Preparation and Research of Modified Carbon Fiber Reinforced PoIymide Composites

Polyamide (Polyamide, PA) which is the most widely used in industrial production as an

engineering plastic plays a very significant role in the automotive lightweight because of its

excellent mechanical properties, heat resistance, wear resistance, ease of processing and

recyclability. In this paper, we do the study of carbon fiber reinforced modification, mechanical

and interface performance simulation and thermal oxygen aging performance in accordance

with practical application of nylon in the field of automotive applications. The main contents

of the paper are as follows:

1) Carbon fiber reinforced nylon composites (CF/PA6) were prepared by carbon fiber (CF)

which was treated by silane coupling agent KH550 as a reinforcement and the effects of

different fiber content and modification effect on the composites were studied. The results show

the surface roughness of carbon fiber is obviously increased after the treatment with silane

coupling agent and the interface bonding property between the carbon fiber and the nylon

matrix is improved a lot. The final effect is that the modified carbon fiber reinforced nylon

composite material (MCF/PA6) has improved performance in comparison with the unmodified

carbon fiber reinforced nylon composites. Moreover, the carbon fiber after surface treatment

provides the nucleation point for the crystallization of nylon 6 (PA6), so that PA6 is attached

to the surface of carbon fiber to form a unique "string crystal" phenomenon, which in turn

enhances the crystallization temperature of the composite material and promotes the

crystallization of PA6, also enhance the modulus and strength of the composite to an extent.

2) Based on the experimental data of the tensile properties of CF/PA6 composites with

different fiber contents, the model is fitted and the suitability of the relevant models is discussed

for the short fiber reinforced nylon composites The results demonstrate that the ROM hybrid

model can fit the tensile mechanical properties of CF/PA6 well, and the Kelly-Tyson model can

better reveal the interface properties of CF/PA6.

3) The thermal aging performance of CF/PA6 samples up to 1600 hours at different

temperatures is investigated by using commercially available glass fiber reinforced nylon

(Ultramid®B3WG7) as a control sample. After a certain period of time at a certain temperature,

the surface of the fiber-reinforced composite material is yellowed due to the onset of thermal

oxygen and resulting in the formation of carboxylic acid groups or aldehydes and ketones and

other color groups. The new absorption peak which is about 1716 cm in the infrared spectrum

analysis also confirms the conclusion. Cracks are generated on the surface of the CF/PA6

composites, and quiet a few fibers are exposed to the nylon matrix. The tensile properties

increase first and reduce afterwards with the thermal aging time and are the same as those of

the dynamic mechanical properties. Finally, the tensile strength of CF/PA6 and

Ultramid®B3WG7 is 91.6% and 75% of the initial values after 1600 hours of aging at 180 ℃,

indicating that the stability of carbon fibers is stronger than the glass fiber in the long-term

thermal oxygen aging.

These studies have provided the experimental data and theoretical basis for the extensive

application of nylon in the field of automobile and the future research on the mechanical

properties and thermal aging performance of fiber reinforced nylon composites.

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