PREFACE. Downloaded by on May 14, Publication Date: May 5, 1990 doi: /ba

Transcription

1 PREFACE JL HE CURRENT TECHNOLOGICAL DIRECTIONS of polymer-related industries have been shaped by the operative business and societal driving forces of the past several years. The resultant technological directions affect the product development cycle and shape the required materials characterization needs. The role of polymer characterization in the product development cycle is shown in Figure 1. Product development is no longer a simple straight-line process from product design to product performance, bridged by polymer and product characterization analysis and testing. The product development cycle must take into account the many constraints produced by the operative business and societal driving forces. These constraints include product development costs raw material supply energy conservation safety, health, and environmental considerations public consumerism product quality emphasis on customer needs shorter product development and market introduction cycles improved product-process-customer economics global competition As can be seen from Figure 1, the role of polymer characterization is to facilitate product development subject to these constraints. For example, the development of polymer products has been strongly influenced by environmental considerations and government regulations. Coatings are now being developed with significantly lower volatile organic content. Plastic packaging is being developed with built-in environmental degradability. For containers, it has become very desirable to use plastics that can be readily recycled. On a more basic level, very few new commodity building blocks (monomers) are expected to be developed because of economic and environmental considerations. Increased strategic use of low levels of specialty building blocks is expected in order to add product value. xv

2 CONSTRAINTS GENERATED BY BUSINESS AND SOCIETAL DRIVING FORCES POLYMER AND PRODUCT CHARACTERIZATION., ANALYSIS, AND TESTING y PRODUCT DESIGN POLYMER SYNTHESIS AND PRODUCT PROCESSING PRODUCT PERFORMANCE Figure 1. Role of polymer characterization in the product development cycle. In general, structure-morphology-property considerations are becoming of paramount importance in the development of new products. Examples include high-performance engineering plastics and composites that require strategically designed polymers, polymer alloys, and blends, as well as strategically designed polymers for electronic and biopolymer applications. It is not a question of what building blocks are put together, but how to put them together to make unique polymer products. This approach implies polymer structure-morphology control down to the molecular level to enhance properties. The polymer product development process in Figure 2 shows that polymer characterization methodology is required in each step of the process to acheive two goals: (1) to characterize the molecular architecture and physical properties produced by a particular polymerization method and mechanism, and (2) to characterize the polymer product resulting from product processing to relate surface and bulk properties and morphologies to application and end-use properties. Polymer characterization methodology is an important component of the product development cycle and process. On the basis of the ever-expanding list of constraints to product development produced by the operative business and societal driving forces, in the future polymer characterization will most likely assume an even greater role in the product development cycle. xvi

3 POLYMERIZATION METHOD AND MECHANISM PRODUCT PROCESSING APPLICATION AND END USE.PROPERTIES About the Book SURFACE & BULK PROPERTIES AND MORPHOLOGY^. Figure 2. Product development process. This book covers significant advances in polymer characterization methodology and is organized into four main areas: (1) polymer fractionation and particle size distribution, (2) dynamic mechanical analysis and rheology, (3) spectroscopy, and (4) morphology. Many of the chapters report on the combined use of several characterization methods in order to elucidate the relationship between polymer structure-morphology and polymer performance. The chromatographic method of thermal field flow fractionation (FFF) is complementary to gel permeation chromatography (GPC) for fractionating polymer molecules. It depends upon the thermal diffusion coefficient of the polymer molecule and is sensitive to both the polymer chemical composition and the molecular weight. Giddings et al. show that temperature gradient programming can improve the speed and resolution of the method. The thermal FFF method shows promise for fractionating and elucidating the molecular weight distribution of very high molecular weight polymers up to 60,000,000 daltons that cannot be adequately fractionated by GPC. Recent advances in high-temperature GPC include the use of laboratory robotics in the automation of instrumentation, discussed by Moldovan and Polemenakos, as well as the use of on-line viscosity detection, along with conventional refractive index detection to elucidate the long-chain branching xvii

4 distributions in polyethylene discussed by Mirabella and Wild. The separation and characterization of charge-containing synthetic polymers is a difficult problem that is amenable to solution by gel electrophoresis, a novel and promising technique that is discussed by Smisek and Hoagland. A variety of methods are available to characterize particle size and particle size distribution of latex particles. These can be categorized as fractionation techniques or nonfraetionation (counting) techniques. In this book, three counting techniques based on light-scattering methods are discussed: zero-angle depolarized light scattering, turbidity, and dynamic light scattering. Elicabe and Garcia-Rubio revitalized the turbidimetric method for obtaining particle size distribution information by the application of sophisticated mathematical regularization techniques. Kourti et al. and Nicoli and co-workers, in an unusual academic-industrial collaboration, have shown that dynamic light scattering can be used to monitor on-line, in real time, the particle growth and particle size distribution during the emulsion polymerization of vinyl acetate in a pilot scale reactor. The nine-chapter section on dynamic mechanical analysis and rheology involves the use of a variety of methods applied to study the kinetics and cure of polymerizing systems, as well as resulting polymer properties. The chapter by Wisanrakkit and Gillham is an excellent example of the use of the time-temperature-transformation principle applied to the glass transition temperature for monitoring thermoset cure. The relatively new techniques of thermally stimulated current and relaxation map analysis spectroscopy, discussed by Ibar et al. and Demont et al., represents a significant advance in dynamic methods to study the molecular response of materials such as semicrystalline polymers, copolymers, polyblends, polymer complexes, composites, and coatings. The use of dielectric thermal analysis (DETA) methods to study thermoset cure ex situ by Martin and co-workers and in situ by Kranbuehl et al. illustrates the complimentary nature of this technique to standard rheological measurements and to other methods for elucidating cure such as differential scanning ealorimetry (DSC) and dynamic mechanical analysis (DMA). DETA uniquely monitors the ionic mobility of a curing system and, therefore, can monitor the microviscosity (local viscosity) of a curing system using mobile ions as a probe. Therefore, DETA has excellent potential as a process monitoring method through the use of remote sensors. The chapter by Ishida and Nigro illustrates that the combination of chemical (Fourier transform infrared) and physical (dynamic mechanical testing) methods to study cure can provide a very complete picture of the cure process. Biesenberger and Rosendale demonstrate that a specifically designed rheocalorimeter can follow step and chain polymerization for a variety of polymerizing systems to provide viscosity-conversion data. xviii

5 The nine-chapter section on spectroscopy includes aspects of the many subtechniques of IR spectroscopy, Raman, fluorescence, and NMR spectroscopy. The IR spectroscopic techniques discussed include transmission Fourier transform IR (FTIR), photoacoustic (PA) FTIR, polarized attenuated total reflectance, and evolved-gas analysis. Unfortunately, the PA FTIR technique has generally been underutilized. In an overview chapter, Urban et al. demonstrate the wide range of useful applications of the PA FTIR technique, which include (1) the depth of profiling capability to study surfacetreated fibers, (2) utility to studying cure in a thermoset system, and (3) the ability to perform rheo-optical measurements in a photoacoustic IR cell on polymer systems. Kuo and Provder illustrate the utility of evolved-gas analysis by FTIR to study the kinetics of curing systems through the detection of evolved volatile compounds and demonstrate the complementary nature of the kinetic information to that obtained from thin film transmission FTIR measurements. Schwab and Levy were able to uniquely monitor physical aging of an epoxy resin by using a fluorescent molecular probe to follow the decrease in free volume with time by the increases in fluorescence intensity levels. Chapters that combine spectroscopic and physical methods to elucidate microstrueture of polymers are reported. Mirabella simultaneously monitors the crystalline melting of polyolefinic blends with DSC and FTIR spectroscopy. Mandelkern combines Raman spectroscopy with DSC to characterize crystalline polymers. Tonelli et al. combine solid-state NMR spectroscopy with DSC and X-ray diffraction studies to elucidate polymer microstructure-morphology. The last section deals with two unique studies involving morphological characterization. Sperling et al. studied the morphology of multicomponent and heterogeneous polymer systems, such as block copolymers, latex dispersions, blends, and interpenetrating networks with small-angle neutron scattering. This technique is able to provide information on the physical size of micromorphological domains. Hair and Letts were able to elucidate the morphological structure of gels and foams made from ultra-high-molecularweight polyethylene by using a range of characterization methods including, DSC, viscometry, optical microscopy, scanning electron microscopy, X-ray diffraction, and cloud point measurements. Acknowledgments We are grateful to the authors for their effective oral and written communications and for the effort they have expended to provide well-balanced coverage of the characterization methods included in this book. We also xix

6 acknowledge the many peer reviewers for their critiques and constructive comments. THEODORE PROVDER The Glidden Company (Member of ICI Paints) Strongsville, OH CLARA D. CRAVER Chemir Laboratories Glendale, MO August 14, 1990 XX