Acoustic and mechanical property analysis of value-added composite materials

Abstract

Globalization and modernization has led to plastic waste constituting more than 12% of the waste being generated. Plastic waste is anticipated to be 12000 million metric tonnes by 2050. With South Asian countries banning plastic, developed countries are required to explore alternatives, like recycling, reusing and reducing. Single use plastic consumerism has motivated this study to seek a sustainable re-usage of these plastics. This study is seeks to resolve the world’s second most dangerous environmental risk, which according to World Health Organization is, noise pollution. Noise has numerous negative impacts on humans and the environment. The research innovates material from plastic waste streams to combat noise pollution.

Specifically, the study investigated varying the amount of each constituent in five unique sets of composites. These composites use linear low-density polyethylene (LLDPE) from single-use grain bags as the matrix material. The composition sets include: Set 1 which varies the amounts of flax fiber and ground tire (GTR) in LLDPE; Set 2 varies the flax fiber and LLDPE; Set 3 varies the flax fiber and GTR in LLDPE; Set 4 varies the sand and GTR in LLDPE; and Set 5 varies the sand and GTR in a LLDPE and flax fiber matrix. The samples were manufactured using thermocompression molding at 204°C and 1.4 MPa. The physical and material properties were evaluated; these included density, acoustic absorptivity (ASTM E1050), vibrational damping (ASTM E756), tensile properties (ASTM D638), compressive properties (ASTM C579), and water absorptivity (ASTM D570-98).

While comparing the tensile strength (UTS) with previous studies, around 85% of the tensile strength can be retained without requiring 10 Wt% virgin LLDPE and other processed biomaterial in the composite. Set 2 gave the best tensile results among the composites studied. These composites had a higher weight percentage of matrix material in the composite. Similar trend can be seen for the compressive strength. Set 2 results with the composite containing 70 Wt% matrix material had a compressive strength that was 50% higher than the composite with 30 Wt% matrix material. Comparing 70 Wt% sand with 30 Wt% LLDPE composition with a previous study, the compressive strength of 38.550 MPa (at 18923.18 N) was ~4.5 times greater than the previously reported result of 8.30 MPa (at 4208 N).

Set 1 had the highest vibration damping coefficient (0.112). The lower the weight percentages of polymer and the higher percentage of GTR and fiber appears to increase vibrational damping. Set 4 had the highest sound absorption coefficient of 0.41 at 2000Hz for a composite containing 40 Wt% sand, 30 Wt% GTR and 30 Wt% LLDPE. Again, GTR appears to improve sound absorptivity. Density decreases with increasing flax fiber content and material with a high percentage of sand have higher density; a Set 4 sample with 70 Wt% sand and 30 Wt% LLDPE had the maximum density of 1.47 g/cm3.The water absorption analysis indicated increasing the fiber content results in increasing water absorptivity with a maximum absorption observed in Set 2 had a composition of 70 Wt% fiber and 30 Wt% LLDPE. Water uptake for Set 4 Set 4 was significantly lower than the other sets as it lacked natural fiber.

This research converted waste stream into composites, creating value added sustainable material to reduce pollution and create circular economies. Each composite has unique properties. The material in Set 4 is particularly well suited for controlling noise pollution. This material can be made into sculptures, wall surfaces or other building materials with the ability to absorb up to 40% of the noise from the surroundings.