Improving tensile mechanical properties of aromatic polyimides by thermal imidization after cold drawing of poly (amic acids)

1990 ◽  
Vol 28 (13) ◽  
pp. 2463-2472 ◽  
Author(s):  
Masakatsu Kochi ◽  
Rikio Yokota ◽  
Taka Yuki Iizuka ◽  
Itaru Mita
Keyword(s):  
Mechanical Properties ◽  
Cold Drawing ◽  
Aromatic Polyimides ◽  
Thermal Imidization

scholarly journals Effect of Cold Drawing on Mechanical Properties of Biodegradable Fibers

2017 ◽  
Vol 15 (1) ◽  
pp. 70-76 ◽  
Author(s):  
Francesco Paolo La Mantia ◽  
Manuela Ceraulo ◽  
Maria Chiara Mistretta ◽  
Marco Morreale
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Biodegradable Polymers ◽  
Biodegradable Polymer ◽  
Cold Drawing ◽  
Thermal Characterization ◽  
Systematic Investigation ◽  
Thermomechanical Properties ◽  
Polymer Systems ◽  
The Impact

Purpose Biodegradable polymers are currently gaining importance in several fields, because they allow mitigation of the impact on the environment related to disposal of traditional, nonbiodegradable polymers, as well as reducing the utilization of oil-based sources (when they also come from renewable resources). Fibers made of biodegradable polymers are of particular interest, though, it is not easy to obtain polymer fibers with suitable mechanical properties and to tailor these to the specific application. The main ways to tailor the mechanical properties of a given biodegradable polymer fiber are based on crystallinity and orientation control. However, crystallinity can only marginally be modified during processing, while orientation can be controlled, either during hot drawing or cold stretching. In this paper, a systematic investigation of the influence of cold stretching on the mechanical and thermomechanical properties of fibers prepared from different biodegradable polymer systems was carried out. Methods Rheological and thermal characterization helped in interpreting the orientation mechanisms, also on the basis of the molecular structure of the polymer systems. Results and conclusions It was found that cold drawing strongly improved the elastic modulus, tensile strength and thermomechanical resistance of the fibers, in comparison with hot-spun fibers. The elastic modulus showed higher increment rates in the biodegradable systems upon increasing the draw ratio.

scholarly journals Microstructures, Textures and Mechanical Properties Evolution during Cold Drawing of Pure Mg

2013 ◽  
Vol 01 (02) ◽  
pp. 8-15 ◽  
Author(s):  
Yandang Qiao ◽  
Xin Wang ◽  
Zuyan Liu ◽  
Erde Wang
Keyword(s):  
Mechanical Properties ◽  
Cold Drawing

Synthesis and Characterization of Aromatic Polyimides Bearing Nonlinear Optical Chromophores

2000 ◽  
Vol 12 (1) ◽  
pp. 169-176 ◽  
Author(s):  
L Bes ◽  
A Rousseau ◽  
B Boutevin ◽  
R Mercier ◽  
B Sillion ◽  
...  
Keyword(s):  
Nonlinear Optical ◽  
Second Harmonic ◽  
Uv Spectroscopy ◽  
Harmonic Coefficient ◽  
Aromatic Polyimides ◽  
Relaxation Temperature ◽  
Thermal Imidization ◽  
Nonlinear Optical Chromophores ◽  
Hydroxy Groups ◽  
Optical Chromophores

The syntheses and characterizations of two aromatic polyimides with nonlinear optical (NLO) chromophore side chains were investigated through a two-step synthetic route. These two polymers were prepared by polycondensation of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) with 4-(4-amino, 2-hydroxy) phenoxyaniline (HODA) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP), respectively. First the poly(hydroxy)imides were prepared by direct thermal imidization. The resulting polyimides bearing hydroxy groups were found to react easily with the terminal hydroxy group of the chromophore (Disperse Red1 (DR1)) via the Mitsunobu reaction. The high content of chromophore for the polyimide with 6FAP diamine was confirmed by UV spectroscopy and ellipsometry spectroscopy measures. The resulting NLO polyimides possess high glass transition temperatures ( Tg > 185°C), excellent solubilities and processabilities even though the extent of chromophore grafting is up to 95 mol%. The second harmonic coefficient ( d33) at the wavelength of 1320 nm is close to 30 pm V−1. The thermal and temporal stabilities of the NLO properties were investigated. The relaxation temperature of the SHG signal measured at the 50% decay of the initial SHG signal ( I 2ω/2 at 2°C min−1) was 168°C for the polyimide based on HODA and 157°C for the polyimide based on 6FAP.

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