Frequently ask questions

    Future development of Grafcompounder: what is planned?

    We want to include some new features like
    • Calculation of the specific gravity
    • Compound cost calculation - weight cost and volume cost
    • Bar diagrams to show the spread of ingredients in the database.
      Such diagrams would allow, to decide, whether more data sets are needed, to fill gaps
    • Ability to combine different data sets into one larger table.
      Like in the sample data sets for training, compounds of a family of polymers are in separate worksheets , for example one worksheet for NR - and another for SBR compounds. To some extend this are miscible polymers and it may of advantage to have them integrated into one worksheet.
    We would highly appreciate, if you have additional ideas to consider and help us makeing this program as useful as possible.

    1. The difference of the physical properties between calculated compound properties and confirmation experiment is quite large.
    What can be the reason?

    One major concern can be the precision of measurements. According to my own experience batch to batch variation is quite small in laboratory size mixers but larger in plant scale mixers to some extend. Normally the batch to batch variation and its effect on physical propeties is well known: either from quality control measurement and analysis or from repeated testing in laboratory scale. But if it is not known, I urge you to evaluate.
    The other concern is the measruement error in the testing laboratory. There are a couple of methods / procedures to follow, if there is a problem.

    • One method is a Gage R&R study. Advise and templates for table calculation programms can be found on the internet.
    • The other method would be the use of Statistic Experimental Design (DoE) in your Laboratory. The analysis of the measurement error is inherent in the software (See for example Design Expert® from Stat Ease Inc.).
    • As a third method: Laboratories can participate on Round Robin Tests, which are offered and organized by several institutes and organizations around the world.
    One other important concern are mistakes in the database - like typing error or "real" measurement errors.
    This is the case very often, if data are transferred by hand into the database but not electronically. You need to verify the data in your database either one by one, which is not possible in larger sets of data. At least the data of the compound used for calculation by the Grafcompounder software should be reviewed. Compounds with faulty data should be excluded from further calculations. You may decide to repeat measurements and make correction of the datasets as a corrective action alternatively.

    2. Is there any proof of linear relations between ingredients in a rubber formula and its properties?

    If you analyze a lot of experiments done according the statistic experimental design (DoE) procedure, you have to notice, that almost all relations between ingredients, like fillers and oil, and the physical properties of the compound are in deed linear, made with this ingredients. If Design Expert® is your program of choice, you can visualize these relations with the graphical optimization function. It is easy to create an overlay plot of all physicals included in your research, if their values are put in the "criteria - upper limit" box. The y,x - axis show the factors (filler, oil), the contour lines the value, slope and linearity of the responses (physical properties). The following figure gives an example of an oil / filler experiment based on natural rubber (NR), which was performed recently.

    The factors and responses are shown on the left side of the figure. The author has evaluated numerous investigations similar to the one above.

    Even if a none linear approach is suggested by the DoE software, it was found, that a linear approach is sufficient for almost all cases included in this evaluation, taken into account measurement and experimental errors.
    If it can be said truly, that linear relations between ingredients and physical properties exist, then it seems justified, to use historical or happenstance data sets to perform compound calculations.

    3. How to store compound data?

    Working with version 1..1 compound data are stored in a calculation program like Excel® or Open Office® Spreadsheet. In Colum 1 header is called ingredients:, in the same column in a cell further down it is called properties:. In the second column with the first recipe in a cell above the name of the recipe you put in recipes:

    The data are transferred into the GrafCompounder with copy and paste.

    The following table is shown as an example:

    3.1 How to store compound data with the new Version of GrafCompounder 2.004?

    In GrafCompounder Version 2.004 the compound data can be stored directly in a xx.gc format, which is specific for the software. It can only opened with the GrafCompounder as long as you have the licence key.
    Please see the new tutorial for this Version.

    4. Which compound properties should be stored in the Database?

    It is recommended, that all measurable compound properties should be stored in the database. Especially the basic physical properties should be completly stored. If one of this properties is a target of the calculation, this compound will be ignored when calculating.

    5. How can I compare the compound cost between the newly calculated compound and one of the compounds in my database?

    If the material cost of all the compounds in your database is one of the property, the GrafCompounder will calculate the material cost of your compound like any other property. Of course you can make cost a target and even give cost a weight.

    Because cost - as we say: is one of the important physicals - it is recommended, that the data stored in the database consist of basic physicals and cost.

    6. The confirmation experiment gives not the expected result! What should I do?

    You should control every compound used for the calculation. You may start with the compound, which is used at the highest percentage.

    Mostly one of the properties may show a larger difference, the tensile at break for example. If you have identified a compound with a property value, which is suspicious, you may disable this compound and recalculate.

    Investigate what has changed between the first and the second calculation. Compare the property of the compound after the second caclulation with the compound property, you got through the confirmation experiment.

    Most likely this analysis will be the prove, that a compound with a faulty data is detected.

    You either disable this compound when running further calculations, or you eliminate this compound from your original database.

    7. I have missing data in the properties area. What should I do?

    In case of missing data in the “property:” portion of the table, the empty cells will be taken as 0,000 when calculated. The results will be wrong, because normally physical data will be unequal to zero (like tensile, elongation). Only in case of changes after exposition to heat or storage in media (like oil or water) the change can be zero, like Δ-Hardness for example.
    If cell are empty, because no value is recorded, delete the row and exclude from calculation. Another option is, to disable the compound.
    You may also put in a value, if it was simply forgotten or you may take the compound back to the laboratory and ask for a new set of data.
    It should be mentioned, that missing data values in the “ingredient:” portion of the table are not of concern. The GrafCompounder will take the empty cell as zero, which gives the correct calculation for the final formula. As an example, ingredient A is set as 1,00 phr in formula 1 and the same ingredient is set as 0,00 phr in formula 2 and the final mix is 50/50 %: the value in the calculated new formula will be 0,50 phr. This is a correct value for ingredient A in the newly calculated formula.

    8. In the compound data base there are Polymers with different polarity. How to handle?

    What one has to consider, if there are compound formulas in the database with different polarities is the question, whether the polymers are insoluble or soluble. An estimation can be made, if one investigates the polarity scale (see “CRC Handbook of chemistry and physics” or “polymer handbook” - Brandrup, Immergut). If polymers insoluble, the effect on physicals is none linear and the simulation result with the GrafCompounder will be misleading. Even the author got a solution for an EPDM / SBR Blend (EP1444279A4) with the help of the GrafCompounder, extra care must be taken in interpreting the results of a simulation. Still the best and safe way to handle such problem, the compounds containing an insoluble polymer should be disabled and the calculation should be done without those recipes.

    9. If I want to evaluate new ingredients for my compound, is it possible
    to use the GrafCompounder?

    In case of the evaluation of new ingredients there is nothing in a historic database, which can be calculated. Without any experiments from the past, you can not conclude on unknown effects or correlations. The recommendation would be, that one evaluates the ingredients with the help of statistic experimental design or by any other means. The formulas and results can be used to create a database. Even if the database is small, because of the limited number of experiments done and stored, the GrafCompounder has no restriction on the size of a database.

    10. Is it possible to calculate with negative numbers, like change of Hardness -1°ShA for example?

    In case of negative numbers, which you may have as a result of a property change after storage in hot air or media, you need to consider the number format only.
    Between the minus (-) sign and the number there should be no space. If there is a space in between, the cell would turn yellow, indicating that this value is not accepted by the GrafCompounder. As soon as a space is applied, the the yellow colour will dissapear.

    last updated 27. July 2017