Anal. Chem. 1909, 6 1 , 1870-1873
1070
Characterization of Single-Ply and Polylaminate Films by Nuclear Magnetic Resonance Spectroscopy Galen R. Hatfield’ Corporate Technology, Allied-Signal, Inc., Morristown, New Jersey 07960
The ability of solld-state NMR to obtain detailed information on structure and morphology in poiyiaminate films is demonstrated for the first tlme. The polylamlnates studied here contained layers of polyethylene, Nylon 6, Surlyn, and/or ethylene-vlnyi acetate copolymers. The multilayer films examined were chosen with the Intent of Illustrating the relative strengths and weaknesses of this analyticai approach. The most notable strength Is the ability of NMR to obtain morphological information on the Interior layers of polylamlnates wlthout resorting to ply dissolution or Separation.
Table I. Film Structure and Composition sample
total plies
ply
A
1
1
243.8
B C D E
1 1 1
1 1 1 1
25.4
ADH F
INTRODUCTION Single-ply and polylaminate films are important materials with major applications in the packaging industry (1, 2). Physical properties such as permeability, strength, clarity, and dimensional stability are directly related to the polymer and its morphology in each layer. Unfortunately, these systems have often proven to be difficult and/or tedious to study due to their complexity and physical construction. Most approaches involve separation or dissolution of laminate plies by refluxing in solution and subsequent analysis ( 2 ) . Unfortunately, this procedure is time-consuming and, more importantly, may jeopardize the structural integrity of the system. In addition, morphological information such as crystalline content is lost in solution or may be altered during separation. Finally, these films are frequently thick, often prohibiting an examination of the interior layers by traditional methods such as infrared (IR) and X-ray diffraction (XRD). High-resolution solid-state nuclear magnetic resonance (NMR) has quickly become one of the more powerful tools available for the study of polymer morphology (3, 4). The purpose of this paper is to demonstrate, for the first time, the ability of solid-state NMR in characterizing both single ply and polylaminate films. Examples are chosen specifically to illustrate the relative strengths and weaknesses of this analytical approach. EXPERIMENTAL SECTION NMR Spectroscopy. NMR experiments were carried out at 75.3 MHz on a Chemagnetics CMXBOO NMR spectrometer using standard cross-polarization (CP) and magic angle spinning (MAS) techniques (5-7). The films were packed into rotors and spun at roughly 5.0 kHz. The magic angle was adjusted to within 0.1’ by using the ‘@Brspectrum of KBr (8). The spectra shown in Figures 1-6 were acquired by using a 0.8-ms contact time and a 2-5 repetition time. For the purposes of measuring the a crystallinity of Nylon 6 in sample F, data were also acquired with a 240-s pulse delay. The length of this delay was chosen to ensure total magnetization recovery and therefore accurate quantitative data. Crosspolarization (TCH) and proton rotating frame spin-lattice relaxation (Tl,,(H)) rates were measured ( 3 , 4 , 9) for the peaks at 43 and 40 ppm (see text). TcHwas determined to be 0.03 ms for both resonances. Values of T,,(H) were found to be 5.09 and 4.38 ms Current address: Washington Research Center, W.R. Grace &
Co., 7379 Route 32, Columbia, MD 21044.
2+ADH
thickness, composifim tion
3
2 1 2 3
PE
comment milk bottle
grade N6 EVA 12% VA Surlyn Surlyn adhesive N6 EVA 2% VA N6 EVA 2 % VA
27.9 25.4 140.6
