MODIFICATION OF THE PROPERTIES OF NATURAL RUBBER BY COPOLYMERIZATION WITH A BIOPOLYMER FOR A CONTROLLED RELEASE OF UREA FERTILIZER - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 240

Figure 16. Influence of St on the %age swelling ratio of the ENR/PEG blend crosslinked with
isophorene diisocyanate.
Figure 17. Influence of St on the % swelling ratio of ENR/PEG blend crosslinked with isophorene
diisocyanate.
The crosslinking density of samples was estimated by the swelling ratio both in water and
hot water.
In addition, this implied that maleic acid became crosslinked with starch and PVA after
vulcanization. One explanation for this was that more crosslinking occurred between the
maleic acid and starch or the PVA as the maleic acid content was increased up to 60%. When
the water temperature was increased from 30 o C to 70 o C, the swelling ratio of the polymer
blend sample containing 60% maleic acid increased compared to that at 30 o C after 5 h of
immersion in the water medium (Figure 18). When the starch content in the sample was
increased, a lower water resistance of the polymer blend sample was observed. After
vulcanization, the swelling ratio of the polymer blend sample containing 60% maleic acid