Early Synthetic Polymer Blends

As described in Section 1.1, the first commercial polymers, which were naturally occurring, were polyisoprenes (natural rubber and gutta-percha) and subsequently cellulose derivatives. From the early twentieth century, various totally synthetic polymers were introduced. Farbenfabrrken Bayer introduced bulk polymerized totally synthetic elastomers in 1910. Poly(dimethyl butadiene) synthetic rubber was produced commercially by Bayer in Leverkusen during World War I. The 1920s saw the commercial development of polystyrene (PS) and poly(vinyl chloride) (PVC). In 1934, the IG Farbenindustrie (a combine of Bayer, BASF, Floechst, and other firms) began to commercially manufacture butadiene-acrylonitrile copolymer (N BR) as an oil resistant rubber and in 1937 butadiene-styrene copolymer (SBR) intended for pneumatic tires. 

From the 1960s onwards there have been extensive investigations of polymers blends in both industrial and academic laboratories around the world. 

---

The first patent on PAB was granted to Parkes in 1846 for two natural polymers co-vulcanized during blending in the presence of CS2, i.e., a natural rubber (NR = amorphous c/s-polyisoprene, IR) with gutta-percha (GP = semicrystalline trans-polyisoprene, IR). Thus, mbber PAB predates that of synthetic polymers by ca. 80 years (PMA/PVAc 1929). Notably, while the early plastics were bio-based, their usage fell to <5 wt% nowadays slowly recovering from the absolute dominance of synthetic, petroleum-based plastics. 

Another approach to biodegradability is to blend a biodegradable natural polymer with a thermoplastic synthetic pol5nner. Blends of starch with PE or with poly(vinyl alcohol) have been commercialized as packaging materials (176), although they have mainly been used in niche markets. Early materials were rather poor because the encapsulating effect of the PE on the starch protected it from water access, and, even if the starch was biodegraded, the PE was left... 

Considerable effort is being made (ca 1993) to develop satisfactory flame retardants for blended fabrics. It has been feasible for a number of years to produce flame-resistant blended fabrics provided that they contain about 65% or more ceUulosic fibers. It appears probable that blends of even greater synthetic fiber content can be effectively made flame resistant. An alternative approach may be to first produce flame-resistant thermoplastic fibers by altering the chemical stmcture of the polymers. These flame-resistant fibers could then be blended with cotton or rayon and the blend treated with an appropriate flame retardant for the ceUulose, thereby producing a flame-resistant fabric. Several noteworthy finishes have been reported since the early 1970s. 

Phosphonium Salt—Urea Precondensate. A combination approach for producing flame-retardant cotton-synthetic blends has been developed based on the use of a phosphonium salt—urea precondensate (145). The precondensate is appUed to the blend fabric from aqueous solution. The fabric is dried, cured with ammonia gas, and then oxidized. This forms a flame-resistant polymer on and in the cotton fibers of the component. The synthetic component is then treated with either a cycUc phosphonate ester such as Antiblaze 19/ 19T, or hexabromocyclododecane. The result is a blended textile with good flame resistance. Another patent has appeared in which various modifications of the original process have been claimed (146). Although a few finishers have begun to use this process on blended textiles, it is too early to judge its impact on the industry. 

The development of compormds and blends of polymers dates back almost two centmies to the early rubber and plastics industry, when rubber was mixed with substances ranging from pitch [3] to gutta percha [4]. As each new plastic has been developed, its blends with previously existing materials have been explored. Thus, synthetic rubbers, in the early period of the plastics industry, were mixed into natural rubber and formd to produce superior performance in tire components. Polystyrene (PS) was blended with natiual and synthetic rubbers after its commercialization, and this led to high impact polystyrenes (HIPS), which now hold a... 

Polymerization of vinyl monomers intercalating into the montmorillonite (MMT) clay was first reported in the literature as early as 1961. The most recent methods to prepare polymer-layered-siUcate nanocomposites have primarily been developed by several other groups. In general these methods (shown in Fig. 5.1) are able to achieve molecular-level incorporation of the layered silicate (e.g. montmorillonite clay or synthetic layered silicate) in the polymer matrix by addition of a modified silicate either to a polymerization reaction (in situ method), to a solvent-swollen polymer (solution blending), or to a polymer melt (melt blending). Recently, a method has been developed to prepare the layered silicate by polymerizing silicate precursors in the presence of a polymer. ... 

---