Maciej Combrzyński

A STUDY OF THE SOLUBILITY OF BIODEGRADABLE FOAMS OF THERMOPLASTIC STARCH

The paper presents the results of a study on the water absorption capacity and solubility of biodegradable starch foams produced with single-screw extruder TS-45 with L/D=12. Two different moulding dies were used: one with a circular hole with the diameter of 3 mm and one with a ring hole with the inner diameter of 5 mm. During the extrusion process, the temperature of the cylinder ranged from 80 to 130°C and the screw speeds applied were: 100 and 130 rpm. For the application of the ring die, it was observed that regardless of the speed of the screw, the use of the raw material of higher moisture content led to the production of materials with higher solubility. As a result, the obtained materials revealed solubility at a level of 40%. The results demonstrate good solubility of the starchy fillers of the packaging, which may indicate their susceptibility to decomposition in the conditions of high ambient humidity. A statistical analysis showed a significant impact of moisture of the raw material on the WSI of starch foams used irrespective of the other parameters of the extrusion-cooking process. The raw material moisture had a significant effect on the water absorption capacity of only TPS foams produced in the ring die at the screw speed of 100 rpm.

Simulation of the process kinetics and analysis of physicochemical properties in the freeze drying of kale

Abstract Investigations were performed to study the freeze-drying process of kale (Brassica oleracea L. var acephala). The process of freeze-drying was performed at temperatures of 20, 40, and 60°C for whole pieces of leaves and for pulped leaves. The kinetics of the freeze-drying of both kale leaves and kale pulp were best described by the Page model. The increasing freeze-drying temperature from 20 to 60°C induced an approximately two-fold decrease in the drying time. Freeze-drying significantly increased the value of the lightness, delta Chroma, and browning index of kale, and had little influence on the hue angle. The highest increase in the lightness and delta Chroma was observed for whole leaves freeze-dried at 20°C. An increase in the drying temperature brought about a slight decrease in the lightness, delta Chroma and the total colour difference. Pulping decreased the lightness and hue angle, and increased browning index. Freeze-drying engendered a slight decrease in the total phenolics content and antioxidant activity, in comparison to fresh leaves. The temperature of the process and pulping had little influence on the total phenolics content and antioxidant activity of dried kale, but significantly decreased the contents of chlorophyll a and chlorophyll b.

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams

The aim of this work was to determine selected physical properties of biodegradable thermoplastic starch (TPS) filling foams manufactured by extrusion-cooking technique from different combinations of potato starch and two additives: poly(vinyl alcohol) PVA and Plastronfoam PDE. Foams were processed with seven starch/additives combinations at two different extruder-cooker’s screw rotational speeds. The densities of starch foams depended significantly on the additive type and content. The linear relationship between the Young modulus and the ultimate compression force and apparent density was found. The foams processed with the addition of PVA had low density, porosity and lower values of the Young modulus than the foams prepared with PDE.

Moisture sorption characteristics of extrusion-cooked starch protective loose-fill cushioning foams

Abstract The aim of this work was to determine the water vapour sorption properties of thermoplastic starch filling foams processed by extrusion-cooking technique from various combinations of potato starch and two foaming agents: poly(vinyl) alcohol and Plastronfoam, in amount of 1, 2 and 3% each. Foams were processed with the single screw extruder-cooker at two different screw rotational speeds 100 and 130 r.p.m. The sorption isotherms of samples were determined and described using the Guggenheim-Anderson-de Boer model. Also, the kinetics of water vapour adsorption by foams, as a function of time, was measured and fitted with Peleg model. On the basis of the analysis the influence of the applied foaming agents, as well as the technological parameters of extrusion-cooking process in relation to water vapour adsorption by thermoplastic starch foams was demonstrated. There was no difference between the shapes of the isotherms for poly(vinyl) alcohol foams while for Plastronfoam foams a notable difference among foams extruded at 100 r.p.m. was observed in the regions of low and high humidity content. The analysis of the Guggenheim-Anderson-de Boer model parameters showed that the water molecules were less strongly bound with the foam surface when extruded at a lower screw speed.

Selected Mechanical Properties of Polypropylene/TPS Composites as a Material for Flowerpots and Horticulture Containers

Thermoplastic starch (TPS) was prepared from native potato starch:glycerol:keratin (70:20:10 wt.%) blends and processed using a modified single screw extruder at L/D=16. Recycled polypropylene was mixed with TPS at the ratio of 90:10 and 60:40 and re-granulated at various screw speeds in the extrusion-cooking process. The obtained composites were shaped into big flowerpots using an injection-molding machine. The samples collected from the external pot surface were tested with puncture tests to evaluate the mechanical properties of the material. The addition of 10% of starch-based biopolymer to the recycled PP enhanced the mechanical properties of the tested flowerpots. Selecting the proper composition and processing conditions may help to manage production of pots more sustainable. The results also confirmed the possibility to increase the TPS content up to 40% in horticultural containers and the option of processing such composites with injection-molding as more environmentally friendly than using conventional polymers.