Scratch resistant polymers

With all the strategies listed above, we hope that as our imderstanding on scratch behavior of polymers accumulates, a more complete formulation of theoretical framework on surface deformation and damage phenomena can be developed. Only when such framework relating all relevant materials parameters and mechanics with deformation mechanism is available, can we establish predictive model that is useful for polymer engineering and design of scratch-resistant polymers. 

Surface texture, surface roughness, adhesive friction coefficient, scratch resistance, polymer material. 

Scratch resistance of polymer from DADC is improved by novel mixtures of peroxide initiators such as 5% isopropyl percarbonate with 3.5% benzoyl peroxide (16). In order to force completion of polymerization and attain the best scratch resistance in lenses, uv radiation is appHed (17). Eyeglass lenses can be made by prepolymerization in molds followed by removal for final thermal cross-linking (18). 

An issue that has been receiving increasing attention is the deleterious effect of fillers on the scratch resistance of polymers, as measured by the loss in surface appearance. The understanding of this problem is still at a rudimentary stage, but it appears that the problem can be minimised by control of particle morphology [28] and correct choice of surface treatments [29]. 

Resistance to abrasion is measured by determining the weight loss at the abraded surface. Scratch resistance may be measured by using materials of known hardness to scratch the polymer surface. Pencils with known degrees of hardness may be used for this test. 

The relative scratch resistance of two polymers may be readily determined by scratching the surface of one with the comer of the other. 

The scratch resistance of rigid polymers is related to abrasion. In general, for rigid polymers scratch resistance runs parallel with modulus. Cross-linked rubber shows a high scratch resistance, however, which is due to easy deformation combined with complete resilience. 

The choice of materials available for long-term drug contact is very limited—borosilicate glass, bromobutyl or chlorobutyl rubber closures, certain inert polymers such as polytetrafluoroethylene (PTFE), tetrafluor-oethylene (TFE), and derivatives thereof, and stainless steels. Since the Code of Federal Regulations mandates that it be possible to inspect the drug product after filling, steel cannot be used as the primary drug container. In addition, polycarbonates, which would be ideal materials from durability, scratch-resistance, and cost perspectives, have very poor moisture vapor and extractables profiles. 

Silicic acid esters, Si(OR)4, are produced by the reaction of SiCl4 with the appropriate alcohols. The most important representative of this group is tetraethoxysilane (tetraethyl orthosilicate) Si(OC2H5)4, which is used directly, or after hydrolysis to ethylpolysilicates, as a binder for ceramic pastes, for inorganic zinc dust paints (corrosion protection), for the surface treatment of glass and for the modification of silicates. Silicic acid esters are further used for rendering polymer surfaces scratch-resistant. 

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