This work aims to disclose the strengths and limitations of utilizing hydroxyl-compatible fillers, rice husks and silica (SiO2), in citric acid-crosslinked thermoplastic starch foams. FTIR characterization demonstrated that citric acid could establish ester linkages with starch molecules for both neat and composite foams, with the C = O peak shifting from 1724 cm−1 (neat foam) to 1730–1732 cm−1 (composite foams). The key role of hydroxyl-compatible fillers was the strong starch-filler interactions that enabled more thermally stable composite foams, which elevated thermal decomposition temperatures to 300–302°C with higher residue weights of 22.73–25.33%. These strong starch-filler interactions were also responsible for retarding cell foam expansion. The composite foams showed 16.61–92.03% improved flexural strength, 2.82–10.67% increased densities and lower moisture absorption. However, incorporation of hydroxyl-compatible fillers in composite foams increased water solubility to 16.84–20.73%, compared to 12.14% for a neat foam. These experimental results indicate that the employed fillers might interfere with the crosslinking process, leading to decreased crosslink formation in composite foams. Consequently, possible interruption mechanisms of crosslink formation by the fillers were suggested and confirmed by qualitative analysis. The findings of the strengths and limitations of hydroxyl-compatible fillers illustrate crucial trade-offs in using starch-based composite foams as sustainable food packaging materials.
GeorgesACatherineLMarie LeB, et al.Effect of the formulation of starch-based foam cushions on the morphology and mechanical properties. J Cell Plast2014; 51(1): 31–44. https://doi.org/10.1177/0021955X14527979
2.
XieYGaoSZhangD, et al.Bio-based polymeric materials synthesized from renewable resources: a mini-review. Resour Chem Mater2023; 2(3): 223–230. https://doi.org/10.1016/j.recm.2023.05.001
3.
ItkorPSinghAKLeeM, et al.Scaling-Up production of recycled paper/starch–citric acid biocomposite sheets with improved attributes for sustainable packaging applications: from waste to resource. J Polym Environ2024; 32(4): 1907–1920. https://doi.org/10.1007/s10924-023-03109-0
4.
KavasETerzioğluPSıcakY. Betanin and nano-calcium carbonate incorporated polyvinyl Alcohol/starch films for active and intelligent packaging applications. J Polym Environ2023; 31(11): 4919–4929. https://doi.org/10.1007/s10924-023-02868-0
5.
SukkaneewatBPanrotTRojruthaiP, et al.Plasticizing effects from citric acid/palm oil combinations for sorbitol-crosslinked starch foams. Mater Chem Phys2022; 278: 125732. https://doi.org/10.1016/j.matchemphys.2022.125732
6.
PengXSongJAlanN, et al.Microwave foaming of starch-based materials (II) thermo-mechanical performance. J Cell Plast2013; 49(2): 147–160. https://doi.org/10.1177/0021955X13477439
7.
WilpiszewskaKAntosikAKZdanowiczM. The effect of citric acid on physicochemical properties of hydrophilic carboxymethyl starch-based films. J Polym Environ2019; 27(6): 1379–1387. https://doi.org/10.1007/s10924-019-01436-9
8.
SheydaiANikzadMPeyraviM. Improvement in mechanical and physical properties of starch-based films provided by cellulose nanocrystals extracted from rice straw. J Thermoplast Compos Mater2022; 36(8): 3332–3360. https://doi.org/10.1177/08927057221128197
9.
Cruz-TiradoJPVejaranoRTapia-BlácidoDR, et al.Biodegradable foam tray based on starches isolated from different Peruvian species. Int J Biol Macromol2019; 125: 800–807. https://doi.org/10.1016/j.ijbiomac.2018.12.111
PrapruddivongsCWongpreedeeT. Use of eggshell powder as a potential hydrolytic retardant for citric acid-filled thermoplastic starch. Powder Technol2020; 370: 259–267. https://doi.org/10.1016/j.powtec.2020.05.076
ChiarathanakritCRiyajanS-AKaewtatipK. Transforming fish scale waste into an efficient filler for starch foam. Carbohydr Polym2018; 188: 48–53. https://doi.org/10.1016/j.carbpol.2018.01.101
14.
SeligraPGMedina JaramilloCFamáL, et al.Biodegradable and non-retrogradable eco-films based on starch–glycerol with citric acid as crosslinking agent. Carbohydr Polym2016; 138: 66–74. https://doi.org/10.1016/j.carbpol.2015.11.041
15.
Estrada-MonjeAAlonso-RomeroSZitzumbo-GuzmánR, et al.Thermoplastic starch-based blends with improved thermal and thermomechanical properties. Polymers2021; 13(23): 4263. https://doi.org/10.3390/polym13234263
PuniaBSSunoojKVNavafM, et al.Recent advancements in cross-linked starches for food applications-a review. Int J Food Prop2024; 27(1): 411–430. https://doi.org/10.1080/10942912.2024.2318427
18.
BodîrlǎuRTeacǎCASpiridonI. Green composites comprising thermoplastic corn starch and various cellulose-based fillers. Bioresour2014; 9(1): 39–53. https://doi.org/10.15376/biores.9.1.39-53
19.
BodirlauRTeacaC-ASpiridonI. Influence of natural fillers on the properties of starch-based biocomposite films. Compos Part B Eng2013; 44(1): 575–583. https://doi.org/10.1016/j.compositesb.2012.02.039
20.
JiMLiFLiJ, et al.Enhanced mechanical properties, water resistance, thermal stability, and biodegradation of the starch-sisal fibre composites with various fillers. Mater Des2021; 198: 109373. https://doi.org/10.1016/j.matdes.2020.109373
21.
JulinováMVaňharováLJurčaM, et al.Effect of different fillers on the biodegradation rate of thermoplastic starch in water and soil environments. J Polym Environ2020; 28(2): 566–583. https://doi.org/10.1007/s10924-019-01624-7
22.
GutiérrezTJAlvarezVA. Bionanocomposite films developed from corn starch and natural and modified nano-clays with or without added blueberry extract. Food Hydrocoll2018; 77: 407–420. https://doi.org/10.1016/j.foodhyd.2017.10.017
23.
ZhangRWangXChengM. Preparation and characterization of potato starch film with various size of Nano-SiO2. Polymers2018; 10(10). https://doi.org/10.3390/polym10101172
24.
LiuYFanLXiongJ, et al.Effect of different particle size of silica on structure, morphology, and properties of thermoplastic cassava starch. Polym Polym Compos2020; 29(7): 863–875. https://doi.org/10.1177/0967391120939664
25.
IsmailHZaabaNF. The mechanical properties, water resistance and degradation behaviour of silica-filled sago starch/PVA plastic films. J Elastomers Plast2012; 46(1): 96–109. https://doi.org/10.1177/0095244312462163
26.
KamiyaHMitsuiMTakanoH, et al.Influence of particle diameter on surface silanol structure, hydration forces, and aggregation behavior of alkoxide-derived silica particles. J Am Ceram Soc2000; 83(2): 287–293. https://doi.org/10.1111/j.1151-2916.2000.tb01187.x
27.
BaishyaPMajiTK. Enhancement in physicochemical properties of citric acid/nano SiO2 treated sustainable wood-starch nanocomposites. Cellulose2017; 24(10): 4263–4274. https://doi.org/10.1007/s10570-017-1399-2
28.
NPChakrabortyIMalSS, et al.Evaluation of physicochemical properties of citric acid crosslinked starch elastomers reinforced with silicon dioxide. RSC Adv2024; 14(1): 139–146. https://doi.org/10.1039/D3RA07868J
29.
ZarskiABajerKKapuśniakJ. Review of the Most important methods of improving the processing properties of starch toward non-food applications. Polymers2021; 13(5): 832. https://doi.org/10.3390/polym13050832
30.
AzadMMEjazMShahA, et al.A bio-based approach to simultaneously improve flame retardancy, thermal stability and mechanical properties of nano-silica filled jute/thermoplastic starch composite. Mater Chem Phys2022; 289: 126485. https://doi.org/10.1016/j.matchemphys.2022.126485
31.
LeeEJBitnerTWHaJS, et al.Light-Induced Reactions of Porous and Single-Crystal Si Surfaces with Carboxylic Acids. J Am Chem Soc1996; 118(23): 5375–5382. https://doi.org/10.1021/ja960777l
32.
ShiRZhangZLiuQ, et al.Characterization of citric acid/glycerol co-plasticized thermoplastic starch prepared by melt blending. Carbohydr Polym2007; 69(4): 748–755. https://doi.org/10.1016/j.carbpol.2007.02.010
SchutzGFAlvesRMVVieiraRP. Development of starch-based films reinforced with coffee husks for packaging applications. J Polym Environ2023; 31(5): 1955–1966. https://doi.org/10.1007/s10924-022-02733-6
35.
LiuWWangZLiuJ, et al.Preparation, reinforcement and properties of thermoplastic starch film by film blowing. Food Hydrocoll2020; 108: 106006. https://doi.org/10.1016/j.foodhyd.2020.106006
36.
DonatiNSpadaJCTessaroIC. Recycling rice husk ash as a filler on biodegradable cassava starch-based foams. Polym Bull2023; 80(9): 10231–10248. https://doi.org/10.1007/s00289-022-04557-9
37.
Collazo-BigliardiSOrtega-ToroRChiralt BoixA. Reinforcement of thermoplastic starch films with cellulose fibres obtained from rice and coffee husks. J Renew Mater2018; 6(6): 599–610. https://doi.org/10.32604/JRM.2018.00127
SantosLMdosSMatusinhoIA, et al. Evaluation of the effects of organic acids on the properties of thermoplastic starch. Polym Bull2025; 82: 3063–3083. https://doi.org/10.1007/s00289-025-05653-2
40.
SalgadoPRSchmidtVCMolina OrtizSE, et al.Biodegradable foams based on cassava starch, sunflower proteins and cellulose fibers obtained by a baking process. J Food Eng2008; 85(3): 435–443. https://doi.org/10.1016/j.jfoodeng.2007.08.005
41.
HassanMMTuckerNLe GuenMJ. Thermal, mechanical and viscoelastic properties of citric acid-crosslinked starch/cellulose composite foams. Carbohydr Polym2020; 230: 115675. https://doi.org/10.1016/j.carbpol.2019.115675
42.
ChenWCSyed Mohd JudahSNMGhazaliSK, et al.The effects of citric acid on thermal and mechanical properties of crosslinked starch film. Chem Eng Trans2021; 83: 199–204. SE-Research Articles.
MaXChangPRYuJ, et al.Properties of biodegradable citric acid-modified granular starch/thermoplastic pea starch composites. Carbohydr Polym2009; 75(1): 1–8. https://doi.org/10.1016/j.carbpol.2008.05.020
45.
DekaBKMajiTK. Effect of silica nanopowder on the properties of wood flour/polymer composite. Polym Eng Sci2012; 52(7): 1516–1523. https://doi.org/10.1002/pen.23097
46.
SjöqvistMBoldizarARigdahlM. Processing and water absorption behavior of foamed potato starch. J Cell Plast2010; 46(6): 497–517. https://doi.org/10.1177/0021955X10377802
47.
CabanillasANuñezJCruz-TiradoJP, et al.Pineapple shell fiber as reinforcement in cassava starch foam trays. Polym Polym Compos2019; 27(8): 496–506. https://doi.org/10.1177/0967391119848187
48.
HafizulhaqFAbralHKasimA, et al.Moisture absorption and opacity of starch-based biocomposites reinforced with cellulose fiber from bengkoang. Fibers2018; 6(3): 62. https://doi.org/10.3390/fib6030062
49.
DuquetteDNzediegwuCPortillo-PerezG, et al.Eco-friendly synthesis of hydrogels from starch, citric acid, and itaconic acid: swelling capacity and metal chelation properties. Starch - Stärke2020; 72(3-4): 1900008. https://doi.org/10.1002/star.201900008
50.
GolachowskiADrożdżWGolachowskaM, et al.Production and properties of starch citrates—current research. Foods2020; 9(9). https://doi.org/10.3390/foods9091311
51.
TakahashiRSatoSSodesawaT, et al.High surface-area silica with controlled pore size prepared from nanocomposite of silica and citric acid. J Phys Chem B2000; 104(51): 12184–12191. https://doi.org/10.1021/jp002662g
52.
HoangMTPhamTDPhamTT, et al.Esterification of sugarcane bagasse by citric acid for Pb2+ adsorption: effect of different chemical pretreatment methods. Environ Sci Pollut Res2021; 28(10): 11869–11881. https://doi.org/10.1007/s11356-020-07623-9
53.
PereiraJFMarimBMMaliS. Chemical modification of cellulose using a green route by reactive extrusion with citric and succinic acids. Polysaccharides2022; 3(1): 292–305. https://doi.org/10.3390/polysaccharides3010017
54.
AbbasAAnsumaliS. Global potential of rice husk as a renewable feedstock for ethanol biofuel production. Bioenergy Res2010; 3(4): 328–334. https://doi.org/10.1007/s12155-010-9088-0
55.
LiangYOuyangJWangH, et al.Synthesis and characterization of core–shell structured SiO2@YVO4:Yb3+,Er3+ microspheres. Appl Surf Sci2012; 258(8): 3689–3694. https://doi.org/10.1016/j.apsusc.2011.12.006
56.
PrapruddivongsCRukrabiabJKulwongwitN, et al.Effect of surface-modified silica on the thermal and mechanical behaviors of poly(lactic acid) and chemically crosslinked poly(lactic acid) composites. J Thermoplast Compos Mater2019; 33: 1692–1706. https://doi.org/10.1177/0892705719835286
57.
ChandrasiriKWDKNguyenCCParimalamBS, et al.Citric acid based Pre-SEI for improvement of silicon electrodes in lithium ion batteries. J Electrochem Soc2018; 165(10): A1991–A1996. https://doi.org/10.1149/2.0161810jes
58.
BattegazzoreDBocchiniSAlongiJ, et al.Rice husk as bio-source of silica: preparation and characterization of PLA–Silica bio-composites. RSC Adv2014; 4(97): 54703–54712. https://doi.org/10.1039/C4RA05991C
59.
ZouWBaiHGaoS, et al.Investigations on the batch performance of cationic dyes adsorption by citric acid modified peanut husk. Desalin Water Treat2012; 49(1-3): 41–56. https://doi.org/10.1080/19443994.2012.708197
60.
WilpiszewskaKAntosikAK. Effect of grain husk microfibers on physicochemical properties of carboxymethyl polysaccharides-based composite. J Polym Environ2022; 30(8): 3129–3138. https://doi.org/10.1007/s10924-022-02424-2
61.
MallakpourSShahrokhpourM. Role of surface modification of SiO2 with bio-safe citric acid on the morphological and thermal properties of nanocomposites based on N-trimellitylimido-l-methionine diacid and 4,4′-diaminodiphenyl ether: using ultrasound irradiation and ionic liquid. Polym Bull2017; 74(6): 2203–2215. https://doi.org/10.1007/s00289-016-1829-6
62.
NazSUroosMAyoubM. Cost-effective processing of carbon-rich materials in ionic liquids: an expeditious approach to biofuels. ACS Omega2021; 6(43): 29233–29242. https://doi.org/10.1021/acsomega.1c04881
63.
KimH-SYangH-SKimH-J, et al.Thermogravimetric analysis of rice husk flour filled thermoplastic polymer composites. J Therm Anal Calorim2004; 76(2): 395–404. https://doi.org/10.1023/B:JTAN.0000028020.02657.9b
64.
JiHXiangZQiH, et al.Strategy towards one-step preparation of carboxylic cellulose nanocrystals and nanofibrils with high yield, carboxylation and highly stable dispersibility using innocuous citric acid. Green Chem2019; 21(8): 1956–1964. https://doi.org/10.1039/C8GC03493A
