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Centrifuged latex manufacturing industry is one of the most economically
important and rapidly growing industry in Sri Lanka. Centrifuged latex being a
semi finished natural product it undergoes lot of chemical changes during
storage. The consumer is more concerned in getting quality latex to suit his
manufacturing process. The main quality parameters that should be controlled
verycarefully are the VFA number and MST of the latex concentrate.
Fourtypes of concentrated latex were used to study of variation of characteristics
of latex during storage. In LVFA latex, VFA number increases relatively a faster
rate during the first 3 weeks and thereafter the rate of increase is gradually
reduced to almost zero. The VFA number increases in HVF A latex at a relatively
slowerrate during the first 30 days and thereafter starts to rise very sharply.
Increase of MST with maturity time could be approximately divided in to three
stages.In stage L 0-14 days, MST increases very slowly. In stage IL 14-21 days it
increases very rapidly. In Stage IlL after approximately one-month storage MST
remains unchanged or it starts to decrease very slowly. This general pattern of
MST variation is consistent with the pattern of hydrolysis of phospholipids and
glycollpids associated with RP. Results also indicate that HA preserved latex is
consistent latex with properties when compared with LA preserved latex.
Blending of superior quality centrifuged latex with inferior quality latex was also
investigated. Results indicate that HVFA latex can be blended with L VFA latex
even in 1:1 ratio and can be stored for a period of two weeks without any
appreciable increase in VFA.
Precipitation of magnesium by the natural process occurs at a faster rate within
thefirst 6 hrs, and thereafter the rate of precipitation slows down. About 60% of
magnesiumfrom the initial level are precipitated within 24 hrs of storage. Only
60% of magnesium are precipitated by the incorporation of stoichiometric
quantities of DAHP even for prolonged storage.
By centrifugation VFA number is reduced by 75% and the magnesium level by
40-50%.
Investigation of quality of centrifuged latex on the properties of the prevulcanized
latex indicates that HA preserved latex shows higher tear strength when compare
withLApreserved latex and relatively new latex with high MST shows higher tear
strength than HMST old latex.
