Poly P-phenylene Terephthalate Research Articles

Development of a novel PPTA/cellulose composite insulation paper with low dielectric constant and improved mechanical properties by BTCA crosslinking

AbstractThis study investigates the effect of 1,2,3,4‐butane tetracarboxylic acid (BTCA) crosslinking treatment on the electrical properties of poly‐p‐phenylene terephthalate (PPTA)/cellulose insulation paper to prepare a novel composite insulation paper with low dielectric constant and good electrical performance. Three‐layer PPTA/cellulose composite paper crosslinked by BTCA under various conditions, composite paper without crosslinking, directly mixed composite paper, and conventional Kraft paper are prepared. The morphology and surface chemical composition of the paper samples are characterized. Dielectric, mechanical, and thermal properties are investigated. Results show that the BTCA concentration of 0.2 mol L−1 with a 180°C curing temperature is the relatively superior crosslinking condition to prepare a novel composite with low dielectric constant and good comprehensive performance. The dielectric constant and loss of the novel composite paper decrease to 3.21 and 0.392 at 50 Hz. The tensile strength of the BTCA crosslinked three‐layer PPTA/cellulose composite paper (thickness: 130 μm) has reached 10.01 kN m−1, increased by 41.6% than the directly mixed composite paper. The novel BTCA crosslinked composite paper also shows improved thermal stability. The BTCA crosslinking proves to be a promising method to improve the dielectric properties and electrical performance of the PPTA/cellulose composite paper.

Effect of the Linking Structure of Nonlinear Optical Side Groups on the Phase Behavior of an Aromatic Polyester Backbone

The phase behavior of polyp-phenylene terephthalate) (PPT) with pendant side groups, N-(4-nitrophenyl)-ethylaminoethanol (NPE) and N-(4-nitrophenyl)-L-prolinol (NPP) has been studied by using differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and second harmonic generation (SHG). PPT-NPE showed a layered liquid crystalline morphology while PPT-NPP showed a completely amorphous structure. Compressive or shear stress applied on the polymer melt surface at 210 °C induced a more prominent layered structure of PPT-NPE whereas the amorphous structure of PPT-NPP remained unchanged under the stress. In order to understand this phase difference in terms of the repeat structure, we attempted theoretical ab initio Hartree-Fock, and DFT calculations for the monomers and molecular dynamics for the bulk state. The results indicated that molecular configurations are a good way of microscopically understanding the phases of rigid backbone polymers with functional side groups: The NPT (constant particle number, pressure, and temperature) simulation data at 210 °C agree qualitatively with the experimental data and the difference between PPT-NPE and PPT-NPP could be understood using rotational energy barrier, steric hindrance and inter-chain interactions. X-ray diffractometer (XRD) simulation patterns for the oligomers are also in qualitative agreement with the experimental WAXS data and the structural parameters of stacks of PPT-NPE chains are estimated to be layer distance (4.6 A), backbone distance (21.5 A), and side distance (12 A).