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Understanding and minimizing polycaprolactone degradation during processing using multi-detector GPC and rheology Application Note

Polycaprolactone (PCL) is a synthetic polymer that has recently received increasing attention thanks to its biodegradability. Its most common use is in the manufacture of polyurethanes or as a plasticizer for other polymers such as PVC. It is also often used in molding and prototyping thanks to its low melting temperature and is used as a feedstock in some additive manufacturing (3D printing) systems. Finally, it is also used in some drug delivery applications as a control release mechanism, in the same way as polylactic acid (PLA) or polylactic-co-glycolic acid (PLGA). A potential advantage over PLA and PLGA is that PCL has a slower degradation rate and therefore may allow for slower drug release.. As with all polymers, PCL’s molecular properties (e.g. molecular weight) will strongly affect its bulk properties such as strength, toughness, and melt-flow. Being biodegradable, PCL is at a high risk of degradation during processes such as extrusion for molding, particularly at high temperatures. Some mechanisms have been described in the literature to reduce this. For instance, extrusion in the presence of carbon dioxide (CO2) can reduce the melt flow viscosity of PCL by acting as a ‘molecular lubricant’. Decreasing the viscosity of the polymer reduces the temperature at which extrusion can be performed and could thereby protect the polymer from degradation during the process [1].. In this application note, a commercially available sample of PCL was extruded alone and in the presence of CO2­. Multi-detector GPC measurements were made of the virgin sample before and after extrusion, while rotational rheometry was used to study the polymer’s melt viscosity..

Produkte:
Kinexus lab+
Datum:
April 27 2017
Sprache:
English

Molecular and bulk characterization of PLA and PLGA samples using multi-detector GPC and rheometry Application Note

Poly(lactic acid) is a biodegradable polymer derived from natural resources (corn starch), that has received significant attention in recent years. It is one of the most prevalent biodegradable polymers in the market place due to availability, low cost of production, and when derived from natural sustainable sources it is a truly renewable polymer. PLA is often used as a copolymer with glycolic acid to form PLGA and is routinely used with varying compositions of lactic and glycolic acids. Being a versatile polymer, it is used in a wide variety of applications from additive manufacture (3D printing) to disposable cutlery, biodegradable sutures, drug delivery, or as biodegradable packaging.. It is widely recognized that the bulk properties of polymers are strongly dependent on their molecular properties. Most commonly, the strongest determinant of a polymer’s strength is assumed to be its molecular weight. However, in copolymers such as PLGA, it is also likely that copolymer composition will also strongly affect those properties.. This application note uses two Malvern technologies to explore the relationship between the molecular and bulk properties of PLA and PLGA. Multi-detector GPC is used to measure molecular weight and intrinsic viscosity (which is dependent on copolymer composition), while rotational rheology is used to study melt-viscosity. The two results are then compared to study which molecular properties best correlate with melt-viscosity..

Produkte:
Kinexus ultra+
Datum:
April 27 2017
Sprache:
English

Characterizing polymer degradation during processing using multi-detector GPC and capillary rheometry Application Note

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) are two of the most widely used synthetic polymers. Polystyrene is used as a protective packaging for anything from foods to CD cases and disposable cutlery, while PMMA is regularly used as a polymeric alternative to glass and even in some medical technologies, and countless other consumer products.. In both cases, melting and molding are regular processes that these polymers must endure. It is therefore important to understand how they will respond to this kind of treatment. It is well recognized that the bulk properties of a polymer such as strength, toughness, flexibility, etc. are strongly dependent on molecular properties such as molecular weight and branching. If the molecular properties of these polymers change as a consequence of the processing, then it is likely that the final properties of the molded product will vary from those expected of the virgin polymer. . A study was therefore undertaken to explore how these polymers respond to the stresses of molding. This application note describes the molecular and rheological changes that occurred as samples of PS and PMMA were repeatedly extruded through a capillary rheometer, simulating molding. The capillary rheometer was used to measure changes in melt viscosity, while multi-detector GPC (Gel Permeation Chromatography) was used to characterize changes in molecular weight and structure in the samples after each cycle through the rheometer..

Produkte:
Rosand Linie
Datum:
April 27 2017
Sprache:
English

Characterizing different polymer degradation routes during processing using multi-detector GPC and capillary rheology Application Note

The degradation mechanisms of two different polymers were studied using multi-detector GPC and capillary rheology. While polystyrene was observed to degrade through polymer chain scision, PMMA was seen to aggregate through cross-linking.


Differential scanning calorimetry as a diagnostic tool for cancer patients Application Note

Blood serum is a source of cancer biomarkers. Tumor development is accompanied by metabolic malfunction that may result in altered serum composition: proteins that are up/downregulated and low molecular weight metabolites undergoing changes in concentration. Nowadays, researchers analyze blood serum through multifactorial techniques profiling to transform the current scenario in cancer therapy by: 1) determining patient prognosis; 2) monitoring tumor recurrence and therapeutic responses in real-time; 3) identifying new therapeutic targets; 4) elucidating drug resistance mechanisms; and 5) improving our current understanding of tumor progression and metastatic disease. One of the main advantages of using plasma samples is that only a minimally invasive assay such as a routine blood test analysis is required.. In this context Differential Scanning Calorimetry (DSC) has reveal its potential as a technique for a global analysis of serum samples. Traditionally, DSC has been employed for determining the partial heat capacity of a macromolecule as a function of temperature, from which the thermodynamic parameters associated with the structural stability of the macromolecule by thermal denaturation can be estimated1. Due to its high sensitivity, the precise determination of the thermally-induced conformational transitions of biomolecules that are present in plasma can be readily performed using DSC. The ten most abundant proteins in blood serum (albumin, IgG, fibrinogen, haptoglobin) account for 90% (w/w) of serum. Another twelve proteins represent the next 9% and 3000 proteins account for the final 1%. Interestingly, the normal serum thermogram can be reasonably reproduced with just the most abundant proteins. Therefore, serum thermograms do not provide direct information about the remaining, low-concentration serum proteins. However, the ability of those proteins, as well as disease-associated metabolites, to bind to and alter the unfolding temperatures of the most abundant proteins is responsible for the changes observed in the thermograms from disease states (that is, the interactome hypothesis). .

Produkte:
MicroCal VP-DSC
Datum:
April 18 2017
Sprache:
English

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