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TREF Frequently Asked Questions

We are aware that acquiring a lab instrument is an important decision, furthermore if Polyolefins’ research is related with your core business.

Although you can ask directly to our consultants whenever you want, you may prefer to know first the answers to the most typical questions about our instruments. Here are packed the most relevant questions about TREF.


Questions


Answers

What kind of results can be obtained from TREF?
TREF technique (Temperature Rising Elution Fractionation) was developed to obtain the Chemical Composition Distribution curve during the elution cycle. Therefore, at the end of a TREF run, a distribution in concentration versus elution temperature is obtained.

Does TREF provide the physical fractions in temperature?
Although it may be possible to collect the fractions as they elute from the column, the instrument is not optimized for this and the process is not automated. Please refer to the PREP mc2 for an automated fractionation instrument.

How many samples can be run at a time and how long will it take?
Up to 5 samples can be sequentially run with no supervision required in about 5 hours per sample. After the analysis, an automated cleaning is performed by the instrument and therefore it is ready to start another run immediately. For higher throughputs the CEF apparatus is more appropriate.

How many grams of sample do I need for a TREF analysis?
The standard amount used in TREF analysis is around 80mg per sample.

Which solvents can be used?
1.2.4-Trichlorobenzene (TCB) and Orto-Dichlorobenzene (oDCB) are the most used solvents. Perchloroethylene could be used too. To use other solvents please consult Polymer Char first.

What kind of sample preparation is required by the user?
No samples preparation is required by the user but weighing the dry samples and putting them inside of the vessels. The rest of the steps are performed by the instrument automatically: filling, dissolution, column loading, crystallization, elution, final cleaning, etc. Therefore, when a run is finished, another one can be started immediately.

Do I need to handle solvents?
Solvents don’t need to be handled at any time; the whole process is fully automated and the instrument performs all the needed steps: filling, dissolution, column loading, crystallization, elution, final cleaning, etc.

How long will my TREF column last? Are temperature or flow changes affecting my TREF column?
TREF column is not a consumable part of the instrument and it is not affected by temperature or flow changes. It has been designed in Polymer Char especially for TREF instrument to achieve a good resolution when analyzing 5 samples a day.

Which kind of samples can be analyzed?
LLDPE, LDPE, HDPE, PP, E-P copolymers, multicatalyst reactor resins, and any semicrystalline polymer soluble in TCB or oDCB, giving response to C-H absorption.

Which detector is used for concentration in TREF?
TREF incorporates an infrared detector to measure the concentration of the solution which is being eluted and going out of the TREF column. This detector is Polymer Char’s IR4 in its OEM version and therefore a composition sensor can be incorporated as well to obtain methyls or carbonyls content information.

Can I couple additional detectors to TREF?
A capillary viscometer detector can be connected optionally to TREF technique, to obtain information on composition-molar mass interdependence.

How can I access and review my results?
The TREF Software incorporates a database to access the analyzed samples results at any time, even while the instrument is running. Results obtained are the concentration profile and the cumulative curve versus temperature. When adding a comonomer calibration, CCD results are showed vs. the corresponding comonomer content.

Which are the differences between CRYSTAF and TREF techniques?
CRYSTAF obtains the CCD curve during the crystallization step, and TREF does need an additional temperature cycle called elution to obtain the same results.

TREF obtains the CCD curve directly and in a continuous way, meanwhile the CRYSTAF technique does so in a discontinuous way: A series of data points from the cumulative composition distribution curve are actually measured and used to obtain the differential distribution by means of a smoothing splines fitting algorithm.

CRYSTAF obtains the CCD curve during the crystallization process, and TREF does need an extra temperature cycle called elution to obtain the same results. The results obtained with both techniques are very similar but when expressed in temperature scale there exists a shift to lower temperatures in CRYSTAF due to undercooling effects.

Why are both techniques, CRYSTAF and TREF, convenient when analyzing the CCD in polyolefins?
For most of the polyolefins, results obtained by CRYSTAF or by TREF will be equivalent, and therefore only one of the techniques is enough in most cases. However, for some specific type of polyolefins, separation might be better achieved by CRYSTAF or by TREF due to the different behavior of the components in the crystallization or elution process. In this sense, having both techniques available, the best possible separation will be achieved for every sample.

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