The effects of the chemical structure of polyurethane binders on the mechanical properties of adhesively bonded polyester nonwoven fabrics

Author

Dong-Hwa Shin

Date of Award

5-1989

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Human Ecology

Major Professor

Kermit E. Duckett

Committee Members

Larry Wadsworth, J. L. Spruiell, John L. Crouse, Jacquelyn O. DeJonge

Abstract

The purpose of this study was to synthesize totally amorphous polyurethanes with glass transition temperatures {T_{g<\sub>}] below -50° C in order to achieve flexibility below the freezing temperature (0° C) . This was used as binder for polyester nonwoven fabrics, and the effects of the chfemical structures of the binder on the mechanical properties of the fabrics were investigated.}

Based upon experimentation, the reactants selected in order to synthesize the 100% amorphous polyurethane binders were hexamethylene diisocyanated-extended polyprc^plene glycol with trimethylol propane [crosslinking agent] and stannous octoate [catalyst]. Methylene chloride was added to the reactants to lower the exothermic heat of reaction and to avoid a substantial increase in viscosity by the chain-extending reaction. Again, based upon experipnents, the standard conditions of curing time (48 hours) and temperature (60° C) were determined to produce satisfactory polymer films.

For web formation and bonding, the fibers were carded to form a unidirectional web and spray bonded with five different degrees of crosslinked polyurethane binders and three different amounts of binder add-ons. Various techniques were utilized to characterize and examine the polyurethane films. The degree of crosslinking was determined by the swelling technique, and differeritial scanning calorimetry monitored theT_g of the binders. Intrinsic viscosity and differential refractive index were measured for the polymer films to ensure the replication of polyurethane synthesis each time.

The mechanical performance of nonwoven fabrics was analyzed using the Instron tensile tester to investigate the stress-strain behavior of the final product. The relationship between the binder properties with the chemistry of polyurethane and the effects of binder add-ons were also investigated. In the lower binder add-on region, the density of crosslink in the binder played an important role for an increase in tensile strength; however, in the highly crosslinked binder region, it was observed that the effect of binder modulus on fabric modulus became sinaller with increasing binder techniques. The optimum mechanical properties were obtained at the ratio of PPG to TMP of 0.7 to 0.3 with 50% binder add-on.

Unlike conventional latex binders, the advantage of this particular polyurethane indicated that the binder toughness did not affect the flexibility of the nqnwoven fabrics, due to their 100% amorphous nature. Furthermore, this binder maintained flexibility in the extremely cold region because the T for the linear polyurethane was -58° C; the T_g for the crosslinked polyurethane film was also g loWf ranging from -49 to -52° C. As a result of the chemical structure of this polyurethane, a large numbpr of H-bonding provide inter- and/or intra-molecular forced that greatly enhance the adhesive and cohesive abilities o^ this binding polymer. The apparent disadvantage of the use of this polyurethane as a binder was its high viscosityf such that a solvent had to be employed to dilute the solutfon in order to effectively disperse the binder onto the fabfic.

Future studies indicated by the above results phould include the synthesis of aqueous polyurethanes, binder adhesion and cohesion investigations, and the development of new research areas in composites for polyurethanes.

Recommended Citation

Shin, Dong-Hwa, "The effects of the chemical structure of polyurethane binders on the mechanical properties of adhesively bonded polyester nonwoven fabrics. " PhD diss., University of Tennessee, 1989.
https://trace.tennessee.edu/utk_graddiss/11765