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CRYSTAF 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 CRYSTAF.


Questions


Answers

What kind of results can be obtained from CRYSTAF?
CRYSTAF technique (Crystallization Analysis Fractionation) was developed to obtain the Chemical Composition Distribution curve during the crystallization step. Therefore, at the end of a CRYSTAF run, a distribution in concentration versus temperature of crystallization is obtained.

Does CRYSTAF provide the physical fractions in temperature?
CRYSTAF is an analytical instrument which was designed to obtain the chemical composition distribution curve, but it doesn’t provide any physical fraction. For this purpose, please read about PREP mc2.

How many samples can be run at a time and how long will it take?
Up to 5 samples can be run in about 8 hours with no supervision required. After the run, an automated cleaning is performed by the instrument and therefore it is ready to start another run immediately.

How many grams of sample do I need for a CRYSTAF analysis?
The standard amount used in CRYSTAF analysis is around 40mg per sample, therefore the instrument can be used both for research and also for quality control.

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 crystallization vessels. The rest of the steps are performed by the instrument automatically: filling, dissolution, crystallization, 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 the rest of all the needed steps: solvent filling, dissolution, crystallization, final cleaning, etc. So after a run, the instrument is ready to start again immediately.

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 is the detector used for concentration measurement in CRYSTAF?
CRYSTAF incorporates an infrared detector to measure the concentration of the solution while the temperature is decreasing in the crystallization cycle. 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.

How can I access and review my results?
The CRYSTAF Software incorporates a database to easily access all the analyzed samples, which is connected to the calculations and results screens. Any result can be accessed and reviewed at any time, even when the instrument is running other samples.

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.

What is the reason to have two different techniques, CRYSTAF and TREF, to analyze the CCD in polyolefins?
Results obtained by CRYSTAF or by TREF will be equivalent in most of the polyolefins; therefore only one of the techniques is enough in most cases. However, for some specific kind of polyolefin blends, separation might be better achieved by CRYSTAF or by TREF due to the different behavior of the components in composition. In this sense, having both techniques available, the best possible separation will be achieved for every sample.

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