Influence of microstructure on space charges of polypropylene

The correlation of chemical structure, crystalline morphology, and space charge distribution under a dc electrical field was investigated with three kinds of poly(propylene) (PP) with a different chemical structure, that is, homogeneous PP and block copolymer and random copolymer of PP. The space charge distribution of the samples was prominently affected by their chemical sequence structure and crystalline microstructure. Among samples of different PPs, all isothermally crystallized at 140 °C, the sample of random coPP represents the most well proportional space charge distribution and the smallest number of space charges. The effect of thermal history on the space charge distribution was also investigated by the samples of block coPP. The sample thermally treated at 50 °C clearly represents a better proportional distribution than that at higher temperature of 140 and 100 °C. Subsequent experiments indicate that the better proportional distribution attributes to imperfect and fine sperulites with the fine distribution of the “amorphous” region. The imperfect and fine sperulites originate from the random incorporation of ethylene segments or units into PP chains or from the low annealing temperature, and play an important role in the formation of shallow traps and transportation of space charges. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 365–374, 2002; DOI 10.1002/polb.10100

[1]  F. Bates,et al.  Semicrystalline blends of polyethylene and isotactic polypropylene: Improving mechanical performance by enhancing the interfacial structure , 2000 .

[2]  N. Guarrotxena,et al.  On a novel molecular microstructure based approach to the extrinsic space charges releasing in polypropylene (PP) , 1997 .

[3]  K. Suh,et al.  Charge distribution in polyethylene/ethylene vinylacetate laminates and blends , 1996 .

[4]  Jung-Ki Park,et al.  Effects of sample preparation conditions and short chains on space charge formation in LDPE , 1996 .

[5]  Ying Li,et al.  Pulsed electroacoustic method for measurement of charge accumulation in solid dielectrics , 1994 .

[6]  M. Keating,et al.  Conformation of ethylene/propylene copolymers (random or block) as seen by 13C NMR, IR and thermal methods , 1990 .

[7]  D. Tu,et al.  The influence of morphology on the electrical breakdown strength of polypropylene film , 1990 .

[8]  V. Vittoria.  Effect of annealing on the structure of quenched isotactic polypropylene , 1989 .

[9]  Y. Inoue,et al.  13C n.m.r. spectral assignments and hexad comonomer sequence determination in stereoregular ethylene-propylene copolymer , 1988 .

[10]  A. Gupta,et al.  Crystallization of PP in PP/SEBS blends and its correlation with tensile properties , 1984 .

[11]  M. Kakugo,et al.  Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethylaluminum chloride , 1982 .

[12]  Masayuki Ieda,et al.  Observation of Dielectric Breakdown Sites in Polyethylene Thin Film , 1980 .

[13]  J. C. Randall,et al.  Quantitative measurement of ethylene incorporation into propylene copolymers by carbon-13 nuclear magnetic resonance and infrared spectrometry , 1978 .

[14]  Paul E. Johnson,et al.  Carbon-13 Nuclear Magnetic Resonance Determination of Monomer Composition and Sequence Distribution in Ethylene-Propylene Copolymers Prepared with a Stereoregular Catalyst System , 1977 .

[15]  R. Harrington,et al.  Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by13C NMR. 3. Use of Reaction Probability Model , 1977 .

[16]  C. Tosi.  The shape of calibration curves in the IR analysis of copolymer composition , 1973 .

[17]  J. Schaefer,et al.  Carbon-13 Overhauser Effect in Polymer Solutions , 1972 .