Poly p-phenylene benzobisthiazole

Scherf, J., Cohen, Y. and Wagner, H.D. (1992). Interfacial strength measurements in poly (p-phenylene benzobisthiazole)/epoxy composites. Intern. J. Adhesion Adhesive, 12, 251-256. 

Fibers and films obtained from lyotropic solutions of rigid polymers exhibit high tensile modulus and strength and are therefore of interest for structural applications. Poly(p-phenylene benzobisthiazole) (PBT) is a rigid polymer from which high... 

Lyotropic polymers consisting solely of ring structures are also known, and are exemplified by poly(p-phenylene benzobisthiazole) (IV), which forms a nematic phase in several strongly protonating acids including polyphosphoric acid. Its synthesis and application, like those of the aromatic amide polymers, are discussed later. 

Although aramid fiber is by far the most successful fiber made via the liquid crystal route, there are some other important fibers that have been made by this process. For example, poly(p-phenylene benzobisthiazole) (PBT) (Wolfe et al, 1981a, 1981b) is synthesized from terephthalic acid and 2,5-diamino-l,4-ben-zenedithiol dihydrochloride (DBD). The DBD is first dissolved in poly-phosphoric acid (PPA), followed by dehydrochlorination. Terephthalic acid and more PPA are then added and the mixture is heated to 160°C to make a solution. The solution is heated to 180 C and reacted for 18 hours to obtain the... 

Thermoset molecular composites reported by Chuah etal. [1989] investigated poly(p-phenylene benzobisthiazole) reinforcement of bisbenzocy-clobutene (BCB) terminated imide oligomers. Samples were prepared via extrusion of a solution of the blend followed by coagulation. Samples were compression molded to advance the thermosetting constituent. Phase separation (domain size of 100-200 nm) occurred during coagulation... 

One of the basic problems confronting molecular composites is the difficulty of finding miscible combinations of rigid rod polymers with flexible chain polymers. Poly(p-phenylene benzobisthiazole)/poly(-2,5(6)-benzimidazole block copolymers have been reported by Tsai et al. [1985] and are noted to exhibit better processability and mechanical properties than the simple blends of the block copolymer constituents. Chang and Lee [1993] prepared poly(p-benzamide)/Pl block copolymers and reported on the liquid crystalline behavior. Such approaches would appear to have future implications. As an example PA e.g., PA-66) block copolymers with rigid rod polyamides could be prepared and used in blends with PA-66 to yield the desired molecular composite. 

Molecular composites as an extension of fiber reinforcement Molecular composites is designed to use rigid rodlike molecules as reinforcement for the flexible coil molecules as matrix. The patent applications on the molecular composites were made almost in the same age independently by Takayanagi in Japan in 1977 and by Helminiak in the United States in 1978. Takayanagi proposed thermoplastic nylon reinforced by poly(p-phenylene terephthalamide)(PPTA) and Helminiak proposed wet process using poly(p-phenylene benzobisthiazole)(PBT)-reinforced poly(2,5(6)benzimidazole) (ABPBI). In molecular composite (MC) [15,16,17], the fineness of reinforcement was pursued to its limit, i.e. to the molecular dimension. 

PPTA poly(p-phenyleneterephthalamide) 0 50 100 150 200 250300 350 PBT poly(p-phenylene benzobisthiazole) Specific Tensiie Moduius... 

The aromatic heterocyclic rodlike polymers poly(p-phenylenebenzobisoxazole) (PBO) and poly(p-phenylene-benzobisthiazole) (PBZT or PBT) [14—20] possess rigid rodlike structures which provide superior tensile properties and excellent thermal stability. Thermal analysis of PBO and PBT reveals minimal weight loss in air at 316 °C. Thermal decomposition of both polymers begins at 600 °C and reaches a maximum between 660 and 700 °C. The total weight loss for both PBO and PBT is about 28% at 1,000 °C [16]. 

The early work on properties of molecular composites was done by Hwang et al. (1983a, b). They performed experimental studies of solution processing of films based on poly(p-phenylene benzobisthiazole) with both poly(2,5 (6 ) benzimidazole (ABPBI) and poly(2,5 (6 ) benzothiazole) (ABPBT). The films were shown to possess very high modulus and strength values, which improve upon heat treatment. The uniaxial modulus of highly oriented molecular composites was shown to follow the linear rule of mixtures. 

H. Akita, H. Kobayashi, Studies on molecular composite. IV. Block copolymer as a singlecomponent nano composite consisting of poly(p-phenylene benzobisthiazole) and thermoplastic aromatic polyamide. Polymer Journal 31 (10) (1999) 890-894. 

There are several other aromatic polymers, not polyamides, but which form fibers with high chain rigidity and similar properties. These would include poly(p-phenylene benzobisthiazole) (PBT) and poly(p-phenylene benzobisoxazole) (PBO) (Ref 4, Chapt. VII) ... 

Molecular composites by ion-ion interaction enhanced miscibility were described in the early 1990s for poly(2-acrylamido-2-methylpropanesulfonic acid)/poly(p-phenylene-benzobisthiazole) (PPBT) [50]. 

Another, closely related heterocyclic polymer poly(p-phenylene benzobisthiazole) (PBT) has a similar sOucture but contains sulfur in its monomeric units. 

High modulus fibers from lyotropic aromatic polyamides, poly(p-phenylene terephthalamide) (PPTA), were first conunercialized imder the Kevlar trademark by DuPont [414]. The aromatic polyamides, or aramids, are produced by a dry jet-wet spinning process where the nematic structure in solution is responsible for the high modulus fiber performance [415-419]. Another class of lyotropic fibers, also produced by dry jet-wet spinning, are the rigid rod polymers developed as part of the U.S. Air Force Ordered Polymers Program [420-424]. The most conunon of these ordered polymers, poly(p-phenylene benzobisthiazole) (PBZT), is difficult to process, but it exhibits the highest tensile properties of all the LCP fibers produced to date. 

Northolt and Sikkema [62] also noted that yielding is most pronounced in lower modulus LLCP fibers and that this phenomenon is less apparent in samples that have increased modulus. Furthermore, they quantified yield strain values of 0.7% for poly(p-phenylene benzobisthiazole) (PBTZ), 0.8% for poly(p-phenylene benzobisoxazole)(PBO), and 0.5% for poly(p-phenylene terephthalamide) fibers. The similarity of these levels with that of HBA/HNA TPCP suggests that these materials are governed by a common deformation process. This supports the application of the aggregate model to describe elastic extension of this less-crystalline TLCP. 

Poly(p-phenylene benzobisthiazole) is one of a group of polymers with rod-like molecules, spun into high strength fibers as part of the Air Force Ordered Polymers Research Program [343]. Allen et al. [383] described the development of high mechanical properties from anisotropic solutions of the polymer. The structure-property... 

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