Surface Properties of Chemically Modified Polyimide Films

INDRAJIT GHOSH, J. KONAR and ANIL K. BHOWMICK*
Rubber Technology Center, Indian Institute of Technology, Kharagpur 721 302, India

Abstract
Surface modification of Kapton polyimide film (325 nm thick) by means of chromic acid and  perchloric acid at different times and temperatures has been carried out. The contact angle of water decreased from 82 to 550 and the surface energy increased accordingly from 26 to 45 mJ/m² with  times of etching by chromic acid up to 45 min at 330^oC. Etching at higher temperatures increased the surface energy. Chromic acid was more effective than perchloric acid. IR and XPS studies  indicated multiple bonding and generation of polar groups on the surface. The peak at 1778 cm^-1  due to the imide group decreased on acid etching. The O/C ratio increased and the N/C ratio decreased. The peel strength of the joint polyimide film/copper film/epoxy adhesive/aluminium sheet increased about two-fold on modification of the polyimide (PI) film at 33^oC for 45 min, although the changes were marginal for the PI film/silicone rubber/PI film joint. The peel strength is a function of the time and temperature of etching.

* Professor to be contacted as a reference.

ACS Symposium Series 1998 (submitted)

Blends of Biodegradable Thermoplastics with Lignin Esters

INDRAJIT GHOSH, RAJESH K. JAIN and WOLFGANG G. GLASSER*
Biomaterials/Recycling Center and Department of Wood Science and Forest Products,
Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.

Abstract
    Thermoplastic blends of several biodegradable polymers with lignin and lignin esters were prepared by solvent casting and melt processing. Among the biodegradable thermoplastics were cellulose acetate butyrate (CAB), a starch-caprolactone copolymer/blend (SCC), and poly(hydroxybutyrate)(PHB). Lignin esters included the acetate, butyrate, hexanoate, and laurate of organosolv lignin, LA, LB, LH, and LL, respectively. Blend properties were analyzed by thermal, mechanical, and optical (transmission electron microscopy, TEM) analysis. The results indicate widely different levels of interaction between the two polymer constituents. Blends of LA and LB with CAB exhibited a high level of compatibility that was lost when the acyl substituent increased in size. The addition of lignin to PHB greatly retarded crystallization and produced blends with lower melting points. The same was true for SCC blends, which were found to crystallize and melt at lower temperatures if lignin was present. However, a significantly increased modulus at room temperature resulted when lignin was present, and this was attributed to increased crystallinity in the presence of lignin.

* Professor to be contacted as a reference

Multiphase Materials with Lignin. XV. Blends of Cellulose Acetate Butyrate with Lignin Esters

INDRAJIT GHOSH, RAJESH K. JAIN and WOLFGANG G. GLASSER*
Biobased Materials/Recycling Center and Department of Wood Science and Forest Products,
Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.

Abstract
Commercially available cellulose acetate butyrate (CAB, unplasticized) was blended in melt and solution with lignin esters having different ester substitutents-acetate (LA), butyrate (LB), hexanoate (LH), and laurate (LL). All lignin esters formed phase-separated blends with CAB with domain size depending on processing conditions and the interaction between phases depending on blend components. CAB/LA and CAB/LB revealed the strongest interactions with domain sizes on the 15-30 nm scale as probed by dynamic mechanical thermal analysis and differential scanning calorimetry. The glass transition (T_g) followed the Fox equation. Broader transitions corresponding to the T_gs of the two parent components were observed for CAB blends with LH and LL. Transmission electron micrographs revealed differences in the phase dimensions of the blends in accordance with chemical and processing (i.e., melt vs solvent) differences. Modest gains in modulus were observed for low contents (<20 wt.%) of LA and LB. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 448-457, 1999.

* Professor to be contacted as a reference