Polycarbodiimide and polyimide/cyanate thermoset in situ molecular composites

1998 ◽  
Vol 13 (7) ◽  
pp. 1840-1847 ◽  
Author(s):  
D. R. Wiff ◽  
G. M. Lenke ◽  
P. D. Fleming
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Phase Separation ◽  
Molecular Mechanics ◽  
High Molecular Weight ◽  
Molecular Composites ◽  
Rigid Rod ◽  
Composite Reinforcement

The synthesis of polycarbodiimide and polyimide in a cyanate resin precursor was achieved. A unique procedure for achieving a high molecular weight of the molecular composite reinforcement molecules was demonstrated. In spite of phase separation being present during the processing, the final cured composites were transparent. The enhanced mechanical properties and the presence of a single Tg, which increases with rigid rod content, were indications that a molecular composite was achieved. The agreement between measured mechanical properties and those predicted using molecular mechanics simulations CERIUS2 software was encouraging.

Molecular Weight Dependence of Domain Structure in Silica-Siloxane Molecular Composites

1992 ◽  
Vol 274 ◽  
Author(s):  
Tamara A. Ulibarri ◽  
Greg Beaucage ◽  
Dale W. Schaefer ◽  
Bernard J. Olivier ◽  
Roger A. Assink
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Composite Materials ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Precursor Polymer ◽  
Molecular Weight Dependence ◽  
Molecular Composites ◽  
Filler Phase

ABSTRACTA detailed investigation of the molecular weight dependence of silica growth in in situ filled polydimethylsiloxane/tetraethylorthosilicate (PDMS/TEOS) materials was conducted using small angle neutron scattering (SANS). Composite materials were produced by using TEOS to simultaneously produce the glassy filler phase and to crosslink linear, hydroxyl terminated PDMS of variable molecular weight, M. Correlated domains of glassy filler were produced. The morphology of the in situ filled material showed a definite dependence on the molecular weight of the precursor polymer. The scale, R, of the glassy domains follows de Gennes' description of phase separation in a crosslinked system (R ∝ M1/2).

scholarly journals Melt- vs. Non-Melt Blending of Complexly Processable Ultra-High Molecular Weight Polyethylene/Cellulose Nanofiber Bionanocomposite

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 404
Author(s):  
Nur Sharmila Sharip ◽  
Hidayah Ariffin ◽  
Tengku Arisyah Tengku Yasim-Anuar ◽  
Yoshito Andou ◽  
Yuki Shirosaki ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Tensile Strength ◽  
Yield Strength ◽  
Young’S Modulus ◽  
High Molecular Weight ◽  
Melt Processing ◽  
Cellulose Nanofiber ◽  
Melt Blending ◽  
Ultra High Molecular Weight

The major hurdle in melt-processing of ultra-high molecular weight polyethylene (UHMWPE) nanocomposite lies on the high melt viscosity of the UHMWPE, which may contribute to poor dispersion and distribution of the nanofiller. In this study, UHMWPE/cellulose nanofiber (UHMWPE/CNF) bionanocomposites were prepared by two different blending methods: (i) melt blending at 150 °C in a triple screw kneading extruder, and (ii) non-melt blending by ethanol mixing at room temperature. Results showed that melt-processing of UHMWPE without CNF (MB-UHMWPE/0) exhibited an increment in yield strength and Young’s modulus by 15% and 25%, respectively, compared to the Neat-UHMWPE. Tensile strength was however reduced by almost half. Ethanol mixed sample without CNF (EM-UHMWPE/0) on the other hand showed slight decrement in all mechanical properties tested. At 0.5% CNF inclusion, the mechanical properties of melt-blended bionanocomposites (MB-UHMWPE/0.5) were improved as compared to Neat-UHMWPE. It was also found that the yield strength, elongation at break, Young’s modulus, toughness and crystallinity of MB-UHMWPE/0.5 were higher by 28%, 61%, 47%, 45% and 11%, respectively, as compared to the ethanol mixing sample (EM-UHMWPE/0.5). Despite the reduction in tensile strength of MB-UHMWPE/0.5, the value i.e., 28.4 ± 1.0 MPa surpassed the minimum requirement of standard specification for fabricated UHMWPE in surgical implant application. Overall, melt-blending processing is more suitable for the preparation of UHMWPE/CNF bionanocomposites as exhibited by their characteristics presented herein. A better mechanical interlocking between UHMWPE and CNF at high temperature mixing with kneading was evident through FE-SEM observation, explains the higher mechanical properties of MB-UHMWPE/0.5 as compared to EM-UHMWPE/0.5.

scholarly journals Achieving Good Protection on Ultra-High Molecular Weight Polythene by In Situ Growth of Amorphous Carbon Film

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 584
Author(s):  
Rui Dang ◽  
Liqiu Ma ◽  
Shengguo Zhou ◽  
Deng Pan ◽  
Bin Xia
Keyword(s):  
Molecular Weight ◽  
Epitaxial Growth ◽  
High Molecular Weight ◽  
Amorphous Carbon ◽  
Transition Layer ◽  
In Situ Growth ◽  
Good Protection ◽  
Ultra High Molecular Weight ◽  
Carbon Plasma

Ultra-high molecular weight polythene (UHMWPE), with outstanding characteristics, is widely applied in modern industry, while it is also severely limited by its inherent shortcomings, which include low hardness, poor wear resistance, and easy wear. Implementation of feasible protection on ultra-high molecular weight polythene to overcome its shortcomings would be of significance. In the present study, amorphous carbon (a-C) film was fabricated on ultra-high molecular weight polythene (UHMWPE) to provide good protection, and the relevant growth mechanism of a-C film was revealed by controlling carbon plasma currents. The results showed the in situ transition layer, in the form of chemical bonds, was formed between the UHMWPE substrate and the a-C film with the introduction of carbon plasma, which provided strong adhesion, and then the a-C film continued epitaxial growth on the in situ transition layer with the treatment of carbon plasma. This in situ growth of a-C film, including the in situ transition layer and the epitaxial growth layer, significantly improved the wetting properties, mechanical properties, and tribological properties of UHMWPE. In particular, good protection by in situ growth a-C film on UHMWPE was achieved during sliding wear.

scholarly journals The Effect of Stereocomplex Polylactide Particles on the Stereocomplexation of High Molecular Weight Polylactide Blends

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2018
Author(s):  
Muhammad Samsuri ◽  
Ihsan Iswaldi ◽  
Purba Purnama
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Nucleating Agent ◽  
Solution Casting ◽  
Casting Method ◽  
Crystalline Fraction ◽  
Crystalline Structures ◽  
Solution Casting Method

Stereocomplexation is one of several approaches for improving polylactide (PLA) properties. The high molecular weight of poly L-lactide (PLLA) and poly D-lactide (PDLA) homopolymers are a constraint during the formation of stereocomplex PLAs (s-PLAs). The presence of s-PLA particles in PLA PLLA/PDLA blends can initiate the formation of s-PLA crystalline structures. We used the solution casting method to study the utilization of s-PLA materials from high molecular weight PLLA/PDLA blends for increasing s-PLA formation. The s-PLA particles initiated the formation of high molecular weight PLLA/PDLA blends, obtaining 49.13% s-PLA and 44.34% of the total crystalline fraction. In addition, the mechanical properties were enhanced through s-PLA crystalline formation and the increasing of total crystallinity of the PLLA/PDLA blends. The s-PLA particles supported initiation for s-PLA formation and acted as a nucleating agent for PLA homopolymers. These unique characteristics of s-PLA particles show potential to overcome the molecular weight limitation for stereocomplexation of PLLA/PDLA blends.

Stereo-chemical contributions to the glass transition and liquid–liquid phase separation in high molecular weight poly(N-vinyl carbazole)

RSC Advances ◽  
2016 ◽  
Vol 6 (35) ◽  
pp. 29326-29333 ◽  
Author(s):  
Abdul G. Al Lafi ◽  
James N. Hay
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Phase Separation ◽  
Liquid Phase ◽  
High Molecular Weight ◽  
Structural Properties ◽  
Thermal History ◽  
Liquid Phase Separation ◽  
High Molecular Weight Poly ◽  
Liquid Liquid Phase Separation

Thermal history and purification effects on the structural properties of PVK were investigated. Liquid–liquid phase separation is suggested to occur by separation of isotactic rich segments from a matrix which is predominantly atactic.

Effect of N2 Ion Bombardment on Optical and Mechanical Properties of Ultra-High Molecular Weight Polyethylene (UHMWPE)

2013 ◽  
Vol 341 ◽  
pp. 169-180 ◽  
Author(s):  
A.M. Abdul-Kader ◽  
Y.A. El-Gendy ◽  
Awad A. Al-Rashdi ◽  
A.M. Salem
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Ion Beam ◽  
Surface Hardness ◽  
Conjugation Length ◽  
High Fluences ◽  
Pristine Sample ◽  
Optical And Mechanical Properties ◽  
Ultra High Molecular Weight

The effect of ion beam bombardment on the optical and mechanical properties of ultra-high molecular weight polyethylene (UHMWPE) was investigated. UHMWPE polymer samples were bombarded with 150 keV N2ions under vacuum at room temperature to high fluences ranging from 1x1016to 2x1017ions cm-2. The untreated as well as treated samples were investigated by ultraviolet-visible (UV-Vis) spectrophotometer and Vickers micro-hardness techniques. The direct and indirect optical band gap decreased from 2.9 and 1.65 eV for pristine sample to 1.7 and 1 eV for those bombarded with N2ion beam at the highest fluence, respectively. With increasing ion fluence, an increase in the number of carbon atoms per conjugation length, N and number of carbon atoms per cluster, M in a formed cluster were observed. A significant improvement in surface hardness was obtained by increasing the ion fluence.

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.

Wear behavior of in situ polymerized carbon nanotube/ultra high molecular weight polyethylene composites

2013 ◽  
Vol 21 (9) ◽  
pp. 965-970 ◽  
Author(s):  
Hong-Jo Park ◽  
Jihun Kim ◽  
Yongsok Seo ◽  
Junho Shim ◽  
Moon-Yong Sung ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Carbon Nanotube ◽  
High Molecular Weight ◽  
Wear Behavior ◽  
Ultra High Molecular Weight ◽  
Polyethylene Composites
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