摘要:

AbstractThe aim of this third part is to analyze the structure and properties of the interfacial region between carbon fibers and PEEK as a function of different thermal conditioning treatments. First, it is shown by means of optical microscopy that the interfacial zone is not different from the bulk matrix when standard cooling conditions are used. On the contrary, a transcrystalline interphase is formed near the carbon fiber surface in systems that have been subjected to isothermal treatments. By comparison with previous results concerning the mechanical properties of the fiber–matrix interface, it appears that the interfacial shear strength decreases in the presence of a transcrystalline interphase or when the crystallization rate of PEEK increases. Moreover, it seems that the “constraint state” of the amorphous phase of PEEK near the fiber surface could also play a role in the interfacial shear strength. Secondly, a method is proposed in order to estimate the elastic modulus of crystalline interphases. It seems that this modulus is strongly dependent on the crystallization rate of the polymer. Finally, the determination of the stress‐free temperature, defined as the temperature at which a longitudinal compressive stress just appears on the carbon fiber during the processing of the composites, is performed by recording the acoustic events corresponding to the fragmentation process in single‐fiber composites. The results confirm that the crystallization rate and the “constraint state” of the amorphous phase of the matrix play an important role in the mechanical behavior of carbon fiber–

ISSN:1042-7147    

DOI:10.1002/pat.1991.220020401

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe aim of the last part of this general study is to analyze the influence of the interfacial properties and, more precisely, the adhesion energy, between carbon fibers and PEEK on the final performance of unidirectional composites. A set of mechanical properties, i.e. interlaminar shear strength, longitudinal tensile and compressive and transverse tensile properties, of different unidirectional laminates with the same content (60% by volume) of carbon fibers is determined. It is first shown that the interlaminar shear strength is constant, whatever the type of materials. Therefore, this test is not appropriate to characterize the strength of the fiber–matrix interface in PEEK‐based composites. On the contrary, in agreement with previous work on other systems, it appears that the ultimate properties (longitudinal tensile and compressive as well as transverse tensile strengths and strains) of the laminates increase with the interfacial adhesion energy, whereas the stiffness of these composites remains unaffected in all ca

ISSN:1042-7147    

DOI:10.1002/pat.1991.220020402

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractGraft copolymer and graft terpolymer were prepared by solution grafting of maleic anhydride (MAH) or acrylonitrile (AN) alone and mixture of MAH and AN on to ethylene–propylene–diene terpolymer (EPDM) using benzoyl peroxide (BPO) as an initiator. The resulting EPDM‐g‐MAH, EPDM‐g‐AN and EPDM‐g‐(MAH‐co‐AN) have been used to obtain a binary blend of Nylon 6/functionalized EPDM and a ternary blend of polyethylene/Nylon 6/functionalized EPDM by melt blending. The effects of the nature and the amount of the grafted species on the phase morphology, crystallization behavior and mechanical properties of the blends were characterized through scanning electron microscopy, optical microscopy, infrared spectroscopy and using a dynamic mechanical analyzer. From the morphological study, it can clearly be seen that the presence of the functionalized EPDMs in these blends resulted in an improvement of the dispersion degree in incompatible polyethy

ISSN:1042-7147    

DOI:10.1002/pat.1991.220020403

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe compatibility of cast films of a vinylchloride–vinylacetate–maleic acid terpolymer (VMCH) and nitrocellulose (NC) blends is influenced by solvents. Transparent films of VMCH/NC blends are obtained when cast from solvents such as tetrahydrofuran or cyclohexanone, whereas hazy films are obtained when cast from solvents such as acetone or ethylacetate. Visible spectroscopy and phase morphology were used to analyse the compatibility–incompatibility of the blend. Differential scanning calorimetry (DSC) studies demonstrate that the transparent film is compatible, but the hazy film is incompatible. Fourier transform infra‐red (FTIR) studies establish that a greater interaction is observed between the polymer pair in case of the compatible blend than in the case of the incompatible blend.A solvent dependency of blend compatibility is reflected in this study. The conformational state of the polymers in solution, which is responsible for the compatibility phenomena, may depend on the donor number and/or Taft‐β value of the solvent. The greater the donor number and/or the Taft‐β value, the higher may be the level of interaction between the solvent and the polymer molecules, which in turn may give a compatible blend after removal o

ISSN:1042-7147    

DOI:10.1002/pat.1991.220020404

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractEpoxy Phenolic novolac resins were prepared from the acid catalyzed condensation products of various phenols such as phenol, p‐cresol, p‐tert‐butyl‐phenol and cardanol with formaldehyde. All of these resins have been utilized to prepare the glass‐reinforced composites. The fabricated composites were evaluated for their mechanical and dielectric properties. The incorporation of an epoxy fortifier yielded a significant improvement in mechanical p

ISSN:1042-7147    

DOI:10.1002/pat.1991.220020405

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA method is proposed to determine the interfacial tension of immiscible blends containing a liquid crystalline polymer (LCP) and a flexible‐molecule polymer, under flow conditions.The method is based on Taylor's theorem for immiscible fluids, i.e., that a suspended drop of liquid A in liquid matrix B is deformed in shear or elongational flow in proportion to the ratio of interfacial to viscous stresses. Taylor's theorem, as originally derived, applies to low concentrations, Newtonian fluids and small deformations. Thus, the theorem was modified to account for “Power Law” fluids in elongational flow and large deformations, more applicable to the system under investigation.The elongational viscosities of the LCP and the flexible polymer (polycarbonate) as a function of elongational rate were determined using converging type flow. The two polymers exhibited a Power‐Law behavior in elongational flow and, hence, the experimental constitutive equations of state were used to quantify the viscous stresses.The interfacial stresses were modified for large deformations by taking into consideration the deformed shape and hence increased surface area of the elongated LCP particle. Using the modified expression, the interfacial tension of LCP and PC was determined to be in the range of 5–6.

ISSN:1042-7147    

DOI:10.1002/pat.1991.220020406

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractChanges in water wettability, improvement in adhesion of vapor deposited aluminum and increases in dielectric breakdown voltage in thin, 12 micron PVDF films were observed following brief exposure of these films to low‐temperature gas plasma

ISSN:1042-7147    

DOI:10.1002/pat.1991.220020407

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY