Abstract
This work is aimed at studying the suitability of ultra-high molecular weight polyethylene (UHMWPE) fibers for the production of polyethylene homo-composites processed by rotational molding. Initially pre-impregnated bars were produced by co-extrusion and compression molding of UHMWPE fibers and linear low-density polyethylene (LLDPE). A preliminary screening of different processing routes for the production of homo-composite reinforcing bars was performed, highlighting the relevance of fiber impregnation and crystalline structure on the mechanical properties. A combination of co-extrusion and compression molding was found to optimize the mechanical properties of the reinforcing bars, which were incorporated in the LLDPE matrix during a standard rotational molding process. Apart from fiber placement and an increase in processing time, processing of homo-composites did not require any modification of the existing production procedures. Plate bending tests performed on rotational molded homo-composites showed a modulus increase to a value three times higher than that of neat LLDPE. This increase was obtained by the addition of 4% of UHWMPE fibers and a negligible increase of the weight of the component. Dart impact tests also showed an increased toughness compared to neat LLPDE.
Highlights
Rotational molding is a pressure-free process, which allows the production of hollow plastic containers with different dimensions
The greatest part of the production by rotational molding involves the use of linear low-density polyethylene (LLDPE); the main drawback lies in the poor mechanical properties of LLDPE, which has a low elastic modulus, and an operating temperature range of 80 to 120 ◦ C
Processing temperature must be lower than the melting point of the ultra-high molecular weight polyethylene (UHMWPE) fibers, since the fibrous structure must be preserved in order to preserve high mechanical properties
Summary
Rotational molding is a pressure-free process, which allows the production of hollow plastic containers with different dimensions. The greatest part of the production by rotational molding involves the use of linear low-density polyethylene (LLDPE); the main drawback lies in the poor mechanical properties of LLDPE, which has a low elastic modulus, and an operating temperature range of 80 to 120 ◦ C. Several additives, such as inorganic fillers, can be added to improve the mechanical response of the material. The addition of inorganic fillers involves an increase of viscosity, which in turn does not allow for a good distribution of the fillers inside the mold during the process
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