The Art and Science of Controlling Alkaline Earth Oxide ... · Viscosities at 15 min. of Paste Mixed to Various Temperatures (0.7MR / 0.11%H2O) 95F 105F 115F Increasing initial paste

The Art and Technology of The Art and Technology of Controlling Alkaline Earth OxideControlling Alkaline Earth Oxide

Thickeners in SMCThickeners in SMC

Cheryl LudwigCheryl Ludwig

Thermoset Process Development SpecialistThermoset Process Development Specialist

Goals of this Presentation:Goals of this Presentation:

•• Provide basic overview of SMC formula Provide basic overview of SMC formula componentscomponents

•• Discuss importance of rheology during Discuss importance of rheology during compound and part manufacturingcompound and part manufacturing

•• How to manage SMC paste viscosity build to How to manage SMC paste viscosity build to achieve desired end resultsachieve desired end results

Sheet Molding Compound (SMC)Sheet Molding Compound (SMC) Basic ComponentsBasic Components

Required Base Raw Materials Required Base Raw Materials

–– Thermosetting Thermosetting resin(s)resin(s)

–– Reactive Reactive monomer(s)monomer(s)

–– Filler(sFiller(s) / reinforcement(s)) / reinforcement(s)

–– Organic Organic peroxide(s)peroxide(s)

““Other” Raw MaterialsOther” Raw Materials

–– Thickening Thickening agent(s)agent(s)

–– Release Release agent(s)agent(s)

–– thermoplastic resin(s)thermoplastic resin(s)

–– Colorant(sColorant(s))

–– Inhibitor(sInhibitor(s))

–– Processing Processing aid(s) aid(s)

–– “Special“Special" additive(s) " additive(s)

Designing a SMC FormulaDesigning a SMC Formula

•• An extensive, almost limitless, list of RM An extensive, almost limitless, list of RM choices available for considerationchoices available for consideration

•• Key RM properties regulate / dictate Key RM properties regulate / dictate selection, combinations, %’sselection, combinations, %’s

•• Variation in above choices allow for an Variation in above choices allow for an infinite number of SMC formulas designed to infinite number of SMC formulas designed to meet: meet: –– Specific compound processing parametersSpecific compound processing parameters

–– Desired final part requirements Desired final part requirements

ONE Commonality Necessary for ONE Commonality Necessary for ‘Successful’ Compounding and ‘Successful’ Compounding and

Molding of ALL SMC….Molding of ALL SMC….

•• PREDICTABLE AND RELIABLE VISCOSITY PREDICTABLE AND RELIABLE VISCOSITY BUILD RESULTING IN A COMPOUNDED BUILD RESULTING IN A COMPOUNDED MATERIAL WITH A CONSISTENT MATERIAL WITH A CONSISTENT RHEOLOGY PROFILE!RHEOLOGY PROFILE!

Why is Repeatable Rheology Profile Why is Repeatable Rheology Profile Necessary?Necessary?

•• Consistent paste delivery through pumps, dams or slit diesConsistent paste delivery through pumps, dams or slit dies •• Wetting of the filler(s) / reinforcement(s)Wetting of the filler(s) / reinforcement(s) •• Mat weight controlMat weight control •• Stabilization of the liquid phasesStabilization of the liquid phases •• Packaging (saggy rolls, containment of product within Packaging (saggy rolls, containment of product within

carrier film, separation at festoon folds, etc.)carrier film, separation at festoon folds, etc.) •• Preparation and handling of the sheet prior to moldingPreparation and handling of the sheet prior to molding •• Impart a viscoelastic characteristic to carry the filler / Impart a viscoelastic characteristic to carry the filler /

reinforcement in a consistent flow pattern during mold fillreinforcement in a consistent flow pattern during mold fill •• Help to develop a resin rich surface Help to develop a resin rich surface •• Consistent final molded product characteristicsConsistent final molded product characteristics

What Causes an Increase in Paste What Causes an Increase in Paste Viscosity? Viscosity?

•• Chemical thickenersChemical thickeners –– Alkaline earth (Group IIA metal) oxides and / or hydroxidesAlkaline earth (Group IIA metal) oxides and / or hydroxides

•• Magnesium oxides / hydroxides are industry "norm" Magnesium oxides / hydroxides are industry "norm" –– PG2PG2

•• Proprietary liquid thickener chemistryProprietary liquid thickener chemistry •• Similar thickening profile as Similar thickening profile as isocyanatesisocyanates but does not but does not

require controlled hydroxyl functionalityrequire controlled hydroxyl functionality –– Polymeric Polymeric isocyanatesisocyanates

•• Polymeric Polymeric isocyanatesisocyanates require controlled hydroxyl require controlled hydroxyl functionality in the resin, are VERY sensitive to moisture, functionality in the resin, are VERY sensitive to moisture, thicken quickly thicken quickly

•• Physical thickeners Physical thickeners ---- fillers / reinforcementsfillers / reinforcements –– Physical thickening is difficult and appropriate for few types of Physical thickening is difficult and appropriate for few types of

SMCSMC

How is the SMC Thickening ProfileHow is the SMC Thickening Profile (Viscosity Increase) Controlled?(Viscosity Increase) Controlled?

•• To achieve repeatable viscoelastic response To achieve repeatable viscoelastic response batch to batch it is imperative the SMC has:batch to batch it is imperative the SMC has: –– Consistent raw materials Consistent raw materials –– Controlled process parameters Controlled process parameters –– Stable storage conditionsStable storage conditions

•• Technology developments in industry over last Technology developments in industry over last 40 years has resulted in: 40 years has resulted in: –– Advanced manufacturing controls and equipment Advanced manufacturing controls and equipment

resulting in tighter tolerances of SMC raw materialsresulting in tighter tolerances of SMC raw materials –– Innovative compounding and molding processes and Innovative compounding and molding processes and

equipmentequipment

Why is Why is MgOMgO the Candidate of Choice the Candidate of Choice to Impart a Viscosity Build?to Impart a Viscosity Build?

•• Meets the basic needs of SMCMeets the basic needs of SMC

•• Most widely used chemical thickener in Most widely used chemical thickener in processing of SMC and therefore readily processing of SMC and therefore readily availableavailable

•• Cost effectiveCost effective

•• Potentially can be manipulated and Potentially can be manipulated and controlledcontrolled

What is the Mechanism Causing What is the Mechanism Causing Viscosity Build?Viscosity Build?

•• The The resins’ acid resins’ acid functionality and the functionality and the MgOMgO are the reacting species causing viscosity are the reacting species causing viscosity increaseincrease

•• Characteristics of each contribute / dictate Characteristics of each contribute / dictate the viscosity profilethe viscosity profile

Characteristics Characteristics of of Resins Resins with with AcidAcid Functionality Functionality Affecting Affecting ThickeningThickening ProfileProfile::

•• Acid valueAcid value

•• Hydroxyl numberHydroxyl number

•• Molecular weight average, distribution, Molecular weight average, distribution, oligomers, etc.oligomers, etc.

•• Distribution of acid groups on polymer chainDistribution of acid groups on polymer chain

•• MoistureMoisture

Characteristics of Characteristics of MgOMgO Affecting Affecting Thickening ProfileThickening Profile::

•• ?????????????????????????????????? ??????????????????????????????????

•• No No easily tested physical or chemical easily tested physical or chemical property of property of MgOMgO has been identified that has been identified that correlates to thickening performancecorrelates to thickening performance

Proposed Mechanism for Thickening Proposed Mechanism for Thickening Reaction:Reaction:

•• Acid Acid group of resin is chemisorbed to surface anion group of resin is chemisorbed to surface anion vacancies vacancies of of MgOMgO and/or and/or by the basic O2 surface ionsby the basic O2 surface ions

•• Chain extension is by linking polymer chains with "crystals" Chain extension is by linking polymer chains with "crystals" of of MgOMgO not Mg ionsnot Mg ions

•• Prior Prior mechanism for thickening relied on dissociation of mechanism for thickening relied on dissociation of MgOMgO BUT research data does not support this BUT research data does not support this mechanism, mechanism, i.e.i.e. –– Dead Dead burn / sintered and reagent burn / sintered and reagent grades grades thicken thicken negligiblynegligibly

–– EquimolarEquimolar amounts of Mg(OH)2 amounts of Mg(OH)2 and and MgOMgO do do not thicken equallynot thicken equally

Proposed Mechanism for Thickening Proposed Mechanism for Thickening ReactionReaction::

SMC SMC Formula Development using Formula Development using MgOMgO Thickeners Thickeners

•• Determine Determine type type and concentration by conducting thickening and concentration by conducting thickening studiesstudies

–– Conduct Conduct thickening studies at 3 thickening studies at 3 MgOMgO levels; 2 levels; 2 moisture moisture levelslevels –– Monitor initial, 15', 1hr; and, 1 to 7+ day viscosityMonitor initial, 15', 1hr; and, 1 to 7+ day viscosity –– Bracket Bracket %%MgOMgO based on initial study that yields intended viscosity based on initial study that yields intended viscosity

profile required for SMC processing and moldingprofile required for SMC processing and molding –– Include a H2O range IF moisture sensitivity of AInclude a H2O range IF moisture sensitivity of A--paste to thickener is paste to thickener is

extremeextreme

•• If appropriate thickening rate cannot be achieved with initial If appropriate thickening rate cannot be achieved with initial grade of grade of MgOMgO, as, as--is moisture or temperature control, is moisture or temperature control, thenthen

–– Evaluate different grades / Evaluate different grades / reactivitiesreactivities of of MgOMgO –– Evaluate different types of Evaluate different types of thickenersthickeners –– Consider adjusting for H2O by moisture scavengers or water additionConsider adjusting for H2O by moisture scavengers or water addition

Effect of Initial TemperatureEffect of Initial Temperature on Aon A--Paste ViscosityPaste Viscosity

0

5

10

15

20

Th

ou

sa

nd

s ,c

ps

95F

105F

115F

Increasing initial paste temperature will reduce paste viscosity to assist flow through dam and glass wet-out

Effect Effect of Initial Temperature on 15’of Initial Temperature on 15’ SMC Paste Viscosity Varying %SMC Paste Viscosity Varying %MgOMgO

1.00E+00

2.00E+05

4.00E+05

6.00E+05

8.00E+05

Bro

ok

field

Vis

co

sit

y,

cp

s

Viscosities at 15 min. of Paste Mixed to Various Temperatures (0.5MR / 0.11%H2O)

95F

105F

115F

1.00E+00

2.00E+05

4.00E+05

6.00E+05

8.00E+05

Bro

ok

field

Vis

co

sit

y,

cp

s


95F

105F

115F

-6.00E+00

2.00E+05

4.00E+05

6.00E+05

8.00E+05

1.00E+06

Bro

okfi

eld

Vis

co

sit

y,

cp

s


95F

105F

115F

Increasing initial paste temperature will reduce paste viscosity to assist flow through dam and glass wet-out

BUT, increasing initial paste temperature will increases thickening rate

Glass wet-out, mat weight, phasing, etc. will be affected

15 Min., 1 Day, 7 Day, 14 Day Brookfield Viscosity 15 Min., 1 Day, 7 Day, 14 Day Brookfield Viscosity

vs. Molar Ratio and %H2Ovs. Molar Ratio and %H2O

-1.00E+01

5.00E+05

1.00E+06

1.50E+06

0.50 0.60 0.70 0.80 0.90 1.00 Molar Ratio

0.06%H2O

0.11%H2O

0.18%H2O

15’ Brookfield Viscosity, cps

5.00E+05

5.50E+06

1.05E+07

1.55E+07

0.50 0.60 0.70 0.80 0.90 1.00 Molar Ratio

0.06% H2O

0.11%H2O

0.18%H2O

6.80E+05

1.07E+07

2.07E+07

3.07E+07

4.07E+07

0.50 0.60 0.70 0.80 0.90 1.00

Molar Ratio

0.06% H2O

0.11%H2O

0.18%H2O

1 Day Brookfield Viscosity, cps


6.80E+05

1.07E+07

2.07E+07

3.07E+07

4.07E+07

0.50 0.60 0.70 0.80 0.90 1.00

Molar Ratio

0.06% H2O

0.11%H2O

0.18%H2O


Increased H2O increases sensitivity / viscosity response to % thickener at all levels during initial processing, 15 minutes

At 1 day high moisture paste is still tracking higher than lower moisture pastes

At 1 week viscosities of the high and low moisture pastes SWITCH--the low moisture is as high or higher in viscosity than the high moisture paste

At 2 weeks the low moisture paste is higher in viscosity than all pastes with high moisture

Influence of Influence of StorageStorage Temperature Temperature on Thickening on Thickening ResponseResponse

0.00E+00

5.00E+06

1.00E+07

1.50E+07

2.00E+07

2.50E+07

3.00E+07

3.50E+07

0 100 200 300 400

Time, Hrs.

Effect of Storage Temperature on Paste Viscosity Over Time

55F,0.6MR

95F,0.6MR

55F,0.7MR

95F,0.7MR

Storing / shipping SMC in extreme hot / cold temperatures can affect thickening rate and ultimately the SMC quality

Technology Advances in Technology Advances in MgOMgO

Capabilities Capabilities

•• New SMC applications, environmental New SMC applications, environmental concerns, cost containment, etc. have concerns, cost containment, etc. have prompted development of new / different prompted development of new / different chemistries being used in SMC formulatingchemistries being used in SMC formulating

•• Manufacturers continue to “push the Manufacturers continue to “push the envelope” with raw material and processing envelope” with raw material and processing changes changes

New ‘Tools’ for the New ‘Tools’ for the Changing SMC WorldChanging SMC World

•• Available are various grades of Available are various grades of MgOMgO with with different thickening reactivity and moisture different thickening reactivity and moisture sensitivitysensitivity

•• Have the potential to “tailor” thickening rate Have the potential to “tailor” thickening rate with changing Awith changing A--side reactivityside reactivity

Some Comparative Thickening….Some Comparative Thickening….

•• AA--side paste was adjusted to three water side paste was adjusted to three water levels, 0.05, 0.10 and 0.15% BOP H2Olevels, 0.05, 0.10 and 0.15% BOP H2O

•• Four individual grades of Four individual grades of MgOMgO were mixed were mixed with carrier resin at 40% loadingwith carrier resin at 40% loading

•• A constant loading of each A constant loading of each MgOMgO dispersion dispersion was mixed with the Awas mixed with the A--paste to 90Fpaste to 90F

•• Viscosity was monitored by BrookfieldViscosity was monitored by Brookfield

H2O Influence on SMC Paste Thickening rate at 15 and 60 Min. H2O Influence on SMC Paste Thickening rate at 15 and 60 Min. Comparing Four Comparing Four MgOMgO GradesGrades

#1L #1M #1H

15 min. 126,400 178,400 393,600

60 min. 196,800 556,800 1,372,000

-200,000

300,000

800,000

1,300,000

1,800,000

Bro

okf

ield

, cp

s

MgO #1 15 Minute and 1 Hour Viscosity

#2L #2M #2H

15 min. 125,600 232,800 450,400

60 min. 242,400 1,024,000 1,556,000

0

500,000

1,000,000

1,500,000

2,000,000

Bro

okf

ield

, cp

s


#3L #3M #3H

15 min. 86,400 114,400 174,400

60 min. 142,400 183,200 553,600

-200,000

300,000

800,000

1,300,000

1,800,000

Bro

okf

ield

, cp

s


#4L #4M #4H

15 min. 100,000 176,800 220,800

60 min. 160,000 387,200 960,000

-200,000

300,000

800,000

1,300,000

1,800,000

Bro

okf

ield

, cp

s


H2O WILL affect thickening rate and plateau viscosity of MgO containing SMC H2O% and MgO grade will determine the magnitude of rate change H2O addition will always increase the 15’ and 60’ thickened viscosity

H2O Influence on SMC Paste Thickening rate at H2O Influence on SMC Paste Thickening rate at 1 thru 13 Days 1 thru 13 Days Comparing Comparing Four Four MgOMgO GradesGrades

#1L #1M #1H

1 Day 11,920,000 28,400,000 18,880,000

2 Day 40,720,000 50,480,000 25,520,000

3 Day 56,000,000 58,400,000 28,000,000

7 Day 150,400,000 124,800,000 44,800,000

13 Day 200,000,000 175,000,000 59,200,000

1,000,000

41,000,000

81,000,000

121,000,000

161,000,000

Bro

okf

ield

, cp

s

MgO #1, 1 thru 13 Day Viscosity

#2L #2M #2H

1 Day 22,800,000 24,480,000 10,160,000

2 Day 52,080,000 42,400,000 13,280,000

3 Day 67,200,000 92,800,000 14,400,000

7 Day 158,400,000 96,000,000 30,400,000

13 Day 210,000,000 132,800,000 44,800,000

1,000,000

41,000,000

81,000,000

121,000,000

161,000,000

Bro

okf

ield

, cp

s


#3L #3M #3H

1 Day 1,520,000 9,440,000 22,080,000

2 Day 5,360,000 34,160,000 36,080,000

3 Day 16,000,000 50,400,000 43,200,000

7 Day 113,600,000 126,400,000 88,000,000

13 Day 160,000,000 175,000,000 112,000,000

1,000,000

41,000,000

81,000,000

121,000,000

161,000,000

Bro

okf

ield

, cp

s


#4L #4M #4H

1 Day 4,400,000 16,080,000 13,760,000

2 Day 19,200,000 31,680,000 29,200,000

3 Day 36,000,000 39,200,000 36,400,000

7 Day 120,000,000 86,400,000 43,200,000

13 Day 170,000,000 116,800,000 56,000,000

1,000,000

41,000,000

81,000,000

121,000,000

161,000,000

Bro

okf

ield

, cp

s


All MgO grades indicate slower thickening rate at low H2O; increasing H2O levels increase thickening rate and ‘usually’ decreases plateau; each MgO grade responds differently to varying moisture levels; adjusting moisture and proper selection of MgO grade are other tools for process adjustment.

Past Past Control Control Measures of Measures of MgOMgO Dispersions for Use in SMC Dispersions for Use in SMC

•• In the beginning…….In the beginning……. –– Paste can thickening studies were conducted and monitored for 48 or 72 Paste can thickening studies were conducted and monitored for 48 or 72

hours usually with Brookfield viscometershours usually with Brookfield viscometers

–– Adequate mixing in cans, temperature control and imparted shear were very Adequate mixing in cans, temperature control and imparted shear were very difficult to controldifficult to control

–– Delayed approval or rejection was very costly with respect to time, material, Delayed approval or rejection was very costly with respect to time, material, etc.etc.

–– Limited understanding and few manufacturing controls yielded variable Limited understanding and few manufacturing controls yielded variable productproduct

–– Industry goal Industry goal -- "lights out" molding facility drove understanding and "lights out" molding facility drove understanding and refinement of raw materials, their function and processingrefinement of raw materials, their function and processing

Current Current Control Measures of Control Measures of MgOMgO Dispersions for Use in SMC Dispersions for Use in SMC at at

ChromofloChromoflo TechnologiesTechnologies •• Current practices……Current practices……

–– Oscillatory Oscillatory chemorheologychemorheology procedure refined at procedure refined at ChromofloChromoflo Technologies Technologies is current method for is current method for incoming QC of incoming QC of MgOMgO powder and final powder and final thickener thickener dispersiondispersion

–– Method provides a rapid, repeatable and reliable Method provides a rapid, repeatable and reliable test (~30 minutes) to characterize reactivitytest (~30 minutes) to characterize reactivity

–– Use of aggressive high speed Use of aggressive high speed centrifugal centrifugal mixer allows mixer allows consistent mixing to a consistent temperatureconsistent mixing to a consistent temperature

–– Comparison of a standard / control lot to the Comparison of a standard / control lot to the incoming raw material or final product ensures incoming raw material or final product ensures consistencyconsistency

ChemoChemo--Rheology Slope Rheology Slope vs. Brookfield Viscosityvs. Brookfield Viscosity

R² = 0.9675 0

2,000,000

4,000,000

6,000,000

8,000,000

10,000,000

0 0.1 0.2 0.3 0.4 0.5 0.6

1 Day Paste Viscosity vs. Slope1 Day Paste Viscosity vs. Slope

R² = 0.9252 0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

0 0.1 0.2 0.3 0.4 0.5 0.6


R² = 0.8351 0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

30,000,000

0 0.1 0.2 0.3 0.4 0.5 0.6


R² = 0.8586 0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

30,000,000

0 0.1 0.2 0.3 0.4 0.5 0.6


SummarySummary

•• SMC applications are becoming more demanding SMC applications are becoming more demanding •• Regulations have limited the use of some traditional Regulations have limited the use of some traditional

RM’sRM’s •• Formulators have to be more creativeFormulators have to be more creative •• Rheology / viscosity profile more important and more Rheology / viscosity profile more important and more

challenging than everchallenging than ever •• Industry understanding of Industry understanding of MgOMgO, moisture and , moisture and

temperature affects are imperative to the manufacturing temperature affects are imperative to the manufacturing of consistent productof consistent product

•• Advanced testing capabilities allow for predictable, Advanced testing capabilities allow for predictable, repeatable viscosity build in a variety of SMC repeatable viscosity build in a variety of SMC chemistries chemistries

Documents

The Art and Science of Controlling Alkaline Earth Oxide ... · Viscosities at 15 min. of Paste Mixed to Various Temperatures (0.7MR / 0.11%H2O) 95F 105F 115F Increasing initial paste