Influence of chemical architecture of PET on ability to stretch blow moulding

International audiencePET specific properties make this material a good candidate for stretch blow moulding. However chemical architecture of the resin can be varied by the supplier. These changes induce different draw abilities or different behaviours whilst blowing. In this study some well controlled PET resins are characterized both from the point of view of their intrinsic properties and from the point of view of their process abilities. Results enlighten clearly the tight correlation between the chemical structure and the behaviour of the polymer. Coupling effects between the structure, the laboratory properties and the process ability exist making this process a highly not intuitive processing. This study allows, in parallel, proposing a global approach to estimate blowing ability from laboratory analysis

Stretch-blow molding of PET copolymers - Influence of molecular architecture

International audienceThe purpose of the paper is to study the influence of molecular architecture of poly(ethylene terephthalate) (PET) on its ability to be processed by stretch-blow molding, which is not well documented in the literature. To evaluate this process ability, it proposes an original strategy combining laboratory analyses and experiments on a prototype machine. PET copolymers were prepared from three types of comonomers: diethylene glycol (DEG), isophthalic acid (IPA) and trimethylolpropane (TMP). It is first shown, through laboratory experiments, that the nature of the polymer in terms of chain constitution (copolymerization), chain length (intrinsic viscosity) and purity (catalytic residues) greatly affects many properties: melt crystallization, thermal properties, polymer rigidity and drawability. These different properties obviously induce very different behaviours at the different steps of the stretch-blow molding process: injection-molding of the preform (quenchability), heating (IR absorption), stretch-blow (rigidity and drawability). The stretch-blow step has been simulated on a prototype apparatus designed in our laboratory. It has been shown that free blowing can be used to characterize the process ability of the polymer. A statistical analysis has confirmed the great differences between the materials investigated and pointed out the complexity of the material response during blowing

Crystallization kinetics of polypropylenes. Effect of nucleating agents?

International audienceThermal conditions and formulation affect the crystallization mechanisms of polymers and the associated kinetics in a coupled manner. In that field, the objective of this investigation is to compare overall crystallization kinetics and structural organization of one clarified polypropylene (specifically designed for stretch-blow molding) and a homopolypropylene. Liquid/solid transitions are investigated in- and ex-situ under isothermal and non-isothermal conditions combining crossed-polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. Clarified polypropylene has a very 'singular behavior' compared to homopolymer since no spherulites can be observed. However, it exhibits a semi-crystalline structure. The major α-phase coexists with some γ-phase even under quiescent conditions. Overall crystallization kinetics is rapid suggesting the existence of very efficient nucleating agent(s) and resulting in an increase of crystallization temperature. In parallel, the melting temperature of copolymer decreases by 20 °C compared to homopolymer, suggesting a drastic change in lamellae thickness. It is concluded that this unusual structure results from nucleation, which enforces high temperature crystallization, and copolymerization, which constraints the crystalline organization

An Analysis of Transcrystallinity in Polymers

International audiencePolymer crystallization often occurs in the presence of foreign bodies, such as walls of processing tools. In such cases, there is a competition between nucleation in the bulk polymer and nucleation on well-identified surfaces. If many nuclei are activated at the surfaces, their proximity imposes that entities emanating from these nuclei grow preferentially normal to the surfaces, leading to transcrystalline zones. The competition between surface and bulk nucleation can be studied through crystallizations of thin polymer films in contact with pan surfaces in a DSC apparatus. These experiments show that in thin samples transcrystallinity is limited by sample thickness. When thickness increases, the transcrystalline zones can grow, but up to a limiting value, because at a certain stage their development is stopped by the growth of bulk spherulites. A specific analysis of these DSC experiments gives access to crystallization parameters such as the number of nuclei per unit surface or the growth rate, and makes it possible to determine the crystallization kinetics of the polymer not disturbed by transcrystallinity

Thyroid hormone receptor {beta} (TR{beta}) and liver X receptor (LXR) regulate carbohydrate response element binding protein (ChREBP) expression in a tissue selective manner.

Thyroid hormone- (TR) and Liver X- (LXR)receptors are transcription factors involved in lipogenesis. Both receptors recognize the same consensus DNA response element in vitro. It was previously shown that their signalling pathways interact in the control of cholesterol elimination in the liver. In the present study ChREBP, a major transcription factor controlling the activation of glucose-induced lipogenesis in liver, is characterized as a direct target of thyroid hormones(TH) in liver and white adipose tissue(WAT), the two main lipogenic tissues in mice. Using genetic and molecular approaches ChREBP is shown to be specifically regulated by TRbeta, but not by TRalpha in vivo even in WAT where both TR isoforms are expressed. However this isotype specificity is not found in vitro. This TRbeta specific regulation correlates with the loss of TH-induced lipogenesis in TRbeta-/- mice. Fasting/refeeding experiments show that TRbeta is not required for the activation of ChREBP expression particularly marked in WAT following refeeding. However TH can stimulate ChREBP expression in WAT even under fasting conditions suggesting completely independent pathways. Since ChREBP has been described as an LXR target, the interaction of LXR and TRbeta in ChREBP regulation was assayed both in vitro and in vivo. Each receptor recognizes a different response element on the ChREBP promoter, located only eight base pairs apart.There is a crosstalk between LXR and TRbeta signalling on the ChREBP promoter in liver but not in WAT where LXR does not regulate ChREBP expression. The molecular basis for this crosstalk has been determined in in vitro systems

Pulse Rate Analysis in Case of Central Sleep Apnea: A New Algorithm for Cardiac Rate Estimation

Annual International Conference of the IEEEInternational audienceThis paper first describes the AM-FM demodulation of an arterial pressure signal. Although it is known to be efficient on signals modulated by breathing, we demonstrate that in case of lack of respiratory modulation (central sleep apnea), the AM-FM algorithm doesn't perform well in heart rate extraction. We introduce then a new algorithm based on Singular Spectrum Analysis eigen values which performs better cardiac frequency estimation in this context. The error for cardiac frequency estimation is around 0.2 BPM (Beats Per Minute) versus 5.5 BPM for the AM-FM demodulation. Further experimentations will be performed (with this time both cardiac and respiratory assessments) and will deal with real sleep apnea cases

Évaluation du stress : application à la détection des chutes

National audienceThis paper deals with the association of several physiological parameters in order to estimate a stress level that can be use in the detection of falls or the evaluation of fear of falling among elderly people

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility.

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel Na1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on Na1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings