Morphology and molecular mobility of several kinds of polyethylene specimens by 13C solid-state NMR and x-ray diffraction techniques

Abstract

The morphology and molecular mobility of polyethylene were investigated by X-ray diffraction and 13C solid-state NMR as a function of temperature. The test specimens chosen are melt films, single-crystal mats, undrawn dry gel films, and ultradrawn films with a draw ratio of 300. The semilogarithmic plot of the 13C magnetization of the peak height of the line at 33 ppm indicated the existence of three different kinds of spin-lattice relaxation time (Tic): a slow decay time, an intermediate decay time, and a rapid decay time for the orthorhombic crystal form. Among the test specimens, the decay time of the ultradrawn gel film was the longest. The spin-spin relaxation time (^c) indicated that the noncrystalline component consists of an interfacial region and a rubber-like amorphous region with extensive molecular mobility. For single-crystal mats and dry gel films, the lenght of the interfacial region calculated using both the mass fraction of the interfacial region by 13C NMR and the long period by X-ray scattering was almost equal to the length of the interfacial region estimated by analyzing a systematic deviation of the X-ray scattering curves at large angle tail from Porod's law. Furthermore, the crystallinity at room temperature estimated by 13C NMR was also in good agreement with the results by density and X-ray diffraction. With increasing temperature, Tic for the crystalline region became shorter, while Tic for the noncrystalline region became longer, indicating more active molecular mobility. The crystallinity estimated by 13C NMR was confirmed to decreased with increasing temperature. This tendency was in good agreement with the results obtained by X-ray diffraction using Ruland's method.

Solid-State 13C NMR Analyses of the Crystalline−Noncrystalline Structure for Metallocene-Catalyzed Linear Low-Density Polyethylene

“…Each LLDPE sample consists of the crystalline, interfacial, and rubbery components like HDPE samples. 7,10,12,25,26 The longest T 1C value of MLLDPE is significantly shorter than the values for ZLLDPE as well as for bulkcrystallized HDPE. 7,27 Such differences are associated with the difference in lamellar thickness.…”

Stress Relaxation Behavior of Knitted Fabrics under Uniaxial and Strip Biaxial Excitation as Estimated by Corresponding Principle between Elastic and Visco-Elastic Bodies

“…The same concept was also reported for activation energies of several kinds for representing visco-elastic properties of polymers such as α, β and γ, dispersions [20,21]. Of course, their analysis contains the problem, since the T 1 relaxation time observed by solid state 13 C NMR [18,19] has the possibility to give as a function, different from the concept concerning the specific three relaxation values. Furthermore, a visco-elastic behavior must be essentially represented as a relaxation spectrum.…”

“…). exp + = Such a treatment has been reported for the analysis of spin-lattice (T 1 ) relaxation by solid state 13 C NMR [18,19].…”

“…Substituting equation ( 15) into equation ( 16), is written as follows: (18) where is the stress relaxation modulus given as Laplace transformation. Then, one has:…”

Poly(epichlorohydrin) modified with 3,4,5‐tris(dodecyloxy)benzoate: The structure and dynamics of the aliphatic side chains in the columnar mesophase

“…The values of T 1C in the crystalline state range between 3.5 and 1.44 s. They are comparable to the short components found in the orthorhombic crystal form of PE33 For PE, the short T 1C 's arise from the crystal carbons at the exterior of the orthorhombic crystals, which can migrate quickly into the noncrystalline regions and relax. This interpretation may also suit the system under examination; its x c value is expected to be lower than that of PE.…”