The sleeve material is extremely important because it comes into direct contact with the printed surface and more importantly with the playing surface of the CD. Sliding a CD in and out of a CD storage sleeve rubs the disc surface against the sleeve material and can leave micro scratches on the CD. Micro scratches can impair the quality of the play back and worst case make the CD unplayable.
High storage quality sleeves utilize non-woven fabrics made from inert materials like polypropylene. CD Storage Sleeves from DiscSox are a great example of an archival quality storage solution.
The playing surface of the CD is not the only part that needs protection. Certain chemicals found in materials like vinyl can dissolve the print on the CD and make the surface sticky. In some cases these chemicals eat through the polycarbonate of the disc and can distroy the CD. So for archiving CDs inert materials without added chemicals are required. See also CD Storage Materials for more info.
Non-woven polypropylene fabric is most effective solution to protect the playing surface and matte transparent polypropylene works ery well for showing the graphics or printed side of the disc. Protective, archival quality sleeves use this material combination for maximum protection and usability.