Polymer blend Subject

Because of the great diversity of multiphase polymers, coverage of the entire field In a single volume Is neither possible nor practical. Instead, this book concentrates on two specific subjects polymer blends, including Interpenetrating polymer networks, and lonomers. Even with this specialization, a comprehensive treatise on both subjects is not possible, and this book focusses on selected contemporary topics from the two fields. 

Recent work on thermoplastic vulcanizates (TPVs) will not be included in this chapter since it is being reviewed elsewhere in the book. Abbreviations for some mbbers and accelerators will be used throughout in place of their full names as shown in Table 11.1. Acronyms for other polymers and additives wUl be provided in the text as required. A short discussion of polymer miscibility and compatibUization of polymer blends will be provided for better appreciation of the subject. 

Intermolecular forces also play an important role in determining the compatibility of two or more polymers in a polymer blend or polymer alloy. Although the distinction between a polymer blend and a polymer alloy is still the subject of some debate, we will use the convention that a polymer alloy is a single-phase, homogeneous material (much as for a metal), whereas a blend has two or more distinct phases as a result of polymer-polymer immiscibility (cf. Section 2.3.3). In general, polymers are... 

A number of classes of polymer blends containing block copolymers have been studied. Namely, binary blends of a block copolymer with a homopolymer, ternary mixtures of a block copolymer with two homopolymers and blends of two block copolymers. Experimental and theoretical studies of all these mixtures are the subject of Chapter 6. 

Our understanding of the physics of block copolymers is increasing rapidly. It therefore seemed to me to be timely to summarize developments in this burgeoning field. Furthermore, there have been no previous monographs on the subject, and some aspects have not even been reviewed. The present volume is the result of my efforts to capture the Zeitgeist of the subject and is concerned with experiments and theory on the thermodynamics and dynamics of block copolymers in melt, solution, and solid states and in polymer blends. The synthesis and applications of these fascinating materials are not considered here. 

No attempt is made to review solution theory. For a thorough treatment on this subject, numerous authoritative monographs (3, 4, 5, 6, 7) are available. We discuss only those thermodynamic considerations which have some bearing on the discussion of compatibility of polymer blends. 

Since we want to treat polymer blends subjected to an inhomogeneous temperature field (produced, e.g., by light absorption), the heat equation... 

The final chapter on applications of optical rheometric methods brings together examples of their use to solve a wide variety of physical problems. A partial list includes the use of birefringence to measure spatially resolved stress fields in non-Newtonian flows, the isolation of component dynamics in polymer/polymer blends using spectroscopic methods, the measurement of the structure factor in systems subject to field-induced phase separation, the measurement of structure in dense colloidal dispersions, and the dynamics of liquid crystals under flow. 

Blending of polymers is an attractive method of producing new materials with better properties. Blends of aliphatic polyesters, especially of poly(e-CL), have been investigated extensively and have been the subject of a recent review paper [170]. Poly(e-CL) has been reported to be miscible with several polymers such as PVC, chlorinated polyethylene, SAN, bisphenol A polycarbonate, random copolymers of Vdc and VC, Vdc and AN, and Vdc/VAc, etc. A single composition-dependent Tg was obtained in the blends of each of these polymers with poly(e-CL). This is of interest as a polymeric plasticizer in these polymers. Blends of PVC and poly(e-CL) with less than 50 wt % of poly(e-CL) were homogeneous and exhibited a single Tg. These blends were soft and pliable because the inherent crystallinity of poly(e-CL) was destroyed and PVC was plasticized... 

Our group was the first to report imaging with a diamond ATR accessory that provided a field of view of ca. 1 mm2 and the spatial resolution of ca. 15 pm without the use of an infrared microscope [18], The demonstration of the applicability of a diamond ATR accessory for FTIR imaging opened up a range of new opportunities in polymer research, from compaction of tablets [21-23] to studying phase separation in polymer blends subjected to supercritical fluids [24], This imaging approach was successfully utilised for the study of dissolution of tablets in aqueous solutions [25], We have also demonstrated macro... 

Finally, we draw attention to a topic somewhat neglected in this review, namely the interplay between concentration inhomogeneities ( > p,z near the surfaces and interfaces and the local configurational properties of the polymer coils (enrichment of chain ends, orientation and possibly distortion of polymer coils, etc.). The reason for this omission was that not so much general features are known about these questions. Clearly, the subject of phase transitions of polymer blends and block copolymer melts in thin film geometry will remain a challenge in the future. 

Polymer blends have become a very important subject for scientific investigation in recent years because of their growing commercial acceptance. Copolymerizalion and blending are alternative routes for modilications of properties of polymers. Blending is the less expensive method. It does not always provide a satisfactory alternative to copolymerization, of course, but polymer blends have been successfully used in an increasing number of applications in recent years. Such successes encourage more attempts to apply this technique to a wider range of problems in polymer-related industries. 

The quantitative study of polymer surfaces and interfaces is about ten years old and so is a relatively recent subject. It is therefore not surprising that there are many possibilities for future research. Many of the phenomena that occur at polymer interfaces are related to self-assembly. Even the simplest example, that of surface segregation of one component of a polymer blend to an interface is self-assembly. This is because where we initially had a homogeneous film, we now have one with two layers, a bulk layer and a surface segregated layer. We have shown how even such a well-studied phenomenon as surface segregation can have a future because with it one can generate a surface which could provide an excellent precursor to an interface. 

Polymer blends and solutions are subjected to nonlinear flows when processed, and this can have important effects on the lengthscale of the ultimate morphology. Flow-concentration couplings in polymer solutions due to molecular deformation is an old problem, and much is known experimentally and... 

In summarizing the results from the last three sections, one can conclude that the systematic variation of microhardness under strain performed on (a) homo-PBT (Section 6.2.1), (b) its multiblock copolymer PEE (Section 6.2.2) and (c) on blends of both of these (this section) is characterized by the ability of these systems to undergo a strain-induced polymorphic transition. The ability to accurately follow the strain-induced polymorphic transition even in complex systems such as polymer blends allows one also to draw conclusions about such basic phenomena as cocrystallization. In the present study of a PBT/PEE blend two distinct well separated (with respect to the deformation range) strain-induced polymorphic transitions arising from the two species of PBT crystallites are observed. From this observation it is concluded that (i) homo-PBT and the PBT segments from the PEE copolymer crystallize separately, i.e. no cocrystallization takes place, and (ii) the two types of crystallites are not subjected to the external load simultaneously but in a sequential manner. 

Blends. There has been considerable research in recent years on polymer blends that contain an LCP. This subject was recently reviewed by Dutta et al. (67). The addition of an LCP to another thermoplastic melt effectively lowers the melt viscosity and improves processability. In addition, if the flow field contains an extensional stress component, the LCP dispersed phase is extended into a fibrous morphology and oriented in the flow direction. This microstructure can be retained in the solidified blend to provide self-reinforcement. 

This chapter provides a broad overview of the subjects of polymer blends and lonomers. Specific topics concerning polymer blends Include the thermodynamics of mixing of polymer-polymer pairs, polymer Interfaces, rheology, and mechanical properties. For lonomers, the chemistry, structure, rheology and solution properties are discussed. 

The field of multiphase polymers is tcx) broad for any single volume. Two of the more important topics within the field from the perspectives of both applications and scientific challenges are polymer blends and ionomers. The high level of interest in these areas is evidenced by the explosive growth of the literature and patents devoted to these subjects. With this in mind, we felt that a book devoted to recent advances in these fields was justified. 

Although immiscible polymer blends and ionomers share a common feature in that both exhibit more than a single phase, a major difference between the two systems involves the dispersed phase size. For blends, this is generally of the order of micrometers and may be detected optically. Ionomers, however, are microphase-separated with domain sizes of the order of nanometers. Thus, blends and ionomers represent two extremes of the subject of multiphase polymers. In this book, the reader will observe similarities as well as differences in the problems... 

The polymer-blend dispersions of PTFE and fluorinated-pitch with various concentration of fluorinated-pitch have been coated on stainless steel (SUS-304). The various coated polymer-blend were heat-treated at 350 °C 5 °C for 30 minutes. Further, samples were subjected to EB irradiation with a 200keV from EB accelerator (CURETRON , NHV Corporation) up to 1000 kGy at 330 °C 3 °C in nitrogen gas atmosphere. 

In the following part, a discussion on the crystallization behavior in immiscible polymer blends is given, including the nucleation behavior, spheiuhte growth, overall crystallization kinetics, and final semicrystalline morphology. Each topic is illustrated with several examples from the literature, to allow the reader to find enough references on the discussed subject for further information. 

Table 5.2 shows further examples of dispersed phase coalescence in blends of PA dispersed phase in a less viscous PE or PS matrix. The data show that the mean PA particle size increases dramatically with simple heating under static conditions in the absence of any mechanism for morphology stabilization. The same coalescence can occur in molded parts of uncompatibilized polymer blends subjected to further thermal treatment after molding (fi.g., in a paint drying oven). The mechanical properties of these blends are quite poor. 

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