If I may, Mark has brought up...IMO...a two part question. which covers, or involves:
1.)
Solvents...CarPro Erasure and other solvents brought up during this thread's discussion such as: IPA, PrepSol, PS21 TAW, etc.
And how they may affect (Such as swelling):
2.)
A cataylized two-part polyurethane paint system...
clear-coat paint film coating (Can it be absorbent)
-In order to understand this relationship,
IMO, there should be some parameters set forth for each individual component of how I see Mark's question.
For those parameters, and as they may pertain to this thread's discussion....Here goes..
.IMO, that is.
First:
A.) What are solvents?
-Solvents are usaually considered liquid substances that are capable of dissolving other substances by, and through, creating mixtures that are then called solutions.
-These solutions also, then, should not affect, or "harm" as it were, an underlying substance.
B.) Is a Clear-Coat paint film coating permeable?
-Polyurethane clear-coat paint is formulated to be elastic, flexible, scratch resistant, and other attributes.
-Freshly cured, straight from the OEM's factory paint kitchen ovens, is when clear-coats are considered the most dense...meaning thickest, hardest,
least permeable, clearest, shiniest, etc.
This is un-aged paint
(Resprays from aftermarket sources, although they may be applied in multiple coats and be "thicker", will never be as "hard" in the same terms as OEM's because of the different temperatures during the respective heat-curing methods. "Softer" is often a term that is used for this difference.)
-Upon leaving the OEM plant, the clear-coat begins its journey towards the end of its expected life-cycle. It is being continually bombarded by contaminates. Some of the most destructive contaminates are brake and rail dust...They permeate the clear-coat causing microscopic openings/fissures/crazing, thus allowing other contaminates to permeate into the a-few mils thick clear-coat, furthering its degradation.
-Couple that with all the effects that: UV rays, bird bombs, weather related events, unintended scratches, washing, claying, drying, polishing, etc., and the wear & tear of the clear-coat continues, making it even more, and more permeable as time passes.
This is "aged-paint"
Secondly:
Choosing Solvents that will be effective, and as such, will cause no harm:
-Trial & Error
-Word of Mouth
-"Like dissolves Like"
-Experience....Empirical/Real world testing
-Scientific testing evidence that shows:
Strength, evaporation rate, viscosity, health & safety, environmental impact, etc.
A person shouldn't have to be Rocket Scientist or a Chemist in order to choose a solvent!
And so...There are solvent organization systems that may assist in those selections of solvents and how they affect substances.
In this thread's interest: Solvent-polymer substances interactions/behavior.
Some of the solvent organization systems are really just simple mathematical graphs...and one doesn't have to understand the chemistry behind them...But,
So why bother with them?
Unless a person is inclined to do otherwise, the SAE and automotive paint engineers have joined in with the paint manufacturers, and their engineers to figure out what solvents will do to polyurethane paint, as well as all other automotive surfaces....on top, around, inside, and under.
They use these "solvent charts" that include, among others:
Solubility scales, solvent grades/classes, aromatic properties, cloud-points, Hildebrand NO., hydrogen bonding, Teas graphs, Van der Waals forces, vaporization (boiling points), temperature, dispersion forces, polar forces (electromagnetic), and etc., and etc.
-These charts are used by the above mentioned and varied paint-engineers, because they give comprehensive information about the "strengths" of solvents, thus allowing them to easily determine what solvents or solvent blends can be used to dissolve a particular materials, such as, in this case, polyurethane paint systems.
Note:
-It has been both scientifically, and, by accepted engineering protocols, proven that polyurethane will decompose before its level of vaporization heat could be attained, and that its
swelling behavior is one of the ways that these solvent charts/values are utilized.
Here's one such chart:
Solvent 100 fd 100 fp 100 fh
Alkanes
1 n-Pentane 100 0 0
1 n- Hexane 100 0 0
1 n-Heptane 100 0 0
1 n-Dodecane 100 0 0
2 Cyclohexane 94 2 4
3 V M& P Naphtha 94 3 3
4 Mineral Spirits 90 4
Aromatic Hydrocarbons
5 Benzene 78 8 14
6 Toluene 80 7 13
7 o-Xylene 83 5 12
8 Naphthalene 70 8 22
9 Styrene 78 4 18
10 Ethylbenzene 87 3 10
11 p-Diethyl benzene 97 0 3
Halogen Compounds
12 Methylene chloride 59 21 20
13 Ethylene dichloride 67 19 14
14 Chloroform 67 12 21
15 Trichloroethylene 68 12 20
16 Carbon tetrachloride 85 2 13
17 1,1,1 Trichloroethane 70 19 11
18 Chlorobenzene 65 17 8
19 Trichlorotrifluoroethane 90 10 0
Ethers
20 Diethyl ether 64 13 23
21 Tetrahydrofuran 55 19 26
22 Dioxane 67 7 26
23 Methyl Cellosolve 39 22 39
24 Cellosolve 8 42 20 38
25 Butyl Cellosolve 46 18 36
26 Methyl Carbitol 44 21 35
27 Carbitol ® 48 23 29
25 Butyl Carbitol 46 18 36
Ketones
28 Acetone 47 32 21
29 Methyl ethyl ketone [53] [30] [17]
30 Cyclohexanone 55 28 17
Diethyl ketone 56 27 17
Mesityl oxide 55 24 21
31 Methyl isobutyl ketone 58 22 20
32 Methyl isoamyl ketone 62 20 18
Isophorone 51 25 24
33 Di-isobutyl ketone [67] [16] [17]
Esters
34 Methyl acetate 45 36 19
35 Propylene carbonate 48 38 14
36 Ethyl acetate 51 18 31
Trimethyl phosphate [39] [37] [24]
Diethyl carbonate 64 12 24
Diethyl sulfate 42 39 19
37 n-Butyl acetate 60 13 27
Isobutyl acetate 60 i 5 25
38 Isobutyl isobutyrate 63 12 25
39 Isoamyl acetate 60 12 28
40 Cellosolve® acetate 51 i 5 34
Ethyl lactate 44 21 35
Butyl lactate 40 20 32
Nitrogen Compounds
41 Acetonitrile 39 45 16
42 Butyronitrile 44 41 15
43 Nitromethane 40 47 13
44 Nitroethane 44 43 13
45 2-Nitropropane 50 37 13
46 Nitrobenzene 52 36 12
47 Pyridine 56 26 18
48 Morpnoline 57 15 28
49 Aniline 50 19 31
50 N-Methyl-2-pyrrolidone 48 32 20
Diethylenetriamine 38 30 32
51 Cyclohexylamine [64] [12] [24]
Formamide 28 42 30
52 N N-Dimethylformamide 41 32 27
Sulfur Compounds
88 8 4
53 Carbon disulfide
54 Dimethylsulfoxide 41 36 23
Alcohols
55 Methanol 30 22 48
56 Ethanol 36 18 46
57 1-Propanol 40 16 44
58 2-Propanol [41] [16] [43] (IPA)
59 1-Butanol 43 15 42
2-Butanol [44] [16] [40]
Benzyl alcohol 48 16 36
60 Cyclohexanol 50 12 38
61 n-amyl alcohol 46 13 41
62 Diacetone alcohol 45 24 31
2-Ethyl-1-hexanol 50 9 41
Polyhydric Alcohols
63 Ethylene glycol 30 18 52
64 Glycerol 25 23 52
65 Propylene glycol 34 16 50
66 Diethylene glycol 31 29 40
67 Water 18 28 54
Miscellaneous Liquids
68 Phenol 46 15 39
69 Benzaldehyde 61 23 16
70 Turpentine 77 18 5
71 Dipentene 75 20 5
Formic acid [33] [28] [39]
Acetic acid [401 [22] [38]
Oleic acid [62] [14] [24]
Stearic acid [65] [131 [22]
Linseed oil 66 17 17
Cottonseed oil 67 15 18
Neets foot oil 69 14 17
Pine oil 70 14 16
Sperm oil 75 11 14
1 Mineral oil 100 0 0
It is recommended by the: Paint manufacturers, Automotive engineers, and the SAE to:
-Use no more than a 10% IPA solution on
softer paints
-Use no more than 15-18% IPA solution on
harder paints
-Use a dedicated solvent such as, or similar to: PrepSol, 3m Prep Solvent, at the recommended dilution ratios.
Thirdly:
-Besides what is mentioned above [in regards to clear-coat paint becoming more permeable (by "aging-processes")] and being that it is a polymer that has been formulated to have elasticity, heat associated with "buffing" will also cause an increased amount of swelling. This is especially true when buffing for an extended amount of time in one area, and when a panel's temperature is already "hot-to-the-touch".
-Sure, more often than not, the swelling will appear to go down...be reduced. But, like anything having elasticity, keep stretching it enough and a lot of the elasticity begins to disappear.
-Another thing that can occur by over-heating polyurethane paints is that, even though it will swell, it will also start the delamination process (paint resins/binders softened from excess heat (stress), with imminent clear-coat failure in the near future.
(If one sees a "cloudy" look in the clear-coat after polishing processes...More than likely delamination has begun.)
-A huge question: How to determine
softness/hardness of a OEM applied clear-coat, and not create more "aging"?
Fourth Aspect:
-Solvents by design will create heat while dissolving substances. If the clear-coat paint film has been compromised by the "aging processes", they will, because of their molecular size, permeate the clear-coat film...carrying with it "heated" substances (that are now in solution form) into the clear-coat paint film matrix.
Besides the extra heat, the now absorbed liquid solution will,
in fact, cause swelling.
It has been proven, that an unprotected clear-coat will even absorb enough water during a rain-event to cause swelling. [as witnessed by clouding (delamination)] to occur
That makes it paramount to wax/seal/coat even a new, right off the car-hauler vehicle. Even though a person may protest when a dealership "details" their brand new vehicle...That's standard protocol advisement from the OEM's...to protect their paint warranties.
BTW...It's either done at the dealership or at the port-of-call's "get-ready" detail guys! Then the shipping wrap goes on at least the vehicles' horizontal surfaces.
Epilogue:
I realize it's am individual's choice, but if I'm going to clean/strip from the paint surfaces as much polishing oils, and other unwanted "filler" substances, I much rather prefer to use the recommended solvents in the recommended dilution ratios....
There's enough swelling going on, in regards to polyurethane clear-coat paint, as it is. Investing the energy to decide what solvent to use in situations, will prolong the inevitable end-of-life-cycle for what I have always considered: A large investment.
Bob