TY - JOUR

T1 - Transcrystalline interphases in natural fiber-PP composites

T2 - Effect of coupling agent

AU - Sanadi, A. R.

AU - Sanadi, A. R.

N1 - Funding Information: The authors would like to acknowledge funding from USDA NRI / CSRS (#9701817). One of the authors (ARS) would like to thank the Forest Product Laboratory for funding, facilities and space provided during the course of the study. The authors are grateful to C. C. Clemons for help with the transcrystallinity studies, and C. A. Fink who carried out the transcrystallinity work.

PY - 2000/1/1

Y1 - 2000/1/1

N2 - The interest in lignocellulosic fiber composites has been growing in recent years because of their high specific properties. In this work, a new technique was used to prepare specimen to observe the transcrystalline zones in kenaf fiber-polypropylene composites. A maleated polypropylene (MAPP) coupling agent was used to improve the stress-transfer efficiency in the composites. Transcrystallinity was observed for both the uncoupled and coupled composites, although the rate of growth was higher for the coupled composites. Dynamic mechanical spectroscopy was used to observe the relaxations of the composites. The peak temperature of the β-relaxation, associated with the glass-rubber transition of the amorphous molecules, of the coupled composites was higher than that of the uncoupled composites. Restricted molecular mobility due to covalent interactions between the MAPP and the lignocellulosic surface may account for the shift to higher temperatures. It appears that during compounding the extractives sheared from the fiber surface is an important factor in determining the β-relaxation of these composites. The intensities of the α-transition, related to molecular mobility associated with the presence of crystals, is proportional to the fiber volume fraction. Thus it is possible that the molecules responsible for the α-transition are predominantly in the transcrystalline zone. These ‘rigid’ amorphous molecules in the transcrystalline zone do play a role in composite behavior and need to be considered when tailoring interphases.

AB - The interest in lignocellulosic fiber composites has been growing in recent years because of their high specific properties. In this work, a new technique was used to prepare specimen to observe the transcrystalline zones in kenaf fiber-polypropylene composites. A maleated polypropylene (MAPP) coupling agent was used to improve the stress-transfer efficiency in the composites. Transcrystallinity was observed for both the uncoupled and coupled composites, although the rate of growth was higher for the coupled composites. Dynamic mechanical spectroscopy was used to observe the relaxations of the composites. The peak temperature of the β-relaxation, associated with the glass-rubber transition of the amorphous molecules, of the coupled composites was higher than that of the uncoupled composites. Restricted molecular mobility due to covalent interactions between the MAPP and the lignocellulosic surface may account for the shift to higher temperatures. It appears that during compounding the extractives sheared from the fiber surface is an important factor in determining the β-relaxation of these composites. The intensities of the α-transition, related to molecular mobility associated with the presence of crystals, is proportional to the fiber volume fraction. Thus it is possible that the molecules responsible for the α-transition are predominantly in the transcrystalline zone. These ‘rigid’ amorphous molecules in the transcrystalline zone do play a role in composite behavior and need to be considered when tailoring interphases.

KW - Coupling agents

KW - Dynamic mechanical analysis

KW - Fiber-reinforced PP composite

KW - Kenaf fiber

KW - Natural fiber composites

KW - Transcrystallinity

UR - http://www.scopus.com/inward/record.url?scp=0033721173&partnerID=8YFLogxK

U2 - 10.1163/156855400300183560

DO - 10.1163/156855400300183560

M3 - Journal article

AN - SCOPUS:0033721173

VL - 7

SP - 31

EP - 43

JO - Composite Interfaces

JF - Composite Interfaces

SN - 0927-6440

IS - 1

ER -