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This method is useful for analysis of complex polymer systems like polymer blends, copolymers  and branched polymers. These samples are usually heterogeneous in terms of chemical composition, functionality and structure. Since GPC separates only according to size, GPC is not sufficient  to describe such a system. Therefore, the combination of two chromatographic methods to  separate the mixture into more homogeneous fractions (i.e. functional groups) followed by separation by molar masses constitutes a better approach. WinGPC software allows the automatic transition from one dimension to the other. PSS offers the development of 2D applications and performs the analysis for you, with our special software for data acquisition, quantitative interpretation and data plotting, the WinGPC 2D Chromatography module. 

Results provided: 

• complete deformulation 
• composition
• molecular weight distribution
• molecular weight averages, Mw, Mn, Mz 
• copolymer composition

For more information  about the principles and use of 2D chromatography  see:

"Facing the Challenge of Analyzing Complex Polymers: A Primer in 2 Dimensional  Liquid Chromatography"

Conventional GPC/SEC is an excellent method for sample comparison and the determination of  molecular weight of a sample. Conventional GPC/SEC analysis yields the complete molar mass and is more reliable and informative than a method that only yields an average value (Mw or Mn). PSS offers testing in aqueous and organic mobile phases. An internal standard is used to monitor the  constant flow of the pump and for flow-correction as needed. Afterwards the molecular weight distribution is calculated from the elugram using the corresponding calibration curve.

Calculation of the percentage of a given molar mass (eg. < 500 g/mol) from  the molecular weight distribution is usually requested for product approval in the USA. Additives and stabilizers can be separated from the polymer and a quantitative determination of these compounds is possible. The analysis report lists all relevant  parameters of the measurement and documents  the sample preparation. 

Results provided: 

•   simple comparison of polymer samples 
•   molecular weight distribution 
•   molecular weight averages: Mw, Mn, Mz
•   percentage of mass, eg. < 500 g/mol 
•   chemical composition

GPC/SEC with RI and UV detection is often used to measure the molar mass distribution and to quantify the amount of oligomeric species. Additional information is available if a ESI-MS-spectrometer is on-line attached to the GPC/SEC system. This technique combines the separation ability of GPC/SEC with the sensitivity and specificity of detection from mass spectrometry and allows to identify oligomeric species. GPC/SEC-MS is one of the techniques with the most developments in recent years and particularly useful for analysis for REACH (determine the polymer status).

 

Results provided:

• molecular weight distribution
• absolute molecular weights
• quantification
• substance identification  

 

For more information about the principles see our PSS Streamliner Mass Matters.

FTIR is used to identify chemical substances. The coupling of liquid chromatography (LC) with Fourier-Transform-Infrared (FTIR) spectroscopy  allows the identification of unknown fractions with the help of a spectra database. When used in combination with a chromatographic system, the substrate is collected on a rotating Ge-disk. FTIR-spectra can be gained for each point of the chromatogram. PSS uses a special interface to remove the solvent on-line after the chromatographic separation is done. This method allows for identification of the substance as well as for the evaluation of chemical heterogeneity.

 

Results provided:

• chemical structure  - chemical purity  
• information about additives
• chemical composition

 

 

The light scattering detector provides absolute molar masses without requiring the appropriate polymer calibration standards. GPC/SEC separates the sample by size and the on-line light scattering detector directly determines the molar mass. You get the absolute weight average (Mw) and the molecular weight distribution of the polymer. The method is limited by the molecular weight of the sample (depending on the type of polymer), the minimum molar mass normally has to be above 5000 g/mol. PSS uses a low angle (LALLS) and a multi angle light scattering detector (MALLS) during routine operation. The MALLS detector  provides additional information about the radius of gyration, which is derived from the angle  dependency of the scattered light. From the combination of absolute molecular masses and corresponding radius of gyration, it is  possible to obtain important structure information and branching.

Results provided:

•   molecular weight distribution
•   absolute molecular weight average Mw
•   radius of gyration 
•   branching/structure information

The capability to get exact molar masses without having the proper polymer standards is offered by online viscosity detection. This method uses the concept of universal calibration and provides  the correct masses, the molecular weight distributions, and information about the structure of the  polymer. With viscosity detection you can also analyze small molecules (e.g. oligomers), a big  advantage over online light scattering measurements.  

The GPC - viscosity coupling allows you to determine the important relationship between intrinsic  viscosity and molar mass of a polymer within one measurement. From this data, you can calculate the Mark-Houwink parameter of the investigated polymer - solvent system containing the structural information.  

Results provided:  

•   intrinsic viscosity  
•   Mark-Houwink parameter  
•   molecular weight distribution  
•   molecular weight averages, Mw, Mn, Mz  
•   branching/structural information

Some polymers are insoluble at room temperature. Polyolefins and their co-polymers are soluble at temperatures over 130°C. PSS offers testing of polymers soluble in 1,2,4-trichlorobenzene at 155°C, using a HT-GPC system equipped with a refractive index detector, a viscosity detector, a FTIR-coupling interface and a column-switching system that permits the use of 4 different POLEFIN columns. This gives us the possibility to run polyolefins in a range from hundreds to more than 20 000 000 g/mol. We can offer you a standard calibration with polystyrene or polyethylene or a universal calibration using a differential capillary viscosity detector.

Static light scattering is an established and exact method for the absolute determination of the weight average molar mass (Mw) of a polymer. The measurement is carried out in a light scattering cell without prior separation of the polymer solution. The measured quantity is the intensity of the scattered light (Excess-Rayleigh scattering), which is proportional to the average molecular size of the dissolved substance. A series of measurements,  performed with different concentrations (c) at various scattering angles (theta), results in the weight average molecular mass Mw. One requirement is the knowledge of the refractive index increment (dn/dc) of the polymer in the solvent used. The molecular weight average Mw is determined by plotting the data and extrapolation of c and theta to zero (Zimm-plot). Another parameter derived from the Zimm - plot is the second virial coefficient A2.  

Results provided:

• absolute molecular weight average Mw
• radius of gyration
• second virial coefficient A2

Viscosity measurements have a special significance in the quality control of polymers. These measurements, performed under standardized conditions (DIN, ASTM etc.), provide important parameters e.g. for polymer processing. The method in general averages over the whole sample, producing integral values as a result. PSS is able to determine various kinds of viscosities, e.g. relative viscosity, inherent viscosity, intrinsic viscosity etc., even in uncommon solvents like HFIP, meta-Cresol, ortho-Dichlorobenzene and formic acid at temperatures up to 302°F (= 150°C).

 

Results provided: 

• absolute, relative, inherent and intrinsic viscosities
• Huggins/Krämer constants

The molar mass determination by osmometry is one of the most important methods for evaluating the number average molecular weight Mn. This is an important parameter for the interpretation of kinetic data in polymerization and copolymerization reactions. <the method is also of interest for prepolymers with lower molar masses. PSS provides sample&nbsp;testing service using vapour pressure osmometry measurements of polymers with masses Mn <&nbsp; 10 000 g/mol in toluene and ultra pure water. A run includes the determination of the device scaling&nbsp;factor and the measurement at four different sample concentrations. The number average&nbsp;molecular weight Mn and the second virial coefficient&nbsp;A2 is evaluated graphically.

 

Results provided:

• number average molecular weight Mn

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