Development and Characterization of Polymer Eco-Composites Based on Natural Rubber Reinforced with Natural Fibers

Abstract

Natural rubber composites filled with short natural fibers (flax and sawdust) were prepared by blending procedure and the elastomer cross-linking was carried out using benzoyl peroxide. The microbial degradation of composites was carried out by incubating with Aspergillus niger recognized for the ability to grow and degrade a broad range of substrates. The extent of biodegradation was evaluated by weight loss and cross-linking degree study of composites after 2 months incubation in pure shake culture conditions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) have proved to be precious and valuable instruments for morphological as well as structural characterization of the composites before and after incubation with Aspergillus niger.

Keywords: Aspergillus niger; ecocomposites; natural fibers; natural rubber.

Figure 1

Seven disks of control sample (free natural fibers) placed in Petri dish (15 cm diameter), containing Sabouraud Dextrose Agar medium.

Figure 2

Appearance of NF (free natural fibers) and NR with 10 phr flax samples after 15 days.

Figure 3

Weight loss of the composites.

Figure 4

Gel fraction of the composites before and after incubation with Aspergillus niger.

Figure 5

Cross-link density of the composites before and after incubation with Aspergillus niger.

Figure 6

V_rf (volume fractions of rubber in the fiber-filled swollen composite) of the composites before and after incubation with Aspergillus niger.

Figure 7

V_r0/V_rf ratio of the composites before and after incubation with Aspergillus niger.

Figure 8

Mechanism of natural rubber cross-linking by peroxide.

Figure 9

The chemical modification of flax or sawdust fibers by peroxide reaction.

Figure 10

Water uptake depending on the amount of filler in composites at 23 ± 2 °C: (a) 0 phr; (b) 10 phr; (c) 20 phr.

Figure 11

Biodegradation reaction mechanism of natural rubber.

Figure 12

Infrared spectrum of the A sample: (a) in the range of 650–1800 cm⁻¹ and (b) in the range of 2600–3600 cm⁻¹.

Figure 13

Infrared spectrum of the B-1 sample: (a) in the range of 650–1800 cm⁻¹ and (b) in the range of 2600–3600 cm⁻¹.

Figure 14

Infrared spectrum of the B-2 sample: (a) in the range of 650–1800 cm⁻¹ and (b) in the range of 2600–3600 cm⁻¹.

Figure 15

Infrared spectrum of the C-1 sample: (a) in the range of 650–1800 cm⁻¹ and (b) in the range of 2600–3600 cm⁻¹.

Figure 16

Infrared spectrum of the C-2 sample: (a) in the range of 650–1800 cm⁻¹ and (b) in the range of 2600–3600 cm⁻¹.

Figure 17

SEM of the natural rubber vulcanizate (A sample). (a) after 60 days of incubation with Aspergillus niger; (b) after 60 days of incubation with Aspergillus niger and after 72 h immersed in toluene; (c) the blanks (before incubation with the Aspergillus niger) and after 72 h immersed in toluene.

Figure 18

SEM of the B-1 composite. (a) after 60 days of incubation with Aspergillus niger; (b) after 60 days of incubation with Aspergillus niger and after 72 h immersed in toluene; (c) the blanks (before incubation with the Aspergillus niger) and after 72 h immersed in toluene.

Figure 19

SEM of the B-2 composite. (a) after 60 days of incubation with Aspergillus niger; (b) after 60 days of incubation with Aspergillus niger and after 72 h immersed in toluene; (c) the blanks (before incubation with the Aspergillus niger) and after 72 h immersed in toluene.

Figure 20

SEM of the C-1 composite. (a) after 60 days of incubation with Aspergillus niger; (b) after 60 days of incubation with Aspergillus niger and after 72 h immersed in toluene; (c) the blanks (before incubation with the Aspergillus niger) and after 72 h immersed in toluene.

Figure 21

SEM of the C-2 composite. (a) after 60 days of incubation with Aspergillus niger; (b) after 60 days of incubation with Aspergillus niger and after 72 h immersed in toluene; (c) the blanks (before incubation with the Aspergillus niger) and after 72 h immersed in toluene.