DOI: http://dx.doi.org/10.1590/1980-5373-MR-2018-0416
Materials Research. 2019; 22(2): e20180416
Thermomechanical Properties of Corn Starch Based Film Reinforced with Coee Ground
Waste as Renewable Resource
Elisa Camarin Gazonato
a
, Amanda Alves Domingos Maia
a
, Virgínia Aparecida da Silva Moris
a
,
Jane Maria Faulstich de Paiva
a,b
*
Received: June 15, 2018; Revised: October 02, 2018; Accepted: November 23, 2018
Starches polymeric lms oer several advantages for the replacement of synthetic polymers due
to their biodegradability, non-toxicity, availability and low cost. However, the high biodegradation
potential can cause fragility, considering some fundamental mechanical properties. Therefore, starch
based polymeric lms were reinforced incorporating lignocellulosic waste from coee grounds post-
consume. The eect of incorporation of coee ground in cornstarch matrix and polymer interaction
on morphology, thermal and mechanical properties were investigated. The characterization analyzes
were based on Dynamic Mechanical Thermal Analysis (DMTA), Dierential Scanning Calorimetry
(DSC), Thermogravimetric Analysis (TGA) and Scanning Eletronic Microscopy (SEM). The coee
ground behaved as reinforcement agent according tensile values. Thermochemical conversion showed
that polymeric lms molding did not change his thermal stability. In temperature range was possible to
observe the devolatilization, organic and inorganic compounds decomposition. SEM images showed
the coee ground adhesion in the polymer matrix promoting a better mechanical tensile strength.
Keywords: Coee ground, reuse of waste, reinforcement agent, cornstarch lm.
*
e-mail: jane@ufscar.br.
1. Introduction
Industrial process produces an enormous amount of
waste materials, which may be not deposited safely. The
population increasing is responsible for the amount and
type of waste generated
1,2
, promoting an environmental
problems. Furthermore, fossil fuels consumption are related
to environmental degradation that threatens human health,
through climate changes and greenhouse gas emissions
3
.
Recycling is an eective process for the reuse of some types
of waste, however, in Brazil, recycling of solid urban and
industrial wastes is still a problem
4,5
. The last IBGE ocial
data reported that only 1.4% of Brazilian urban solid waste
is sent to sorting and after, recycling facilities
6
.
Therefore, nowadays, environmentally alternatives to
unsustainable waste disposal techniques are being sought
5
. The current interest of industries is to use the cleaner
technologies, reusing or avoiding the generation of waste
and by-products of the productive processes
7,8
. Furthermore,
there is diculty in recycling synthetic polymers, which
encourages the study and development of biodegradable
materials
9
.
The polymer biodegradation is considered a natural
process, caused by the microorganisms action modifying
and consuming the product, changing in its properties
10,11
.
Most biodegradable plastic lms are produced from starch,
due to their low cost and abundance in nature, as well as
being renewable
12
. However, starch has high sensitivity to
water and mechanical fragility, which makes it dicult to
expand its applications and justies the need for constant
improvement of its properties
12,13
. Based on this information
and for improving the characteristics of the starch lms,
reinforcing agents can be used, giving to the compound
better mechanical properties, especially elasticity (tensile
and exural) and mechanical strength
14
.
In addition, Brazil began to produce soluble coee in
1962, and it has been a major world producer since then
15,16
and for each ton of coee produced, 480 kg of sludge
of coee ground are generated, considered a solid residue,
which is normally used to generate energy in the boilers and
in the manufacture of animal feed
17,18
.
Coee grounds has a very heterogeneous composition
being considered as a lignocellulosic waste, usually rich
in cellulose, hemicellulose, polysaccharides, fermentable
organic, matter content, caeine, tannins and polyphenols
18-20
,
soluble carbohydrates, oligosaccharides sucrose, polymers,
non-volatile and volatile aliphatic acids, oils, waxes, proteins
and free amino acids
21
. Nevertheless, in literature, few works
related to the coee ground waste valorization have been
reported, and then this is an opportunity because of large
amount of waste and its composition.
a
Departamento de Engenharia de Produção, Universidade Federal de São Carlos - UFSCar, Sorocaba,
SP, Brasil
b
Programa de Pós-Graduação em Ciência dos Materiais - PPGCM, Universidade Federal de São
Carlos - UFSCar, Rod. João Leme dos Santos, km 110, Bairro do Itinga, 18052-780, Sorocaba, SP,
Brasil
Gazonato et al.
2
Materials Research
Thus, the aim of this study was to incorporate coee
grounds waste as a reinforcing agent in starch plastic lms
maintaining the biodegradable potential of this polymer, with
the advantages of low cost and high availability in Brazil.
2. Experimental
2.1 Sample preparation
The coee grounds waste considered was the insoluble
residue that remains after coee beans are dehydrated, milled
and brewed, retained in used paper lters and collected at
Federal University of São Carlos (UFSCar) - Sorocaba,
Brazil, from automatic coee machine, which process
commercial coee beans. Therefore, the coee grounds
post-consume waste was sieved (NBR 200#/0.074 mm).
After some laboratory tests, the particle size the 200-mesh
granulometry facilitated the mixing and dispersion of the
coee ground waste during casting molding of the lms.
The lms preparation involved the total mass was 100g,
cornstarch and glycerin amounts were constant (5g each
one). The water and coee grounds values completed the 90g
remaining. After mixed up, the samples were brought to the
microwave for heating under a power of 40W for 6 minutes
with pauses for mixing and checking the temperature. Then,
it was deposited into three polyacrylic molds (approximately
25g each one) and left in an oven at 32 °C, no air circulation,
for four days. In Table 1 the samples and their respective
concentrations of components can be observed.
2.2 Dynamic mechanical thermal analysis
Analysis was carried out at DMTA equipment (DMA
Q800 - TA Instruments) considering a force ramp rate of 0.8
N/min was applied until 18 N. For this type of analysis was
set isotherm at 25°C, the mode of adjustment was controlled
force and the grip was of the strain lm type. Because of
the analysis mode selected, the lms were analyzed through
stress x strain curves, in which the values of maximum tensile
(MPa) and deformation (%) were found. Ten specimens of
each type of lm were tested. Each lm sample tested had
a length of 35 mm and a width of 5 mm.
2.3 Dierential scanning calorimetric analysis
The samples were carried out to DSC analysis on DSC-
50-Shimadzu equipment, under inert atmosphere, ow rate
of 100 mL/min, heating rate of 10 °C/min, in a temperature
range of -50 °C to 400 °C. Approximately 5 mg was deposited
was placed in aluminum pan.
2.5 Thermogravimetric analysis
The thermal stability of the samples was studied by using
thermogravimetric analysis (TGA) and were performed on
the Shimadzu TGA-50 equipment under nitrogen atmosphere,
ow rate of 50 mL/min, a heating rate of 10 °C/min and
temperature range of 20ºC to 800 °C. Approximately 5mg
was placed on platinum pan.
2.6 Morphological analysis
Scanning Eletronic Microscopy (SEM) analyzes were
carried out at microscopy TM 3000, Hitachi, using carbon
tapes and 50x and 150x magnications.
3. Results and Discussion
3.1 Dynamic mechanical thermal analysis
Mean values and standard deviation of tensile mechanical
properties of the polymeric lms were obtained and are
shown in Table 2.
According to the Table 2 and Figure 1 it is possible to note
that the incorporation of coee grounds can be responsible
for increasing tensile strength for almost all samples.
The type of lm number 7 (Table 2), specimens with
0.50% of coee ground, did not present a satisfactory value,
its can mean that coee ground it was just a ller and not
as a reinforcing agent. The coee ground presence caused
a reduction in the deformation capacity (Table 2 and Figure
1) of the lms because became more rigid. The sample
without coee ground presented an average deformation
of about 43%.
It is possible to observe that increasing coee ground
concentration in the lms occurs deformation values variation.
Table 1. Composition of lms with dierent concentrations of coee grounds.
Samples
Coee ground
concentration (%)
Coee grounds (g) Glycerol (g) Starch (g) Water (g)
1
0% 0 5.0 5.0 90.00
2
0.10% 0.10 5.0 5.0 89.90
3
0.15% 0.15 5.0 5.0 89.85
4
0.20% 0.20 5.0 5.0 89.80
5
0.25% 0.25 5.0 5.0 89.75
6
0.30% 0.30 5.0 5.0 89.70
7
0.50% 0.50 5.0 5.0 89.50
3Thermomechanical Properties of Corn Starch Based Film Reinforced with Coee Ground Waste as Renewable
Resource
It is can be related to the non-homogeneous dispersion during
molding process.
3.2 Dierential scanning calorimetry
According DSC analysis it was noted a rst endothermic
peak between temperature range of 93.34°C and 114.30°C
representing residual water evaporation, which was used
during the molding process. Thus, higher is coee ground
concentration lower is the amount of water in the process
and higher the temperature of the residual water. A similar
behavior was observed in literature
22
reporting an endothermic
peak at approximately 108°C representing residual water
evaporation, which was a plasticizer in a cornstarch lm.
Higher concentration of water during molding process
is probably responsible for residual water bound to the
polymeric matrix of the material.
The melting temperatures of the crystalline structure
can be observed in the range 149.41°C to 155.48°C. The
lm containing 0.25% of coee grounds presented a higher
melting temperature (155.48°C). However, there was no great
variation between the values found. An endothermic peak
approximately at 140ºC can be associated with the melting
of the crystalline structure of the polymer matrix
23
. It was
probably caused by lignosulfonates addiction in cornstarch,
which promoted a higher thermal stability, as both its crystalline
melt and thermal decomposition values were higher. The
thermal decomposition temperature, as well as the melting
temperature of the crystalline structure can be considered as
an indicator of the thermal stability of the lms. The values
indicated that the molding process did not alter the thermal
stability of the lms, because the degradation temperatures
did not show signicant dierences. Figure 2 shows the DSC
curves of the lms and the Table 3 presents the temperature
of the volatilization, melting and degradation stages.
3.3 Thermogravimetric analysis
The thermal degradation stages of these lms can be
observed in Figure 3 and for better comparison between these
curves. Table 4 shows stage of mass loss, its temperature
range (ΔT (°C)), mass loss percentage (ΔMassa (%)), mass
loss maximum temperature (max. temp. (°C)) and total
mass loss (%).
The determination of thermal stability and the degradation
temperature of the lms can also be observed. The rst
stage of mass loss, which occurred in temperature range of
35.14 and 163.71 °C, observed at all samples, can represents
plasticizers devolatilization, as well as a residual water and
glycerin, used in the process of gelatinization of the lms. The
highest percentage of mass loss in this stage was observed
in the sample with 0.20% of coee grounds (approximately
16.76%) and, in this case, the maximum mass loss temperature
was 70.76 °C. In previous study, also carried out cornstarch
lms, it was possible to observe a similar thermal behavior.
The mass loss was approximately 10% and it was
attributed to residual water devolatilization at temperature
range of 51.82 and 149.80 °C
22
.
In temperature range of 151.78 and 287.80°C can be
observed the second stage of mass loss. It was also observed
that the highest percentage of mass loss was of the sample
with 0.30% of coee grounds presented a maximum loss
temperature of 187.91 ° C. This behavior it was probably
caused by degradation of the coee ber components
(cellulose and hemicellulose), temperature range for cellulose
was about 240 °C and 360 °C, hemicellulose decomposition
temperature range was 200 °C and 260 °C
24,25
.
The Figure 3A, does not present coee grounds in its
composition, so its decomposition behavior represents
cornstarch thermochemical conversion. Figure 3 shows
the TG and DTG curves of the analyzed lms. In the third
stage, the temperature range was about 274.14 and 358.17°C,
observing a greater percentage of mass loss (41.73%) in the
sample A, without coee grounds and maximum mass loss
temperature of 290.30 °C. This thermal conversion can be
associated with amylose and amylopectin decomposition in
the starch polymer matrix. After 600 ºC, the main products
were mainly the inorganic residues, oxides and carbonates.
Table 2. Tensile strength and deformation average, and standard
deviation.
Samples
Tensile (MPa) Deformation (%)
Average
Standard
deviation
Average
Standard
deviation
1
0.404 0.053 42.982 9.761
2
0.628 0.080 41.582 8.491
3
0.639 0.079 39.113 8.602
4
0.658 0.048 32.330 10.521
5
0.674 0.148 30.861 10.879
6
0.679 0.061 31.693 5.716
7
0.437 0.125 30.949 6.096
Figure 1. Tensile strength and deformation properties of starch
lms according to coee ground addition.
Gazonato et al.
4
Materials Research
Figure 2. DSC curves under inert atmosphere. Samples containing dierent concentrations of coee ground. Samples:
(A) - 0% coee ground; (B) - 0.1% coee ground; (C) - 0.15% coee ground; (D) - 0.20% coee ground; (E) - 0.25%
coee ground; (F) - 0.30% coee ground and (G) - 0.50% coee ground.
5Thermomechanical Properties of Corn Starch Based Film Reinforced with Coee Ground Waste as Renewable
Resource
In literature
26
, it was noticed that most of the thermal
degradation of the lm was caused by starch decomposition,
characterizing the hydroxyl groups volatilization and
depolymerization of carbon chains, as well as, between
temperature range of 314.10 and 358.10 °C thermal
decomposition of amylose and amylopectin
27
. These thermal
behaviors allowed to understand that polymer decomposition
is relate to the organic macromolecules inside the polymer
matrix as well as low- molecular weight organic molecules
are stable only up to a certain temperature range.
3.4 Scanning eletron microscopy
The SEM images allowed to observe that the coee
ground it was adhered the polymer matrix, probably due to
his low granulometry promoting a better mechanical tensile
strength. The micrographs can be observed in the Figure 4.
SEM analyzes indicated that the lm without the coee
grounds (Figure 4A, B) did not present granules in the
cornstarch matrix. Its can be explained by good interaction
between the plasticizer and the starch, promoting an ecient
gelatinization of the lm during molding process. In addition,
no precipitates, voids and cavities were observed and it proves
the good bonding between cornstarch and coee ground.
However, it can be observed that there are some spots with
cracks or cracks along the fracture of the analyzed lm.
The Figure 4 (C,D) 0.10% coee grounds, it is possible to
observe small points indicating the reinforcing agent presence
(Figure 4D). In addition, a roughness increasing was also
noted. Figure 4 (E,F), sample with 0.15% of coee ground,
shows an intense coee grounds appearance and moderately
smooth fractured surface deformation.
In Figure 4 (G,H), 0.20% coee grounds, a small crack
increasing can be noted. Figure 3 (I,J), 0.25% coee grounds,
irregularities and deformations were observed. Figure 4 (K,L),
0.30% coee ground, revealed a heterogeneous fracture
surface and ruptures. Figure 4 (M,N), no cracks and fractures
are observed, the presence of several coee grounds can be
noted, as well as small bubbles that are generally responsible
for concentrating the tension, causing a decrease in values
of mechanical properties.
The bubbles formation can interfere directly in the
quality of the lm
28,29
decreasing its mechanical resistance.
Moreover, polymers exposure to ambient conditions, such as
air humidity and high temperatures, can promotes the voids
appearance, favoring water absorption by matrix, aecting its
mechanical and physical properties. At greater percentage of
coee ground, the distance decreases leading to agglomerated
within the matrix and more uniform distribution suggests
that the coee ground and matrix were thoroughly mixed.
4. Conclusions
The results of the mechanical characterization indicated
an increase in the tensile strength of the samples that had
the coee residue in their composition. All of the lms,
except for the one with 0.50% of coee ground waste, had
higher values of tension higher than that of the lm without
coee grounds, and the best result was that of the lm with
0.30% of coee ground. Thus, it can be considered that the
coee grounds acted as a reinforcing agent, improving the
mechanical properties of the polymer lms. Scanning Electron
Microscopy (SEM) conrmed that during molding process was
observed a better incorporation of coee ground waste into
the matrix, reducing the amount of stress concentration points
that are harmful to the mechanical properties of the lms.
These behaviors occurred because the residues of coee
ground are lignocellulosic and its present a good chemical
compatibility with the starch and glycerol matrix. In terms
of particle size the 200-mesh granulometry facilitated the
mixing and dispersion of the coee ground waste residues
during casting of the lms.
The thermal characterization of the lms indicated that
although there is no standard of improvement of the thermal
properties associated to the increase of the concentration of
the coee grounds in the samples, these are better considering
lms without coee ground, since they begin their thermal
degradation at higher temperature, considering the various
stages of mass loss. The DSC analyzes did not reveal a better
lm in relation to the thermal characteristics, since for both
crystalline melting temperature and thermal decomposition
of the lms, the values did not present great dierences.
Therefore, it is possible to consider the use of these
lms as an alternative to substitute some types of packages,
as they oer advantages of low cost and high availability
of materials used for molding, as well as better tensile and
thermal properties.
5. Acknowledgments
This study was nanced in part by the Coordenação
de Aperfeiçoamento de Pessoal de Nível Superior - Brasil
(CAPES) - Finance Code 001, and FAPESP (06/60885-2).
Table 3. Volatilization, melting and degradation temperatures
according DSC curves.
Samples Tv (°C) Tm (°C) Td (°C)
1
93.34 151.27 266.80
2
105.34 151.12 262.23
3
97.24 149.41 264.56
4
103.46 153.84 256.78
5
95.83 155.48 262.49
6
106.82 150.47 267.87
7
114.30 153.83 263.74
Tv: Temperature of volatilization; Tm: Melting temperature; Td:
Temperature of degradation.
Gazonato et al.
6
Materials Research
Figure 3. TGA and DTG curves under inert atmosphere. Samples containing dierent concentrations of coee ground.
Samples of lms: (A) - 0% coee ground; (B) - 0.10% coee ground; (C) - 0.15% coee ground; (D) -0.20% coee
ground; (E) - 0.25% coee ground; (F) - 0.30% coee ground and (G) - 0.50% coee ground.
7Thermomechanical Properties of Corn Starch Based Film Reinforced with Coee Ground Waste as Renewable
Resource
Table 4. Decomposition stages observed in the TGA and DTG curves.
Samples
Step one Step two Step three
Total
Mass
loss (%)
ΔT(°C)
Δ Mass
(%)
T loss
max (°C)
ΔT(°C)
Δ Mass
(%)
T loss
max (°C)
ΔT(°C)
Δ Mass
(%)
T loss
max (°C)
1
35.1–
151.7
16.16 66.07
151.7–
274.1
26.64 231.94
274.1–
352.9
41.73 290.3 96.94
2
42.1–
160.6
16.56 71.19
160.6–
276.8
25.64 190.83
276.8–
358.0
41.31 294.7 94.53
3
36.7–
154.6
16.02 72.8
154.6–
278.6
26.73 223.68
278.6–
352.0
39.82 307.1 94.64
4
36.3–
163.7
16.76 70.76
163.7–
281.4
30.53 188.39
281.4–
355.6
36.71 310.5 96.67
5
42.4–
157.1
15.3 72.3
157.1–
279.2
26.22 188.14
279.2–
358.1
41.39 306.4 94.72
6
41.5–
161.6
15.24 67.45
161.6–
287.8
31.23 187.91
287.8–
356.0
35.46 308.6 95.67
7
40.5–
157.4
14.57 67.44
157.4–
285.7
30.6 185.29
285.7–
353.1
36.56 310.2 96.51
Figure 4. Scanning electron micrographs. Samples containing dierent concentrations of coee ground. Samples of lms: (A, B) - 0%
coee ground - 50x and 150x; (C, D) - 0.10% coee ground - 50x and 150x; (E, F) - 0.15% coee ground - 50x and 150x; (G, H) - 0.20%
coee ground - 50x and 150x; (I, J) - 0.25% coee ground - 50x and 150x; (K, L) - 0.30% coee ground - 50x and 150x and (M,N) -
0.50% coee ground - 50x and 150x.
Gazonato et al.
8
Materials Research
6. References
1. Anupam AK, Kumar P, Ransinchung RN GD. Use of Various
Agricultural and Industrial Waste Materials in Road Construction.
Procedia - Social and Behavioral Sciences. 2013;104:264-273.
2. Avelar NV, Rezende AAP, Carneiro ACO, Silva CM. Evaluation
of briquettes made from textile industry solid waste. Renewable
Energy. 2016;91:417-424.
3. Vamvuka D. Bio-oil, solid and gaseous biofuels from biomass
pyrolysis processes-An overview. International Journal of Energy
Research. 2011;35(10):835-862.
4. Brazil. Ministério do Planejamento, Desenvolvimento e Gestão. IPEA
Instituto de Pesquisa Econômica Aplicada. TD 2268. A organização
Coletiva de Catadores de Material Reciclável no Brasil: dilemas e
potencialidades sob a ótica da Economia Solidária. Brasília: IPEA;
2017.
5. Jacobi PR, Besen GR. Solid Waste Management in São Paulo: The
challenges of sustainability. Estudos Avançados. 2011;25(71):135-
158.
6. Brazil. Ministério do Meio Ambiente. Plano Nacional de Resíduos
Sólidos. Brasília: Ministério do Meio Ambiente; 2011.
7. Ioppolo G, Cucurachi S, Salomone R, Saija G, Ciraolo L. Industrial
Ecology and Environmental Lean Management: Lights and Shadows.
Sustainability. 2014;6(9):6362-6376.
8. Basu AJ, van Zyl DJA. Industrial ecology framework for achieving
cleaner production in the mining and minerals industry. Journal of
Cleaner Production. 2006;14(3-4):299- 304.
9. Miller L, Soulliere K, Sawyer-Beaulieu S, Tseng S, Tam E. Challenges
and Alternatives to Plastics Recycling in the Automotive Sector.
Materials (Basel). 2014;7(8):5883-5902.
10. Restrepo-Flórez JM, Bassi A, Thompson MR. Microbial degradation
and deterioration of polyethylene - A review. International
Biodeterioration & Biodegradation. 2014;88:83-90.
11. Shah AA, Hasan F, Hameed A, Ahmed S. Biological degradation
of plastics: A comprehensive review. Biotechnology Advances.
2008;26(3):246-265.
12. Mbey JA, Hoppe S, Thomas F. Cassava starch-kaolinite composite
lm. Eect of clay content and clay modication on lm properties.
Carbohydrate Polymers. 2012;88(1):213-222.
13. Tang S, Zou P, Xiong H, Tang H. Eect of nano-SiO2 on the
performance of starch/polyvinyl alcohol blend lms. Carbohydrate
Polymers. 2008;72(3):521-526.
14. Mirjalili F, Chuah L, Salahi E. Mechanical and Morphological
Properties of Polypropylene/Nano a-Al2O3 Composites. The
Scientic World Journal. 2014;2014:718765.
15. Nugroho A. The Impact of Food Safety Standard on Indonesia's
Coee Exports. Procedia Environmental Sciences. 2014;20:425-433.
16. Lamine SM, Ridha C, Mahfoud HM, Mouad C, Lot B, Al-Dujaili
AH. Chemical Activation of an Activated Carbon Prepared from
Coee Residue. Energy Procedia. 2014;50:393-400.
17. Reas A, Bernardet V, David B, Reinert L, Lehocine MB,
Dubois M, et al. Carbons prepared from coee grounds
by H3PO4 activation: Characterization and adsorption
of methylene blue and Nylosan Red N-2RBL. Journal of
Hazardous Materials. 2010;175(1-3):779-788.
18. Wobiwo FA, Ercoli Balbuena JL, Nicolay T, Larondelle Y,
Gerin PA. Valorization of spent coee ground with wheat
or miscanthus straw: Yield improvement by the combined
conversion to mushrooms and biomethane. Energy for
Sustainable Development. 2018;45:171-179.
19. Campos-Vega R, Loarca-Piña G, Vergara-Castañeda HA,
Dave Oomah B. Spent coee grounds: A review on current
research and future prospects. Trends in Food Science &
Technology. 2015;45(1):24-36.
20. Scully DS, Jaiswal AK, Abu-Ghannam N. An Investigation
into Spent Coee Waste as a Renewable Source of Bioactive
Compounds and Industrially Important Sugars. Bioengineering
(Basel). 2016;3(4). pii: E33.
21. Esquivel P, Jiménez VM. Functional properties of coee
and coee by-products. Food Research International.
2012;46(2):488-495.
22. Silva-Pereira MC, Teixeira JA, Pereira-Júnior VA, Stefani
R. Chitosan/corn starch blend lms with extract from
Brassica oleraceae (red cabbage) as a visual indicator of
sh deterioration. LWT - Food Science and Technology.
2015;61(1):258-262.
23. Campagner MR, Moris VAS, Pitombo LM, do Carmo JB,
de Paiva JMF. Filmes poliméricos baseados em amido e
lignossulfonatos: preparação, propriedades e avaliação da
biodegradação. Polímeros. 2014;24(6):740-751.
24. Morais LC, Maia AAD, Guandique MEG, Rosa AH. Pyrolysis
and combustion of sugarcane bagasse. Journal of Thermal
Analysis and Calorimetry. 2017;129(3):1813-1822.
25. Maia AAD, de Morais LC. Kinetic parameters of red pepper
waste as biomass to solid biofuel. Bioresource Technology.
2016;204:157-163.
26. Taghizadeh MT, Abdollahi R. A Kinetic Study on the Thermal
Degradation of Starch/Poly (Vinyl Alcohol) Blend. Chemical
and Materials Engineering. 2015;3(4):73-78.
27. Wang L, Xie B, Xiong G, Du X, Qiao Y, Liao L. Study on the
granular characteristics of starches separated from Chinese
rice cultivars. Carbohydrate Polymers. 2012;87(2):1038-
1044.
28. de Moraes JO, Reszka A, Laurindo JB. Espalhamento e secagem
de lme de amido-glicerol-bra preparado por "tape-casting".
Pesquisa Agropecuária Brasileira. 2014;49(2):136-143.
29. Czaputa K, Brenn G, Meile W. The drying of liquid lms on
cylindrical and spherical substrates. International Journal
of Heat and Mass Transfer. 2011;54(9-10):1871-1885.