Other Polymer Types

A plasticizer is a substance the addition of which to another material makes that material softer and more flexible. This broad definition encompasses the use of water to plasticize clay for the production of pottery, and oils to plasticize pitch for caulking boats. A more precise definition of plasticizers is that they are materials which, when added to a polymer, cause an increase in the flexibiUty and workabiUty, brought about by a decrease in the glass-transition temperature, T, of the polymer. The most widely plasticized polymer is poly(vinyl chloride) (PVC) due to its excellent plasticizer compatibility characteristics, and the development of plasticizers closely follows the development of this commodity polymer. However, plasticizers have also been used and remain in use with other polymer types. 

Lamination of polymer films, both styrene-based and other polymer types, to styrene-based materials can be carried out during the extmsion process for protection or decorative purposes. For example, an acryUc film can be laminated to ABS sheet during extmsion for protection in outdoor apphcations. Multiple extmsion of styrene-based plastics with one or more other plastics has grown rapidly from the mid-1980s to the mid-1990s. 

Anthracene-containing monomers of the methacrylic series (e.g. anthrylmethyl methacrylates) can also be used to obtain polymers with LM by copolymerization. The monomers of this type are successfully used for the introduction of LM (Table 1 LMj and LMa) into side groups not only of various methacrylate polymers (e.g. from methyl to cetyl- and cholesteryl methacrylates) also of other polymer types. In the latter case, it is advisable to use monomers in which the position 10 is substituted (e.g. by a methyl group). In this case, the probability of side homolytical reactions with the participation of anthracen groups con-sinderably decreases ... 

The long-term stress-strain behavior of polymers is generally more important than shortterm properties where the product is expected to sustain a stress or strain in service. Creep is dearly the most relevant where the product or component is to be subjected to a more or less constant stress. This is the case for a great many uses of rigid plastics and for such products as rubber mountings. Hence, creep data is often an essential design factor for plastics but is only used for other polymer types when particular applications are in mind. 

Details of the experimental procedures for rubbers are given in Chapter 15. and these could be used for other polymer types if required. 

Polyurethanes are distinguished from other polymer types in containing the repeating urethane group throughout its structure ... 

Acrylate adhesives differ from other polymer types in their ability to be cured rapidly by exposure to UV and/or visible light. Their main advantage over heat-curing adhesives is in bonding heat-sensitive electronic devices in 5-30 seconds at room... 

Now, while many rubber polymers exhibit many of these properties, none of them exhibits all of them, nor equally well. Each polymer type has its own unique set of properties and characteristics, which allows for an expanding array of choices for assembly applications. Listed below are the major areas in which elastomeric adhesives provide an advantage over other polymer types. 

Variety Although there are only a few basic categories of rubber polymers that make up the majority of applications, these polymers come in a wide array of distinct product grades within each category. In addition, most of these polymers are compatible with, and can be mixed freely with, other rubbery polymers to provide even more choices of properties, not to mention the virtually endless numbers of fillers, additives, reinforcing and tackifying resins, other polymer types, plasticizers, and other ingredients that can be used to further modify basic properties. 

As previously noted, the primary use for this elastomer has been as solvent-based adhesives and sealants. Solvent-based products are losing market share to water-based poly-chloroprenes, to other polymer types such as acrylics and polyurethanes, and to hot melt adhesives. However, where the processing facility is able to contain the vapor emissions, a solvent-based adhesive or sealant is preferred because of better wetting of surfaces, faster drying, and higher performance of the cured or dried product. Many rubber bonding... 

The mechanical and electrical properties of acrylates are similar to those for many other polymer types. Tensile strengths range from approximately 1,300 psi to 4,500 psi and shear strengths of PCB lap samples range from 424 to 566 psi. Aluminum-to-aluminum lap-shear strengths are reported at approximately 3,000 psi. Electrical volume resistivities under room ambient conditions ranged from 1 x ohm-cm to 1.4 x 10 ohm-cm. dielectric constants from 3.15 to 3.43 at 10 MHz and dissipation factors... 

Although acrylates have received the most attention, a number of other polymer types have been reported in... 

The main problem associated with using narrow-MMD calibrants is the restricted range of polymer types available. Poly(styrene) calibrants are the main type used, and a very wide range of molecular masses is available. A small number of other polymer types is obtainable, but the molecular mass range is often rather limited. Poly(ethylene oxide) and poly(ethylene glycol) calibrants deserve special mention, because they can frequently be employed where poly(styrene) behaves anomalously, for instance in polar solvents such as dimethylformamide. Some of the narrow-distribution polymer calibrants available are listed in Table 3.1 and Appendix 2. 

The move away from OBPA is evident in the product lines sold by Akcros Chemicals, a company that addresses both the material protection and hygienic surface markets. Akcros sells biocides imder the Intercide name for use in PVC, polyolefins and other polymer types. Between them these products can deal with all the various types of microorganism (fungi, bacteria, yeasts). 

By comparison, as other polymer types are of higher density and generally more expensive, they tend to be used where their physical and/or chemical properties significantly out-perform those of polypropylene. For example, fibres and filaments in the polyamide family, whilst unable to compete with polypropylene in strongly acidic conditions, are notably tougher and more durable than polypropylene. As a result, they are often found in less demanding chemical environments where high resistance to harsh abrasive... 

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