摘要:

The potential offered by intrinsically conductive polymers is limited by their poor mechanical properties. Blending with common thermoplastics can improve processability and mechanical properties and still preserve the electrical conductivity. In such blends, the morphology determines the mechanical and electrical properties. In this research, blends of polyaniline (PANI)-dodecyl benzene sulfonic acid (DBSA) with either polystyrene (PS) in xylene or polyvinylchloride (PVC) in bromobenzene were solution cast. The morphologies of the blends were characterized by optical microscopy (OM), electron microscopy, and small-angle X-ray scattering (SAXS). Electrical conductivity was measured for various compositions. The formation of a continuous network was strongly associated with percolation and conductivity. The morphologies of the two blends are significantly different. This difference arises from the different solvents used and their ability to swell the PAN1 aggregates and to promote their disintegration into small particles. Molecular calculations show that, indeed, bromobenzene, used in the PVC system, is able to penetrate the PANI-DBSA aggregates, while xylene, used in the PS system, cannot. Nevertheless, the small PANI-DBSA particles in the PVC matrix form a conductive network only at a relatively high content, while the coarse aggregates in the PS matrix form conductive paths at a relatively low content. These results are discussed in terms of the formation and stability of the PANI-DBSA dispersion.

ISSN:0022-2348    

DOI:10.1080/00222349908248111

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Isotactic polypropylene consisting of uniaxially oriented P-phase lamellae was crystallized in a temperature gradient. The β → α transition was investigated by simultaneous measurements with differential scanning calorimetry (DSC) and X-ray diffraction using synchrotron radiation (SR). To compare the transition mechanism, the β-phase sample was deformed by rolling it along the direction of the crystallization. During rolling, the β-crystal is deformed by interlamellar and interchain slip, which inducesc-axis-oriented molecules along the rolling direction. The melting behavior is changed by the rolling deformation. For the as-grown β-crystal, the DSC thermogram has three peaks: the β-melting endotherm at 150°C, an exotherm by recrystallization into the °-form, and the endotherm at 167°C caused by melting of the recrystallized α-form. After the rolling deformation, the β-endotherm is extinguished by the successive exotherm. Simultaneous X-ray measurements reveal that the β → α transition is shifted to a lower temperature and that the recrystallized α-form has ac-axis-orientation caused by the rolling deformation. In the process of the β→ α transition, higher-order lamellar structure is developed earlier than formation of the crystalline structure. In this study, the heating phenomena, such as the β α transition and thickening of the β- and α-lamellae, are consistently explained by a mechanism involving melting and subsequent recrystallization.

ISSN:0022-2348    

DOI:10.1080/00222349908248112

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor