ISSN:0007-1641    

DOI:10.1002/pi.4980210102

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSince the first tentative applications of SIMS to study polymer surfaces around 1980 the field has developed very rapidly. The important experimental parameters which allow true ‘static’ SIMS analysis of polymers are now well established following systematic studies of ion beam damage cross‐sections and the methodology of surface potential control is sufficiently understood to allow both positive and negative ion spectra to be routinely obtained from highly insulating materials.The principal advantage of SIMS over X‐ray photoelectron spectroscopy (XPS or ESCA) comes from the molecular specificity inherent in a mass spectrometric technique. Several classes of polymers have been studied to establish fragmentation processes; in the case of acrylic polymers these studies have been extensive and detailed. From the technological point‐of‐view it is the ability to identify ‘small’ organic molecules on polymer surfaces which is most exploited. The information depth in typical systems has been established by correlation with angle‐resolved XPS studies to be ∼ å, this degree of surface sensitivity allows bulk‐surface segregation effects in block copolymers to be followed as exemplified by studies of segmented poly (ether urethanes). Use can also be made of the isotope specificity of SIMS in derivatisation schemes or in polymerisation mechanism studies. Quantification of SIMS intensity data is now being explored. In the case of random methacrylate copolymers quantitative information on sequence statistics has been obtained.SIMS also has the potential for high spatial resolution analysis. The problems associated with unacceptable damage rates when working with sub‐micron focussed beams have been studied and this has led to the development of the time‐of‐flight (TOF) imaging SIMS instrument. TOF SIMS is capable of accessing a mass range of an order of magnitude greater than the conventional quadrupole instrument and the application of both imaging and non‐imaging TOF instrumentation to polymer surface a

ISSN:0007-1641    

DOI:10.1002/pi.4980210103

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractRaman microscopy has been used to study the deformation of carbon fibres and an experimental grade carbon‐fibre/PEEK composite prepreg. It has been found that the peak position of the Raman‐active bands in the fibres are sensitive to the level of applied strain. Examination of the peak positions from the carbon fibres near the surface of the prepreg shows that the fibres are subjected to a residual compressive strain. The application of a tensile stress to the composite causes the fibre strain to become tensile although significant scatter is found in the measurements. The scatter is thought to be due to variations in the local carbon‐fibre strain at the 1 μm level. It is demonstrated that residual compressive strain is expected from differential shrinkage between the fibres and matrix on cooling the composite from the processing temperature to room tempe

ISSN:0007-1641    

DOI:10.1002/pi.4980210104

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSince its inception in the late 1950s, pyrolysis gas‐liquid chromatography has rapidly become an important tool for the polymer chemist. Applications range from polymer characterisation to the elucidation of polymer degradation mechanism. Typical analytical applications include the characterisation of complex polymer mixtures, the assessment of copolymer composition and microstructure, structural analysis and the assignment of polymer tacticity. Recent advances in the technique are reviewed and examples of results are given.Most current GLC equipment is perfectly adequate for polymer/copolymer analysis provided that certain basic requirements are satisfied. For polymer characterisation, furnace and Curie‐Point methods are not the most appropriate and even simple filament methods are preferable to these. Refined filament techniques are the most suitable methods for studying degradation kinetics, and can provide a highly precise specification of polymer structure.For example, studies on the dependence of the specific rate of pyrolysis can distinguish anionic and free‐radical polymers. Analysis of the energetics of the degradation may indicate the activation energy for end initiation; this may be compared with bond‐strengths of possible end‐group structures. A similar process can be used to elucidate the nature of possible ‘weak‐links’ within the polymer backbone. The effects of polymer modification, for example oxidation, may also be assessed. Examples are quoted for these situations and the requirements of the techniq

ISSN:0007-1641    

DOI:10.1002/pi.4980210105

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractCoupled column chromatography has been performed with two chromatographic systems in which fractions from a size exclusion column are injected into a second column where retention is determined by non‐exclusion mechanisms. This has been accomplished by directing the eluent from the first column system through the injection valve of the second column system. The first column system contained crosslinked polystyrene gel with the eluent tetrahydrofuran as good solvent. The second column system contained crosslinked polystyrene gel (or crosslinked polyacrylamide gel) with a mobile phase consisting of a solvent/non‐solvent mixture which is a poor solvent promoting non‐exclusion mechanisms for statistical copolymers of styrene andn‐butyl methacrylate. Separations dependent on copolymer composition as a function of the non‐solvent component in the mobile phase and the polarity of the stationary phase in the second column system have been accomplished by isocratic

ISSN:0007-1641    

DOI:10.1002/pi.4980210106

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe utility of mass spectrometry as a technique for the characterisation of polymeric formulations is discussed in general terms. The use of thermal techniques in which sufficient energy is given to the system to liberate volatile components of the formulation and, in some cases, to induce small amounts of polymer degradation, is described. Results obtained using this technique for a variety of polymer systems are discussed and the advantages of using this approach outlined. Recent developments in field desorption‐mass spectrometry for the direct characterisation of modern polymer systems are discussed and some early results presente

ISSN:0007-1641    

DOI:10.1002/pi.4980210107

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPoly(p‐methylstyrene)‐graft‐poly(oxyethylene) copolymers were prepared fromp‐methylstyrene and æ‐hydroxy‐ω‐methyl‐poly(oxyethylene) using a ‘grafting on to’ technique. A total of 10 copolymers were synthesized varying in the hydrophobic back bone chain lengths, hydrophilic branch lengths and frequency of branches. The stabilizing efficiency of these amphipathic copolymers was studied in the emulsion polymerization of styrene. Using the number, size and size distribution of the particles as the criterion of stability, it was found that the polyoxyethylene (PEO) chain length is not as crucial for stability as the availability of the backbone for anchoring. A change in the backbone chain length (from M̄n= 1000 to 24000) with the same percent PEO had no effect on the outcome of the reaction: the latices stabilized to the same number of part

ISSN:0007-1641    

DOI:10.1002/pi.4980210108

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis work reports adhesion behaviour of polyethylene on paper, and deals with the surface energy of the materials involved in the manufacture of these composites, and its influence on the adhesion strength, at constant roughness, for the paper substrates. The surface energy of different papers treated with various sizing agents was determined by measuring contact angles according to the Owens‐Wendt method. The peeling energy was shown to follow a linear relationship versus the reversible energy of adhesion. This result is explained by the fact that rupture takes place at the interface and that the size of the defect at the interface depends on the spreading coefficient. Corona treatment, applied to strongly sized papers before making the composites, restored the adhesion strength to its original range of values, again demonstrating the thermodynamic character of adhesion in thermoplastic‐paper composi

ISSN:0007-1641    

DOI:10.1002/pi.4980210109

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe mass spectra were determined of three epoxy resin precursors:N,N‐bis‐(2,3‐epoxypropyl)‐N′,N′‐dimethyl‐4,4′‐diaminodiphenylenemethane (G2A);N,N′‐bis‐(2,3‐epoxypropyl)‐N,N′‐dimethyl‐4,4′‐diaminodiphenylene methane (G2S); andN′,N′,N′,N′‐tetrakis‐(2,3‐epoxypropyl)‐4,4′‐diaminodiphenylene methane (TGDDM); and of three related model compounds:N,N‐dimethylaniline (DMA);N‐methyl‐N‐glycidylaniline (MGA) andN,N‐digrycidylaniline (DGA). The results helped to confirm the structure of the resin precursors and are intended to pave the way for subsequent thermal degradation studies of cured resin samples. Despite the similarity in chemical structure of the compounds studied th

ISSN:0007-1641    

DOI:10.1002/pi.4980210110

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractBenzyl chloride has been used in a kinetic study of chlorine replacement by acetoxy groups to model the behaviour of allylic chlorine during the acetoxylation of poly(vinyl chloride). Chlorine substitution was carried out in tetrahydrofuran at 30°C using a potassium acetate‐crown ether complex with methanol to ensure homogeneous solution. The process followed an SN2 mechanism. The orders of reaction with respect to benzyl chloride and potassium acetate were close to one, and the second order velocity constant was 4.2 x 10−5litre mol−1s−1when the molar ratio of crown ether to potassium acetate was approximately unity. Higher ratios caused a slight increase in rate constant. Substitution was followed by NMR spectroscopy which also revealed a proton exchange between methanol and acetate anion with an equilibrium constant 9.4 x 10−2. This observation has suggested an explanation for the effect of some free‐radical inhibitors on the rate of acetoxylation of poly(vinyl chloride) by potassium acetate in the presence of

ISSN:0007-1641    

DOI:10.1002/pi.4980210111

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY