Improving of Adhesion in Laminated Rubber Glove Process and

Incorporation of Recycled Coagulated Centrifuged Latex

R.G.N LakmaliUWU/PLT/09/0020Palm and Latex Technology and Value AdditionUva Wellassa University

IntroductionNatural Rubber Latex is the major synthesizedcommercial product by the rubber (Hevea brasiliensis) tree

Production of NR 2011(Actual) to 2014(forecast) (‘000tonnes)

Source: International Rubber Study Group ( IRSG )

Region 2011 2012 2013 2014

Asia 10281 10659 10986 11628

Africa 470 491 518 548

Latin America 48 48 50 52

World 11004 11406 11771 12453

Natural rubber based products-Dry rubber products

eg: Laminated gloves,Tyre, Caster wheels-Latex products

eg: balloons, surgical gloves, cast products

What is a Laminated glove?

It is coming under household category use for heavy dutypurposes and for construction industry which is made byusing a laminated rubber sheet as a composite to palmarea with textile fabrics(Kevlar ,Cotton)

Problem IdentificationLow adhesion property of laminated gloves

-reducing of other mechanical properties (abrasion , tear, punch, cut)

- lower the quality and the demand in the international market

High moisture content of coagulated centrifuged latex-unable to direct incorporate with laminated rubber sheet process- large wastage avoiding recycling with high cost

Main Objective

Enhance the adhesion ability between the laminatedrubber sheet and two types of fabrics, Kevlar and Cotton

Introducing of new recycle method to reduce themoisture content coagulated centrifuged latex

Specific ObjectivesFix the accurate amount of secondary solvent (SBP) to adjust the correct viscosity and the TSC of the adhesive

Modify the current existing process line with controlling steps and new technical adjustments

Change the amount of ingredients of existing formula of adhesive

Check the potential of incorporation of recycled rubber as a filler to fulfill 20% of requirement

Materials and Methods

Basic Ingredients

Crepe rubber Compounding materials

(Chemicals) Fabric (Kevlar, Cotton) Coagulated centrifuged

latex

Machines

Two roll mill ,Mixing machine

Calendaring roll Bale cutter Drying machine

, Oven, Autoclave Brook field Viscometer Tensile TesterHardness testing machine Cut resistance machine Digital weighting Machine

Preliminary Experiment

Identification of mostly affecting process steps and factors for adhesion ability by observation

•The adhesive preparation•Smoothing•Maturing•curing Conditions( temperature, time)•type of the fabric (Kevlar , the Cotton

Crepe

Fabric

Coating

Drying

Sticking

Curing

Glove

Milling

CalendaringAdhesive

Smoothing

Maturing

Laminated Rubber Glove Process

Experiment 1:Fix the accurate amount of secondary solvent (SBP) to adjust the correct viscosity and the TSC(Total Solid Content) of the adhesive

Complete Randomized Design(CRD)

Necessary SBP Amount to the Blend

1 sample

2 sample

3 sample

4 sample

5 sample

6 sample

Adhesive compound + Primary solvent(ml)

100 100 100 100 100 100

SBP volume(ml) 0 50 100 200 300 400

Treatment Name T1 T2 T3 T4 T5 T6

Experiment 2: Modify the Current Existing ProcessLine with Controlling Steps and New TechnicalAdjustmentsSmoothing turns

Maturing period(hours)

Curing temperatureand Time

Sample number

Adhesion Value

0Ϲ Minute

One turn Just after unloading from former

155 40 3

160 30 10

120 90 11

24 155 40 5

160 30 6

120 90 7

48 155 40 2

160 30 8

120 90 9

Smoothing turns

Maturing period(hours)

Curing temperatureand Time

Sample number

Adhesion Value

0Ϲ Minute

Two turn Just after unloading from former

155 40 1160 30 13120 90 12

24 155 40 14160 30 15120 90 16

48 155 40 4160 30 17120 90 18

Modified Steps of process linesCRD method

Experiment 3: Changing the Amount(parts) of Ingredients of Existing Formula of Adhesive

Two Factors Factorial CRD methodIngredients Former amount Changed amount Examples

Raw Rubber 0.5 same Crepe rubber

Activator 0.025 same Zinc Oxide

Accelerator, Scorch Resistance 0.007 same M.B.T.S

Dispersing agent, plasticizer 0.006 same Stearic acid

Accelerator 0.001 same T.M.T.D

Lubricant 0.005 same

Coupling agent 0.01 same

Tackifier 0.125 0.140 Wood Resin

lubricant, softening agent 0.0125 Same Petroleum jelly

Cross linking agent 0.008 Same Sulphur

Experiment 4

Reduce the moisture content of coagulated centrifuged latex

CRD method

Coagulated centrifuged latex(5kg)

Drying(sun drying- 4 days, 1.5 days, near autoclave )

Laminated sheet

Partition

Milling with batch

Measuring moisture content

For experiment I, II, III and IV – Adhesion test

For experiment IV - mechanical tests (abrasion , tear, punch, cut)

-Tensile test(After and before ageing)-Rheograph -Moisture content

Minitab statistical software was used to analyze the data

Results and Discussion

Experiment 01:Adhesion of laminated gloves

0

5

10

15

20

25

T0 T1 T2 T3 T4 T5 T6

Mean adhesion(N)

T0T1T2T3T4T5T6

Treatment Name

Adhe

sion

(New

ton)

Experiment 01:Adhesion of laminated gloves Treatment Name Mean ± SD

T0 11.983±1.535BC

T1 18.95±3.73AB

T2 14.97±1.90ABC

T3 12.48±1.44BC

T4 20.613±0.757A

T5 11.16±2.64C

T6 15.40±4.02ABC

Value with the differentletter as superscripts issignificantly different at thelevel of 5%. Results arepresent as mean ± SD

Ratio of amount of Adhesive compound and Primary solvent to SBP - 1:2

Viscosity and TSC values for each adhesion level of adhesive

Mean ValueTreatmentName

T0(control)

T1 T2 T3 T4 T5 T6

Viscosity(rpm)

10.5 100 100 100 78.7 20.3 0.3

TSC 86 70.7 88.7 90.3 93.7 96.3 96

Experiment 02:adhesion under modified process lines

0

5

10

15

20

25

30

T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17 T18

Mean Adhesion T1T2T3T4T5T6T7T8T9T10T11T12T13T14T15T16T17T18

Treatment Name

Adhe

sion

(New

ton)

Value with thedifferent letter assuperscripts issignificantly differentat the level of 5%.Results are present asmean ± SD

Treatment Mean ± SD Treatment Mean ± SD

T1 8.26±0.551E T10 14.89±1.649BC

T2 11.067 ±1.67CDE T11 15.95±1.64B

T3 9.110±0.721DE T12 10.73± 0.643CDE

T4 6.653 ±1.166E T13 17.10± 1.637B

T5 14.417±0.52BC T14 14.37±2.97BC

T6 13.493±0.50BCD T15 10.89±0.185CDE

T7 9.800±0.346DE T16 26.03± 3.19A

T8 17.36± 0.651B T17 10.55±1.91CDE

T9 16.90±0.954B T18 14.50±0.436BC

T16 Process line

Two smoothing turns- creates the even and the smooth surface ,prevent bends, remove the trapped air and barrier to entering the moisture

24 hour maturing period- Optimum chemical reactions and bonding formation

Curing Conditions (120 0Ϲ,90 minutes) - optimum curing and bonding formation

Smoothing Two Turns

24 hour Maturing

period

Curing ,120 0Ϲ,90 minutes

Fabr

ic

Lam

inat

ed sh

eet

Coat

ing

Adhe

sive

Experiment 03-Adhesion under changed woodresin amount and curing conditions

Adhesion of gloves against wood resin and changed curing temperature and Time

Value on the same line with the same letter assuperscripts is not significantly different at the level of 5%.Results are present as mean ± SD

Temperature 0Ϲ/Time (minutes)

Wood Resin(g) 1200Ϲ /90min 1550Ϲ /40min 1600Ϲ/30min

125 11.3±0.93B 8.1±1.183 B 8.8±1.240 B

140 23.5±3.35 A 11.9±0.907B 9.6±1.303B

Wood Resin- Common raw material to increasing of adhesion ability

Experiment 04 - Comparison of Adhesion , Punch , Tear , Cut , Abrasion, Tensile strength Before Ageing and After Ageing , Moisture content and Rheograph Characteristics of controlled and blend sample

0

2

4

6

8

10

12

14

16

Control

Blend

0

10

20

30

40

50

60

70

Maximum Torque Scorch Time T 90

Control

Blend

P values for relevant tests

Moisture content- 0.8554

Mechanical Testing

Abrasion(levels) - 0.957 Cut(levels) - 0.685 Tear(levels) - 0.988 Punch(levels)- 0.653 Tensile Strength (Before

ageing) MPa- 0.6359 Tensile Strength(After ageing)

Mpa - 0.216

Rheograph Characteristics

Maximum Torque(Lb-in)-0.1843 Scorch Time (Minutes)-0.632 T90 (Minutes)-0.156

• There is no significant difference between the control and the blend at the level of 5%

• The blend with recycled rubber suitable as the filler ingredient

Conclusion

The accurate viscosity and TSC values which are78.7rpm and 93.7 of the adhesive with the 1:2 ratio ofsolvents , the high amount of wood resin with lowcuring temperature with 120 0Ϲ and the high curingtime 90 minutes, two times smoothing times and the24 hours maturing period are majorly affect for thehighest value of the adhesion

There is a potential to incorporate the recycled coagulatedcentrifuged latex as the cost reduction filler ingredient withthe compounding to fulfill the 20% of requirement instant thecrepe rubber under the accurate operation conditions

Limitations

Uneven application of the adhesive on the laminated sheet

Excessive stock /deficiency of stock cause to change the maturing period

More time taken with drying of coagulated centrifuged latex

Recommendations

Punctually measuring of viscosity and TSC of the adhesive and following of modified process line with recommended wood resin content

Recycle of coagulated centrifuged latex as a cost reduction process

Reducing of drying time with Proper oven system of coagulated centrifuged latex

ReferencesMartin,J.M,(M.Sc,Ph.D,C.Eng),Smith W.K,(C.Eng),Handbook of RubberTechnology. Volume 03, Identification ,Testing, Recycling and PollutionControl in Rubber Industry,ed.by Bhatia,C.S. (B.E(Chemical),M.B.A),PUBLISHERS AND DISTRIBUTERS,NEW DELHI,BANGALORE

White J.L, Rubber Processing Technology. Materials andPrinciples,Hanser Publishers, Munich Vienne New York, Hanser/GenderPublications,Inc,Cincinati

Freakley P.K, Rubber Process and Production Organization, Institute ofPolymer Technology, Southborough University ofTechnology, Loughborough,United Kingdom, Plenum Press, New York andLondon

Polaski G, Means J, Stull B, Warren P, Allen K, Mowrey D, and CarneyB,Bonding Elastomers: A Review of Adhesives and Processes, (LordCorporation)

AcknowledgementDr. G . Chandresena, Dean , Faculty of Animal Science and Export Agriculture

Dr. Saman Herath, Faculty of Animal Science and Export Agriculture

Mr.Thameera Ranasinghe,External Supervisor, Manager Technical,Workwear Lanka(Pvt) Ltd

Ms. H.A.S.L Jayasinghe,Internal Supervisor, Faculty of Animal Science and Export Agriculture

Dr. Susantha Siriwardhene,Head of Dry Rubber Department , Rubber Research Institute ,Rathmalana