Christine Sun

Corona treatment of polyolefin films—A review

Corona discharge introduces polar groups into the polymeric surfaces and, as a consequence, improves the surface energy, wettability, and adhesion characteristics. The main chemical mechanism of corona treatment is oxidation. This article further discusses some special problems that are related to corona treatment of polyolefin films by reviewing the recent developments in this field, such as effect of corona treatment on adhesion, effect of resin additives on corona treatment, insufficient treatment and over-treatment of corona discharge, aging, and re-treatment.

Development of Innovative Cotton-Surfaced Nonwoven Laminates

Cotton-based nonwovens have been developed at Textiles and Nonwovens Development Center (TANDEC), The University of Tennessee, with the cotton fibers on the surface or in the core layer laminated with meltblown (MB) and/or spunbonded (SB) webs. Both Cotton-Surfaced Nonwovens (CSN) and Cotton-Core Nonwovens (CCN) have excellent soft hand, breathability, absorbency, and tensile properties making them ideal for many medical applications such as isolation gowns, hospital drapes and gowns, shoe covers, head covers, underwear, pillowcases, diaper components (acquisition, core, back sheet), feminine hygiene pads, baby wipes, etc. In this paper, the processes to produce these cotton-surfaced nonwovens will be presented, including as-bonded, heat-stretched CSN fabrics, and foam-finished CSN nonwovens.

Processing and Property Study of Cotton-Surfaced Nonwovens

Cotton-surfaced nonwovens have been developed by thermally bonding cotton precur sor webs with unbonded spunbond (SB) PP webs on a spunbond line, with cotton on one or both sides. The novel two- or three-layered laminates have a hand similar to cotton knits or hydroentangled fabrics, and also exhibit excellent strength and elongation properties, making them more suitable for some highly desirable disposable and short-wear-cycle applications such as medical and personal hygiene products. The cotton precursor webs are thermally bonded cotton and PP staple (TCPP) webs (25-27 g/m2). Six different TCPP webs are used with three blend ratios of cotton/pp (60/40, 50/50, 40/60) and two different deniers (1.9 and 2.2 denier) and two lengths (1.0 and 1.5 inches) of PP staple fibers. A comprehensive study is made of the effect of processing conditions on the properties of the laminates as bonded on the SB line, with SB web weights of 17 and 34 g/m2.

Innovative Polytrimethylene Terephthalate (PTT) polymers for technical nonwovens

PTT (polytrimethylene terephthalate) (PTT) based meltblown and spunbonded webs have been produced by using Reicofil® Bi-Component Meltblown Line at TANDEC at the University of Tennessee and Reicofil® 3 Spunbonding system at Reifenhauser, Germany. The processability of meltblown and spunbonding in a wide range of operating windows was extensively investigated. The produced webs were characterized to optimize this process. It was found that the PTT grade studied is quite suitable for the meltblown and spunbonding process. The PTT/PP based bico meltblown webs showed enhanced barrier properties and heat resistance and the PTT spunbonded nonwovens showed advanced drapability and elastic recovery. Staple PTT fibers were also made into nonwovens using hydroentangling, thermobonding and needlepunching. Properties of these nonwovens were studied.

Bicomponent Meltblown Nonwovens and Fibre Splitting

Side-by-side bicomponent meltblown fibre webs are produced on Reicofil® bicomponent (bico) meltblown line at TANDEC using polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polytrimethylene terephthalate (PTT), polylactide (PLA), etc. In this study, fibre splitting of the bico meltblown webs is investigated by several approaches, including hydroentanglement, hot water treatment, benzoic acid treatment, and alkali treatment. The web properties and the interfacial adhesion within the bico fibre are also discussed.

Modeling the Mono- and Bicomponent Fiber Meltblown Process with Surface Response Methodology

Mono- and bicomponent (bico) meltblown webs are produced on a 24-inch wide Reicofil® side-by-side bicomponent meltblown system using polypropylene (PP), polyethylene (PE), poly[ethylene terephthalate] (PET), poly[butylene terephthalate] (PBT), polyamide (PA), and their bicomponent (bico) combinations, such as PP/PE, PP/PET, PE/PET, PP/PA, PBT/PE, and PBT/PP. Extensive tests reveal the character of the webs, including their fiber diameter, bulk density, web uniformity, filtration efficiency, air permeability, hydrostatic head, bursting strength, flexural rigidity, and tensile strength. In addition, DSC and SEM are used to examine bico distribution across the die and fiber structure in the webs. Fiber diameters in the range of 1.64-2.85 μm and high uniformity are achieved for both mono and bico meltblown webs at polymer throughputs of 0.55-1.1 g/hole/min (20-40 kg/hr). Since meltblowing is a highly complex and multivariable process where knowledge of the mechanistic model is lacking, and because the new bico capability makes the process much more complicated, surface response methodology (SRM) is suggested for further study of the process. Preliminary work shows that SRM is an efficient and effective method for meltblown process optimization and product development.

Effect of Selected Additives on Surface Energy of Fibers and Meltblown Nonwovens

In this article a small amount (4%) of a series of polymer additives were blended with polypropylene (Exxon 3746G) and polyester (Eastman 14965) polymers and the mixtures were processed. The effect of these additives on the surface energy of the polymers was characterized by the contact angle measured on single fibers and by surface energy on nonwoven webs. The results indicate that fibers modified by silicone-containing polymer additives showed the greatest increase in hydro-phylicity. Meltblown webs of PP and PET with selected additive also shared the same potential increase of hydrophilicity.