ASTM E2015-04(2014)

Standard Guide for Preparation of Plastics and Polymeric Specimens for Microstructural Examination

SIGNIFICANCE AND USE
4.1 One of the fundamental objectives of microstructural examination of manufactured materials, especially plastics and polymers, is to gain a more complete understanding of the relationships between the manufacturing processes, the microstructure and texture of the material, and the product's performance (that is, physical, optical, or mechanical properties, or combination thereof). Under nearly all conditions, the proper selection and preparation of the specimen are of major importance.  
4.2 Because of the wide range of available equipment; physical, chemical, and mechanical properties of materials; and the personal element, specimen preparation is an art based upon scientific principles. However, like metallographic specimen preparation, certain methods, practices, and procedures can be used to routinely produce acceptable quality plastic and polymeric specimens for microstructural examination. Acceptable quality means:  
4.2.1 The observed microstructure is free of thermal, mechanical, and chemical alterations, artifacts, damage, or defects resulting from the specimen preparation process.  
4.2.2 A surface finish appropriate for the microscopical techniques to be used.  
4.2.3 The microstructure is reproducibly displayed for a given specimen.  
4.3 The mounting, sectioning, grinding, and polishing procedures in this guide may introduce thermal, mechanical, and chemical stresses on the material being prepared for microstructural examination. Thus, knowledge of the material's physical, mechanical, and chemical properties is of importance in selecting the most appropriate technique(s) to reveal its true microstructure and to minimize the total number of steps needed to produce high quality polished specimens.  
4.4 The general guidelines presented below will need to be modified for each type of plastic or polymer to be prepared. Table X1.1 presents general procedures for preparing plastics and polymers. Tables X1.2-X1.5 present procedures for preparing four ...
SCOPE
1.1 This guide covers recommended procedures and guidelines for the preparation of plastic and polymeric specimens for microstructural examination by light and electron microscopy.  
1.2 This guide is applicable to most semi-rigid and rigid plastics, including engineering plastics. This guide is also applicable to some non-rigid plastics.  
1.3 The procedures and guidelines presented in this guide are those which generally produce satisfactory specimens. This guide does not describe the variations in techniques required to solve individual problems.  
1.4 Many detailed descriptions of grinding and polishing of plastics and polymers are available (1-7).2  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 30-Sep-2014
• ICS: 83.140.99 - Other rubber and plastics products
• Technical Committee: E04 - Metallography
• Drafting Committee: E04.01 - Specimen Preparation

Standards Content (Sample)

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 − 04 (Reapproved 2014)
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 3.1.2 For definitions used in this guide of terms directly
related to plastics and polymers, refer to Engineering Materials
1.1 This guide covers recommended procedures and guide-
Handbook, Vol 2 (8) and Terminology D883.
linesforthepreparationofplasticandpolymericspecimensfor
3.1.3 plastic(s)—a material that contains as an essential
microstructural examination by light and electron microscopy.
ingredient one or more organic polymeric substances of large
1.2 This guide is applicable to most semi-rigid and rigid
molecular weight; is solid in its finished state; and at some
plastics, including engineering plastics. This guide is also
stageinitsmanufactureorprocessingintofinishedarticles,can
applicable to some non-rigid plastics.
be shaped by flow.
1.3 The procedures and guidelines presented in this guide
3.1.4 polymer(s)—a substance consisting of molecules char-
are those which generally produce satisfactory specimens.This
acterized by the repetition (neglecting ends, branch junctions,
guide does not describe the variations in techniques required to
and other minor irregularities) of one or more types of
solve individual problems.
monomeric units.
1.4 Many detailed descriptions of grinding and polishing of
4. Significance and Use
plastics and polymers are available (1-7).
4.1 One of the fundamental objectives of microstructural
1.5 This standard does not purport to address all of the
examination of manufactured materials, especially plastics and
safety concerns, if any, associated with its use. It is the
polymers, is to gain a more complete understanding of the
responsibility of the user of this standard to establish appro-
relationships between the manufacturing processes, the micro-
priate safety and health practices and determine the applica-
structure and texture of the material, and the product’s perfor-
bility of regulatory limitations prior to use.
mance (that is, physical, optical, or mechanical properties, or
combination thereof). Under nearly all conditions, the proper
2. Referenced Documents
selection and preparation of the specimen are of major impor-
tance.
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
4.2 Because of the wide range of available equipment;
E3 Guide for Preparation of Metallographic Specimens
physical,chemical,andmechanicalpropertiesofmaterials;and
E7 Terminology Relating to Metallography
the personal element, specimen preparation is an art based
upon scientific principles. However, like metallographic speci-
3. Terminology
men preparation, certain methods, practices, and procedures
can be used to routinely produce acceptable quality plastic and
3.1 Definitions:
polymeric specimens for microstructural examination.Accept-
3.1.1 For definitions used in this guide of terms directly
able quality means:
related to metallography, refer to Terminology E7.
4.2.1 The observed microstructure is free of thermal,
mechanical, and chemical alterations, artifacts, damage, or
defects resulting from the specimen preparation process.
ThisguideisunderthejurisdictionofASTMCommitteeE04onMetallography
4.2.2 A surface finish appropriate for the microscopical
and is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.
techniques to be used.
Current edition approved Oct. 1, 2014. Published December 2014. Originally
approved in 1999. Last previous edition approved in 2009 as E2015 – 04(2009).
4.2.3 The microstructure is reproducibly displayed for a
DOI: 10.1520/E2015-04R14.
given specimen.
The boldface numbers in parentheses refer to the list of references at the end of
this standard.
4.3 The mounting, sectioning, grinding, and polishing pro-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
cedures in this guide may introduce thermal, mechanical, and
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
chemical stresses on the material being prepared for micro-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. structural examination. Thus, knowledge of the material’s
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2015 − 04 (2014)
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
8. Preliminary Sectioning and Mounting of Specimens
modified for each type of plastic or polymer to be prepared.
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
minimize damage during sectioning.
5.1 The selection of test specimens is extremely important
and dependent upon the purpose of the examination, the
8.2 Ingeneral,specimensshouldbemountedforsectioning,
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
medium to the specimen surface.
6. Size of Specimens
8.5 Inmanycases,theremaybesomereactivitybetweenthe
6.1 The grinding and polishing procedures presented in this
mounting medium and the specimen. Coating the specimen
guide require the use of automated grinding and polishing
with a 20 to 60-nm thick metal film of gold or gold/palladium
equipment. Therefore, the specimen size will be limited by the
provides an excellent barrier between the mounting medium
holders available for the equipment to be used.
and the specimen. This metal coating also acts as an interface
7. Cleaning of Specimens
that will improve the adhesion of the mounting medium to the
specimen. The sputter coaters and vapor deposition coaters
7.1 Most plastics and polymers are very soft and subject to
used to prepare conductive coatings for electron microscopy
abrasionfromdebrisproducedduringsectioning,grinding,and
specimens work very well for this application. In some cases,
polishing. In addition, oils and other surface films inhibit
electrolessplatingcanbeusedtoproducemetalcoatingsonthe
uniform coating and adhesion of the mounting resin to 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
results will be achieved.
7.2 The least aggressive solution, which effectively cleans
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
many plastic and polymeric materials, cleaning with an aque- available from various manufacturers. The molds may be
ous solution of dish soap is very effective. However, some reusable or not; the choice is a matter of convenience and cost.
plastics and polymers are subject to physical and chemical Handling of these resins requires care. They all can cause
changes when placed in contact with aqueous solutions. dermatitis as well as other problems.
E2015 − 04 (2014)
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 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
thenattachingthespecimentotheadhesiveinsidetheringform 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
coating ( see section 8.5) will help improve the contrast at the
10. Grinding
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
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
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2015 − 04 (Reapproved 2009) E2015 − 04 (Reapproved 2014)
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
1.1 This guide covers recommended procedures and guidelines for the preparation of plastic and polymeric specimens for
microstructural examination by light and electron microscopy.
1.2 This guide is applicable to most semi-rigid and rigid plastics, including engineering plastics. This guide is also applicable
to some non-rigid plastics.
1.3 The procedures and guidelines presented in this guide are those which generally produce satisfactory specimens. This guide
does not describe the variations in techniques required to solve individual problems.
1.4 Many detailed descriptions of grinding and polishing of plastics and polymers are available (1-7).
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
E3 Guide for Preparation of Metallographic Specimens
E7 Terminology Relating to Metallography
3. Terminology
3.1 Definitions:
3.1.1 For definitions used in this guide of terms directly related to metallography, refer to Terminology E7.
3.1.2 For definitions used in this guide of terms directly related to plastics and polymers, refer to Engineering Materials
Handbook, Vol 2 (8) and Terminology D883.
3.1.3 plastic(s)—a material that contains as an essential ingredient one or more organic polymeric substances of large molecular
weight; is solid in its finished state; and at some stage in its manufacture or processing into finished articles, can be shaped by flow.
3.1.4 polymer(s)—a substance consisting of molecules characterized by the repetition (neglecting ends, branch junctions, and
other minor irregularities) of one or more types of monomeric units.
4. Significance and Use
4.1 One of the fundamental objectives of microstructural examination of manufactured materials, especially plastics and
polymers, is to gain a more complete understanding of the relationships between the manufacturing processes, the microstructure
and texture of the material, and the product’s performance (that is, physical, optical, or mechanical properties, or combination
thereof). Under nearly all conditions, the proper selection and preparation of the specimen are of major importance.
4.2 Because of the wide range of available equipment; physical, chemical, and mechanical properties of materials; and the
personal element, specimen preparation is an art based upon scientific principles. However, like metallographic specimen
This guide is under the jurisdiction of ASTM Committee E04 on Metallography and is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.
Current edition approved May 1, 2009Oct. 1, 2014. Published September 2009December 2014. Originally approved in 1999. Last previous edition approved in 20042009
as E2015 – 04.04(2009). DOI: 10.1520/E2015-04R09.10.1520/E2015-04R14.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2015 − 04 (2014)
preparation, certain methods, practices, and procedures can be used to routinely produce acceptable quality plastic and polymeric
specimens for microstructural examination. Acceptable quality means:
4.2.1 The observed microstructure is free of thermal, mechanical, and chemical alterations, artifacts, damage, or defects
resulting from the specimen preparation process.
4.2.2 A surface finish appropriate for the microscopical techniques to be used.
4.2.3 The microstructure is reproducibly displayed for a given specimen.
4.3 The mounting, sectioning, grinding, and polishing procedures in this guide may introduce thermal, mechanical, and
chemical stresses on the material being prepared for microstructural examination. Thus, knowledge of the material’s physical,
mechanical, and chemical properties is of importance in selecting the most appropriate technique(s) to reveal its true microstructure
and to minimize the total number of steps needed to produce high quality polished specimens.
4.4 The general guidelines presented below will need to be modified for each type of plastic or polymer to be prepared. Table
X1.1 presents general procedures for preparing plastics and polymers. Tables X1.2-X1.5 present procedures for preparing four
polymers with very different mechanical properties.
5. Selection of Specimens
5.1 The selection of test specimens is extremely important and dependent upon the purpose of the examination, the material,
and the microscopical technique to be used. The principles of specimen selection presented in Practice E3 should be used as a
primary guide for the selection of a plastic or polymeric test specimen.
5.2 The selection criteria must include the following considerations:
5.2.1 The size or scale of homogeneity/heterogeneity of all structures, textures, and other features within the material being
studied;
5.2.2 The size or scale and distribution of the structures to be studied;
5.2.3 The microscopical technique(s) to be used; and
5.2.4 The need for control/reference specimens.
5.3 Once the specimen locations have been selected, these locations should be well documented. Macrographs or micrographs,
or both, of the specimen locations along with brief specimen location descriptions accompanying the written results are usually
sufficient.
6. Size of Specimens
6.1 The grinding and polishing procedures presented in this guide require the use of automated grinding and polishing
equipment. Therefore, the specimen size will be limited by the holders available for the equipment to be used.
7. Cleaning of Specimens
7.1 Most plastics and polymers are very soft and subject to abrasion from debris produced during sectioning, grinding, and
polishing. In addition, oils and other surface films inhibit uniform coating and adhesion of the mounting resin to the specimen
surface. Therefore, it is essential that the specimen and all specimen preparation surfaces be kept as clean as possible. Thorough
cleaning after each grinding and polishing step will minimize contamination from the carry-over of coarser abrasives and debris
that may cause damage during the next preparation step.
7.2 The least aggressive solution, which effectively cleans the specimen surface, should be used. This requires knowledge of
the specimen’s reactivity in potential cleaning solutions. For many plastic and polymeric materials, cleaning with an aqueous
solution of dish soap is very effective. However, some plastics and polymers are subject to physical and chemical changes when
placed in contact with aqueous solutions.
7.3 The use of ultrasonic baths to promote cleaning is usually an acceptable practice. However, materials such as partially cured
resins may be damaged by excessive cavitation in ultrasonic cleaning.
8. Preliminary Sectioning and Mounting of Specimens
8.1 Contrary to traditional metallographic procedures, small specimens or parts, or both, with the plane of interest not parallel
to a flat surface may require mounting prior to sectioning to facilitate sectioning of the specimen parallel to the desired plane to
be polished. Also, laminated, friable, or very ductile materials may be mounted prior to section to minimize damage during
sectioning.
8.2 In general, specimens should be mounted for sectioning, grinding, and polishing. Mounted specimens are typically easier
to handle and less susceptible to damage. Specimens are usually mounted in castable resins but may also be mechanically mounted.
For very soft, flexible materials, it is often necessary to use a combination of mechanical mounting and mounting in a castable
resin. Compression mounting in thermoplastic or thermosetting plastic is generally not recommended but may be suitable for high
temperature engineering plastics.
E2015 − 04 (2014)
8.3 Preliminary sectioning may be necessary prior to mounting. This is usually accomplished by cutting or sawing of the
unmounted part (see Section 9). These cuts should be made sufficiently far from the area of interest to minimize damage due to
sectioning yet close enough to minimize the next material removal step.
8.4 The pre-sectioned specimen must be thoroughly cleaned and dried to remove any debris and oils from the suface that might
inhibit the wetting and adhesion of the mounting medium to the specimen surface.
8.5 In many cases, there may be some reactivity between the mounting medium and the specimen. Coating the specimen with
a 20 to 60-nm thick metal film of gold or gold/palladium provides an excellent barrier between the mounting medium and the
specimen. This metal coating also acts as an interface that will improve the adhesion of the mounting medium to the specimen.
The sputter coaters and vapor deposition coaters used to prepare conductive coatings for electron microscopy specimens work very
well for this application. In some cases, electroless plating can be used to produce metal coatings on the plastics and polymers.
8.6 Room temperature-cured, castable resins are generally used to encapsulate plastic and polymeric specimens.
8.6.1 It is critical that the manufacturer’s recommended mixing proportions be followed precisely and that mixing of the
components be thorough so that uniform and reproducible results will be achieved.
8.6.2 Molds for castable resins can be easily produced in the laboratory and a wide variety of shapes and compositions are
available from various manufacturers. The molds may be reusable or not; the choice is a matter of convenience and cost. Handling
of these resins requires care. They all can cause dermatitis as well as other problems.
8.6.3 Styrene, latex, or other plastic spheres or particles can be mixed into the mounting resin to modify the mechanical
properties of the cured resin to more closely match those of the specimen.
8.6.4 Many plastics and polymers tend to float in the mounting resins. Floating can be inhibited by placing a phenolic or other
ringform on adhesive tape or by placing double-sided adhesive tape on the interior bottom of the mold, then attaching the specimen
to the adhesive inside the ringform or mold and covering it with the mounting resin. Floating can also be inhibited by partially
surrounding the specimen with the mounting resin and allowing the resin to partially cure, then repeating this step one or more
times until the specimen is completely encased in mounting resin.
8.6.5 Many plastic and polymeric materials may be damaged by the heat produced during curing of castable resins. This can
be minimized or eliminated by using the smallest volume of resin necessary to encapsulate the specimen and by placing the
mounted specimen in a refrigerator or ice bath while the resin cures.
8.7 Vacuum impregnation is a recommended method for ensuring high quality mounts.
8.8 The contrast between the specimen and castable mounting resin is often quite poor, making it difficult to identify edges or
study edge structures. A thick (>100 nm) metal coating ( see section 8.5) will help improve the contrast at the specimen-resin
interface. Another approach is to charge the resin with a colorant or fluorescent dye, such as fluorescein.
9. Cutting or Sectioning of Specimens
9.1 In general, sectioning should produce a flat, relatively damage-free surface very near to the region of interest.
9.1.1 Cutting with a sharp blade, scalpel, knife, or scissors is one of the fastest and most common methods for sectioning plastic
and polymer films, tubing, and thin flexible parts. This technique will introduce a strain (typically dominated by ductile
deformation) in the region near the cut face. The width of the strain region can be minimized by properly securing the sample
during cutting, using a sharp instrument, making the cut with uniform speed and force, and making the cut at the appropriate
temperature (often below room temperature). The cut face from a (cryogenically)microtomed specimen is often ready for
microstructural examination with minimal final polishing or without additional preparation.
9.1.2 Sawing either manually or by machine is generally a convenient method for sectioning rigid plastics. Sawing produces
a rather rough surface with a region of non-uniform strain that is generally wider than that produced by cutting. The deformation
is often easily removed by the subsequent grinding and polishing steps. The width of the deformation region can be minimized
by choosing a sharp, fine, short-toothed blade; a feed rate equal to the material removal rate; a coolant/lubricant that is non-reactive
with the specimen; and a blade speed that does not cause a significant temperature rise in the specimen and by presenting a
minimum cross-sectional area of the part to the saw blade.
9.1.3 Cutting or sectioning may also be accomplished by the use of an abrasive cut-off wheel. This technique generally produces
a cut surface with deformation that can be removed by fine grinding and polishing. Abrasive wheels with 80 to 120-grit abrasive
cut soft epoxies quickly but leave a rough finish, often with a relatively thick layer of ductile deformation. Finer grit (240 and
above) abrasive wheels cut soft epoxies quite slowly, tend to be quickly clogged with plastic or polymer, and tend to wander. The
force or load should be sufficient to ensure a cutting or feed rate that is equal to the removal rate. The blade speed should provide
high removal rate without causing a significant temperature rise in the spe
...