Cu nanoparticles (CuNPs) were modified by organic surfactant, then CuNP-modified high-density polyethylene (CuNP/HDPE) monofilaments were prepared by melt spinning. The effect of CuNP content on the morphology and properties of nanocomposite monofilaments was investigated. FT-IR and dynamic light scattering proved the successful surface modification for CuNP. Scanning electron microscope was used to observe the dispersed behavior of the CuNP. When the CuNP content was less than 1.0 wt%, the CuNPs were well dispersed in these nanocomposite monofilaments, and the increase of crystallization rate, the breaking strength, and knot strength were observed by differential scanning calorimeter and tensile test. Therefore, nanocomposite monofilaments showed comparable properties at low CuNP contents. With increasing CuNP content, the width of tanδ peak and △Ea for α-relaxation from dynamic mechanical analysis were increased, indicating more amorphous components near the crystalline regions. In addition, burst release of Cu ions in seawater was observed. The coupon tests demonstrated that CuNPs could significantly improve antibiofouling performance of CuNP/HDPE fishing netting. CuNP/HDPE fishing netting have a strong potential for using in marine antifouling mitigation.

Biofouling is a serious problem in marine aquaculture facilities, exerting several negative effects on cage structures. In this study, different materials of nets were placed in the Fujian Sea area of China, and the main biological adhesion species were determined. The drag force of different materials of fouled nets was studied by a physical test in a flume tank. The drag force coefficient of a clean polyethylene terephthalate (PET) net was 0.53. The drag force coefficients of ultrahigh-molecular-weight polyethylene (UHMWPE) and polyethylene (PE) nets were 161.2% and 133.5% higher, respectively, compared with those of PET nets. Crustaceans, mollusks, and algae were the main organisms that adhered to the nets. Compared with the clean nets, the drag force of PET, UHMWPE, and PE nets increased by 1.29–5.06 times, 1.11–2.85 times, and 0.55–2.46 times, respectively. Based on backpropagation (BP) neural network training, the relationship between biological characteristics (average adhesion thickness and density) and the drag force of three kinds of net materials was determined. The drag force of the biofouled net at various time points throughout the year can be predicted based on this model, which can guide the cleaning and maintenance of nets in cage structures.

The starch-based fishing composite fibers were prepared by one-step reactive extrusion and melt spinning. The effects of starch contents on the microstructural, thermal, dynamic mechanical, and mechanical properties of starch-based composite fibers were studied. And the degradation behaviors in soil of the fibers were also investigated. The compatibility between starch and HDPE is improved significantly by grafting maleic anhydride (MA) using one-step reactive blending extrusion. As the starch content increased, the melting temperature and the crystallinity of the fibers gradually decreased due to fluffy internal structures. Dynamic mechanical analysis showed that the transition peak α in the high-temperature region was gradually weakened and narrowed with increasing starch content; moreover, a shoulder appeared on the low-temperature side of the α peak was assigned to the β-relaxation related to starch phase. In addition, the mechanical results showed the significant decrease in the breaking strength and increase in the elongation at break of the starch-based composite fibers as the starch content increased. After degradation in soil for 5 months, the surface of the composite fibers had been deteriorated, while flocculent layers were observed and a large number of microfibers appeared. And the weight loss rate of the starch-based composite fibers (5.234.8) significantly increased with increasing starch content (5090wt).

Biofouling on aquaculture netting increases hydrodynamic drag and restricts water exchange across net cages. The solidity ratio is introduced as a quantitative parameter to characterize fouling severity. Towing tank experiments and computational fluid dynamics (CFD) simulations were used to assess the hydrodynamic behavior of netting under different fouling conditions. Experimental results indicated a nonlinear increase in drag force with increasing solidity. At a flow velocity of 0.90 m/s, the drag force increased by 112.2%, 195.1%, and 295.7% for netting with solidity ratios of 0.445, 0.733, and 0.787, respectively, compared to clean netting (S_n = 0.211). The drag coefficient remained stable within 1.445–1.573 across Re of 995–2189. Numerical simulations demonstrated the evolution of flow fields around netting, including jet flow formation in mesh openings and reverse flow regions and vortex structures behind knots. Under high solidity (S_{n =} 0.733–0.787), complex wake patterns such as dual-peak vortex streets appeared. Therefore, this study confirmed that the solidity ratio is an effective comprehensive parameter for evaluating biofouling effects, providing a theoretical basis for antifouling design and cleaning strategy development for aquaculture cages.

Ultra-high molecular weight polyethylene (UHMWPE) and graphene (GR) was melt compounded by reactive extrusion. Nanocomposite monofilaments were prepared by melt spinning through a co-rotating screw extruder and drawing at hot water. GR/UHMWPE nanocomposite ropes were twisted using nanocomposite monofilaments. A structure and mechanical properties of the GR/UHMWPE nanocomposite monofilaments and its ropes had been characterized by scanning electron microscopy (SEM), and mechanical test. Results showed that the monofilaments surface of monofilaments became rougher with introducing of GR nanosheets, which could be related to stacking of GR. The breaking load of GR/UHMWPE nanocomposite ropes was remarkably improved upon nanofiller addition, with the decrease of the elongation at break.