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Structure and Properties of Thermoplastic Polyimides and Their Blends

Author: WangBin
Tutor: SunGuangPing；WangZhen
School: Jilin University
Course: Materials Science
Keywords: Polyimides Thermoplastic Isomeric Blends Adhesives
CLC: TQ323.7
Type: Master's thesis
Year: 2009
Downloads: 196
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Abstract

Thermoplastic Polyimides (TPIs) have high glass transition temperature (Tg), excellent thermal oxidation stability and good flexibility.In this dissertation, two series of Thermoplastic Polyimides and their blends were synthesized and investigated. One of them was synthesized based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride (4,4′-BPDA) and 4,4′-Methylene dianiline (4,4′-MDA) without molecular-controlled reagent and the other was endcapped with phthalic anhydride (PA) based on 2,3′,3,4′-biphenyltetracarboxylic dianhydride (3,4′-BPDA) and 4,4’-Diaminodiphenyl ether (4,4′-DOA). We investigated their film-forming ablity, thermal properties of films and powders, tensile properties of films, rheological behaviours of powders and especially the Lap Shear Strength (LSS) based on stainless steel at room temperature (RT) and 200℃. The main conclusions were shown as following.(1) Thermoplastic Polyimides1. The glass transition temperatures (Tgs) of TPIs films increase as the increasing of imidization temperature and the difference is 15.26℃. The same Tg discipline was found as the increasing of BPTC contents and the difference is 5.21℃. The T5%s of TPIs films all exceed 550℃, which show that the thermal oxidation stability of TPIs is excellent.2. Beneath the same imidization temperature, the tensile strength and modulus of TPIs films decrease as the increasing of BPTC contents, compared with the elongation increasing. When fixed the BPTC contents, the tensile strength and elongation of TPIs films decrease as the increasing of imidization temperature, compared with the modulus increasing.3. The T peel strength (Flexible to Flexible) of TPI Adhesives decrease to the bottom and increase as the increasing of BPTC contents. The Lap Shear Strength (LSS) of TPI Adhesives tested at RT decrease as the increasing of BPTC contents. (2) Polyimides Endcapped with PA (PAPIs)4. The four series Polyimides Endacapped with PA, which the degrees of polymerization (n) are 9, 7, 5 and 3, can’t form films due to the low molecular weight. And the Tgs of PAPIs powders decrease as the n decreases from 9 to 3 with the difference of 23.31℃.5. The T5%s of PAPIs all exceed 500℃, but are obviously lower than the T5%s of TPIs films (all exceed 550℃), and decrease as the decreasing of the n.6. The processing windows of PAPIs are so wide enough from 350℃~420℃that they can be easily processed with the melt viscosities are all lower than 30 Pa.s and the lowest of 2.311 Pa.s (n=5).7. The LSS of PAPI-1 (n=9) Adhesive tested at RT and 200℃are separately 21.30 MPa and 18.45 MPa. As the decreasing of n, the LSS tested at RT and 200℃decrease, but still retain at high level. The LSS of PAPI-4 (n=3) Adhesive tested at RT and 200℃are separately 14.02 MPa and 12.10 MPa. (3) Thermoplastic Polyimides Blends8. All the Thermoplastic Polyimides Blends (TPBs) can’t form films except for the blend of w(PAA-0): w(PAPI-1)= 80: 20 due to the exist of gel.9. The Tgs for the four series of TPBs powders are all lower than the Tgs of PI-0 (313.03℃) and PAPI-1 (280.13℃), and increase as the increasing of w(PAPI-1).10. The T5%s of TPBs are all exceed 500℃except for TPB-1 (80: 20), and TPB-2 (65: 35) has the highest T5%.11. The processing windows of TPBs are narrow. But the blends can be more and more easily processed as the increasing of w(PAPI-1). The lowest viscosity is 372.60 Pa.s of TPB-4 (20: 80) at 420℃.12. The LSS tested at RT and 200℃of TPBs increase to the peak at w(PAPI-1)= 65% and decrease as the increasing of w(PAPI-1). The TPB of this ratio has high LSS and retention of 82.7%.

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CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polycondensation resin and plastic > The polyimide Class and plastic
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