ASTM E2015-04(2021)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2015 − 04 (Reapproved 2021)
Standard Guide for
Preparation of Plastics and Polymeric Specimens for
Microstructural Examination
This standard is issued under the fixed designation E2015; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This guide covers recommended procedures and guide- 3.1 Definitions:
linesforthepreparationofplasticandpolymericspecimensfor 3.1.1 For definitions used in this guide of terms directly
microstructural examination by light and electron microscopy. related to metallography, refer to Terminology E7.
3.1.2 For definitions used in this guide of terms directly
1.2 This guide is applicable to most semi-rigid and rigid
related to plastics and polymers, refer to Engineering Materials
plastics, including engineering plastics. This guide is also
Handbook, Vol 2 (8) and Terminology D883.
applicable to some non-rigid plastics.
3.1.3 plastic(s)—a material that contains as an essential
1.3 The procedures and guidelines presented in this guide
ingredient one or more organic polymeric substances of large
are those which generally produce satisfactory specimens.This
molecular weight; is solid in its finished state; and at some
guide does not describe the variations in techniques required to
stageinitsmanufactureorprocessingintofinishedarticles,can
solve individual problems.
be shaped by flow.
1.4 Many detailed descriptions of grinding and polishing of
3.1.4 polymer(s)—a substance consisting of molecules char-
plastics and polymers are available (1-7).
acterized by the repetition (neglecting ends, branch junctions,
1.5 This standard does not purport to address all of the and other minor irregularities) of one or more types of
monomeric units.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Significance and Use
priate safety, health, and environmental practices and deter-
4.1 One of the fundamental objectives of microstructural
mine the applicability of regulatory limitations prior to use.
examination of manufactured materials, especially plastics and
1.6 This international standard was developed in accor-
polymers, is to gain a more complete understanding of the
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the relationships between the manufacturing processes, the micro-
structure and texture of the material, and the product’s perfor-
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical mance (that is, physical, optical, or mechanical properties, or
combination thereof). Under nearly all conditions, the proper
Barriers to Trade (TBT) Committee.
selection and preparation of the specimen are of major impor-
2. Referenced Documents tance.
2.1 ASTM Standards: 4.2 Because of the wide range of available equipment;
D883 Terminology Relating to Plastics physical,chemical,andmechanicalpropertiesofmaterials;and
E3 Guide for Preparation of Metallographic Specimens the personal element, specimen preparation is an art based
E7 Terminology Relating to Metallography upon scientific principles. However, like metallographic speci-
men preparation, certain methods, practices, and procedures
can be used to routinely produce acceptable quality plastic and
1 polymeric specimens for microstructural examination.Accept-
ThisguideisunderthejurisdictionofASTMCommitteeE04onMetallography
and is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.
able quality means:
Current edition approved Sept. 1, 2021. Published November 2021. Originally
4.2.1 The observed microstructure is free of thermal,
approved in 1999. Last previous edition approved in 2009 as E2015 – 04(2009).
mechanical, and chemical alterations, artifacts, damage, or
DOI: 10.1520/E2015-04R14.
defects resulting from the specimen preparation process.
The boldface numbers in parentheses refer to the list of references at the end of
this standard.
4.2.2 A surface finish appropriate for the microscopical
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
techniques to be used.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.2.3 The microstructure is reproducibly displayed for a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. given specimen.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2015 − 04 (2021)
4.3 The mounting, sectioning, grinding, and polishing pro- many plastic and polymeric materials, cleaning with an aque-
cedures in this guide may introduce thermal, mechanical, and ous solution of dish soap is very effective. However, some
chemical stresses on the material being prepared for micro- plastics and polymers are subject to physical and chemical
structural examination. Thus, knowledge of the material’s changes when placed in contact with aqueous solutions.
physical, mechanical, and chemical properties is of importance
7.3 The use of ultrasonic baths to promote cleaning is
in selecting the most appropriate technique(s) to reveal its true
usually an acceptable practice. However, materials such as
microstructure and to minimize the total number of steps
partially cured resins may be damaged by excessive cavitation
needed to produce high quality polished specimens.
in ultrasonic cleaning.
4.4 The general guidelines presented below will need to be
modified for each type of plastic or polymer to be prepared. 8. Preliminary Sectioning and Mounting of Specimens
Table X1.1 presents general procedures for preparing plastics
8.1 Contrary to traditional metallographic procedures, small
and polymers. Tables X1.2-X1.5 present procedures for pre-
specimens or parts, or both, with the plane of interest not
paring four polymers with very different mechanical proper-
parallel to a flat surface may require mounting prior to
ties.
sectioning to facilitate sectioning of the specimen parallel to
the desired plane to be polished. Also, laminated, friable, or
5. Selection of Specimens
very ductile materials may be mounted prior to section to
5.1 The selection of test specimens is extremely important
minimize damage during sectioning.
and dependent upon the purpose of the examination, the
8.2 In general, specimens should be mounted for sectioning,
material, and the microscopical technique to be used. The
grinding, and polishing. Mounted specimens are typically
principles of specimen selection presented in Practice E3
easier to handle and less susceptible to damage. Specimens are
should be used as a primary guide for the selection of a plastic
usually mounted in castable resins but may also be mechani-
or polymeric test specimen.
cally mounted. For very soft, flexible materials, it is often
5.2 The selection criteria must include the following con-
necessary to use a combination of mechanical mounting and
siderations:
mounting in a castable resin. Compression mounting in ther-
5.2.1 The size or scale of homogeneity/heterogeneity of all
moplastic or thermosetting plastic is generally not recom-
structures, textures, and other features within the material
mended but may be suitable for high temperature engineering
being studied;
plastics.
5.2.2 The size or scale and distribution of the structures to
8.3 Preliminary sectioning may be necessary prior to
be studied;
mounting.Thisisusuallyaccomplishedbycuttingorsawingof
5.2.3 The microscopical technique(s) to be used; and
the unmounted part (see Section 9).These cuts should be made
5.2.4 The need for control/reference specimens.
sufficiently far from the area of interest to minimize damage
5.3 Once the specimen locations have been selected, these
due to sectioning yet close enough to minimize the next
locations should be well documented. Macrographs or
material removal step.
micrographs, or both, of the specimen locations along with
8.4 The pre-sectioned specimen must be thoroughly cleaned
brief specimen location descriptions accompanying the written
and dried to remove any debris and oils from the suface that
results are usually sufficient.
might inhibit the wetting and adhesion of the mounting
6. Size of Specimens medium to the specimen surface.
6.1 The grinding and polishing procedures presented in this 8.5 Inmanycases,theremaybesomereactivitybetweenthe
guide require the use of automated grinding and polishing mounting medium and the specimen. Coating the specimen
equipment. Therefore, the specimen size will be limited by the with a 20 nm to 60 nm thick metal film of gold or gold/
holders available for the equipment to be used. palladium provides an excellent barrier between the mounting
medium and the specimen. This metal coating also acts as an
7. Cleaning of Specimens
interface that will improve the adhesion of the mounting
medium to the specimen. The sputter coaters and vapor
7.1 Most plastics and polymers are very soft and subject to
deposition coaters used to prepare conductive coatings for
abrasionfromdebrisproducedduringsectioning,grinding,and
electron microscopy specimens work very well for this appli-
polishing. In addition, oils and other surface films inhibit
cation. In some cases, electroless plating can be used to
uniform coating and adhesion of the mounting resin to the
produce metal coatings on the plastics and polymers.
specimen surface. Therefore, it is essential that the specimen
and all specimen preparation surfaces be kept as clean as
8.6 Room temperature-cured, castable resins are generally
possible. Thorough cleaning after each grinding and polishing
used to encapsulate plastic and polymeric specimens.
step will minimize contamination from the carry-over of
8.6.1 It is critical that the manufacturer’s recommended
coarser abrasives and debris that may cause damage during the
mixing proportions be followed precisely and that mixing of
next preparation step.
the components be thorough so that uniform and reproducible
7.2 The least aggressive solution, which effectively cleans results will be achieved.
the specimen surface, should be used.This requires knowledge 8.6.2 Moldsforcastableresinscanbeeasilyproducedinthe
of the specimen’s reactivity in potential cleaning solutions. For laboratory and a wide variety of shapes and compositions are
E2015 − 04 (2021)
available from various manufacturers. The molds may be the specimen and by presenting a minimum cross-sectional
reusable or not; the choice is a matter of convenience and cost. area of the part to the saw blade.
Handling of these resins requires care. They all can cause 9.1.3 Cuttingorsectioningmayalsobeaccomplishedbythe
dermatitis as well as other problems. use of an abrasive cut-off wheel. This technique generally
8.6.3 Styrene, latex, or other plastic spheres or particles can produces a cut surface with deformation that can be removed
be mixed into the mounting resin to modify the mechanical by fine grinding and polishing.Abrasive wheels with 80 grit to
properties of the cured resin to more closely match those of the 120 grit abrasive cut soft epoxies quickly but leave a rough
specimen. finish,oftenwitharelativelythicklayerofductiledeformation.
8.6.4 Many plastics and polymers tend to float in the Finer grit (240 and above) abrasive wheels cut soft epoxies
mounting resins. Floating can be inhibited by placing a quite slowly, tend to be quickly clogged with plastic or
phenolic or other ringform on adhesive tape or by placing polymer, and tend to wander. The force or load should be
double-sided adhesive tape on the interior bottom of the mold, sufficient to ensure a cutting or feed rate that is equal to the
then attaching the specimen to the adhesive inside the ringform removal rate. The blade speed should provide high removal
or mold and covering it with the mounting resin. Floating can rate without causing a significant temperature rise in the
also be inhibited by partially surrounding the specimen with specimen. A non-reactive coolant/lubricant, which contains a
themountingresinandallowingtheresintopartiallycure,then surfactant, will allow for high blade speeds, faster cutting, and
repeating this step one or more times until the specimen is minimal damage. The effectiveness of abrasive cut-off wheels
completely encased in mounting resin. canbegreatlyimprovedbyrotatingthespecimenaboutanaxis
8.6.5 Many plastic and polymeric materials may be dam- that is parallel to the axis of rotation of the cut-off wheel.
aged by the heat produced during curing of castable resins.
9.2 For machine assisted cutting or sectioning, it is always
This can be minimized or eliminated by using the smallest
advisable to orient the specimen so that the blade, cutting tool,
volume of resin necessary to encapsulate the specimen and by
orabrasivewheelmovesfromtheweakestorleastsupportedto
placing the mounted specimen in a refrigerator or ice bath
strongest or best supported portion of the specimen while
while the resin cures.
presenting the smallest cross-sectional area to the cutting tool.
8.7 Vacuum impregnation is a recommended method for
9.3 Carefully inspect the cleaned, cut face of mounted
ensuring high quality mounts.
porous specimens. If the cut face exhibits open pores, re-
8.8 The contrast between the specimen and castable mount- impregnate the surface with a small amount of the mounting
ing resin is often quite poor, making it difficult to identify resin.
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 colorant or fluorescent dye, such as fluorescein.
Practice 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
interest while producing a flat surface and removing the
damage-free surface very near to the region of interest.
9.1.1 Cuttingwithasharpblade,scalpel,knife,orscissorsis deformation caused by the preceding sectioning and mounting
steps.
one of the fastest and most common methods for sectioning
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 separated into two steps: rough and
9.1.2 Sawing either manually or by machine is generally a fine. However, rough grinding (240[P220] grit and coarser) is
convenient method for sectioning rigid plastics. Sawing pro- usually too aggressive for plastics and polymers.
duces a rather rough surface with a region of non-uniform 10.4.1 Typically a single grinding step using 15 µm fixed
strainthatisgenerallywiderthanthatproducedbycutting.The abrasive, such as 600(P1200)-grit SiC abrasive papers, is
deformation is often easily removed by the subsequent grind- sufficient to produce flat surfaces ready for polishing.
ing and polishing steps. The width of the deformation region 10.4.2 With proper sectioning and mounting, only moderate
can be minimized by choosing a sharp, fine, short-toothed pressures and short times are needed to complete the grinding.
2 2
blade; a feed rate equal to the material removal rate; a Pressuresfrom13800N/m to34500N/m (2psito5psi)and
coolant/lubricant that is non-reactive with the specimen; and a effective wheel (12 in. diameter) speeds from 90 rpm to
bladespeedthatdoesnotcauseasignificanttemperaturerisein 150 rpm are common.
E2015 − 04 (2021)
10.4.3 Thespecimensurfaceshouldbeinspectedafterevery 11.5.1 Six or nine micrometer abrasive is often an appro-
15 s to 30 s of grinding to monitor material removal and priate starting point for the first step in rough polishing
...