2010 High Tunnel and Open Field Studies
Report for Molecular Weight Values
Douglas G. Hayes
03/2011
(Spreadsheet format available upon request. Values represent average and standard deviation of Reps A-D. Results for an individual Rep can
be obtained upon request.)
1. Spunbond-PLA-2010
NUMBER-AVERAGED
MOLECULAR WEIGHT
StDev
Time, wk
High Tunnel
Mn
StDev
1.42E+05
1.43E+05
1.35E+05
1.09E+03
5.71E+03
2.46E+03
0
8
19
1.32E+05
1.28E+05
1.29E+05
1.20E+03
4.22E+02
1.90E+03
1.53
1.47
1.48
0.01
0.00
0.01
1.57
1.50
1.44
0.01
0.00
0.01
0
6
11
23
1.43E+05
1.36E+05
1.36E+05
1.35E+05
2.27E+03
2.13E+03
5.35E+02
2.25E+03
0
6
11
23
1.43E+05
1.32E+05
1.40E+05
1.32E+05
2.27E+03
1.62E+03
1.56E+03
2.75E+03
1.46
1.54
1.47
1.62
0.01
0.00
0.00
0.01
1.46
1.44
1.52
1.49
0.01
0.00
0.00
0.01
0
8
19
1.39E+05
1.35E+05
1.37E+05
9.54E+02
3.48E+02
2.32E+03
0
8
19
1.39E+05
1.35E+05
1.36E+05
9.54E+02
1.55E+02
9.57E+02
1.51
1.51
1.45
0.00
0.02
0.01
1.51
1.50
1.50
0.00
0.00
0.01
Site
Time
Time, wk
TN
One
Two
Three
0
7
16
TX
One
Two-a
Two-b
Three
WA
One
Two
Three
Field
Mn
POLYDISPERSITY INDEX
Field
High Tunnel
PDI
StDev
PDI
StDev
Comment on TX-HT-Time 2a: The molecular weight value appears to be abnormally low, since it is smaller than Time 2b. We have verified that
the trend is consistent. Perhaps deterioration of the sample occurred during its storage and shipping. It is noted during Time 2a that severe
flooding occurred in TX.
1
1.5E+05
Number-Averaged Molecular Weight
TN, Field
TN, HT
TX, Field
TX, HT
WA, Field
WA, HT
1.4E+05
1.3E+05
1.2E+05
0
5
10
15
Time, Weeks
2
20
25
2. Biobag
Site
Time, wk
Time
POLYDISPERSITY INDEX
Field
High Tunnel
NUMBER-AVERAGED MOLECULAR WEIGHT
High Tunnel
Field
Mn
StDev
Time, Wk
Mn
StDev
PDI
StDev
PDI
StDev
TN
1
2
3
0
7
16
9.55E+04
8.24E+04
7.47E+04
3.96E+02
9.74E+02
2.99E+03
0
8
19
1.00E+05
9.62E+04
6.29E+04
9.65E+02
3.16E+03
4.62E+03
2.00
2.36
2.15
0.04
0.10
0.08
1.96
2.30
2.20
0.05
0.08
0.03
TX
1
2a
2b
3
0
6
11
23
9.62E+04
8.53E+04
8.50E+04
7.07E+04
2.51E+03
5.62E+03
1.82E+03
1.93E+03
0
6
11
23
9.62E+04
8.51E+04
8.73E+04
7.94E+04
2.51E+03
1.34E+03
1.87E+03
2.15E+03
1.80
2.31
3.62
2.83
0.02
0.13
0.16
0.11
1.80
2.48
2.26
2.16
0.02
0.06
0.05
0.12
WA
1
2
3
0
8.8
19.5
9.94E+04
8.40E+04
8.31E+04
9.97E+02
1.12E+03
9.41E+02
0
8
19
9.94E+04
8.47E+04
7.91E+04
9.97E+02
1.57E+03
3.59E+03
2.01
2.16
2.17
0.06
0.06
0.06
2.01
2.03
2.20
2.01
0.05
0.13
ND: Biobag samples for Texas, Time 3, were not received
3
Number-Averaged Molecular Weight
1.E+05
1.E+05
9.E+04
8.E+04
TN, Field
TN, HT
TX, Field
7.E+04
TX, HT
WA, Field
WA, HT
6.E+04
0
5
10
15
Time, Weeks
4
20
25
3. Biotelo
NUMBER-AVERAGED MOLECULAR WEIGHT
Field
Time,
wk
PD INDEX
High Tunnel
Field
Mn
StDev
PDI
High Tunnel
Time, wk
Site
Time
TN
One
Two
Three
0
7
16
8.37E+04
7.11E+04
6.40E+04
9.86E+02
2.00E+03
6.58E+03
0
8
19
8.53E+04
8.26E+04
6.05E+04
1.36E+03
2.17E+03
2.24E+03
1.70
2.24
2.35
0.01
0.03
0.15
1.67
1.80
1.83
0.08
0.10
0.02
TX
One
Twoa
Twob
Three
0
6
7.95E+04
7.87E+02
0
6
7.95E+04
7.87E+02
1.60
0.16
1.60
1.60
6.87E+04
1.83E+03
7.75E+04
8.19E+02
2.36
0.10
2.23
0.07
WA
One
Two
Three
Mn
StDev
11
StDev
PDI
StDev
11
23
6.93E+04
6.62E+04
8.66E+02
2.20E+03
23
7.38E+04
7.32E+04
3.12E+03
1.58E+03
2.22
2.15
0.06
0.21
2.18
1.89
0.18
0.06
0
8.8
19.5
8.29E+04
7.17E+04
7.08E+04
2.51E+03
4.97E+02
1.66E+03
0
8
22
8.29E+04
7.51E+04
6.85E+04
2.51E+03
1.67E+03
8.14E+02
1.76
2.00
2.02
0.03
0.06
0.05
1.76
2.00
2.06
0.03
0.10
0.08
5
9.0E+04
Number-Averaged Molecular Weight
TN, Field
TN, HT
TX, Field
TX, HT
8.0E+04
WA, Field
WA, HT
7.0E+04
6.0E+04
0
5
10
15
Time, Weeks
6
20
25
Notes:



GPC analysis could not be performed on Weedguard (cellulosic) and “Black Plastic” (polyethylene) mulch due to their insolubility in
chloroform, the solvent employed for GPC
Biobag and Biotelo were only partially soluble in chloroform. It is believed that the soluble fraction represents a proprietary polymer;
insoluble fraction consists at least in part of starch.
Data collection completed by Mr. Tyler Pannell and Ms. Galina Melnichenko
Experimental description:
Gel permeation chromatography (GPC) was used to determine the number-averaged molecular weight (Mn) and polydispersity index (PDI) of the
mulch specimens based on polystyrene standards. Two replicates were analyzed per mulch specimen. Samples (approximately 20 mg) were
dissolved in 5 mL of chloroform and stirred for one hour. Chloroform-dissolved samples were then centrifuged at 10,000 rpm (radius of 5.5 cm)
for 1 min, and filtered (nylon, 0.45μm for untreated samples; 0.20 mm for Time 2 and 3 samples). The solution (200 L) was injected into a dualpump HPLC system obtained from Varian, equipped with model Mark III evaporative light scattering detector from Alltech Associates, a division
of WR Grace (Deerfield, IL), equipped with a 300 x 7.5 mm ID PLgel Mixed C column from Varian, Inc. (Walnut Grove, CA), possessing packing of
nominal 5 m. Chloroform (0.8 mL min-1) was used as the mobile phase, with the HPLC system containing an evaporative light scattering
detector.
The chromatogram’s underlying area was divided into a series of N trapezoids; then, the number- and weight- averaged molecular weight (Mn
and Mw, respectively) were calculated using the following formulae:
(1)
N
M n   yi MWi
i 1
N
M w   yi MWi 2
(2)
i 1
where the subscript i refers to the ith trapezoid and MWi to the average molecular weight of trapezoid i. The index of polydispersity, PDI, is
then calculated from the ratio of the two:
PDI 
Mw
Mn
(3)
7
8