Bisbenzocyclobutene: A thermoset matrix host for rigid-rod molecular composites

1989 ◽  
Vol 29 (2) ◽  
pp. 107-112 ◽  
Author(s):  
H. H. Chuah ◽  
L.-S. Tan ◽  
F. E. Arnold
Keyword(s):  
Molecular Composites ◽  
Rigid Rod

Morphology of High-Performance Rigid-Rod Polymer Fibers and Molecular Composites

1989 ◽  
Vol 47 ◽  
pp. 338-339
Author(s):  
W.W. Adams ◽  
S. J. Krause
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Liquid Crystalline ◽  
Molecular Level ◽  
Synergistic Effects ◽  
Tensile Modulus ◽  
Commercial Development ◽  
The Matrix ◽  
Molecular Composites ◽  
Rigid Rod

Rigid-rod polymers such as PBO, poly(paraphenylene benzobisoxazole), Figure 1a, are now in commercial development for use as high-performance fibers and for reinforcement at the molecular level in molecular composites. Spinning of liquid crystalline polyphosphoric acid solutions of PBO, followed by washing, drying, and tension heat treatment produces fibers which have the following properties: density of 1.59 g/cm3; tensile strength of 820 kpsi; tensile modulus of 52 Mpsi; compressive strength of 50 kpsi; they are electrically insulating; they do not absorb moisture; and they are insensitive to radiation, including ultraviolet. Since the chain modulus of PBO is estimated to be 730 GPa, the high stiffness also affords the opportunity to reinforce a flexible coil polymer at the molecular level, in analogy to a chopped fiber reinforced composite. The objectives of the molecular composite concept are to eliminate the thermal expansion coefficient mismatch between the fiber and the matrix, as occurs in conventional composites, to eliminate the interface between the fiber and the matrix, and, hopefully, to obtain synergistic effects from the exceptional stiffness of the rigid-rod molecule. These expectations have been confirmed in the case of blending rigid-rod PBZT, poly(paraphenylene benzobisthiazole), Figure 1b, with stiff-chain ABPBI, poly 2,5(6) benzimidazole, Fig. 1c A film with 30% PBZT/70% ABPBI had tensile strength 190 kpsi and tensile modulus of 13 Mpsi when solution spun from a 3% methane sulfonic acid solution into a film. The modulus, as predicted by rule of mixtures, for a film with this composition and with planar isotropic orientation, should be 16 Mpsi. The experimental value is 80% of the theoretical value indicating that the concept of a molecular composite is valid.

Morphology of Rigid-Rod Molecular Composites: An Overview

1988 ◽  
Vol 134 ◽  
Author(s):  
Stephen J. Krause
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Morphological Characterization ◽  
High Ratio ◽  
Structure Property ◽  
Chain Polymer ◽  
Specific Strength ◽  
Composite Systems ◽  
Molecular Composites ◽  
Rigid Rod

ABSTRACTRigid-rod molecular composites are a new class of high performance structural polymers which have high specific strength and modulus and also high thermal and environmental resistance. A rigid-rod, extended chain polymer component is used to reinforce a matrix of a ductile polymer with the intent of achieving a “composite” on the molecular level. After synthesis, the key to producing a molecular composite is to control morphology to disperse the reinforcing rod molecules as finely as possible in the matrix polymer. Individual rod molecules or bundles of molecular rods must have dimensions which result in a high ratio of length to width (aspect ratio) for efficient reinforcement. To achieve this, the reinforcing rod component must not phase separate at any stage of processing. Morphological characterization techniques, which can measure the orientation and dispersion (or, conversely, the degree of phase separation) of rod molecules provide the tools for correlating theoretically predicted and experimentally observed mechanical properties. Various morphological techniques which have been applied to molecular composite systems will be reviewed, including wide angle x-ray scattering and scanning and transmission electron microscopy. Structure-property correlations for molecular composite systems will be discussed with regard to models for mechanical properties. Application of new morphological techniques will also be discussed.

Recent Advances in Morphology and Mechanical Properties of Rigid-Rod Molecular Composites

1989 ◽  
Vol 171 ◽  
Author(s):  
Stephen J. Krause ◽  
Wen-Fang Hwang
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Low Voltage ◽  
Orientation Distribution ◽  
Short Fiber ◽  
Chain Polymer ◽  
Structural Applications ◽  
Molecular Composites ◽  
Rigid Rod ◽  
Aromatic Heterocyclic

ABSTRACTRigid-rod molecular composites are a new class of high performance structural polymers which have high specific strength and modulus and also high thermal and environmental resistance. The concept of using a rigid-rod, extended chain polymer to reinforce a ductile polymer matrix at the molecular level has been demonstrated with morphological and mechanical property studies for aromatic heterocyclic systems, but new materials systems and processing techniques will be required to produce thermoplastic or thermoset molecular composites. Improved characterization and modeling will also be required. In this regard, new results on modeling of mechanical properties of molecular composites are presented and compared with experimental results. The Halpin-Tsai equations from ‘shear-lag’ theory of short fiber composites predict properties reasonably well when using the theoretical modulus of rigid-rod molecules in aromatic heterocyclic systems, but newer matrix systems will require consideration of matrix stiffness, desired rod aspect ratio, and rod orientation distribution. Application of traditional and newer morphological characterization techniques are discussed. The newer techniques include: Raman light scattering, high resolution and low voltage SEM, parallel EELS in TEM, synchrotron radiation in X-ray scattering, and ultrasound for integrity studies. The properties of molecular composites and macroscopic composites are compared and it is found that excellent potential exists for use of molecular composites in structural applications including engineering plastics, composite matrix resins, and as direct substitutes for fiber reinforced composites.

Rigid-rod molecular composites via ionic interactions

Polymer ◽  
1991 ◽  
Vol 32 (8) ◽  
pp. 1376-1379 ◽  
Author(s):  
Loon-Seng Tan ◽  
Fred E. Arnold ◽  
Hoe H. Chuah
Keyword(s):  
Ionic Interactions ◽  
Molecular Composites ◽  
Rigid Rod

Synthesis, Characterization, and Dynamics of a Rod/Sphere Organoceramic Composite Liquid

1992 ◽  
Vol 274 ◽  
Author(s):  
Mark A. Tracy ◽  
R. Pecora
Keyword(s):  
Experimental Studies ◽  
Liquid System ◽  
Organic Coating ◽  
Molecular Weights ◽  
Naturally Occurring ◽  
Wide Range ◽  
Molecular Composites ◽  
Ceramic Precursors ◽  
Rigid Rod ◽  
System 1

ABSTRACTComposite liquids – liquids composed of polymers, particles, and small molecule solvents – constitute an important class of synthetic and naturally occurring materials. Examples include molecular composites, ceramic precursors, lubricants, adhesives, and the cytoplasm in biological cells. Due to the complexity of these liquids, experimental studies of precisely defined systems are essential in developing an understanding of the interactions between all components in the liquid. Unfortunately, such fundamental studies have been relatively rare due to both the difficulty of synthesizing precisely defined composite liquids and the lack of adequate experimental methods to monitor the motions of the various constituents.We have recently reported the synthesis, characterization and some studies of the dynamics of a rod/sphere composite liquid system [1]. In our case the “polymer” constituent is a rigid rod polymer, poly(γ-benzyl-α,L-glutamate) (PBLG). Rigid rod polymers are frequently used in composite liquids as viscosity enhancers. PBLG is commercially available in a wide range of molecular weights and its static and dynamic behavior in dilute and nondilute solutions has been studied. It, in addition, forms mesophases in the concentrated regime. The ceramic “particles” in our composite liquid are coated silica spheres. These spheres are synthesized by the method of Stober et. al. [2] and coated with an organic coating (3-(trimethoxysilyl)propyl methacrylate (TPM)) following a procedure based on that of Philipse et. al. [3] to render them dispersible in organic solvents. The spheres with sizes in the range from 10 nm up to almost 1μm can be synthesized with a relatively narrow size distribution. The solvent in our studies is dimethylformamide (DMF). Both polymer and particle are dispersible as singlets (nonaggregating) in these solvents and the PBLG retains its rigid (or nearly rigid) rod conformation. The diffusion of both the polymer and the sphere in the composite liquid is measured by dynamic light scattering (DLS) [4]. In this paper, we focus on the spheres and examine the effects of rod concentration and rod length on the diffusion of different size spheres. This study suggests that the solution microstructure has an important influence on sphere diffusion.

Electron microscopy of rod/coil molecular composites

1983 ◽  
Vol 41 ◽  
pp. 32-33
Author(s):  
S. J. Krause ◽  
W. W. Adams
Keyword(s):  
Critical Factor ◽  
High Strength ◽  
Chain Polymer ◽  
New Class ◽  
Reinforced Composite ◽  
Transmission Electron ◽  
The Matrix ◽  
Molecular Composites ◽  
Flexible Coil ◽  
Rigid Rod

Molecular composites are a new class of structural polymers which are lightweight, high-strength, high-modulus, and environmentally resistant. A rigid-rod, extended chain, polymer is used to reinforce a matrix of flexible, coil-like polymer with the intent of achieving a composite on the molecular level which is analagous to a macroscopic chopped-fiber reinforced composite. The critical factor in making a molecular composite is that the rod-like reinforcing molecules be well dispersed and not phase separate from the matrix polymer to insure that the aspect ratio (ratio of length to width) of the reinforcing phase has a high value. This paper reports the first transmission electron microsopy (TEM) study of phase separation in molecular composites.

Electron microscopy of a triblock copolymer molecular composite

1986 ◽  
Vol 44 ◽  
pp. 790-791
Author(s):  
T. Haddock ◽  
S. J. Krause ◽  
W. W. Adams
Keyword(s):  
Triblock Copolymer ◽  
Critical Factor ◽  
High Strength ◽  
Fiber Spinning ◽  
Chain Polymer ◽  
The Matrix ◽  
Molecular Composites ◽  
Polymer Component ◽  
Flexible Coil ◽  
Rigid Rod

Molecular composites are a new class of structural polymers which are high-strength, high-modulus, thermally stable, and environmentally resistant. A rigid-rod, extended chain polymer component is used to reinforce a matrix of flexible, coil-like polymer component with the intent of achieving a composite on the molecular level. The critical factor in processing a molecular composite is that the rod-like reinforcing component be well dispersed and not phase separate from the matrix component. We previously reported on the morphology of a molecular composite from a physical blend of rigid-rod and flexible-coil homopolymers. In this paper we are reporting on the morphology of a rigid-rod, flexible-coil, triblock copolymer processed by vacuum casting or fiber spinning from a dilute solution.

Processing, Properties and Structure of Bulk Poly(P-Phenylene Benzobisthiazole)/Poly(Ether Ether Ketone) Molecular Composites

1988 ◽  
Vol 134 ◽  
Author(s):  
C. S. Wang ◽  
S. J. Bai
Keyword(s):  
Consolidation Process ◽  
X Ray ◽  
Composite Systems ◽  
X Ray Scattering ◽  
Ether Ether Ketone ◽  
Poly Ether Ether Ketone ◽  
Molecular Composites ◽  
Rigid Rod ◽  
Ether Ketone ◽  
Processing Properties

ABSTRACTThe wet-state-consolidation process was used to fabricate bulk rigid-rod/thermoplastic molecular composites of poly(p-phenylene benzobisthiazole) and poly(ether ether ketone). The composites were molded into bar-shaped specimens. The morphology of those specimens was studied throughout the entire process using X-ray scattering and scanning electron microscopy to correlate processing conditions and properties. The mechanical properties of the bulk composites were comparable to those of other rigid-rod/thermoplastic molecular composite systems.

Molecular entanglement for rigid rod molecular composites: Poly(p-phenylene-2,6-benzbisthiazole)/poly(hexamethylene adipamide)

1987 ◽  
Vol 27 (6) ◽  
pp. 424-432 ◽  
Author(s):  
Donald R. Wiff ◽  
S. Timms ◽  
Thaddeus E. Helminiak ◽  
Wen-Fang Hwang
Keyword(s):  
Molecular Composites ◽  
Rigid Rod
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