Overview of the Cast Polyolefin Film Extrusion Technology for Multi-Layer Packaging Applications.

The review article presents the technology of producing polyolefin-based films by extrusion casting. Due to the wide use of this type of film as packaging for food and other goods, obtaining films with favorable properties is still a challenge for many groups of producers in the plastics market. The feedblock process and multimanifold process are the main methods of producing multi-layer film. In the case of food films, appropriate barrier properties are required, as well as durability and puncture resistance also at low temperatures. On the other hand, in order to properly pack and present products, an appropriate degree of transparency must be maintained. Therefore, processing aids such as anti-slip, anti-block and release agents are commonly used. Other popular modifiers, such as waxes, fatty acid amides and mineral fillers-silica, talc or calcium carbonate-and their use in film extrusion are discussed. The article also presents common production problems and their prevention.

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

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.

The Influence of the Hybridization Process on the Mechanical and Thermal Properties of Polyoxymethylene (POM) Composites with the Use of a Novel Sustainable Reinforcing System Based on Biocarbon and Basalt Fiber (BC/BF).

The presented work focuses on the assessment of the material performance of polyoxymethylene (POM)-based composites reinforced with the use of a biocarbon/basalt fiber system (BC/BF). The use of BC particles was aimed at eliminating mineral fillers (chalk, talc) by using fully biobased material, while basalt fibers can be considered an alternative to glass fibers (GF). All materials were prepared with the same 20% filler content, the differences concerned the (BC/BF) % ratio. Hybrid samples with (25/75), (50/50), and (75/25) ratios were prepared. Additionally, reference samples were also prepared (POM BC20% and POM BF20%.). Samples prepared by the injection molding technique were subjected to a detailed analysis of mechanical properties (static tensile and Charpy impact tests), thermomechanical characteristics (dynamic mechanical thermal analysis-DMTA, heat deflection temperature - HDT), and thermal and rheological properties (DSC, rotational rheometer tests). In order to assess fiber distribution within the material structure, the samples were scanned by a microtomography method (µCT). The addition of even a significant amount of BC particles did not cause excessive material brittleness, while the elongation and impact strength of all hybrid samples were very similar to the reference POM BF20% sample. The tensile modulus and strength values appear to be strictly dependent on the increasing BF fiber content. Thermomechanical analysis (DMTA, HDT) showed very similar heat resistance for all hybrid samples; the results did not differ from the values for the POM BF20 sample.

Rotational Molding of Linear Low-Density Polyethylene Composites Filled with Wheat Bran.

Application of lignocellulosic fillers in the manufacturing of wood polymer composites (WPCs) is a very popular trend of research, however it is still rarely observed in the case of rotational molding. The present study aimed to analyze the impact of wheat bran content (from 2.5 wt.% to 20 wt.%) on the performance of rotationally-molded composites based on a linear low-density polyethylene (LLDPE) matrix. Microscopic structure (scanning electron microscopy), as well as physico-mechanical (density, porosity, tensile performance, hardness, rebound resilience, dynamic mechanical analysis), rheological (oscillatory rheometry) and thermo-mechanical (Vicat softening temperature) properties of composites were investigated. Incorporation of 2.5 wt.% and 5 wt.% of wheat bran did not cause significant deterioration of the mechanical performance of the material, despite the presence of 'pin-holes' at the surface. Values of tensile strength and rebound resilience were maintained at a very similar level, while hardness was slightly decreased, which was associated with the porosity of the structure. Higher loadings resulted in the deterioration of mechanical performance, which was also expressed by the noticeable rise of the adhesion factor. For lower loadings of filler did not affect the rheological properties. However, composites with 10wt.% and 20 wt.% also showed behavior suitable for rotational molding. The presented results indicate that the manufacturing of thin-walled products based on wood polymer composites via rotational molding should be considered a very interesting direction of research.

Injection Molding of Highly Filled Polypropylene-based Biocomposites. Buckwheat Husk and Wood Flour Filler: A Comparison of Agricultural and Wood Industry Waste Utilization.

The study presents a comparative analysis for two types of polymer fillers used during the processing of polypropylene by the injection molding technique. The aim of the study was to assess the usefulness of buckwheat husk waste as an alternative to the widely used wood fiber fillers. For this purpose, we prepared composite samples containing 10, 30 and 50 wt % of the filler, which were subjected to mechanical tests, thermal analysis, and structural observations in order to evaluate and compare their properties. Additionally, we evaluated the effectiveness of the composite system's compatibility by using maleic anhydride grafted polypropylene (PP-g-MA). The results of mechanical tests confirmed a more effective reinforcement mechanism for wood fibers; however, with the addition of PP-g-MA compatibilizer, these differences were significantly reduced: we observed a 14% drop for tensile modulus and 5% for strength. This suggests high susceptibility to this type of adhesion promoter, also confirmed by SEM observations. The paper also discusses rheological measurements conducted on a rotational rheometer, which allowed to confirm more favorable flow characteristics for composites based on buckwheat husks.