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ConsultantsConsultants

NR LATEX PROPERTIESNR LATEX PROPERTIES(Hevea Brasiliensis)(Hevea Brasiliensis)

John Woon Sung-LiangJohn Woon Sung-Liang

JW Latex ConsultantsJW Latex Consultantshttp://latexconsultants.blogsphttp://latexconsultants.blogsp

ot.comot.com

NR LATEX PROPERTIES NR LATEX PROPERTIES (Hevea Brasiliensis)(Hevea Brasiliensis)

-- ESSENTIALLY A HYDROSOL CONSISTING OF A 2-PHASE

SYSTEM NAMELY :-

1. DISPERSE PHASE OF RUBBER PARTICLES (ALSO KNOWN AS DISCRETE PHASE, DISCONTINUOS PHASE OR INTERNAL PHASE)

2. DISPERSION MEDIUM (ALSO KNOWN AS AQUEOUS, CONTINUOUS OR EXTERNAL PHASE)

* DENSITY OF DISPERSE PHASE 0.92 g/cc• DENSITY OF DISPERSION MEDIUM 1.02 g/cc

STABILITY OF LATEXSTABILITY OF LATEXJohn Woon Sung-Liang

http://latexconsultants.blogspot.com

1. Presence of - ve Charges on Rubber Particle Surfaces Due to Protein/Lipid Layers.

Mutual Coulombic Repulsion.

PROTEIN LIPID PROTEIN (HYDROLYSED TO FATTY ACID

SOAP IN PRESENCE OF NH 3)

Repulsion

P = Polar side chain OS- of Protein N P-

OS-

N = Non-polar side N OS =Soap chain of protein P- Molecule OS-

N P-

RH/C RH/C

What is What is Nitrile Nitrile oror Buna-N Buna-N oror NBRNBR RubberRubber??

By John Woon Sung-LiangBy John Woon Sung-Liang JW Latex ConsultantsJW Latex Consultants (SA0052392P)(SA0052392P) http://latexconsultants.blogspot.comhttp://latexconsultants.blogspot.com Email: Email:

woonsungliang@yahoo.com.sgwoonsungliang@yahoo.com.sg

WHY Use NBR?WHY Use NBR?

Mainly because of the presence Mainly because of the presence of Acrylonitrileof Acrylonitrile

Acrylonitrile content can be: Acrylonitrile content can be: Low (Low (25%) 25%) Medium (33%) and Medium (33%) and High (45%) *High (45%) *

Acrylonitrile vs Tg Acrylonitrile vs Tg (Tg = -10C to -55C)(Tg = -10C to -55C)

-10-10

-20-20

-30-30

- 40- 40 TgTg(Degree C)(Degree C) -50-50

-60-60

10 20 30 40 50 6010 20 30 40 50 60 Acrylonitrile level (%)Acrylonitrile level (%)

Main Differences in Main Differences in Processing Compared with Processing Compared with

NRNR 1) pH adjustment1) pH adjustment

- Sensitive ……...- Sensitive ……...

- If below 9.0 …………- If below 9.0 …………

- If above 9.8 …………- If above 9.8 …………

Alkali must be added ………..Alkali must be added ………..

Formulation DesignFormulation Design

Review basic findings:Review basic findings:

1) Sulphur X-links ………1) Sulphur X-links ………

2) Ionic X-links …….2) Ionic X-links ……. ZnO gives maximum ………ZnO gives maximum ………

3) Role played by KOH3) Role played by KOH

Latex Dipping Latex Dipping TechnologyTechnology

iohn woon sung-liangiohn woon sung-liang JW Latex Consultants JW Latex Consultants (SA0052392-P)(SA0052392-P)

http://latexconsultants.blogspot.comhttp://latexconsultants.blogspot.com Email: woonsungliang@yahoo.com.sgEmail: woonsungliang@yahoo.com.sg

THE DIPPING PROCESSTHE DIPPING PROCESS

3 MAIN TYPES3 MAIN TYPES :- :-

1.1. STRAIGHT DIPPINGSTRAIGHT DIPPING(OR SIMPLE DIPPING)(OR SIMPLE DIPPING)0.03 – 0.04MM0.03 – 0.04MM

2.2. COAGULANT DIPPINGCOAGULANT DIPPING0.1 – 1.0 MM0.1 – 1.0 MM

3.3. HEAT – SENSITIVE DIPPINGHEAT – SENSITIVE DIPPING0.5 – 3.0MM0.5 – 3.0MM

Properties of Good Antifoaming /Properties of Good Antifoaming /Antiwebbing AgentAntiwebbing Agent

1.1. Surface tension of antiwebbing agent Surface tension of antiwebbing agent must be lower than that of foaming must be lower than that of foaming solution or liquidsolution or liquid

2.2. Solubility of antiwebbing agent in foaming Solubility of antiwebbing agent in foaming solution must be low enough but without solution must be low enough but without causing cissing and oil spots.causing cissing and oil spots.

3.3. It must be readily dispersible in the liquidIt must be readily dispersible in the liquid

4.4. It must have high spreading coefficientIt must have high spreading coefficient

GLOVES FAULTS / GLOVES FAULTS / DEFECTSDEFECTS

By John Woon Sung-LiangBy John Woon Sung-Lianghttp://latexconsultants.blogspot.comhttp://latexconsultants.blogspot.com

FAULTS / DEFECTSFAULTS / DEFECTS

AFFECTINGAFFECTINGWHOLE GLOVEWHOLE GLOVE

LOCALISEDLOCALISED

AFFECTING WHOLE GLOVEAFFECTING WHOLE GLOVE

1.1. THICKNESSTHICKNESS

2.2. POWDER MARKSPOWDER MARKS

3.3. COLOURCOLOUR

4.4. FILM WEAKNESS (OCCLUSIONS ?)FILM WEAKNESS (OCCLUSIONS ?)

5.5. TACKINESSTACKINESS

6.6. SURFACE BLEMISH (BLOOM?)SURFACE BLEMISH (BLOOM?)

7.7. SMELLSMELL

8.8. TASTETASTE

9.9. MOULDYMOULDY **

LOCALISED DEFECTSLOCALISED DEFECTS

1.1. PIN HOLESPIN HOLES

2.2. OCCLUSIONSOCCLUSIONS

3.3. COAGULUMCOAGULUM

4.4. RUNS OR STREAKSRUNS OR STREAKS

5.5. THICK EXTREMITIESTHICK EXTREMITIES

6.6. CRACKS *CRACKS *

Polychloroprene Polychloroprene Rubber (CR) Rubber (CR)

John WoonJohn Woon Sung-LiangSung-Liang

JW Latex ConsultantsJW Latex Consultants (SA0052392-(SA0052392-P)P)

http://latexconsultants.blogspot.cohttp://latexconsultants.blogspot.comm

Polychloroprene Rubber Polychloroprene Rubber (CR)(CR)

- Properties- Properties 1) More polar than Butadiene due to 1) More polar than Butadiene due to carbon-chlorine bond but not as polar as Nitrile carbon-chlorine bond but not as polar as Nitrile

rubber (medium and high acrylonitrile level)rubber (medium and high acrylonitrile level)

2) Tg = - 45C2) Tg = - 45C

3) Moderate resistance to hydrocarbon oil (cf Nitrile 3) Moderate resistance to hydrocarbon oil (cf Nitrile rubber)rubber)

and good resistance to chemicalsand good resistance to chemicals

4) Excellent resistance to Ozone (O3) degradation4) Excellent resistance to Ozone (O3) degradation

5) Good adhesion to polar substrates5) Good adhesion to polar substrates

6) Flame resistance (Self-extinguishing) *6) Flame resistance (Self-extinguishing) *

Compounding of Compounding of Polychloprene LatexPolychloprene Latex

AA BB CC Rubber Rubber 100 100 100100 100 100 ZnO xZnO x y z y z TMTD TMTD a - -a - - ZDEC bZDEC b - - - - S S c d ec d e Thiocarbanilide Thiocarbanilide - g h- g h DPG DPG - - i- - i NaDBC NaDBC - j - - j -

A/O kA/O k l m l m

Typical physical properties of rubber Typical physical properties of rubber filmfilm

from soft version of CR (slower cure from soft version of CR (slower cure than hard version)than hard version)

Film thickness (mm) 0.15Film thickness (mm) 0.15

Tensile strength (MPa) 18.0Tensile strength (MPa) 18.0

Modulus at 500% (Mpa) 1.5Modulus at 500% (Mpa) 1.5

Elongation at Break (%) 1000 Elongation at Break (%) 1000 **

TYPICAL PHYSICAL PROPERTIES OF TYPICAL PHYSICAL PROPERTIES OF PPREVULCANISED DRIED FILMSREVULCANISED DRIED FILMS

GRADE A B C D1.UNAGEDMod. at 700% 8.5 11.0 16.0 10.0 (MPa)

T.S. (MPa) 28.0 28.0 26.0 28.0

Elongation at break (%) 1000 900 800 960

2.AGED (14 days @ 70 deg C) Retention of Modulus at 700% (% min) 50 75 85 75 Retention of T.S. 65 75 87 75 (% min)

COLLOIDAL PROPERTIES OF A COLLOIDAL PROPERTIES OF A TYPICAL COMMERCIAL BATCH OF TYPICAL COMMERCIAL BATCH OF

PVPV TSC % 60.46 ALKALINITY (Meq) 360 pH 10.45 VFA No 0.011 MST (sec) 1510 Magnesium (ppm) Nil KOH No 0.59 Coagulum (ppm) 43

Prevulcanised Latex vs Prevulcanised Latex vs Post-vulcanisable latex Post-vulcanisable latex

compoundcompound

TIME (Days)

X-LINK DENSITY/VISCOSITY

Post Vulcanisable Compound

Prevulcanised Compound

1 2 3 4 5 6

A B

UNDERCURE OVERCURE