Effects of Relative Humidity and Shelf-Life on Selected Properties of Polyvinyl Acetate Adhesive Films

Authors

  • David A. Cowan
  • Paul R. Blankenhorn
  • Wayne K. Murphey

Keywords:

Adhesives, polyvinyl acetate, tensile properties, differential scanning calorimeter, relative humidities, shelf-life, films

Abstract

The effects of various relative humidities and shelf-lives on the tensile and thermal properties of a commercial polyvinyl acetate copolymer emulsion (PVAC) adhesive are reported. Adhesive-free films, from both crosslinkable and uncrosslinkable resins at three different shelf-life periods, were formed in an environmental chamber (72% relative humidity). After curing, specimens were cut from the films and divided into experimental units; and each unit was conditioned at a different relative humidity (0, 40, 60, and 90%). Tensile and differential scanning calorimetry tests were conducted after the films reached equilibrium at the various relative humidities. Tensile testing results indicate that at relative humidities greater than 40% the tensile strength and modulus of elasticity of both uncrosslinked and crosslinked films decrease. Shelf-life periods of 1.5, 2.5, and 3.5 months had relatively little effect on the tensile strength and modulus of elasticity values of either crosslinked or uncrosslinked PVAC films as compared to the effects of relative humidity. Regression analysis established that the mechanical properties varied mainly as a function of relative humidity. Differential scanning calorimetry specimens were cut from the same sheets of free film as the tensile specimens. Crosslinked and uncrosslinked specimens from an initial shelf-life period of 1.5 months were tested to determine the effects of relative humidities on the calorimetric properties of the films. The results indicate that relative humidity, especially at levels greater than 40%, affects some of the calorific values obtained from the films.

References

Armour, W. B., A. I. Goldberg, and V. Jasinski. 1971. Water resistant vinyl acetate copolymer adhesive compositions. U.S. Patent 3,563,851.nCowan, David A. 1977. Effects of relative humidity on selected properties of polyvinyl acetate free films, M.S. thesis. The Pennsylvania State University, University Park. 63 pp.nGalperin, I., and W. Arnheim. 1967. The effect of humidity on the tensile properties of TiO2 filled poly(vinyl) acetate. J. Appl. Polym. Sci. 11:1259-1269.nNewman, A. A. 1968. Glycerol. C.R.C. Press, Cleveland, Ohio.nNeter, J., and W. Wasserman. 1974. Applied linear statistical models. Richard D. Irwin, Inc., Homewood, IL. 842 pp.nSimpson, W. T., and V. R. Soper. 1968. Stress-strain behavior of films of four adhesives used with wood. USDA Forest Ser. Res. Note FPL-198. 7 pp.nTechnical Association of the Pulp and Paper Industry (Tappi). 1970. Zero-span breaking length of pulp. Standard T 231 su-70. 54(4). 4 pp.n

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Published

2007-06-28

Issue

Number 2 / Summer 1978

Section

Research Contributions

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