Commodity Modifications

Applications Research. Specialty chemical producers devote a larger share of their time and costs to appHcations research than do producers of most commodity chemicals. As noted earHer, the most successful specialty chemical producers have been those companies that ate able to respond quickly to customer needs and problems under the conditions found in the customer s plant. This entails having, at the specialty chemical plant, equipment and procedural knowledge which closely approximate those found among customers. Tests can then be mn and a solution to the problem or need may result. If successful, even in part, it can be brought to the customers and tried there. In practice, of course, each customer s plant has some variables which make a single answer or product quite unlikely. Fortunately, slight modifications by the suppHer will often solve the next customer s problem. 

Poly(vinyl chloride). PVC is one of the most important and versatile commodity polymers (Table 4). It is inherently flame retardant and chemically resistant and has found numerous and varied appHcations, principally because of its low price and capacity for being modified. Without modification, processibiUty, heat stabiUty, impact strength, and appearance all are poor. Thermal stabilizers, lubricants, plasticizers, impact modifiers, and other additives transform PVC into a very versatile polymer (257,258). 

Most of the resin systems used in commodity composites are slight modifications of the standard commercial mol ding grade material. Usually certain selected properties, such as purity or molecular weight range or distribution, are enhanced or carehiUy selected. In addition, special additives, such as flow controllers, thermal stabilizers, or antioxidants, are often added by the resin manufacturer prior to shipment. Many of the conventional or commodity-type resins used in thermoplastic composites are Hsted in Table 1 and the preparation of each of these is described. AH resins and blends described in the hterature are not Hsted, and the synthesis described is not the only procedure available, but is usually the most common commercial process. 

Nowadays, a strategic area of research is the development of polymers based on carbohydrates due to the worldwide focus on sustainable materials. Since the necessary multi-step synthesis of carbohydrate-based polymers is not economical for the production of commodity plastics, functionalization of synthetic polymers by carbohydrates has become a current subject of research. This aims to prepare new bioactive and biocompatible polymers capable of exerting a temporary therapeutic function. The large variety of methods of anchoring carbohydrates onto polymers as well as the current and potential applications of the functionalized polymers has been discussed recently in a critical review [171]. Of importance is that such modification renders not only functionality but also biodegradability to the synthetic polymers. 

This concept was introduced in 1948 by Sondheimer and Kertesz who nsed pH values of 2 and 3.4 for analyses of strawberry jams. Since then, the nse of other pH values has been proposed. Fnleki and Francis (1968) used pH 1 and 4.5 bnffers to measure anthocyanin content in cranberries, and modifications of this techniqne have been applied to a wide range of commodities. The absorbance of anthocy-anins at two different pH levels (1 and 4.5) is measured at Kis-max and at 700 mn, which corrects for haze in the sample (Table 6.3.1). The total monomeric anthocy-... 

Due to the necessity for aromatic structure in the commodity isocyanates, and the intensive chemical conversions required to derive the isocyanate reactant, no high-carbon frameworks derived principally from plant sources have been developed into isocyanates. The majority of the derivation of raw materials from high carbon conjugates has been focused on the development of polyols, for which the structural demands are a better fit for available renewable feedstocks. Although there are some notable exceptions [1], as a general rule modification of the... 

Abstract Polyolefins such as polyethylene, polypropylene and their copolymers have excellent bulk physical/chemical properties, are inexpensive and easy to process. Yet they have not gained considerable importance as speciality materials due to their inert surface. Polyethylene in particular holds a unique status due to its excellent manufacturer- and user-friendly properties. Thus, special surface properties, which polyethylene does not possess, such as printability, hydrophilicity, roughness, lubricity, selective permeability and adhesion of micro-organisms, underscore the need for tailoring the surface of this valuable commodity polymer. The present article reviews some of the existing and emerging techniques of surface modification and characterisation of polyethylene. 

PE, being a commodity polymer, is used in its different physical forms viz. fibres, sheets, membranes, moulds with different backbone chemical configurations (LPE, LLDPE, LDPE, HDPE, UHMWPE, UHSPE etc). Each of these forms of PE requires surface modification at some stage of application. The surfaces of PE fibres are often modified to make them compatible in the composites, whereas PE sheets/tapes are modified to achieve adhesion. Moulds are frequently surface-modified for probability and membranes for selective permeation. In the same way, different chemical configurations of PE, by the virtue of their properties, are used for different applications after surface modification. 

There are many polymer chain modification reactions of different types that have been carried out on polymer melts processed in single and twin rotor extruders. This activity, (4-6) in the analysis of polymerization reactors, driven by market forces seeking to create value-added polymers from commodity resins, started in the mid-1960s in industrial research laboratories (7). Indeed much of the early work is to be found in the patent literature.1 Although in recent times more publications, both industrial and academic can be found in the open literature, there is still a good deal of industrial secrecy, because the products of reactive polymer processing are of significant commercial value to industry. Below we will deal briefly with two important examples of such reactions. 

Essentially, then, no new, large-volume, highly profitable fibers have been developed since the mid-1950s. Instead, the existing ones have become commodities with all the economic impact thereby implied. No major chemical engineering processes have been added, although the previously described ones have been modified to allow for spinning of liquid crystalline polymers or the formation of gel spun fibers. Research activity has been reduced and centered essentially on modifications of fiber size, shape, and properties, and many variants now are successfully marketed. Production volumes have increased enormously for nylon, polyester, and polyolefin. 

Consumption = production (sold or used) + imports — exports. Source Buckingham, David A., and Phyllis A. Lyday, USGS Mineral Commodity Survey, modification April 1, 2005. 

These results also demonstrate that the template based polymer modification can be quite fruitful strategy and can lead to libraries of materials for commodity applications as well as for various sophisticated functions. Currently, we are studying comparative catalysis not only to improve the new functional group compatibility but also to explore reversal of regionselectivities and efficiencies. 

Polystyrene is one of the most widely used thermoplastic materials ranking behind polyolefins and PVC. Owing to their special property profile, styrene polymers are placed between commodity and speciality polymers. Since its commercial introduction in the 1930s until the present day, polystyrene has been subjected to numerous improvements. The main development directions were aimed at copolymerization of styrene with polar comonomers such as acrylonitrile, (meth)acrylates or maleic anhydride, at impact modification with different rubbers or styrene-butadiene block copolymers and at blending with other polymers such as polyphenylene ether (PPE) or polyolefins. 

After decreasing the research capacity in the fields of liquid crystalline and high-performance polymers at the beginning of the 1990s the emphasis in development work was placed on the improvement of commodities by special polymerisation techniques and the modification of engineering plastics. The basis of successful research was improved macromolecular and engineering know-how including analytical methods. 

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