Flax fiber-reinforced polylactic acid (PLA) biocomposites were made using a new technique incorporating an air-laying nonwoven process. Flax and PLA fibers were blended and converted to fiber webs in the airlaying process. Composite prepregs were then made from the fiber webs. The prepregs were finally converted to composites by compression molding. The relationship between the main process variables and the properties of the biocomposite was investigated. It was found that with increasing flax content, the mechanical properties increased. The maximum tensile strength of 80.3 MPa, flexural strength of 138.5 MPa, tensile modulus of 9.9 GPa and flexural modulus of 7.9 GPa were achieved. As the molding temperature and molding time increased, the mechanical properties decreased. The thermal and morphological properties of the biocomposites were also studied. The appropriate processing parameters for the biocomposites were established for different fiber contents. POLYM.

Biocomposites of flax reinforced polylactic acid (PLA) were made using a new technique incorporating an air-laying nonwoven process. PLA and flax fibers were mixed and converted to the webs in the air-laying process. Prepregs were then made from the fiber webs by thermal consolidation. The prepregs were finally converted to composites by compression molding. This study was investigated the biodegradability and water absorption properties of the composites. The composites were incubated in compost under controlled conditions. The percentage weight loss and the reduction in mechanical properties of PLA and biocomposites were determined at different time intervals. It was found that with increasing flax content, the mechanical properties of the biocomposites decreased more during the burial trial. The increasing of flax content led to the acceleration of weight loss due to preferential degradation of flax. This was further confirmed by the surface morphology of the biodegraded composites from scanning electron microscope image analysis. Morphological observations indicated severe disruption of biocomposites structure between 60 and 120 days of incubation.

In this study, two bast fibers such as okra and jute were selected to manufacture composites taking polypropylene (PP) as matrix material by means of compression molding technique with maintaining 40% fiber content on the total weight of the composites. Investigation was done on tensile properties such as tensile strength (TS), tensile modulus (TM), elongation at break (EB%), bending properties such as bending strength (BS), bending modulus (BM) and impact properties like impact strength (IS) and hardness (Shore-A) of the composites. From analyzed data, it was found that Okra/ PP composites showed very competitive mechanical properties to Jute/PP composites. Non-irradiated okra composite showed the value of TS, TM, BS, BM, IS and hardness to be 32.2 MPa, 602 MPa, 55.6 MPa, 3.6 GPa, 19.54 kJ/m 2 and 95 (Shore-A), respectively, whereas that value for non-irradiated jute composite was 35.5 MPa, 629 MPa, 71.5 MPa, 4.5 GPa, 21.48 kJ/m 2 and 96 (Shore-A), respectively. The composite samples were exposed to different intensities of gamma radiation (250-1000 krad) at a dose rate of 330 krad/h and changes in mechanical properties were examined. Both irradiated composites (500 krad) showed significant improvement of mechanical properties compared to that of the non-irradiated composites. Maximum TS, TM, BS, BM and IS value were found to be 41.9 MPa, 685 MPa, 72 MPa, 4.7 GPa and 22.6 kJ/m 2 , respectively for irradiated okra composite and 45.3 MPa, 717 MPa, 88 MPa, 6.7 GPa and 24.3 kJ/m 2 , respectively for irradiated jute composite. Fourier transform infrared spectroscopy was used to identify the surface groups of the composites. Water absorption, degradation behavior of the composites under soil and heat medium were also performed. Degradation tests revealed that okra composite retained its original mechanical properties higher than that of jute composite. The morphology of the composites was inspected by scanning electron microscope.

Fully biodegradable flax/polylactic acid (PLA) thermoplastic composites were fabricated by using random (nonwoven mat) and aligned (unidirectional yarn) flax fiber as reinforcements (39% flax by volume) and Polylactic acid (PLA) as matrix. Results revealed that the aligned flax fibers have a greater reinforcing effect due to the uniform distribution of load axially along the fiber length in the composite. The aligned flax/PLA and random flax/PLA showed the tensile strength of (83.0 ± 5.0) and (151.0 ± 7.0) MPa respectively and flexural strength of (130.0 ± 5.0) and (215.0 ± 7.2) MPa respectively. Young's modulus of (9.3 ± 1.5) and (18.5 ± 2.0) GPa and flexural modulus of (9.9 ± 1.0) and (18.8 ± 1.0) GPa was attained for the random and unidirectional fiber composites, respectively. It was also found that both composite constituents, fiber and matrix, were degradable if buried in compost soil (ready soil after composting process), which is a distinctive advantage of the new composite structures. Remarkably, the biodegradation property of aligned flax fiber composites was significantly lower than random mat composites, possibly due to the less water swelling behavior of the aligned fiber composites. After 120 days burial test, the aligned flax/PLA composite displayed the reduction of 19% mass, residual flexural strength and modulus decreased by 57 and 50% respectively, while the random mat composites exhibited the loss of 27% mass, residual flexural strength and modulus declined by 80% at the same period.

The fiber architecture can significantly influence the rate of impregnation of a resin in making composites and the load-bearing ability of individual fibers on testing of the loading directions. Moreover, achieving the maximum mechanical performance of a natural fiber composite selection of yarn liner density and optimization of fabric structure and further modification of the composites remains a great challenge for the composite research community. In this study, a number of jute-based woven derivatives (plain, 2/1 twill, 3/1 twill, zigzag based on a 2/2 twill, and diamond based on a 2/2 twill) have been constructed from similar linear densities of yarn. The effect of the fabric architecture and further modification of optimized composites by applying γ-radiation is also explained in this study. The experimental results show a 54% increase in tensile strength, a 75% increase in tensile modulus, a 69% increase in flexural strength, a 124% increase in flexural modulus, and 64% increase in impact strength of twill (3/1) structured jute fiber polyester composites in comparison to other plain and twill structured composites. A further mechanical improvement of around 20–30% is possible for the optimized twill structured composites by applying γ-radiation on the composites. An FTIR, TGA, and SEM study confirms the chemical, thermal, and fractographic changes after applying the modification of composites.