The Relationship between a Rotational Molding Processing Procedure and the Structure and Properties of Biobased Polyethylene Composites Filled with Expanded Vermiculite

Abstract

Rotational molding is a technology in which polymeric thin-walled products can be made. The newest descriptions of this technology concern the possibility of obtaining polymer composite materials. There are two main methods of incorporating fillers into a polymer matrix. Dry blending is based on mixing fillers with polymer powders before rotational molding by hand or using automatic mixers. In the melt compounding method, fillers are mixed with the polymer in the preliminary step by melt processing and then grinding or pulverization to obtain polymer powders for rotational molding. This work aimed to investigate the impact of the processing procedure on the structure and properties of biobased composites with expanded vermiculite. Produced rotomolded parts were examined using mechanical tests to assess changes in tensile, flexural, and impact properties. The most significant difference in mechanical properties was noted for samples with 10 wt% expanded vermiculite (EV). The elasticity modulus increases by almost 2 fold when the sample is prepared in a two-step process, the tensile strength is 4-fold higher, the flexural modulus is 3-fold higher, and the flexural strength is 5-fold higher. We also investigated thermomechanical properties in DMA measurement. The void volume content was also measured to control the quality of obtained parts. The porosity of dry blended samples containing more than 2 wt% EV is almost 2-fold higher. Other methods to control quality and structure were optical and scanning electron microscopy used for rotomolded parts and polymer powders. The investigations of rotomolded parts were supplemented with a complete description of used materials, including the particle size distributions of polymer powders and filler. Analysis of the thermal properties and chemical structure was also performed despite all the mechanical tests. The emerging conclusions from the research clearly show that the two-step process allows for achieving a more beneficial mechanical performance of the composites made of the biobased polymer in rotational molding technology.

Waste Eggshells as a Natural Filler for the Poly(Vinyl Chloride) Composites

“…The analyzed materials are characterized by low porosity, which excludes the emission of significant amounts of gases during processing, and a strong influence of this parameter on the mechanical properties of the PVC/ES composites [ 58 , 59 ].…”

Recent Developments in Inorganic Composites in Rotational Molding

“…Dry blending consists of a mechanical mix of the polymer and the filler/reinforcement, usually in high-speed mixers. This method requires that the polymer is in powder form, which might lead to final parts with high porosity [ 16 ]. On the other hand, melt compounding allows for obtaining a more homogeneous material, although with higher energy requirements and possible oxidation or thermal degradation [ 16 , 20 ].…”

“…Alternatively, the use of inorganic fillers, such as clays [ 15 , 16 ], quartz [ 17 ], halloysite [ 18 ], glass fibers or powder [ 19 , 20 , 21 ], copper slag [ 22 ], or graphite [ 23 , 24 ] has also been explored. This review focuses on the use of these types of materials in rotational molding, with particular attention to those coming from waste or natural origin.…”

Uniaxial Rotational Molding of Bio-Based Low-Density Polyethylene Filled with Black Tea Waste

“…To improve the mixing and distribution of filler in rotomolded parts, the two-step preparation process can be applied. In our previous study [ 13 ], the introduction of expanded vermiculite into a PE matrix in rotational molding technology was discussed. It was confirmed that the preliminary step concerning melt mixing of polymer with filler helped to obtain parts with increased mechanical properties and better filler distribution than the dry blended composites.…”