CoF and wear reduction in plastics for

tribological applications in PA and POM

PolyTrib 2016 Ljubljana, Slovenia

Clement Descamps & Michal Hrebičík

Agenda

– About Dow Corning

– Improving wear resistance and CoF• In unfilled PA 6

• In glass fiber filled PA6

• In POM

– Conclusion

Dow Corning Corporation is a Global Leader in Silicon-based Technology and Innovation

7,000 products and services

25,000 customers

11,000 employees

$5.7 billion USD in sales in 2013

Focused on sustainability and Responsible Care®

Dow Corning was formed in 1943 to explore the application of the Si atom

Dow Corning is a wholly owned subsidiary of The Dow Chemical Company

Headquartered in Midland, Michigan

Dow Corning and Multibase

Multibase is a

100% Subsidiary

of Dow Corning

SINCE 2002

We simplify access to

the uniqueness of silicone

technology, from fluids

to pellets.

Unfilled PA6

Wear & COF improvement in PA6

3 possible solutions

– Pellets: Dow Corning® HMB-1103 Masterbatch

– Pellets: Dow Corning® 50-011 Masterbatch

– Powder: Dow Corning® 31-441

Features and benefits

– Improved processability

– Improved Slip and Wear

– Maintained mechanical properties and density

Experimental

– PA was predried (3 hrs/80°C)

– Dow Corning® 31-441, Dow Corning® HMB-1103 and

Dow Corning® MB 50-011 were mixed into a dry-PA

and compounded in a TSE 20/40

– Before injection the compound was dried (3 hrs/80°C)

– Injection run on Engel 80 tons press

– Before testing the dumbbels were kept min 1 week

conditioned at 20°C

Test method

Wear measurement by SRV equipment

Counter material 100Cr6

Stoke 2x2.5 mm

Load 25 and 50 N

Frequency 5 Hz

Temperature 25°C

Humidity 40-60%

Duration 1000 s

COF results

COF from the wear test 25 N and a 10 mm ball

0.550

0.1700.150

0.280

0.150

0.235

0.140

0.230

0.100

0.000

0.100

0.200

0.300

0.400

0.500

0.600

Neat PA6 8 % PTFE 15 % PTFE 1% 31-441 2 % 31-4412 % MB50-011

4 % MB50-011

1.65 %HMB-1103

3.3 %HMB-1103

CO

F

Formulations

Average COF - 25 N - 10 mm ball

Wear results

57.50

0.00 0.00

46.25

8.50

31.25

0.00

17.00

0.000.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

Neat PA6 8 % PTFE 15 % PTFE 1% 31-441 2 % 31-441 2 % MB50-011 4 % MB50-011 1.65 % HMB-1103

3.3 % HMB-1103

Avera

ge d

epth

(um

)

Formulations

Average depth of damaged area (25 N - 10 mm ball)measured by perthometer

Wear from the wear test 25 N and a 10 mm ball

Impact results

5.2

3.93.6

7.0577.3

7.03

6.3

5.232

4.8

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

Neat PA6 8 % PTFE 15 % PTFE 1% 31-441 2 % 31-441 2 % MB50-011

4 % MB50-011

1.65 % HMB-1103

3.3 % HMB-1103

RN

I(K

j/m

²)

Formulations

Impact (charpy notched)

Processing

* Performed in a non reinforced PA61 15wt% PTFE benchmark 2 All formulations using 2wt% Si-active (3.3wt% HMB-1103).

3.3wt% Dow Corning® HMB-1103 shows similar torque reduction vs 15wt%

PTFE benchmark while maintaining initial PA injectability.

Torque Relative Spiral Flow

(%)

No additive 31 100

PTFE1 27 83

HMB-11032 27 100

Conclusions

Processing Injectability Mechanics Density Slip Wear

PTFE +++ - 0 - +++ +++

31-441 +++ 0 + 0 +++ ++

HMB-1103 +++ 0 0 0 +++ +++

50-011 +++ +++ + 0 +++ +++

Si additives provide same or better CoF and wear performances

Mechanical properties are not deteriorated as compared to PTFE

- Significant improvement of Notched Impact resistance

- Decreased density of the final compound vs PTFE

- No exudation of silicone

- No blooming because of UHMW silicone (compared to LMW silicone oil)

Glass fibers

reinforced PA6

The issue to be solved in GF PA

Reinforcement of polyamide formulation with glass fibers

always comes at the cost of:

• Processability

• Tribological behaviors

• Density

Processing aids can increase productivity while

optimizing tribological properties

PTFE are commonly used, but they come of the cost of:

- Density

- mechanical properties

- Environmental constraints

Wear and CoF improvment in GF/PA

- Improved processability

- Improved Slip and Wear

- Maintained mechanical properties and density

HMB-1103 DC31-441

Active content 100% 100%

Physical form Pellets Powder

Process Pellets mix Powder mix

Melt temperature 101 C° 60 - 70 C°

Recommended usage level 3 wt% 2 wt%

Compound nature Neat and GF PA GF PA

Experimental

30wt% glass fibers reinforced PA6 compared with 15wt% PTFE

Drying: 80°C/3H

Twin screws extruder L/D = 40, D= 20

Drying: 110°C/1H

Injection of ISO 527

• Injection molding: 80T Engel

Before testing the dumbbels were kept min 1 week conditioned at

20C

Test method

Wear measurement by SRV equipment

Counter material 100Cr6

Stoke 2x2.5 mm

Load 25 and 50 N

Frequency 5 Hz

Temperature 25°C

Humidity 40-60%

Duration 1000 s

COF results

COF from the wear test 25 N and a 10 mm ball

0.550

0.073 0.080

0.420

0.130

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

Neat PA6 8 % PTFE 15 % PTFE 1.65 % HMB-1103 3.3 % HMB-1103

CO

F

Formulations

Average COF - 25 N - 10 mm ball

Wear results

Wear from the wear test 25 N and a 10 mm ball

17.5

0 0

52.5

00

20

40

60

80

100

120

Neat PA6 8 % PTFE 15 % PTFE 1.65 % HMB-1103 3.3 % HMB-1103

Avera

ge d

epth

(um

)

Formulations

Average depth of damaged area (25 N - 10 mm ball)measured by perthometer

Mechanical Properties (ISO 527, ISO 178)

Dow Corning® 31-441 and Dow Corning® HMB-1103 maintain mechanical

properties

Young Modulus

(MPa)

Tensile strength

(Mpa)

Impact charpy

unotched

(kJ/m2)

No additive 8790 161 115

PTFE 9280 142 99

31-441 8670 157 97

HMB-1103 8940 155 115

Processing

Dow Corning® 31-441 increases by minimum 25% throughput & injectability

while reducing torque by 10%.

Torque Melt temperature

(°C)

Relative

Throughputs*

(%)

Relative

Spiral Flow

(%)

No additive 36 340 100 100

PTFE 36 338 116 100

DC 31-441 31 316 127 125

HMB-1103 33 324 113 125

*relative comparisons to maintain a constant machine load

Dow Corning® HMB-1103 demonstrates comparable injectability improvment.

Conclusions

Dow Corning® HMB-1103 provides the same or slightly worse performance in

regards to CoF and wear

- Mechanical properties are not deteriorated as compared to PTFE

- Significant improvement of Unotched Impact resistance

- Decreased density of the final compound vs. PTFE

Processing Injectability Mechanics Density Slip Wear

PTFE 0 0 - - +++ +++

31-441 +++ +++ 0 0 NA NA

HMB-1103 + +++ + 0 +++ +++

50-011 +++ +++ 0 0 NA NA

Conclusions

- Dow Corning® HMB-1103 our best in class Tribological modifiers for

non-reinforced and reinforced PA

- Dow Corning® 31-441 our best in class processing aid

- Improved processability• Up to 25% throuput increase

• Up to 10% torque and Temperature reduction

- Improved Slip and Wear• 3% of DC additives achieve same level of benefit as 15% PTFE

- Maintained mechanical properties and density of GF PA

Polyoxymethylene

Unique Selling Proposition

• Improved COF for POM compounds while maintaining mechanical

performance

• Achieves better COF performance than competing PTFE with

significant lower dosages or Si-Oil with substantial better short and

long-term performance

• Improvement of abrasion resistance

• Improvement of mar resistance for visible areas (e.g. for household

appliances)

• No exudation of Silicone / no blooming because of UHMW Silicone

rather than LMW Silicone oil

• Improved processing (e.g. by torque reduction while extruding/injecting)

• Easy handling: pellet (MB40-606, HMB-1103)

powder (EP5500) form

Product overview

Product overview MB40-006 HMB-1103 EP-5500

Physical form Pellets Pellets Powder

Specific Density 1.23 0.98 0.98

Process Dry Blend Dry Blend Dry Blend

Typical recommended use level 2.5-5wt% 1.5-3.5wt% 1-2wt%

Available packaging 5-25kg’s 5-25kg’s 10-20kg’s

Experimental

− POM dried 3 hours at 100°C

• 3 different types were evaluated – homopolymer, copolymer with 2 different

MVR’s

− HMB-1103 was mixed into a dry-blend and compounded at TSE

20/40

− Before injection the compound was dried (3 hours at 100°C)

− Injection run on Engel 80 tons press

− Before testing the dumbbels were kept min 1 week conditioned at

20C

Test method

Low speed High speed

Testing ball design 12,5mm diameter

Counter Materials Rockwell C hardness 62 or POM

Humidity (%) 55

Force (N) 30 5

Speed (mm/s) 8 200

Test time (min) 45 10 (60*)

T 23 23

Length L (mm) 60 100

# cycles 559 670 (4000*)

Low speed – stick-slip and COF measurement

Equipment: Tribo prufstand 1.6

High speed - COF measurement

Equipment: ball plate polynew

Slow sliding speed COEF: POM ball

High sliding speed COEF: POM ball

Long lasting dynamic COF*

Against POM

Dow Corning’s additives help maintaining long lasting performances while

keeping surface integrity

Surface damages (profilometry*)

POM ball Low Speed High Speed High speed long term

No additive

PTFE

Dow Corning’s

additives

(high loadings)

*surface profilometry measured by mean of perthometer S3P

All Dow Corning brand additives did demonstrate an improvement

of the MAR vs. PTFE

Dow Corning additives for POM

Performance vs neat POM PTFE Dow Corning

MB40-006

Masterbatch

Dow Corning

HMB-1103

Masterbatch

Dow Corning

EP-5500

Powder

Tensile Fmax - +++ +++ +++

Tensile Modulus - +++ +++ +++

Impact - +++ ++ ++

Torque reduction 0 0 0 0

Die pressure 0 ++ + +

POM COF 0 ++ +++ +++

POM long term COF 0 ++ ++ +++

Noise +++ +++ +++ +++

Surface integrity 0 +++ +++ +++

+++ (Excellent) ++ (Good) 0 (Neutral) - (Negative)

Conclusion

- Additive solution for all PA, GF/PA and POM

- Additive level has minimized effect on mechanical

properties, some are even improved (e.g. impact

resistance – anything else)

- Tailored solution for wear and Cof reduction

- Performance comparable and competitive to

PTFE based solutions - brings density and

potential cost in use advantage

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