Preservative selection for shampoo

Please help me choose a good and mild preservative blend for shampoo. 

Which one is the mildest formaldehyde releaser and which one is the most effective for bacteria?
How is that compared to phenoxyethanol in effectiveness and mildness?

I will combine it with a fungicide. Options are caprylhydroxamic acid, Piroctone Olamine, sodium dehydroacetate, sodium benzoate. Which one do you recommend?

Any other suggested preservative blend?

This is the shampoo formula in Active ingredients:
SLES   %9
CAPB  %1.5
APG    %1.5
PQ10  %0.3
Glycol distearate  %2
HPMC %0.5
EDTA  %0.2
EO    %0.4

pH 5

Comments

  • PhilGeisPhilGeis Member, Professional formulator
    Can't address mildness but for efficacy suggest Germall or Glydant with sodium benzoate and EDTA.
  • @PhilGeis thanks
    The upper limit for DMDM hydantoin is %0.6, so why warning above %0.05?

     Finished products containing DMDMH must be labeled with the
    warning “contains formaldehyde” if the (free) formaldehyde
    concentration exceeds 0.05%
  • PhilGeisPhilGeis Member, Professional formulator
    Right - DMDm Hydantoin at 2000-2500 ppm usually gave < 500 ppm free formaldehyde.  "Free" is important.  
  • @PhilGeis Formalin is %37 formaldehyde in water, is that %37 free formaldehyde? 
  • PhilGeisPhilGeis Member, Professional formulator
    Effectively. 
    But to make it complicated - formaldehyde is a gas and formalin is a saturated solution of that gas.  The gas hydrated in solution as methylene glycol. 

    One more that you need to consider.  Formalin includes methanol -maybe 10%.  Please take that into consideration
  • @PhilGeis thanks a lot
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