Spunbond processing produces nonwoven polypropylene (PP) fabrics that have a diverse range of applications. Lighter weight spunbond fabrics are used as layers in laminates for diapers and hygiene products, medical and clean room garments, sterilization wraps, industrial wipers, and towels. Heavier weight spunbond fabrics are used in tents, car covers, and upholstery. The key attributes of a spunbond fabric vary a great deal depending on the target application. For some applications, like diapers, softness is important. For other applications, like clean room garments, low particle emission is critical. However, fabric strength is one characteristic that is valuable for virtually all spunbond applications. The higher the strength at a given fabric weight, the thinner the fabric or fabric layer needed for a given application. A thinner fabric reduces resin cost, product bulk, and weight and often improves other fabric attributes such as drape. In this report, methods for improving the strength of spunbond polypropylene fabrics are examined. First, published studies of fabric strength are presented, and common themes are discussed. Then, several patented polymer systems that give improved fabric strength are described and discussed in light of literature models of fabric strength. Next, experiments are presented that demonstrate that spunbond fabric strength can be affected by modifying individual properties of standard polypropylenes. The results are examined in light of the fabric strength models. Finally, the relative effects of adjusting spunbond process conditions on fabric strength are compared to the effects of changing polypropylene properties.
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