David wecker heating and air conditioning

Research Paper

1. Influence of Sepentine filled PTFE ZHi-ning 2009 wear (week8)

confocal laser scanning microscope-

READ on How the CLSM used

1. A Review of Transfer films and Their Role in ultra – low. Jiaxin Ye Ting Xie and Burris Lubricants vol 4 2016 (week8)

K up when v >10 mm/s44666

K is the coefficient of friction

V is velocity

-free space length

Uesd tools (S.E.M) laser microscope 3d profile measurement apparatus Box

Keyence UK-X200

To find thickness of Transfer film

-Compare Keyence Uk-x200 to the Zygo device on campus

2. Quantitative characterization of solid lubricant. YE and Burris, Wear , 2014 (week8)

-Free Space length and wear

-Camera as measurement Ae2o3 filled PTFE

-Hold on a side as subsequent analysis process

3. Assessing Quantative 2017, Haidar and Burris, wear 2017 (week8)

-More free space length and wear experiment

-unfilled PTFE (baseline) And multiple filler polymers

Application of free soace length, film thickness and wear fraction for various PTFE water

+good Transfer film qualities require filler materials

+film thickness is poor correlation

4. Harris, K and Greg. Swyer, macromolecular of A.C.S. 2020

-read and confirm chemical activity for film formation occurs independent of AC2o3

5. Study on the characterisation of the PTFE transfer film and the dimensional designing of surface texturing in a dry-lubricated bearing system ( Liang Ding , wear 2020 (A))

------- Filled PTFE

----- d, depth = t, thickness of transfer film for best effect

40 mpa 0.15 m/s 8 um film t

10 mpa 0.01 m/s 2 um film t

Optical

Keilence VH-7000 optical mscope

Bruker contour GT-I-3D optical interferometer

6. Transfer film evolution and its role in promoting ultra-low wear, J.YE and D.Burris Wear 2012 (B) (week3-7)

5-10 nm= t film

View by optical microscope

7. A study of the tribological behavior of transfer films of PTFE composites formed under different loads, speeds and morphologies of the counterface Hulin Li wear (2015) (F)

Used for measurement

-SEM

-EDS

- Laser 3-D microscope

4 % cu and PTFE

1 mm diameter

“Sand blast better than grinding”

“too smooth is not good “

Notes from “extra articles” from week 8 material

1.Effect of temperature on the wear of unfilled and filled liquid crystal polymers

Interesting to note the very low wear rates. Also interesting that this paper reflects the results of other papers that transfer films form for a number of different polymers when sliding against steel counterfaces. Not specific enough to your PTFE/steel system

2. Effect of transfer film structure, composition and bonding on the tribological behavior

Abstract

Interesting, but not close enough to PTFE. Interesting to (again) note the importance of transfer films for the wear of other polymers, but they didn’t measure transfer film thickness or note the type of optical microscope that they used

3. Effects of Hydrogen Atmosphere on wear behavior of PTFE

Authors suggest that the alloyed carbon content of AISI 316 steel will affect transfer film formation in a H2 environment. This wasn’t noted in other, typical environments such as wet air, dry air or inert gas (argon).

One has to wonder if this is real – as there appears to be only one data point.

See Figures 4 and 5

Hisham, A quick glace of this paper by Blanchet appears to be an excellent reference! Please read it carefully to see if it will answer many of the questions on your outline.

4. sliding wear mechanism of PTFE and PTFE composites

Either get papers 1 and 2 (below) or if you already have them, see if they offer data on the parameters that affect transfer film formation.

The sliding surface of PTFE: An investigation with the electron microscope

Friction and molecular structure: the behavior of some thermoplastics ( I order it thr school lib)

https://www.jstor.org/stable/78198?seq=1

Read carefully to find possible information on

The parameters that affect transfer film formation

Transfer film thickness

Especially whether filler materials affect (increase or decrease) film thickness formation.

My reading of this paper suggests the following summary:

Neat PTFE wears in a similar fashion to unfilled PTFE – except that the critical speed of transition to the severe wear regime is increased.

Neat PTFE has a low ~ 5 mm/s critical speed to go from mild to severe wear at temperatures between RT and 100C.

The context of the paper suggests that PTFE transfer film formation is similar for both filled and neat PTFE. The very thick transfer film from the severe regime quickly breaks-off and forms the much greater volume of wear debris that is expected for the severe wear regime

This paper cites references that claim that an existing PTFE transfer film on a counterface will not lead to lower wear on a new sliding piece of PTFE.

These summary items suggests and important hypothesis that can really make your paper - that:

The filled PTFE papers can be used to hypothesize the behaviour of PTFE transfer film formation.

5. Tribological behavior of unfilled and composite polyoxymethylene 1991

This paper illustrates that PTFE films form for composites containing PTFE. The films were in the same order of magnitude as the many papers for nano-filled PTFE composites that Dr. Burris’ group at U. Delaware.

Transfer films were not generated by neat but were formed by PTFE filled POM.

Film thickness was inferred from (inaccurate) measurements to be about 20 nm.

Contact stress was 2.5 MPa

Distance slid was 720, 2160, and 7200 m

Speed was 1., .3 and 1 m/s (respectively)

Temperature was 21C

Environment was air at 80% RH

Comment: This transfer film result appears to be in the “equilibrium” range for long-term sliding – when compared to other papers – such as those from Dr. Burris’ group at U. Delaware.

---Week 9—

It has a Zygo information

1. Quantitative in situ 2008

Slick 10EA for future to use Newtons’s rings method

2. Mechanical Properties of Polymers

Good mechanics of materials

---week 10---

Note based on Zygo file

Zegage And Aegage plus

0.25 um at 50x objectives

Assumption ------- 0,25um*5= 2.6 um with A 10x objectives

Have only 5.5x and 10x objectives on campus

-done- Compare 2.6 um optical lateral resolutions to the “free space length” values quoted in Assessing Quantitates 2017 and others from Dr, Burris team at u. Delaware ( free space length is equal about 40 um to 2 mm

Conclusion:

+ Initial Transfer film is visible from Zygo at ( 2um thick , 10 um lateral )

+ Transition may not be visible at ( 5-15 nm thick, 1-5 lateral

+ Steady state at ( >10 um lateral, no vertical height data available)

--week 11—

1. Fluoropolymer surface studies II

+Surface finish of PTFE only. Not about wear fil

---week 12

1. Surface properties of PTFE: effect of an amphipathic additive

Confirm that the definition of “film” is a very thin, separate sheet of material – like the plastic wrap in our kitchen.

2. Sliding wear mechanism of polytetrafluoroethylene (PTFE) and PTFE composites 1992

Key sentence:

Although fillers accumulate at the PTFE wear surface, film formation still occurs atop these fillers and across the counterface, providing low friction similar to the unfilled polymer

Noted 1 – 20 um transfer film thickness.

Read paper carefully and explain by conclusions (1) and (2) occur – and from that extend (if possible) to the conditions that cause a PTFE transfer film to be deposited

3. The sliding surface pf PTFE An Investigation with the electron Microscope ( 1968 )

Does citation 5 offer a process for applying an SEM to “see” these very thin ~ 10 nm transfer films?

[5] R. P. STEIJN, Sliding experiments with polytetrafluoroethylene, ASLE Trans., II (1~68) r-12; ASLE Pveprilat No. 68 AM 6D-I, May, 1968. Not found

The thinking is that if the Zygo (on campus) can’t conslusively “see” the 10 nm thick transfer films, then SEM may be the only option to see them. If that’s the case, then we need a process for applying an SEM.

Pursue this one ONLY if the Zygo doesn’t have the resolution to “see” the ~ 5 nm transfer films

---Week 13 ------

1. Thin solid lubricant in space ( E. Roberts 1990)

+Do not use PTFE for contact stress greater than 1200 mpa load

2. The effect of the transfer film on the friction of dry bearing materials ( M. Low 1979)

+Confirms that thin films are the equilibrium film are very thin. This work was done at 300 C which is too high for typical PTFE applications

+This is confirming the high initial wear rate of PTFE with a very thick film. This suggests that a greater value of surface roughness may lead to an initially higher wear rate and larger initial transfer film thickness.

Good paper. Does this paper have any data on PTFE (especially unfilled PTFE) transfer film thickness as a function of contact stress, sliding distance, surface finish, or temperature?

Copy and comment on Figure 9. The shear stress should be proportional to the friction coefficient. The type of filler material makes little difference to the shear (and therefore) friction coefficient. This suggests that filler materials have minimal effect on PTFE friction performance and as a consequence the transfer film.

In other words, Figure 9 let’s you “hypothesize” that the filler material has only minimal effect on the transfer film. Use in Results and Discussion section of your paper.

The paper also backs-up the typical roughness (Ra) used. The .3 - .4 um centerline average (similar to 11 – 15 microinch) is within the range of the 8 to 16 microinch finish that’s typical “tribal knowledge” for PTFE counterface design.

On the bottom page 355 of the paper, draw a (hypothesis) curve with the transfer film thickness given for a that PTFE test – as a function of sliding distance. For example, assume that the less than 100 nm is 50 nm for the .3 m of sliding and that the 100 transversals of 30 m of sliding generated the 500 nm film thickness. Please note that contact stress, temperature, and filler material and weight %.

--Week 14--

1. 2 polytrafluoroethylene : properties and structure (2017)

+The low intermolecular (Van der Waals) forces lead to low friction, low strength, high elongation, and high creep

2. Transfer of semicrystalline polymers sliding against a smooth steel surface (1982)

Pull data from page 188 figure 3 (d) and use for part of your results. GREAT CATCH! (200 – 1000 psi contact stress)

Incorporate the discussion thoughts from the first paragraph of page 196 Discussion section. Make a hypothesis (draw a curve) to account for the very low % transfer film coverage for the low (1 revolution) sliding distance to a much larger % for 100 revolutions sliding distance. Maybe guess at a % coverage for the 1 and 100 revolutions – base on the area coverage from the “free space length”. Use this to estimate a new effective film thickness based on the total volume deposited over about half of the area. – e.g. compare to the film thicknesses measured by Dr. Burris’ group at U. Delaware

Discussion section 4.3

However, PTFE exhibited an approximately constant wear rate of

about 1.3 X 10-l pm rev-’ under a load of 10 N throughout the wear process.

Although the thickness of transferred polymer also increased rapidly up to

about 100 revolutions, it reached an approximately constant value after

several hundred revolutions. Therefore, the initial high wear rate corresponded

to the initial high transfer rate. However, the steady wear stage does

not correspond exactly to the constant thickness stage of transferred

polymer. In the initial wear stage of high wear rate, polymer transfers to

portions where no transfer occurred in previous passes of the polymer pin.

The initial high wear rate may be mainly due to a higher transfer rate of

polymer on the metal surface. The fact that the thickness of the transferred

polymer layer increases during the wear process indicates clearly that polymer

wear can occur on the transferred film of similar polymer. With electron

microscopy, the friction track after 100 revolutions was similar to that after

10 000 revolutions. However, polymer wear occurs even after 100 revolutions,

which indicates that polymer wear occurs on the transferred film of

similar polymer.

3. Highly oriented polyetrafloroethylene films: a force microscopy study 1995

Section 2.3: w.r.t. parameters for transfer film generation

What’s the sliding distance?

Amorphous SiO2 covered silicon wafer counterface

2 cm of pre-conditioning of the PTFE sample, then an implied 10 mm distance of the oxide wafer counterface.

This paper suggest that PTFE transfer films begin to develop almost immediately, and that they form easily with T > 150 C

4. Preparation and properties of highly oriented polyterafluoethylene films

Question: is this very rapidly formed film of use in a wearing application?

This paper’s about the chemistry of the deposited PTFE