solutions.
specimen.
7.3 The use of ultrasonic baths to promote cleaning is
usually an acceptable practice. However, materials such as 8.6.4 Many plastics and polymers tend to float in the
partially cured resins may be damaged by excessive cavitation mounting resins. Floating can be inhibited by placing a
in ultrasonic cleaning. phenolic or other ringform on adhesive tape or by placing
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
E2015–99
double-sided adhesive tape on the interior bottom of the mold, removal rate. The blade speed should provide high removal
then attaching the specimen to the adhesive inside the ringform rate without causing a significant temperature rise in the
or mold and covering it with the mounting resin. Floating can
specimen. A non-reactive coolant/lubricant, which contains a
also be inhibited by partially surrounding the specimen with surfactant, will allow for high blade speeds, faster cutting, and
themountingresinandallowingtheresintopartiallycure,then
minimal damage. The effectiveness of abrasive cut-off wheels
repeating this step one or more times until the specimen is
can be greatly improved by rotating the specimen about an axis
completely encased in mounting resin.
that is parallel to the axis of rotation of the cut-off wheel.
8.6.5 Many plastic and polymeric materials may be dam-
9.2 For machine assisted cutting or sectioning, it is always
aged by the heat produced during curing of castable resins.
advisable to orient the specimen so that the blade, cutting tool,
This can be minimized or eliminated by using the smallest
orabrasivewheelmovesfromtheweakestorleastsupportedto
volume of resin necessary to encapsulate the specimen and by
strongest or best supported portion of the specimen while
placing the mounted specimen in a refrigerator or ice bath
presenting the smallest cross-sectional area to the cutting tool.
while the resin cures.
9.3 Carefully inspect the cleaned, cut face of mounted
8.7 Vacuum impregnation is a recommended method for
porous specimens. If the cut face exhibits open pores, re-
ensuring high quality mounts.
impregnate the surface with a small amount of the mounting
8.8 The contrast between the specimen and castable mount-
resin.
ing resin is often quite poor, making it difficult to identify
edges or study edge structures. A thick (>100 nm) metal
10. Grinding
coating ( see section 8.5) will help improve the contrast at the
specimen-resin interface. Another approach is to charge the
10.1 The principles of grinding and polishing presented in
resin with a fluorescent dye, such as fluorescein.
Methods E3 should be used for plastics and polymers to
produce a flat polished surface that allows the true microstruc-
9. Cutting or Sectioning of Specimens
ture of the specimen to be examined. In general, grinding is
9.1 In general, sectioning should produce a flat, relatively
used to remove material in order to expose the region of
damage-free surface very near to the region of interest.
interest while producing a flat surface and removing the
9.1.1 Cuttingwithasharpblade,scalpel,knife,orscissorsis
deformation caused by the preceding sectioning and mounting
one of the fastest and most common methods for sectioning
steps.
plastic and polymer films, tubing, and thin flexible parts. This
10.2 Handpolishingmaybeusedinsomeinstancesforrigid
technique will introduce a strain (typically dominated by
engineering plastics. Automated polishing systems with speci-
ductile deformation) in the region near the cut face. The width
men holders that hold the specimen against rotating disks
of the strain region can be minimized by properly securing the
permit automated grinding and polishing to yield surfaces that
sampleduringcutting,usingasharpinstrument,makingthecut
are superior to hand polished specimen surfaces.
with uniform speed and force, and making the cut at the
10.3 The mounted specimen should be examined frequently
appropriate temperature (often below room temperature). The
during grinding to ensure that material removal does not go
cut face from a (cryogenically)microtomed specimen is often
beyond the region of interest.
ready for microstructural examination with minimal final
polishing or without additional preparation. 10.4 Grinding is often s
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