Deodorizing Methods for Recycled High-density Polyethylene Plastic Wastes

The recycling of high-density polyethylene plastic (HDPE) plays a crucial role in sustainable development. However, obstacles to the use of recycled HDPE remain because of the material and processing properties and odors of recycled HDPE. The odor of recycled detergent bottle plastic leads to rejection by most detergent manufacturers. Recently, some recycling enterprises have adapted recycling with odor reduction processes involving the use of solvents, antimicrobial additives, and odor extraction units in feeders and extruders. However, these processes may affect the quality and cost of recycled plastic. Most small and medium businesses (SMBs) may not favor these effects due to their limited models and resources. In addition, most SMBs are unwilling to replace their current recycling operation units. Hence, this study aimed to find alternative and economical ways for odor reduction in the recycling process. A modification of the recycling process was introduced in the pretreatment of plastic flakes before entry into the feeder of an extrusion unit. The effect of selected washing temperatures, i.e., 65℃, 75℃, 85℃, and 95℃, on the removal of odor from recycled HDPE was further studied. The addition of sodium bicarbonate, calcium carbonate, and citric acid into a heated water bath enhanced the deodorizing effect. The relationship of these three chemicals with the deodorization of HDPE plastics was investigated through sensory evaluation. Lastly, the potential of the deodorized recycled HDPE for resin pellet production and commercialization were investigated.

Techno-Assessment of the Use of Recycled Plastic Waste in RE

Effectively consumed plastic waste is an emerging technical and social issue for Australia. Adding plastic waste into construction material and ensuring minimised impact to the mechanical performance of the construction material could bring significant benefits. In this study, plastic waste material was mixed into cement-stabilised rammed earth (RE) material for brick manufacture. Techno framework consisting of compressive strength test and split tensile strength derivation for structural performance assessment and life cycle assessment for determining EE(EE) performance was applied to compare recycled high-density polyethylene (HDPE) added RE with conventional bricks. The compressive properties of different mixtures were studied. The replacement of conventional rock aggregates in stabilised RE brick with recycled plastic waste was found to improve the structural mechanical performance with the developed composition. Following this, an EE analysis was important to assess whether these waste-based bricks can improve environmental performance in a cost-competitive manner while maintaining structural performance. The increase of recycled HDPE in RE was found to likely affect the EE performance of RE, which could possibly be overcome by using less energy-intensive cementitious materials and recycled HDPE.

Some Exploitation Properties of Wood Plastic Composites Based on Mixtures of Virgin and Recycled High Density Polyethylenes and Birch Plywood Sanding Dust

Composites based on birch plywood by-product: plywood sanding dust (PSD) and mixtures of virgin (vHDPE) and recycled high density polyethylenes (rHDPE) physical mechanical properties (tensile, flexural strength and modulus, impact strength and microhardness), water resistance and fluidity of the composite melts, were evaluated. These studies showed the possibility of usage of presented mixtures for preparing of qualitative WPCs containing 50 wt.% PSD. It was observed that the melt flow index values decrease with an increase of the content of rHDPE in polymer matrix. DSC measurements showed the diminishing of melting temperature and melting heat of vHDPE by adding of rHDPE. The tensile strength and modulus of composites decrease about 25 – 30 % but frexural strength and modulus have no changes. In the contrary impact strength and microhardness of the samples increased with an increase of additives of rHDPE. Water uptake kinetics of all composites were similar and the total amount of absorbed water after 850 h of the soaking was 12 – 13 %. The optimal content of recycled HDPE in the composites could be 25 – 30 wt.%. In general presented studies showed successful possibilities of the use of additives of rHDPE to vHDPE to produce cheaper WPCs which have no worse guality. Moreover the chosen type of rHDPE in the some cases can compete with investigated vHDPE matrix.

Morphological, thermal and mechanical properties of recycled HDPE foams via rotational molding

In this study, foamed recycled high density polyethylene (rHDPE) parts were produced by rotational molding using different concentration (0 to 1% wt.) of a chemical blowing agent (CBA) based on azodicarbonamide. From the samples produced, a complete morphological, thermal and mechanical characterization was performed. The morphological analysis showed a gradual increase in the average cell size, while the cell density firstly increased and then decreased with increasing CBA content. As expected, increasing the CBA content decreased the foam density as well as the thermal conductivity. Although increasing the CBA content decreased both tensile and flexural properties, the impact strength showed a similar trend as the cell density with an optimum CBA content around 0.1% wt. Finally, neat rHDPE samples were also produced by compression molding. The results showed negligible differences between the rotomolded and compression molded properties indicating that optimal rotomolding conditions were selected. These results confirm the possibility of using 100% recycled polymers to produce rotomolded foam parts.

Comparison of Composite Quality from PP Plastic with Recycled HDPE Through The Screw Extruder Process

This study examines the composite quality of PP and HDPE plastic waste materials using Microfiber Oil palm empty fruit bunches (OPEFB) as filler, the fiber used is 90 µm. The ratio of matrix: filler used is 60:40 and 70:30 for each type of PP and HDPE polymer. The method used is a melt blending screw extruder, where plastic and fiber materials are dissolved with a compatibilizer and then melt blended in an extruder by providing temperatures of 160 and 170 oC. Tensile tests showed the strength of the PP composite with a filler ratio of 60:40 and 70:30, respectively, of 313.25 N and 336.35 N, while the HDPE composite with a filler ratio of 60:40 and 70:30, respectively are 392.93 N and 187.90 N. The maximum force required to break HDPE composites reaches 21.10 Mpa while for PP composites it reaches 18.56 Mpa. From the morphology of the PP and HDPE composite samples, the overall surface structure of HDPE looks regular with a width from 1 to 13.5 mm. The PP composite shows a uniform and regularly arranged surface structure and the bond between the fibers and the filler looks more compatible but the surface pores are rougher. Heat resistance can be seen from the melting point of PP composites which can reach 163.81oC while HDPE composites only reach 134.21oC.

The Effect of Recycled HDPE Plastic Additions on Concrete Performance

This study examined HDPE (high-density polyethylene) plastic waste as an added material for concrete mixtures. The selection of HDPE was based on its increased strength, hardness, and resistance to high temperatures compared with other plastics. It focused on how HDPE plastic can be used as an additive in concrete to increase its tensile strength and compressive strength. 156 specimens were used to identify the effect of adding different percentages and sizes of HDPE lamellar particles to lower, medium, and higher strength concrete for non-structural applications. HDPE 0.5 mm thick lamellar particles with sizes of 10 × 10 mm, 5 × 20 mm, and 2.5 × 40 mm were added at 2.5%, 5%, 10%, and 20% by weight of cement. The results showed that the medium concrete class (with compressive strength equal to 10 MPa) had the best response to the addition of HDPE. The 5% HDPE addition represented the optimal mix for all concrete types, while the 5 × 20 mm size was best.