Carbodiimide additive to control hydrolytic stability and biodegradability of PLA

Enhanced durability of bio-based polylactic acid (PLA) is one of the prerequisites to be a considered as alternative to petroleum-based polymers in long time application. The effect of bis(2,6-diisopropylphenyl)carbodiimide (BDICDI) additive in various concentration on the extent of hydrolytic stabilization and subsequent degradation kinetics of PLA was studied in the process of abiotic hydrolysis and microbial decomposition under composting conditions. The study showed that BDICDI acts as an efficient stabilizer suppressing the hydrolytic scission of ester bonds of PLA in both degradation processes tested, especially at concentrations above 1.5% w/w. Within the stabilization period which strongly depends on concentrations of BDICDI, suppression of hydrolytic degradation also triggered preservation of thermal and mechanical properties. After the period of stabilization as the dose of stabilizer is depleted, probably via reaction with water molecules and carboxylic groups, the material was hydrolyzed at a comparable or even slightly higher rate than pure PLA. By applying the appropriate amount of BDICDI, the approximate duration of stabilization could be set to suit the desired requirements of the final product. © 2016 Elsevier Ltd15-08287Y, GACR, Czech Science FoundationCzech Science Foundation [15-08287Y]; Ministry of Education, Youth and Sports of the Czech Republic [LO1504]; Internal Grant Agency of the Tomas Bata University in Zlin [IGA/CPS/2016/004

Antimicrobial modification of polypropylene with silver nanoparticles immobilized on zinc stearate

The microwave synthesis of Ag nanoparticles on zinc stearate (ZnSt/Ag) was performed to obtain an antimicrobial additive for a polypropylene matrix. Thermoplastically prepared polymer composites contained (1, 3, 5 and 10) % of mass fractions of ZnSt/Ag. The effect of the presence of additives on the morphology and mechanical properties of composites was studied by scanning electron microscopy and stress-strain analysis. The antimicrobial activity of the composites was studied according to the ISO 22196 standard. The results showed that sufficient antimicrobial activity of the composites against both Gram-positive and Gram-negative bacterial strains was observed in the case of the composites with the highest filling studied.grant of Technology Agency of the Czech Republic [TE02000006]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; Internal Grant Agency of the Tomas Bata University in Zlin [IGA/CPS/2015/004

Copolymer of natural fibre reinforced polyester urethane: effect on physico-chemical properties through modification to interfacial adhesion

This work is dedicated to polyester urethane (PEU)-based biocomposites, with special focus placed on techniques for compatibilisation to heighten interfacial adhesion between the PEU matrix and flax fibres. Tests were conducted on the effects of modification so as to increase interfacial adhesion between the flax fibres and the polyester matrix. These tests involved a commercial silane-based compatibilising additive, two experimentally synthesised agents, oleic acid (OA) and di-tert-butyl peroxide (DTBP). Furthermore, the flax fibres underwent acid or alkali treatment. The biocomposites were characterised by gel permeation chromatography, infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Mechanical properties were investigated through tensile testing. Biocomposites with a commercial silane-based additive and synthesised agent, based on maleic-anhydride, were assessed as the best solution. Nevertheless, all modifications, excluding alkali treatment of fibres, significantly increased the performance of the material.Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; program EUPRO [LE12002]; program Mobility [7AMB13AT024]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2015/003]; Austrian Agency for International Cooperation in Education and Research (OeAD - GmbH) [CZ 06/2013

Effect of a hybrid zinc stearate-silver system on the properties of polylactide and its abiotic and the biotic degradation and antimicrobial activity thereof

This work investigates the degradation and properties of a thermoplastically prepared composite comprising a polylactide/hybrid zinc stearate-silver system. The influence of the zinc stearate-silver system on the properties of the composite is investigated by electron microscopy, differential scanning calorimetry and tensile tests. Furthermore, the antimicrobial activities of the systems are examined. The degradation behaviour of the composites is studied in both abiotic and biotic (composting) environments at an elevated temperature of 58 °C. The results reveal good dispersion of the additive in the PLA matrix, a stabilizing effect exerted by the same on the polylactide matrix during processing, and slight reduction in glass transition temperature. The zinc stearate-silver component also reduces brittleness and extends elongation of the composite. Abiotic hydrolysis is not significantly affected, which is in contrast with pure PLA, although mineralization during the early stage of biodegradation increases noticeably. The composite exhibits antimicrobial activity, even at the lowest dosage of the zinc stearate/silver component (1 wt%). Moreover, Ag and Zn contents were found to be present in the composite during abiotic hydrolysis, which was demonstrated by minimal diffusion of Ag ions from the matrix and very extensive washing of compounds that contained Zn. © 2018, Chinese Chemical Society, Institute of Chemistry, Chinese Academy of Sciences and Springer-Verlag GmbH Germany, part of Springer Nature.Czech Science Foundation [17-16928Y]; Ministry of Education, Youth and Sports of the Czech Republic within the NPU I programme [LO1504