3. Results and discussion
3.1 Effect of carrageenan loading on the swelling index of NR Latex films
The swelling data was used to determine the cross-link density of the NR Latex films. Table 1 shows the swelling
index and cross link density value of NR Latex films for control, Method 1 and Method 2 respectively. The addition
of 2 phr carrageenan as filler in NR Latex films has decreased the value of swelling index which is 329.01% for
Method 1 and 323.59 % for Method 2 compared to control 337.26%. It was found that the swelling index of Method
1, where the compound already exposed to 70o
C temperature in the pre-vulcanization step was slightly higher (1.6%)
than Method 2. This is possibly due to hydration of carrageenan at temperature of 40o
C-70o
C
15
. Furthermore, it was
expected that gelation has occurred upon cooling at temperature below 40-50o
C15
.This gelation produced an
amorphous region in NR Latex films that tends to absorb more toluene during swelling test. This result was also
supported by crosslink density value.
Crosslink density of the unfilled NR Latex films is strongly depending on the number of crosslinking formation
in rubber network. The results showed cross-link density for filled NR Latex films increased compared to unfilled
NR latex films. Carrageenan is a high-molecular-weight linear hydrophilic polysaccharide comprising repeating
disaccharide units of galactose and 3, 6-anhydrogalactose (3, 6 AG), joined by alternating α-(1,3) and β-(1,4)
glycosidic links. This could increase the tendency for physical entanglement between carrageenan and NR Latex
polymer chains. The molecular entanglement between rubber and filler are able to overcome disadvantages of poor
adhesion between rubber and filler. This physical entanglement could resist the polymer chain mobility, thus reduced
penetration of solvents into the samples
21
. Thus resultant the low swelling index and cross-link density for filled NR
Latex films.
3. Results and discussion 3.1 Effect of carrageenan loading on the swelling index of NR Latex films The swelling data was used to determine the cross-link density of the NR Latex films. Table 1 shows the swelling index and cross link density value of NR Latex films for control, Method 1 and Method 2 respectively. The addition of 2 phr carrageenan as filler in NR Latex films has decreased the value of swelling index which is 329.01% for Method 1 and 323.59 % for Method 2 compared to control 337.26%. It was found that the swelling index of Method 1, where the compound already exposed to 70oC temperature in the pre-vulcanization step was slightly higher (1.6%) than Method 2. This is possibly due to hydration of carrageenan at temperature of 40oC-70oC 15. Furthermore, it was expected that gelation has occurred upon cooling at temperature below 40-50oC15 .This gelation produced an amorphous region in NR Latex films that tends to absorb more toluene during swelling test. This result was also supported by crosslink density value. Crosslink density of the unfilled NR Latex films is strongly depending on the number of crosslinking formation in rubber network. The results showed cross-link density for filled NR Latex films increased compared to unfilled NR latex films. Carrageenan is a high-molecular-weight linear hydrophilic polysaccharide comprising repeating disaccharide units of galactose and 3, 6-anhydrogalactose (3, 6 AG), joined by alternating α-(1,3) and β-(1,4) เชื่อมโยง glycosidic ซึ่งสามารถเพิ่มแนวโน้มสำหรับสายกายภาพระหว่างคาราจีแนนและน้ำยาง NR โซ่พอลิเมอร์ สายโมเลกุลระหว่างยางและฟิลเลอร์จะสามารถเอาชนะข้อเสียของแย่ ยึดเกาะระหว่างยางและฟิลเลอร์ สายทางกายภาพนี้สามารถต้านทานการเคลื่อนโซ่พอลิเมอร์ ลดลงจึง การเจาะเกราะของตัวทำละลายลงในตัวอย่าง 21. จึงเอาดัชนีบวมต่ำและความหนาแน่นของลิงก์ข้ามสำหรับเติม NR หนังยาง
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