Major Thermoplastic Addition Polymers

Four thermoplastic addition polymers—polyethylene, poly(vinyl chloride), polypropylene, and polystyrene—comprise the majority of the total amount of polymers manufactured in the United States. In 2002 a total of 33.6 million metric tons of these plastics was produced, distributed as shown in Table 24.1. 

Major suppliers of low-profile thermoplastic additives include Discas Inc. and Union Carbide Chemicals Plastics Co. Major suppliers of low-profile elastomeric additives include Dexco Polymers, Shell Chemical Co., and Union Carbide Chenucals Plastics Co. 

It is our purpose in this book to describe the components and composition of major types of polymer compounds used in both the thermoplastics and rubber industries. We will describe the intended mechanisms of these additives and their sometimes unintended various interactions with one another. 

PVC has grown into one of the major thermoplastic materials, since it was first produced in the 1930 s. There are a variety of PVC polymers available in the current commercial market. However, because of its inherent disadvantages, such as low thermal stability and brittleness, PVC products are subject to some limitations in certain applications. The common approach to overcome these drawbacks has been the utilization of a vast array of additives during the formulation of the resin. 

Performance requirements, environmental issues, and avaUabUity/cost of the material will mainly drive material requirement in the future. In order to face the huge tire wastage problem causing major hazards to the environment, future development in mbbery materials will be focused on development of thermoplastic polymer so that used polymer could be recovered by thermal treatment and separation, biological degradation by radiation/addition of chemical into the mbber compound that could be activated by exposure to radiation and development of biopolymer. 

FIRE RETARDANT FILLERS. The next major fire retardant development resulted from the need for an acceptable fire retardant system for such new thermoplastics as polyethylene, polypropylene and nylon. The plasticizer approach of CP or the use of a reactive monomer were not applicable to these polymers because the crystallinity upon which their desirable properties were dependent were reduced or destroyed in the process of adding the fire retardant. Additionally, most halogen additives, such as CP, were thermally unstable at the high molding temperatures required. The introduction of inert fire retardant fillers in 1965 defined two novel approaches to fire retardant polymers. 

First introduced industrially in the 1930s, thermoplastic polymers are today produced and consumed in vast quantities and play a major role in many aspects of our everyday lives. It is estimated that over 16 million tons were consumed in Western Europe alone in 1991 [1]. Mineral fillers have, since the beginning, made an important contribution to the spectacular growth of thermoplastic polymers. The addition of mineral materials was initially seen mainly as a means of extending or reducing the compound cost but, as the relative cost of the polymers decreased, this became less important and attention was more and more focused on the property improvements that could be achieved. 

TPOs are basically two-component elastomer systems consisting of an elastomer finely dispersed in a thermoplastic polyolefin (such as polypropylene). The thermoplastic polyolefin is the major component. Thermoplastic elastomers (TPEs) include TPOs, TPVs (thermoplastic vulcanizates), etc. Properties of TPOs depend upon the types and amounts of polymers used, the method by which they are combined, and the use of additives such as oils, fillers, antioxidants, and colors. Blends and reactor-made products compete primarily with other TPEs and metals. There are vulcanizates (TPVs) that have higher elastomeric properties. They compete primarily with TS elastomers. 

In addition to their use in large-volume parenterals and IV sets, thermoplastic polymers have also recently found utility as packaging materials for ophthalmic solutions and some small-volume parenterals [43], However, there are many potential issues with using these polymers as primary packaging components that are not major concerns with traditional glass container closure systems, including [44] ... 

In addition to the synthesis problems mentioned above, unsurmountable processing problems were eneountered for the resulting polymers. Extensive erosslinking under melt proeessing eonditions led to a lack of significant thermoplastic properties of the resulting materials, and this also presented a major developmental hurdle. At the end of the 1970s, it was therefore concluded that the polymer baekbone of polyketone was inherently unstable and that polyketones eould not be efficiently produced. Both conclusions proved to be invalid. 

Another class of adherends is that of thermoplastic polymers. In contrast to metal adherends, thermoplastics are not impenetrable and thus absorption effects can be expected in addition to adsorption phenomena. Hence, given sufficient conditions for preferential absorption, a considerable mass uptake by the thermoplastic can occur, potentially resulting in significant stoichiometric imbalances on the epoxy side. Apart from the driving force for absorption of molecules from the liquid epoxy formulation, it is the diffusivity of these molecules within the thermoplastic which plays a major role in the interdiffusion process. In particular, the diffusivity is affected by the mobility of the host molecules. Thus enhancement of diffusivity occurs in the glass transition region and at higher temperatures when intermolecular cooperative motion is activated. 

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