Impact of Humid Environment on Structural and Mechanical Properties of Biobased Polylactide

Abstract The study focused on the material behavior of two commercial polylactide grades affected by structural changes due to exposure to humid environment. Additionally, the impact of temperature and environment humidity on the moisture uptake and drying process of polymer granulate was examined to evaluate the necessary pre-treatment conditions prior to the polylactide processing. Also some process relevant aspects, such as the impact of polymer pre-drying on its degradation were characterised. In the first part of the experimental work, moisture absorption mechanisms in relation to conditioning parameters were investigated using Karl Fischer titration method. It was shown that the moisture uptake rate correlates with temperature and humidity of the environment. Furthermore, the drying process of polylactide pellets was conducted and analysed by additional melt flow rate measurements to determine the effect of drying conditions on the premature polymer degradation and melt properties. Investigated polymers demonstrated rheological behavior dependent not only on the residual moisture content, but also on drying temperature and time. In the last section of the study flexural and tensile tests were performed in order to determine the influence of moisture uptake on the characteristics of conditioned polylactide. Mechanical strength of polylactide decreased in both, flexural and tensile tests with increasing moisture content in the samples. Moreover, distinctive differences in polylactide mechanical behavior were observed in both tests.</jats:p

Wood microfibres reinforced polypropylene as a composite material for thin wall injection moulding

W artykule przedstawiono wyniki badań eksperymentalnych polipropylenu wzmacnianego mączką drzewną jako biokompozytowego materiału na wtryskiwane wyroby cienkościenne. Biokompozyty wytwarzane były przez kompaundowanie na standardowej wytłaczarce dwuślimakowej w skali półtechnicznej, a następnie wtryskiwane na wtryskarce skali przemysłowej celem jak najbliższego odtworzenia warunków przemysłowych wytwarzania wyrobów cienkościennych. Oceniono właściwości przetwórcze i mechaniczne kompozytów o różnej zawartości mikrowłókien drzewnych (od 15 do 30%wag). Opracowane materiały wykazały podwyższone właściwości mechaniczne w porównaniu do niemodyfikowanego polipropylenu przy zachowaniu jednoczesnego dobrego płynięcia podczas przetwórstwa. Tym samym mogą stanowić one przyjazną środowisku alternatywę dla wyrobów cienkościennych produkowanych w całości z materiałów syntetycznych.The present paper introduces the results of experimental research on polypropylene reinforced with wood flour as a biocomposite material for thin-walled injection moulded parts. Biocomposites were manufactured using half-technical scale twin-screw extruder and afterwards injection moulded with industrial-scale injection moulding machine to obtain processing conditions similar to industrial manufacturing of thin-walled products. Processing and mechanical properties of composites with various content of wood microfibres (15 to 30 wt%) were examined. The investigated materials showed improved mechanical characteristics in comparison to unmodified polypropylene while maintaining good flowability and therefore they can be an environmentally friendly alternative to synthetic materials commonly applied for manufacturing thin-walled products

The Transcription Factor STAT-1 Couples Macrophage Synthesis of 25-Hydroxycholesterol to the Interferon Antiviral Response

SummaryRecent studies suggest that the sterol metabolic network participates in the interferon (IFN) antiviral response. However, the molecular mechanisms linking IFN with the sterol network and the identity of sterol mediators remain unknown. Here we report a cellular antiviral role for macrophage production of 25-hydroxycholesterol (cholest-5-en-3β,25-diol, 25HC) as a component of the sterol metabolic network linked to the IFN response via Stat1. By utilizing quantitative metabolome profiling of all naturally occurring oxysterols upon infection or IFN-stimulation, we reveal 25HC as the only macrophage-synthesized and -secreted oxysterol. We show that 25HC can act at multiple levels as a potent paracrine inhibitor of viral infection for a broad range of viruses. We also demonstrate, using transcriptional regulatory-network analyses, genetic interventions and chromatin immunoprecipitation experiments that Stat1 directly coupled Ch25h regulation to IFN in macrophages. Our studies describe a physiological role for 25HC as a sterol-lipid effector of an innate immune pathway

Development and validation of an HPLC-MS method for the simultaneous quantification of key oxysterols, endocannabinoids, and ceramides: variations in metabolic syndrome

Oxysterols, ceramides, and endocannabinoids are three families of bioactive lipids suggested to be involved in obesity and metabolic syndrome. To facilitate the quantification of these potentially interconnected lipids, we have developed and validated a liquid chromatography coupled to mass spectrometry method allowing for their simultaneous quantification from tissues. Sample purification is of great importance when quantifying oxysterols due to the potential artifactual conversion of cholesterol into oxysterols. Therefore, we developed a novel solid-phase extraction procedure and demonstrated that it allowed for good recoveries of the three families of analytes without artifactual oxidation of cholesterol. The oxysterols, ceramides, and endocannabinoids and their respective internal standards were chromatographically separated by HPLC and ionized using the atmospheric pressure chemical ionization (APCI) source of an LTQ-orbitrap mass spectrometer. The repeatability and bias were within the acceptance limits for all 23 lipids of interest. The sensitivity (limit of detection (LOD) and limit of quantification (LOQ)) and specificity of the method allowed us to quantify all the analytes in the liver and adipose tissue of control and high-fat diet-fed C57BL/6 mice. We found that 16 weeks of high-fat diet strongly impacted the hepatic levels of several oxysterols, ceramides, and endocannabinoids. A partial least-squares discriminant analysis (PLS-DA) based on the variations of the hepatic levels of these 23 bioactive lipids allowed differentiating the lean mice from the obese mic