Examples of PowerPoint Slides used by John Woon Latex Consultants for Training of Latex Technologists

1. Examples of Training
Slides Used by John
Woon Latex
Consultants

2. NR LATEX PROPERTIES
(Hevea Brasiliensis)
John Woon Sung-Liang
JW Latex Consultants
http://latexconsultants.blogsp
ot.com

3. NR LATEX PROPERTIES
(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

4. STABILITY OF LATEX
John 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
RH/C SOAP IN PRESENCE
OF NH 3) RH/C
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-

5.  What is Nitrile or Buna-N or NBR
Rubber?
 By John Woon Sung-Liang
 JW Latex Consultants (SA0052392P)
 http://latexconsultants.blogspot.com
 Email: woonsungliang@yahoo.com.sg

6. WHY Use NBR?
 Mainly because of the presence of
Acrylonitrile
 Acrylonitrile content can be:
 Low (25%)
 Medium (33%) and
 High (45%) *

7. Acrylonitrile vs Tg
(Tg = -10C to -55C)
 -10
 -20
 -30

 - 40
 Tg
(Degree C)
 -50
 -60
 10 20 30 40 50 60
 Acrylonitrile level (%)

8. Main Differences in Processing
Compared with NR
 1) pH adjustment
 - Sensitive ……...
 - If below 9.0 …………
 - If above 9.8 …………
 Alkali must be added ………..

9. Formulation Design
 Review basic findings:
 1) Sulphur X-links ………
 2) Ionic X-links …….
 ZnO gives maximum ………
 3) Role played by KOH

10.  Latex Dipping Technology
 iohn woon sung-liang
 JW Latex Consultants (SA0052392-P)
 http://latexconsultants.blogspot.com
 Email: woonsungliang@yahoo.com.sg

11. THE DIPPING PROCESS
3 MAIN TYPES :-
1. STRAIGHT DIPPING
(OR SIMPLE DIPPING)
0.03 – 0.04MM
2. COAGULANT DIPPING
0.1 – 1.0 MM
3. HEAT – SENSITIVE DIPPING
0.5 – 3.0MM

12. Properties of Good Antifoaming /
Antiwebbing Agent
1. Surface tension of antiwebbing agent must be lower than
that of foaming solution or liquid
2. Solubility of antiwebbing agent in foaming solution must
be low enough but without causing cissing and oil spots.
5. It must be readily dispersible in the liquid
4. It must have high spreading coefficient

13. GLOVES FAULTS /
DEFECTS
By John Woon Sung-Liang
http://latexconsultants.blogspot.com

14. FAULTS / DEFECTS
AFFECTING LOCALISED
WHOLE GLOVE

15. AFFECTING WHOLE GLOVE
1. THICKNESS
2. POWDER MARKS
3. COLOUR
4. FILM WEAKNESS (OCCLUSIONS ?)
5. TACKINESS
6. SURFACE BLEMISH (BLOOM?)
7. SMELL
8. TASTE
9. MOULDY *

16. LOCALISED DEFECTS
1. PIN HOLES
2. OCCLUSIONS
3. COAGULUM
4. RUNS OR STREAKS
5. THICK EXTREMITIES
6. CRACKS *

17. Polychloroprene Rubber
(CR)
John Woon Sung-Liang
JW Latex Consultants (SA0052392-P)
http://latexconsultants.blogspot.com

18. Polychloroprene Rubber (CR)
- Properties
 1) More polar than Butadiene due to
 carbon-chlorine bond but not as polar as Nitrile rubber (medium and
high acrylonitrile level)
 2) Tg = - 45C
 3) Moderate resistance to hydrocarbon oil (cf Nitrile rubber)
 and good resistance to chemicals
 4) Excellent resistance to Ozone (O3) degradation
 5) Good adhesion to polar substrates
 6) Flame resistance (Self-extinguishing) *

19. Compounding of Polychloprene Latex
 A B C
 Rubber 100 100 100
 ZnO x y z
 TMTD a - -
 ZDEC b - -
 S c d e
 Thiocarbanilide - g h
 DPG - - i
 NaDBC - j -
 A/O k l m

20. Typical physical properties of rubber film
from soft version of CR (slower cure than hard
version)
 Film thickness (mm) 0.15
 Tensile strength (MPa) 18.0
 Modulus at 500% (Mpa) 1.5
 Elongation at Break (%) 1000 *

22. TYPICAL PHYSICAL PROPERTIES OF
PREVULCANISED DRIED FILMS
GRADE A B C D
1.UNAGED
Mod. 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)

23. COLLOIDAL PROPERTIES OF A TYPICAL
COMMERCIAL BATCH OF PV
 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


24. Prevulcanised Latex vs
Post-vulcanisable latex
compound Vulcanisable Compound
Post
A B
UNDERCURE OVERCURE
X-LINK
DENSITY
/VISCOSITY
Prevulcanised
Compound
1 2 3 4 5 6
TIME (Days)