Polymer blends with ionomers

Blending of ionomers with other homopolymers is also one means of enhancing mechanical performance. Frequently, in ionomer/polymer blends, synergistic effects are realized and properties may be significantly increased over anticipated values based on the rule of mixtures. This area of study has not been extensively explored and the probability clearly exists that new materials and new blends, having even a greater degree of property enhancement, will become available in the near future. 

Ionic bonds, in which electrons are donated to, or received from other atoms, occur in a few polymers. Du Pont Surlyn ionomers are copolymers of ethylene and methacrylic acid. Part of the methacrylic acid is neutralised with zinc or sodium ions. Ionic bonds are relatively strong and ionomers contain clusters of ions, which act rather like crosslinks. Some ionomers are blended with other polymers to improve toughness. 

The results of such contact experiments are highly dependent on the presence of moisture and on the addition of ionic salts to the polymers. Especially interesting are those studies with polymers blended with ionomers. In a model of... 

Another example of favorable synergistic effects in ionomer/homopolymer blends is evident from a study of the tensile properties of blends of an SPS ionomer with PS. Over most of the composition range these two polymers are incompatible. For small additions of the SPS ionomer to PS, TEM studies of cast thin films show that... 

A route to compatibility involving ionomers has been described recently by Eisenberg and coworkers [250-252]. The use of ionic interactions between different polymer chains to produce new materials has gained tremendous importance. Choudhury et al. [60] reported compatibilization of NR-polyolefin blends with the use of ionomers (S-EPDM). Blending with thermoplastics and elastomers could enhance the properties of MPR. The compatibility of copolyester TPE, TPU, flexible PVC, with MPR in aU proportions, enables one to blend any combination of these plastics with MPR to cost performance balance. Myrick has reported on the effect of blending MPR with various combinations and proportions of these plastics and provided a general guideline for property enhancement [253]. 

Thermoplastic elastomers (TPE), 9 565-566, 24 695-720 applications for, 24 709-717 based on block copolymers, 24 697t based on graft copolymers, ionomers, and structures with core-shell morphologies, 24 699 based on hard polymer/elastomer combinations, 24 699t based on silicone rubber blends, 24 700 commercial production of, 24 705-708 economic aspects of, 24 708-709 elastomer phase in, 24 703 glass-transition and crystal melting temperatures of, 24 702t hard phase in, 24 703-704 health and safety factors related to, 24 717-718... 

Sulfonated EPDMs are formulated to form a number of rubbery products including adhesives for footwear, garden hoses, and in the formation of calendered sheets. Perfluori-nated ionomers marketed as Nation (DuPont) are used for membrane applications including chemical-processing separations, spent-acid regeneration, electrochemical fuel cells, ion-selective separations, electrodialysis, and in the production of chlorine. It is also employed as a solid -state catalyst in chemical synthesis and processing. lonomers are also used in blends with other polymers. 

Ionomer polymer mixtures can be blended with various products. The materials used to cut the ionomer are paraffins, microcrystalline waxes, plasticizer free vinyl chloride, polymer mixtures of polyethylene, polypropylene as well as natural and synthetic rubber. Finished materials made from uncrosslinked ionomer mixtures may not be used for contact with fatty foods. 

Recent literature (72, 74) has indicated a considerable interest in blending ionomers (such as du Pont s Surlyn) with a variety of polymers. It is believed that an ionomer-nylon blend is the basis for a new engineering thermoplastic. 

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. 

The chapters in this volume represent the current trends in the fields of polymer blends and ionomers, including materials development, characterization, theory, and processing. They are grouped into six sections the first three are concerned with polymer blends and interpenetrating networks and the latter three with ionomers. 

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... 

PA is the oldest engineering resin. It offers outstanding mechanical performance, easy process-ability and good chemical resistance. It is being widely used in injection molded parts for automotive, appliances, sports and leisure applications. There is consequently a large number of blends based on PA, particularly the impact modified compositions. For example, the Zytel family of PA s include PA-6, PA-66 and PA-612, all of which are available in elastomer-modified versions, blended with ionomers, elastomers or fluorinated polymers. 

Modification of Engineering Resins Specific interaction of the phosphonium ionomer from Exxpro elastomer with selected engineering resins such as Polycarbonates(PC), Polyesters(PET), Polyacrylates(PAE), Polyamides(PA), Polyphenylene Oxide(PPO), and Acetals(PAc) can be utilized to compatibilize, impact modify or nucleate the above resin in blends with similar polymers. Typical examples are ... 

As in conventional glass-ionomers, the acidic component in resin-modified glass-ionomers is either poly(acrylic acid) or acrylic/maleic acid copolymer. In many brands, this polymer is simply blended with the monomer HEMA in aqueous solution. However, in certain brands, the polymeric acid is modified with side chains that allow it to participate in the addition polymerization process and thereby form a copolymer network with the HEMA. 

Valenza, A., Carianni, G., Mascia, L., Radiation grafting functionalization of poly(vinylidene fluoride) to compatibilize its blends with polyolefin ionomers. Polymer Engineering and Science 1998,38(3), 452 60. 

The second part, Chapters 2-9, is concerned with polymer blends, including mechanical blends, graft copolymers, block copolymers, ionomers, and interpenetrating polymer networks. The development of most chapters proceeds from synthesis to morphology, and then shows how morphology affects or controls the physical and mechanical behavior of the finished material. The most exciting development of the past decade, the electron microscope studies of the details of phase separation, is emphasized. 

These polyesters, [-0-t )-C(CH3)2-( )-C02-< )-C0-] (Tg 188 °C and HDT = 120-175 °C), were introduced in 1974. The commercial resins include U-polymer , Ardel , Durel , and Aryloit . Their advantages include transparency, good weatherability, and high HDT. PAr has been blended with nearly all resins, including ABS, EPDM, ionomers, LCP, PA, PB, PBl, PBT, PC, PEI, PEK, PET, phenoxy, PMB, PS, PPE, PPS, etc. Three types of PAr blends are of particular importance - those with polyesters, PEST, polyamides, PA, and polyphenylenesulfide, PPS. A summary of PAr blends is provided in Table 1.75. 

There exist two obvious ways of increasing the active solids content of an adhesive effectively to 100% use of Hot melt adhesives and Reaction setting adhesives. The main constituent of hot melts is a thermoplastic polymer that may be blended with thermoplastic modifiers and extenders and inert fillers to create a system that is a load-bearing solid at the service temperature but a mobile liquid at the (higher) application temperature. Polyolefins, ionomers, polyesters and polyamides are among the polymer types that have been used as bases for Hot melt adhesives. 

Other studies have been carried on TPU blending with other polymers, such as polyvinyl acetate (10-35%) [71], polyhydrooxyether of bisphenol-A (Phenoxy) [72], acrylic polymers [73-74], poly(4,4 -diphenylsulfone terephthalamide) (PSA) [75], and ionomers [76], or ionic groups in nonpolar resins acting as compatibilizers [77]. 

In a further smdy, it was investigated if sulfonated low-cost ionomers can also be used as acidic cross-linkers for PBI polymers in order to reduce membrane costs. For this purpose, sulfonated polystyrene (S4a, Fig. 4.5) and poly (a-methylstyrene sulfonic acid), (S4b, Fig. 4.5) have been blended with commercial PBIOO (B4, Fuma-Tech) to 70 wt% PBIOO/30 wt% sulfonated polystyrene blend membranes. The membranes were characterized in terms of chemical stability by the immersion in Fenton s Reagent, thermal stability in terms of TGA-FTIR coupling and in terms of proton conductivity after PA doping [58]. Poly(-a-methylstyrene sulfonic acid) was chosen for comparison with sulfonated polystyrene since it is known that the main radical attack target of polystyrene is the tertiary C-H bond [59] which is not present in poly(a-methylstyrene), leading to verified better radical stabilities of poly(-a-methylstyrene), compared to poly(styrene) [60]. In Table 4.4, the results of thermal and FT stability of the blend membranes B3/S4a and B3/ S4b are listed. 

It is not out of place to give brief mention to the ionomers introduced by Du Pont in the mid-1960s. To produce these polymers an alkene, usually ethylene, is copolymerized with a few per cent of a second monomer such as an -carboxylic acid in order to introduce a few carboxylic acid groups into the chain. The copolymer is then blended with a metal salt which ionizes the acid group. Heat fugitive ionic cross-links form (between carboxylic groups via the metal... 

The 9%LiSPS ionomer was miscible with PC above 170°C. Samples with different compositions were heated to 210°C, which is well within the one-phase region, and held at that temperature for 40 min. before the scattering was measured in order to allow sufficient time for the polymers to mix. Figure 7 compares the WANS data for a (50/50) 9%LiSPS/PC blend in the two-phase and one-phase regions. A clear and significant change in the scattering profile occurred between two-phase blend and the... 

Polyolefins containing carboxylic acid groups, sometimes neutralized to form ionomers, form much stronger intermolecular hydrogen bonding and ionic attractions than simple polyolefins, and can thus contribute greatly to practical compatibility or even molecular miscibility of polyblends, particularly blends with more polar polymers. Occasionally sulfonated polyolefins offer similar benefits. Carboxylation of polyolefins has been noted occasionally throughout this survey. In the current section the emphasis is on carboxylic and sulfonic acid copolymers and their ionomers. 

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