Investigation of the Orientational Mechanical Properties of Biodegradable Extrusion Films Based on Polyolefins and Beet Pulp

The article discusses the possibility of obtaining biodegradable films based on polyolefins and beet pulp by the extrusion method. Biodegradable composites of two mixes with 15% and 25% beet pulp content have been obtained. Compounding was carried out on a twin-screw extruder, and then samples of biodegradable films were obtained by cast film extrusion. The influence of the vegetable filler particles’ orientation on the composites mechanical properties has been studied. It has been shown that composites mechanical properties significantly increase in the direction of polymer melt stretching.

Biaxial Stretching of Polymer Nanocomposites: A Mini-Review

Polymer nanocomposites with excellent physical and chemical properties and multifunctional performance have been widely used in various fields. Biaxial stretching is not only an advanced film manufacturing process, but also a deformation mode in other processing methods such as blow film extrusion and thermoforming. In recent research, high-performance polymer nanocomposites have been fabricated via sequential and simultaneous biaxial stretching. This fabrication method enhances the mechanical properties, optical performance, and thermal properties of polymer nanocomposites by changing the structure or orientation of materials during the process of stretching. Therefore, it is particularly suitable for use in optimizing material performance and preparing thin films with excellent properties in the packaging industry. With the emergence of new materials and technologies, polymer nanocomposites prepared by biaxial stretching have demonstrated multifunctional properties and their range of applications has further expanded. In this mini-review, the effect of biaxial stretching on the structure and properties of nanocomposites based on various nanofillers is discussed and applications are summarized. In addition, the challenges and future prospects of this technology are analyzed. The presented work will be beneficial for improving preparation processes and improving future research for the production of high-performance polymer nanocomposites.

The Polymer Film Casting Process – An Overview

Cast film extrusion allows producing technical polymer films for packaging and coating applications. Different kinds of defects may be observed. For packaging applications, the challenge is to obtain very thin films in stable conditions at the highest throughput. For coating applications, the challenge is to master the film width reduction (called neck-in) and the induced non-uniform film thickness (called dog-bone defect). Well instrumented experiments point out the influence of the polymer and of the processing conditions on the occurrence of these defects. Numerical models of increasing complexity allow capturing the main experimental features and this makes possible to propose technological solutions to delay or even to suppress defects occurrence.

Structure-property-processing relationships in extruded liquid crystal polymer film

Liquid crystal polymers (LCPs) derive favorable mechanical, chemical, and electrical behavior from long-range molecular ordering. The microstructure gives rise to anisotropic bulk properties that are problematic for industrial applications, and thus the ability to model the polymer directionality is essential to the design of isotropic material manufacturing processes. This investigation proposes a modeling methodology to simulate the 3D director field in full-scale film extrusion geometries. Wide-angle x-ray scattering (WAXS) is used to validate the predicted orientation for a standard coat-hanger die, and is compared with macroscopic mechanical, thermal, and dielectric testing of LCP film to illustrate the morphological dependence of the polymer properties. The highly anisotropic orientation state resulting from cast film extrusion is both predicted by the model and confirmed experimentally, and this preferred orientation is shown to correlate with observed anisotropy in the bulk properties. Additionally, a practical implementation of the modeling tool is presented to simulate directionality in two alternative die geometries designed to improve bulk isotropy, and it is demonstrated that the model is capable of simulating the resulting order for large, irregular domains typical of industrial processing.

Biodegradable Polymer Compounds Reinforced with Banana Fiber for the Production of Protective Bags for Banana Fruits in the Context of Circular Economy

Bags used to protect and accelerate the ripening of bananas are a clear example of the environmental problem of packaging waste. Small pieces of these non-biodegradable bags are frequently disposed on the soil by accident (environmental conditions and poor handling during the harvest) and remain there for years. This work focuses on the development of protective biodegradable bags reinforced with banana fiber, obtained from waste of the banana plants, thus promoting a circular economy and a more environmentally friendly process. To achieve this, different bio-based composites were tested (processability) by compounding extrusion (biopolymer and banana fiber with different process steps) and blown film extrusion. The bags produced were tested in field and sequentially improved in three generations of biofilms. The results showed that the maximum processable fiber content was 5 wt %. Additionally, the micronizing of the compounds was crucial to simplify the blown film extrusion and improve the smoothness of the bags (scratches avoidance on the banana surface). The final bags (Mater-Bi biopolymer, 5% combed and sieved banana fiber, and 2.5 wt % TiO2 for ultraviolet light filtration), performed better than the conventional ones (faster maturing, i.e., earlier harvest, and easier handling) and fulfilled the biodegradability, composting and ecotoxicity test requirements.

Effect of Filler Synergy and Cast Film Extrusion Parameters on Extrudability and Direction-Dependent Conductivity of PVDF/Carbon Nanotube/Carbon Black Composites

In the present study, melt-mixed composites based of poly (vinylidene fluoride) (PVDF) and fillers with different aspect ratios (carbon nanotubes (CNTs), carbon black (CB)) and their mixtures in composites were investigated whereby compression-molded plates were compared with melt-extruded films. The processing-related orientation of CNTs with a high aspect ratio leads to direction-dependent electrical and mechanical properties, which can be reduced by using mixed filler systems with the low aspect ratio CB. An upscaling of melt mixing from small scale to laboratory scale was carried out. From extruded materials, films were prepared down to a thickness of 50 µm by cast film extrusion under variation of the processing parameters. By combining CB and CNTs in PVDF, especially the electrical conductivity through the film could be increased compared to PVDF/CNT composites due to additional contact points in the sample thickness. The alignment of the fillers in the two directions within the films was deduced from the differences in electrical and mechanical film properties, which showed higher values in the extrusion direction than perpendicular to it.

Flow analysis of conical spiral mandrel dies

Spiral dies are divided into three categories, namely: Flat Spiral Die (FSD), Cylindrical Spiral Mandrel Die (SMD), and Conical Spiral Mandrel Die (CSD). These dies are used to produce films via blown film extrusion and multilayer films via co-extrusion. The goal is to improve the flow distribution and to decrease the pressure drop which will result in uniform film thickness and reduced energy dissipation. A viscous power-law fluid model shows that low-pressure drop and proper flow distribution can be achieved in a CSD simultaneously. As the number of grooves and the initial channel depth increases, the flow distribution becomes more uniform and the pressure drop decreases. Also, there is an optimum initial clearance and clearance increment angle. The model results show that the pseudo-plastic fluid has more appropriate performance than the Newtonian and dilatant fluids in improving the flow distribution and reducing the pressure drop.