[Re: Car Dusters
Very simple solutionj for all colors, especially black! Clean and polish the paint removing all swirl marks. Seal with Opti-Coat 2.0. You can use any duster, California duster, etc., and you will not create swirl marks, marring, etc., since the Opti-Coat prevents the duster from actually coming into contact with the paint. The Opti-Coat is too hard and will not get swirl marks, marring, etc. Simple...very simple!] - Rob4092xx
Hard and soft are relative terms; you can scratch the ‘hard’ surface of your car’s paint finish with a ‘soft’ towel with the application of sufficient (localized) pressure. Both pressure and mechanical stress are defined as force per unit area. These two forces are the subject of Newton's third law of motion; the law of reciprocal actions [: to every action there is an equal and opposite reaction]
Low cross-link densities raise the viscosities of the polymer (soft). Intermediate cross-link densities transform gummy polymers into materials that have elastomeric properties and potentially high strengths. Very high cross-link densities (hard) can cause materials to become very rigid with a high gloss
So how can a dense (hard) clear coat be so easily scratched?
It’s a matter of physics, not material density (material hardness). Force acts through a body that has a surface area; if the surface area is really small while maintaining an equal force, the pressure becomes astronomical and the object under pressure capable of penetrating the surface of an otherwise tough material.
Newton's third law of motion [: when a first body exerts a force F1 on a second body, the second body simultaneously exerts a force F2 = −F1 on the first body. This means that F1 and F2 are equal in magnitude and opposite in direction]
That’s why a micro fine thread that is twice as fine as silk and a 100 times finer than a human hair, in an otherwise soft towel will scratch your paint. And the same reason a mosquito can penetrate a rhino hide with its proboscis (stinger).
If you press down on your paint finish with your palm it feels really hard and tough, but that’s because the surface area of your palm is relatively large and what you’re actually feeling is the resistance of the steel underneath the paint. Try pressing your thumb nail into the paint with the same amount of force you used with your palm, if you dare.
Does paint density (hardness) affect its scratch resistance?
Many coating products claim an obtained surface hardness of 9H or 3 Gpa+, but this has little if anything to do with scratch resistance. Scratch resistance can be related to higher cross-link density and elasticity of the polymer network.
This can best be summed up as: your car’s paint finish, though it may feel hard, is actually rather soft. Nearly everything else that comes in contact with it, though it may feel soft, is harder by comparison and will scratch it with enough pressure – sometimes just the slightest of pressure.