Polyethylene & Polypropylene in Flexible Barrier Packaging

1 2009 Consumer Packaging Solutions for Barrier Performance CoursePolyethylene & Polypropylene in Flexible Barrier PackagingPresented by:Kelly R. FreyExtrusion Coating Technical ServiceChevron phillips Chemical Company, LPLearning OutcomesyHow Polyethylene & Polypropylene is used in Barrier Packaging . yBarrier properties of PE & PP. yProperties of PE which affect Barrier film & coating processing influences Barrier does PE & PP fit into Flexible Barrier Packaging ?yBy itself (monolayer)..yCombined (coex or lamination)..How Does PE & PP Provide Barrier ?yPolyethylene is used by itself or combined with other materials to create a torturous path to create a Barrier . yPolyethylene and Polypropylene can have good-moderate moisture Barrier properties.

2 YHDPE MVTR grades are higher in density and can provide improved moisture Barrier over LDPE and PP. yGood moisture Barrier can be achieved with monolayer HDPE MVTR grades. How Does PE & PP Provide Barrier ? yFair moisture Barrier can be achieved with monolayer LDPE grades. yPolyethylene and Polypropylene have poor oxygen (gas) Barrier but good-moderate moisture Barrier properties. PE & PP MVTR PropertiesPE & PP OTR or metPETPVdC or metOPPC elloOPETN ylon (mils)g/100in2/dayHDPE MVTRHDPE MVTR Grade Blown FilmUsing PE & PP for BarrieryPE & PP can be combined (blended, coexed, or laminated) with other materials for exceptional MVTR & & PP properties and processing methods influence Barrier properties.

3 HHHCCHETHYLENEETHYLENEC olorless GasOdor = Slightly SweetOrigins = Refinery Gas &Liquefied Petroleum GasesMol. Wt. = 28 World Capacity*128 Million Tons. (2005 est.)* World Petrochemical Review (Oct 2005)Colorless GasOdor = Slightly SweetOrigins = Refinery Gas &Liquefied Petroleum GasesMol. Wt. = 28 World Capacity*128 Million Tons. (2005 est.)* World Petrochemical Review (Oct 2005)HHHCCHC atalyst/InitiatorTemperaturePressureCata lyst/InitiatorTemperaturePressureHHHCCHH HHCCHHHHCCHP olyethylene ReactionHHHCCHHHHCCHHHHCCHHHHCCHHDPEHDPE LDPELDPELLDPELLDPEMOLECULAR WEIGHTDISTRIBUTION (MWD)HDPEMOLECULAR WEIGHTDISTRIBUTION (MWD)COMONOMBER TYPE (SCB)LLDPEMOLECULAR WEIGHTDISTRIBUTION (MWD)LONG CHAIN BRANCHING (LCB)CRYSTALLINITYCRYSTALLINITYCRYSTALLI NITYLDPEC ritical Polyethylene PropertiesyMelt Index / Mol.

4 Wt. yDensity / CrystallinityyMorphology (shape, size & distribution of the PE molecules & crystals)yMolecular Weight Chain BranchingyRheologyDensityyDensity is a measure of the crystallinity of the density polymers have more closely packed molecules and are more stiff in density polymers have loosely packed molecules and are more is measured as the weight of material occupying a specific volume (g/cc).No Branching High DensityShort Chain Branching Med DensityShort & Long Chain Branching Low DensityCrystallineRegionsAmorphousRegion sDensity TestDensity is an indirect measure ofthe crystallinity of a polymer. Standard Procedure : ASTM D1505 Units = g/ccCalibrated Density StandardsSampleControlled TemperatureGradient ColumnOther accepted techniques for measuring density include ultrasonic velocity and buoyancy (densimeter).

5 As CrystallinityIncreasesThese PropertiesIncreaseDensityStiffnessTensil e StrengthSoftening PointDead FoldCurlChemical ResistanceHeat ResistanceWrinkling TendencySeal Initiation (Moisture, Light, & Grease)DecreaseMD Tear StrengthImpactPuncture ResistanceCOFO ptics (Clarity)CrystallinityyFor Polyethylene , the degree of crystallinity has the largest influence on Barrier oriented, large crystals, create the most tortuous path. y% crystallinity can be measured and is influenced primarily by polymer type, but also by ~ 30% - 55% crystallinityyHDPE up to 85% crystallinityyIn addition to % crystallinity, morphology (alignment, shape & dimensions of crystals), also affects Barrier performance. yProcessing methods also influence the degree of crystallinity and polymer morphology, which will also directly affect Barrier properties.

6 YTypes of processing high Barrier structures by coextruding PE & PP with high Barrier materials, predominantly nylon and high Barrier structures by coextruding PE & PP with high Barrier materials, predominantly nylon and EVOH. Also produces good moisture Barrier monolayer films using HDPE MVTR CostOutputGauge ControlOptical PropertiesRetrofit to CoexAdditive LoadingFilm StrengthBiax OrientationMVTR BarrierCAST FILMBLOWN FILMP rocessing Conditions Affecting (mils)g/100in2/dayHDPE MVTRHDPE MVTR Grade Blow (mils)g/100in2/dayHDPE MVTRHDPE MVTR Grade Blow FilmBUR = = Coating ProcessBarrier Considerations in Extrusion CoatingyHDPE must be blended or coextruded with LDPE for processability in extrusion with highly branched LDPE extrusion coating grades disrupts crystallinity and reduces Barrier .

7 YMost orientation is in machine direction (similar to cast film). Lack of biax orientation reduces Barrier compared to MVTR blown dependent on level of comonomerySome applications only require moderate Barrier and LDPE or HDPE in extrusion coating can work ( sugar pouch). Extrusion Coating 20406080% HDPEg-mil/100in2/dayBlendCoexHow to Destroy Barrier in Extrusion CoatingSummaryyPE & PP are used directly or indirectly in Flexible Barrier Packaging . yTo achieve oxygen (gas) Barrier , PE & PP are typically coextruded or laminated with other materials. yHDPE MVTR grades provide good moisture Barrier methods and process conditions influence Barrier BYKelly R. FreyExtrusion Coating Technical ServiceChevron phillips Chemical Company, LPPlease remember to turn in your evaluation