Rubber blend with gutta percha

Rubber blending predates that of thermoplastics by nearly a century. In 1846, Parkes introduced the first blends of trans- and cw-l,4-polyisoprene, i.e., natural rubber (NR) with gutta-percha (GP). By varying the composition and/or adding fillers, the blends were formed into a variety of flexible or rigid articles. 

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. 

It seems that mixing has been a natural tendency for the human beings from the dawn of civilization. No sooner do two materials become available than someone starts experimenting with them. Blending is a natural way to widen the range of properties. This has been well illustrated by the history of polymer blends. When in 1846 only natural rubber, NR, and gutta percha, GP, were available, these were blended. Once nitrocellulose, NC, was invented, its blend with NR was patented in 1865 — three years before commercialization of NC. Then cellulose acetate, CA, was invented — blends of CA with NC were... 

The polymer industry traces its beginning to the early modifications of shellac, natural rubber (NR — an amorphous c -l,4-polyisoprene), gutta-percha (GP — a semi-crystalline trfl i-l,4-polyisoprene), and cellulose. In 1846, Parkes patented the first polymer blend NR with GP partially co-dissolved in CSj. Blending these two isomers resulted in partially crosslinked (co-vulcanized) materials whose rigidity was controllable by composition. The blends had many apphcations ranging from picture frames, table-ware, ear-trumpets, to sheathing the first submarine cables. 

It was only with the commercial appearance of gutta-percha in about 1845 [14—17] that there were investigations of polymer blends (gutta-percha with natural rubber). These were reported in patents of C. Hancock [17, 18], A. Parkes [13] and W. Brockedon and T. Hancock [19] in 1846. All of these inventors knew each other. Two were brothers (C. Hancock and T. Hancock) and two others (Brockedon and Parkes) were at the time business colleagues of the above T. Hancock. The patents cited above generally cite one or more of the others. This all took place in or near London, England. 

The first polymer blend patent appeared in 1846 in Birmingham, Alabama. A. Parkes blended gutta percha with natural rubber. Soon after the invention of nitrocellulose, blends of nitrocellulose with natural rubber were obtained. The first blend of two synthetic polymers came about in 1928 when polyvinyl chloride was mixed with polyvinyl acetate. By 1993, the polymer blend patent literature reached about 3000 patents a year [1]. 

Polymer blends offer improved performance/cost ratio and flexibility to tailor-made products. Compatible, incompatible, miscible, and immiscible blends are distinguished from each other. Polymer alloys are a commercial blends with improved property balance by use of a compatibilizer. By 1992, the worldwide production of plastics was twice that of steel. The manufacture of polymers would grow by a factor of 10 prior to market saturation. Table 1.1 provided a chronology of events in technology development in the field of polymer blends since the nitrile rubber/gutta percha was blended in 1846 first through the development of PPS/PBT in 1990. 

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... 

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