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Close Tolerance Thermoplastic Machining

Plastic Fabricating Laminate Machining

THERMOPLASTIC IS A TYPE OF PLASTIC THAT IS MADE UP OF POLYMER RESINS, WHICH BECOMES SOFT AS THE MATERIAL IS HEATED AND HARD AS IT IS COOLED. THESE MATERIALS DO NOT SHOW ANY CHEMICAL PROPERTY CHANGES WHEN HEATED OR COOLED MULTIPLE TIMES. THUS, MAKING THEM MORE SUITABLE FOR RECYCLING.

Thermoplastic materials can be homogenous and heterogeneous in their makeup. Unique properties can be achieved by blending thermoplastics, co-extruding thermoplastics or even including special property-enhancing additives.

Thermoplastic can be manufactured and fabricated using several standard methods. Most thermoplastic sheet and film are produced using an extrusion process. However, cast methods can also produce some sheet thermoplastic materials, as well. Nearly any thermoplastic sheet material can be formed using thermoforming, vacuum forming or cold forming methods. Not only that, but thermoplastics with or without reinforcement can also be injection molded into complicated shapes, specifically with features that are not achievable through standard machining. All thermoplastic is often processed similarly. Although, performance characteristics, workability, and cost can vary greatly. 

Thermoplastic materials are suitable for numerous applications and are most commonly utilized in the following industries:

 

Close Tolerance Thermoplastic Products:

  •  Extruded Sheet & Shapes
  • Injection Molded Shapes
  • Cast Sheets
 

Typical Product Names:

  •  Clear Acrylic & Polycarbonate Sheet
  • Polypropylene Sheet (PolyPro FR & Formex)
  • ABS
  • Nylon
  • UHMW
  • PTFE (Teflon) Sheet
 

Thermoplastic-Material

AMORPHOUS VS. SEMI-CRYSTALLINE

Thermoplastics can be broken into two groups by composition: Amorphous and Semi-Crystalline.

While the molecules in semi-crystalline polymers are clustered and structured in a region, the molecules in amorphous polymers are randomly arranged.

AMORPHOUS:

  • Easy to thermoform
  • Typically translucent
  • Softens over a range of temperatures
  • Bonds well using adhesives
  • Good for structural applications
  • Poor fatigue resistance
  • Not ideal for wear applications
  • Subject to cracking from stress
 

SEMI-CRYSTALLINE:

  • Challenging to thermoform
  • Typically opaque
  • Sharp melting point
  • Difficult to bond
  • Good for structural applications
  • Good fatigue resistance
  • Good for wear & bearing applications
  • Good resistance to cracking from stress


AMORPHOUS THERMOPLASTICS:

Amorphous thermoplastics are more conducive to thermoforming. They soften over a range of temperatures and have better bonding ability when combined with adhesives.

Amorphous plastics often have better dimensional stability and impact resistance, when compared to semi-crystalline thermoplastics of a similar grade. However, stress makes amorphous plastics more prone to fatigue and cracking.

 

SEMI-CRYSTALLINE THERMOPLASTICS:

Semi-Crystalline thermoplastics are excellent for wear and structural applications.

Compared to amorphous thermoplastics, semi-crystalline thermoplastics tend to have better chemical resistance, electrical properties and a lower coefficient of friction. However, semi-crystalline plastics are challenging to thermoform, difficult to bond, have a sharp melting point and, additionally, have low impact strength.

 

PLASTIC FAMILIES:

Thermoplastic Materials can be further categorized into families, particularly by temperature rating.

Each family contains amorphous and semi-crystalline plastics with distinct advantages and disadvantages, depending on what is trying to be achieved.

 

 

COMMODITY THERMOPLASTICS:

AT THE BOTTOM OF THE PYRAMID, COST-EFFECTIVE COMMODITY PLASTICS – SUCH AS PP, PE, PVC, PS AND PET POLYMERS – ARE MAINLY UTILIZED IF EXCEPTIONAL PROPERTIES ARE NOT NECESSARY.

These plastics do not require highly-engineered properties and are produced at larger volumes, in order to support many everyday applications.

The operating temperature of these materials is lower, ultimately meaning that they are less resistant to heat. These plastics are generally weaker than higher-performing plastics. In addition to that, these thermoplastics offer moderate mechanical properties. Although, there is variability between commodity plastics, this type of thermoplastic is, by far, the most common plastic that is currently being used worldwide.


APPLICATIONS FOR CLOSE TOLERANCE THERMOPLASTIC MACHINING:

  • Textiles
  • Automotive
  • Toys
  • Containers
  • Electronics
  • Construction
  • Housewares
Commodity Thermoplastics
DescriptionTest MethodUnitspp

PETG

HDPE

ABS

Specific Gravity

ASTM D792

0.905

1.27

0.95

1.04

Water Absorption

ASTM D570

%

<0.01

0.2

<0.01

1

Hardness, Rockwell

ASTM D785

92

115

69

105

Tensile Strength

ASTM D638

psi

4800

7700

4800

6000

Elongation at Break

ASTM D638

%

12

18

900

150

Flexural Modulus

ASTM D790

ksi

180

310

200

340

Flexural Yield Strength

ASTM D790

psi

7000

11200

10000

Compressive Modulus

ASTM D695

ksi

320

Impact Strength

ASTM D256

ft-Ib/in

1.9

1.7

3

2.5

Dielectric Constant

ASTM D150

2.25

2.6

2.3

2.7

Dielectric Strength

ASTM D149

kV/m

660

410

900

500

Dissipation Factor

D150

0.001

0.005

0.0002

0.01

Coefficient of Thermal Expansior

D696

x10^-5in./in/F*

6.2

3.8

6

5

Heat Deflection Temp

D648

F 

210

163

170

198

Glass Transition Temp

D3418

F 

327

180

260

221

Max Operating Temp

F 

180

150

180

176

Thermal Conductivity

AST F433

BTU-in/hr-ft^2-F

0.8

2

2.92

1.73

Other Commodity Thermoplastic Materials include
PolyPro FR®Formex®
Vivak®

Contact Us Today to learn more about commodity thermoplastic materials from The Gund Company or request a quote for your application!

ENGINEERING THERMOPLASTICS

ALTHOUGH THEY SHARE MANY SIMILARITIES WITH COMMODITY THERMOPLASTICS, ENGINEERING THERMOPLASTICS ARE DESIGNED FOR ENVIRONMENTS THAT REQUIRE HIGHER STRENGTH, TEMPERATURE RESISTANCE, AND DURABILITY, AMONG OTHERS.

Common engineering plastics include polycarbonate, nylon (PA), acetal (POM), and UHMW-PE.

Variation in characteristics between these materials does exist, but in general, they are all used in environments unsuitable for commodity thermoplastics. Engineering thermoplastics are generally more expensive than commodity thermoplastics, but both are relatively inexpensive. 

APPLICATIONS:

Engineered Thermoplastic 

DescriptionTest MethodUnits

pC

Nylon

Acetal

UHMW

Specific Gravity

ASTM D792

1.2

1.15

1.41

0.93

Water Absorption

ASTM D570

%

0.15

0.3

0.2

<.01

Hardness, Rockwell

ASTM D785

118

115

120

66

Tensile Strength

ASTM D638

psi

9000

11500

9500

3100

Elongation at Break

ASTM D638

%

110

50

30

30

Flexural Modulus

ASTM D790

ksi

345

450

400

125

Flexural Yield Strength

ASTM D790

psi

13500

15000

12000

Compressive Modulus

ASTM D695

ksi

345

420

400

Impact Strength

ASTM D256

ft-Ib/in

18

0.6

1

N/A

Dielectric Constant

ASTM D150

2.96

3.6

3.8

2.3

Dielectric Strength

ASTM D149

kV/m

380

15.7

420

900

Dissipation Factor

D150

0.0009

0.02

0.005

0.00002

Coefficient of Thermal Expansior

D696

x10^-5in./in/F*

0.375

5.5

5.4

11

Heat Deflection Temp

D648

F 

280

200

220

95

Glass Transition Temp

D3418

F 

310

500

335

280

Max Operating Temp

F 

300

210

180

180

Thermal Conductivity

AST F433

BTU-in/hr-ft^2-F

1.35

1.7

1.6

2.92

Other Engineered Thermoplastic Materials include
Zytel®Lexan®
Valox®Mylar®
Statex®Delrin®

Contact Us Today to learn more about engineering thermoplastic materials from The Gund Company. Request a quote for your application.


Check out our in-depth guide on selecting the right thermoplastic for your application!

HIGH PERFORMANCE AND IMIDIZED 

HIGH-PERFORMANCE PLASTICS AND IMIDIZED PLASTICS MAY BE NECESSARY FOR MORE DEMANDING OR SPECIALIZED APPLICATIONS.

High-performance plastics such as PEEK, PTFE, and PSS can withstand very high temperatures and offer excellent chemical resistance.

Imidized plastics are often suited more for aerospace applications but can also be used for thermal insulators, high-performance bearings, and electrical connectors in extreme environments. Imidized plastics such as polyamide-imide (PAI), polybenzimidazole (PBI), and polyimide (PI) feature the highest temperature resistance and load-bearing capabilities, among other properties.

APPLICATIONS:

  • Aerospace
  • Insulation
  • Wear Components
  • Electronics 
  • Food Service 
  • Medical 
Imidized PlasticsHigh Performance Plastics
DescriptionTest MethodUnits

PI

PAI

PBI

PEEK

PTFE

Ultem

Specific Gravity

ASTM D792

1.43

1.41

1.3

1.31

2.16

1.28

Water Absorption

ASTM D570

%

0.24

0.4

0.4

0.1

<0.01

0.25

Hardness, Rockwell

ASTM D785

50

80

125

103

50

112

Tensile Strength

ASTM D638

psi

12500

18000

20000

16000

3900

16500

Elongation at Break

ASTM D638

%

7.5

10

3

20

300

80

Flexural Modulus

ASTM D790

ksi

450

600

950

600

72

500

Flexural Yield Strength

ASTM D790

psi

16000

24000

32000

25000

N/A

20000

Compressive Modulus

ASTM D695

ksi

350

700

900

500

3.5

480

Impact Strength

ASTM D256

ft-Ib/in

3.76

2

0.5

1

3.5

0.5

Dielectric Constant

ASTM D150

3.55

4.2

3.2

3.3

2.1

3.15

Dielectric Strength

ASTM D149

kV/m

559

580

550

480

285

830

Dissipation Factor

D150

0.026

0.003

0.003

<0.0002

0.0013

Coefficient of Thermal Expansior

D696

x10^-5in./in/F*

3

1.7

0.13

2.6

7.5

3.1

Heat Deflection Temp

D648

F 

532

800

320

132

392

Glass Transition Temp

D3418

F 

754

527

750

644

635

419

Max Operating Temp

F 

466

500

700

480

500

340

Thermal Conductivity

AST F433

BTU-in/hr-ft^2-F

3.7

2.8

1.75

1.7

0.9

 
Other Materials include
Torlon®Udel®
Teflon®Kynar®
Vespel® Radel®
PEEK®Rulon®

Contact Us Today to learn more about high-performance or imidized thermoplastic materials from The Gund Company, or to request a quote for your application!

 
Check out our in-depth guide on selecting the right thermoplastic for your application!