The Impact of the Addition of Compatibilizers on Poly (lactic acid) (PLA) Properties after Extrusion Process

Poly (lactic acid) (PLA), due to its biodegradability, biocompatibility, and renewability, is one of the most promising biobased polymers for replacing some of the petrol-based materials. Low flexibility of PLA is overcome, by blending it with olefin-based polymers, such as polypropylene (PP). However, the use of compatibilizing agents is required to attain final materials with suitable mechanical properties. Such agents, although essential, can affect PLA structure and, consequently, the mechanical properties of the PLA. To the best of our knowledge, this issue was never studied, and the results can contribute to achieving the best formulations of PLA-based blends according to their final applications. The thermal and mechanical properties of the extruded PLA, with three different commercial compatibilizing agents, were evaluated with the purpose of demonstrating how the compatibilizers can introduce structural differences into the PLA chain during the extrusion process. The combination of crystallinity, molecular weight, and the morphology of the samples after extrusion determines the final mechanical properties of PLA. Despite being a fundamental study, it is our aim to contribute to the sustainability of PLA-based industries. The addition of a 2.5% concentration of C1 compatibilizer seems to have less influence on the final morphology and mechanical properties of the blends.

Changes in the Crystallinity Degree of Starch Having Different Types of Crystal Structure after Mechanical Pretreatment

This paper examines the effect of mechanical activation on the amorphization of starch having different types of crystalline structure (A-type corn starch; B-type potato starch; and C-type tapioca starch). Structural properties of the starches were studied by X-ray diffraction analysis. Mechanical activation in a planetary ball mill reduces the degree of crystallinity in proportion to pretreatment duration. C-type tapioca starch was found to have the highest degree of crystallinity. Energy consumed to achieve complete amorphization of the starches having different types of crystalline structure was measured. The kinetic parameters of the process (the effective rate constants) were determined. The rate constant and the strongest decline in the crystallinity degree after mechanical activation change in the following series: C-type starch, A-type starch, and B-type starch.

Analysis of structure and properties of antibacterial vascular patch used in abdominal aorta aneurysm surgeries

BACKGROUND

Biocompatible materials are used for treatment of blood circulatory system diseases, especially abdominal aortic aneurysms. The most popular and often used are knitted and polymer vascular patches. The aim of this study was to optimize the manufacturing process of implantable materials, ensuring antibacterial activity useful for treating abdominal aorta aneurysms.

METHODS

The vascular patch was manufactured from Trevira® yarn. The parameters of the intermediate product and vascular patch were tested according to standard procedures.

RESULTS

The vascular patch, manufactured from microsilver-containing yarn, with crimps on the surface of the patch, has been found useful for treatment of abdominal aorta aneurysms. Introducing crimps on the surface of the patch resulted in reduction of water permeability and enabled cutting of the graft at various angles without fraying at the cut ends of the biomaterial. The final vascular patch was marked by a gradual release of silver within 48 hours.

CONCLUSIONS

On the basis of the performed test, it has been demonstrated that an implantable material for the treatment of abdominal aorta aneurysms was obtained, and that it can be considered as an alternative for currently used vascular patches. The final vascular patch was marked by a gradual release of silver during the first period of incubation. The antibacterial properties of the final product were confirmed by observation of a significant reduction in the number of Staphylococcus aureus and Klebsiella pneumoniae bacterial colonies.

Sensing the structural differences in cellulose from apple and bacterial cell wall materials by Raman and FT-IR spectroscopy

Raman and Fourier Transform Infrared (FT-IR) spectroscopy was used for assessment of structural differences of celluloses of various origins. Investigated celluloses were: bacterial celluloses cultured in presence of pectin and/or xyloglucan, as well as commercial celluloses and cellulose extracted from apple parenchyma. FT-IR spectra were used to estimate of the I_β content, whereas Raman spectra were used to evaluate the degree of crystallinity of the cellulose. The crystallinity index (X_C^RAMAN%) varied from −25% for apple cellulose to 53% for microcrystalline commercial cellulose. Considering bacterial cellulose, addition of xyloglucan has an impact on the percentage content of cellulose I_β. However, addition of only xyloglucan or only pectins to pure bacterial cellulose both resulted in a slight decrease of crystallinity. However, culturing bacterial cellulose in the presence of mixtures of xyloglucan and pectins results in an increase of crystallinity. The results confirmed that the higher degree of crystallinity, the broader the peak around 913 cm⁻¹. Among all bacterial celluloses the bacterial cellulose cultured in presence of xyloglucan and pectin (BCPX) has the most similar structure to those observed in natural primary cell walls.