Metallographic Compression Mounting

COMPRESSION MOUNTING


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Compression mounts are quick and easy to produce, requiring several minutes at the appropriate mounting temperature. Most of the time required in compression mounting occurs in the heating and cooling stages. A number of manufacturers produce compression mounting machines with the better machines having the heater physically connected to the mounting chamber for rapid heating along with water jacket cooling. These machines vary between manufacturers and careful examination of the heating and cooling mechanisms should be noted.

Compression mounting resins include:




Compression Mounting Resin Properties

Phenolics

Acrylics

Epoxy (glass filled)

Diallyl Phthalates

Cost

Low

Moderate

Moderate

Moderate

Ease of use

Excellent

Moderate

Good

Good

Availability of colors

Yes

No

No

No

Cycle times

Excellent

Moderate

Good

Good

Edge retention

Fair

Good

Excellent

Excellent

Clarity

None

Excellent

None

None

Hardness

Low

Medium

High

High

Resin

Phenolic

Acrylic

Epoxy

Diallyl Phthalate

Form

Granular

Powder

Granular

Granular

Specific gravity
(gm/cm3)

1.4

0.95

1.75-2.05

1.7-1.9

Colors

Black, Red, Green

Clear

Black

Blue

Shrinkage (compression)(in/in)

0.006

 

0.001-0.003

0.001-0.003

Coefficient of Linear Thermal Expansion
(in/in/°C 10-6)

50

 

28

19

Chemical resistance

Glycol, petrochemicals, solvents, some acids and bases

Alcohol, dilute acids & alkalies, and oxidizers

Solvents, acids, alkalies

Solvents, acids, alkalies

Molding temperature

150°-165°C
(300°-330°F)

 

143°-177°C
(290°-350°F)

160°-177°C
(320°-350°F)

Molding pressure

21-28 Mpa
(3050-4000 psi)

 

17-28 MPA
(2500-4000 psi)

24-41 MPA
(3500-6000 psi)

Hardness

 

Rockwell M63

Barcol 72

 

Curing time
(1/2" mount @ temp.
and pressure)

90-120 seconds

2-4 minutes

90-120 seconds

90-120 seconds


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COMPRESSION MOUNTING PROCESS DESCRIPTION

Following cutting or sectioning the specimen is typically mounted. Mounting provides the following advantages:
Specimen mounting is accomplished with compression mounting resins (thermosets or thermoplastics.

Compression Mounting Resins

Heating (120-150° C)

Pressure (2500-3500 psi)

Requires compression mounting equipment


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RECOMMENDED COMPRESSION MOUNTING PROCEDURES
  1. Clean specimens to remove cutting and handling residues
  2. Remove debris from mold assembly
  3. Apply thin coat of mold release compound to mold assembly
  4. Raise mold ram to up position
  5. Center specimen on ram
  6. Lower ram assembly
  7. Pour predetermined amount of resin into mold
  8. Clean excess resin around mold assembly threads
  9. Lock mold assembly cover
  10. Slowly raise ram into up position
  11. Apply recommended heat and maintain pressure for specified period of time
  12. Cool to near room temperature
  13. Remove mounted specimen
  14. Clean mold and ram assembly
  15. Optional
    • Preheat resin and sample to 35°C (95°F) to expedite the initial heating process
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COMPRESSION MOUNTING TROUBLE SHOOTING

Symptom

Cause

Action

Large bubbles in acrylic resins

Insufficient mounting pressure

Increase mounting pressure or reduce temperature

Soft surfaces on mount

Mount did not completely polymerize because of polymer incompatibility with mold release or oil on the specimen surface

Clean specimen and mounting machine to remove incompatible coatings. Use a compatible mold release

Voids or cracks

High internal stress due to overly rapid cooling

Allow mounts to cool more slowly and longer

Haze around specimen (acrylic mounts)

Specimen contains moisture


Specimens contain copper or some other polymerization retarding alloy

Use a desiccator or low
temperature oven to dry specimen

Coat specimens with an appropriate lacquer before mounting

Phenolic dye leaching out with alcohol rinsing

Insufficient mounting temperature

Increase mounting temperature or service check heater element

Distortion or cracking of specimen

Autoclave pressure is too great for the specimen

Reduce mounting pressure or use a castable epoxy resin


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PRODUCT DESCRIPTIONS

PHENOLIC RESINS

Description

Quantity

Catalog Number

Phenolic powder - Black (wood flour)

5 lbs (2.3 kg)

CM-2001B-5

Phenolic powder - Black (wood flour)

25 lbs (11.4 kg)

CM-2001B-25

Phenolic powder - Red (wood flour)

5 lbs (2.3 kg)

CM-2001R-5

Phenolic powder - Red (wood flour)

25 lbs (11.4 kg)

CM-2001R-25

Phenolic powder - Green (wood flour)

5 lbs (2.3 kg)

CM-2001G-5

Phenolic powder - Green (wood flour)

25 lbs (11.4 kg)

CM-2001G-25

1.25-inch PHENOLIC PREFORMS

Description

Quantity

Catalog Number

1.25" Phenolic PREFORMS - Black

100/pkg

PCM-2125B-100

1.25" Phenolic PREFORMS - Black

500/pkg

PCM-2125B-500

1.25" Phenolic PREFORMS - Red

100/pkg

PCM-2125R-100

1.25" Phenolic PREFORMS - Red

500/pkg

PCM-2125R-500

1.25" Phenolic PREFORMS - Green

100/pkg

PCM-2125G-100

1.25" Phenolic PREFORMS - Green

500/pkg

PCM-2125G-500

1.50-inch PHENOLIC PREFORMS

Description

Quantity

Catalog Number

1.50" Phenolic PREFORMS - Black

100/pkg

PCM-2150B-100

1.50" Phenolic PREFORMS - Black

100/pkg

PCM-2150B-500

1.50" Phenolic PREFORMS - Red

100/pkg

PCM-2150R-100

1.50" Phenolic PREFORMS - Red

100/pkg

PCM-2150R-500

1.50" Phenolic PREFORMS - Green

100/pkg

PCM-2150G-100

1.50" Phenolic PREFORMS - Green

100/pkg

PCM-2150G-500

TRANSACRYLIC COMPRESSION MOUNTING RESIN

Description

Quantity

Catalog Number

TRANSACRYLIC Resin powder (transparent)

5 lbs (2.3 kg)

CM-2101A-5

TRANSACRYLIC Resin powder (transparent)

25 lbs (11.4 kg)

CM-2101A-25

EPOXY (Glass Reinforced) COMPRESSION MOUNTING RESIN

Description

Quantity

Catalog Number

EPOCOMP Epoxy Compression Resin powder

5 lbs (2.3 kg)

EP-2201A-5

EPOCOMP Epoxy FINE Compression Resin powder

5 lbs (2.3 kg)

EPF-2201A-5

EPOCOMP Epoxy Compression Resin powder

25 lbs (11.4 kg)

EP-2201A-25

DIALLYL PHTHALATE COMPRESSION MOUNTING RESIN

Description

Quantity

Catalog Number

Diallyl Phthalate Compression Resin powder (short-glass filled)

5 lbs (2.3 kg)

DY-2301A-5

Diallyl Phthalate Compression Resin powder (short-glass filled)

25 lbs (11.4 kg)

DY-2301A-25


CONDUCTIVE MOUNTING RESIN

Description

Quantity

Catalog Number

Conductive (graphite) Compression Resin powder

2.5 lbs (1.1 kg)

CONDUCTO-1

Conductive (graphite) Compression Resin powder

5 lbs (2.8 kg)

CONDUCTO-5

Conductive (copper) Compression Resin powder

2.5 lbs (1.1 kg)

CONDUCTO-CU1

Conductive (copper) Compression Resin powder

5 lbs (2.8 kg)

CONDUCTO-CU5


MISCELLANEOUS MOUNTING ACCESSORIES

Description

Quantity

Catalog Number

1.0 oz measuring scoop

1.0 oz

MS-1000-01

Mold release

8 oz (0.24l)
16 oz (0.47l)

MR-1000-08
MR-1000-16


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