The effect of pH on hydrolysis, cross-linking and barrier properties of starch barriers containing citric acid

Starch is highly promising biopolymer for the production of packaging material since it gives ﬁlms a good tensile and gas barrier properties. However, non-plasticized starch ﬁlms are brittle and their hydrophilic character results in poor moisture barrier properties and high water sensitivity. In order to improve ﬁlms formation and material properties of starch, plasticization and chemical modiﬁcation such as cross-linking of the starch is required. The cross-linking reaction able to improve thermal stability, tensile strength and decreased the dissolution of starch films in water and formic acid. From the study, the percentage of water uptake reduced when the blending ratio of citric acid increased.The percentage of water uptake highly affected by curing time compared to blending ratio. Increasing the curing time from 1 hour to 2 hour significantly reduced the percentage of water uptake. At 4 hour curing time, the percentage water uptake reached equilibrium faster than 3 hour curing time. This shows that more citric acid molecules were chemically bonded with the starch chains, resulting in higher cross link degree and thus, reduced the percentage of water uptake.

Download Full-text

The Effect of Cross-Linking with Citric Acid on the Properties of Agar/Fish Gelatin Films

Polymers ◽

10.3390/polym12020291 ◽

2020 ◽

Vol 12 (2) ◽

pp. 291

Author(s):

Jone Uranga ◽

Bach T. Nguyen ◽

Trung Trang Si ◽

Pedro Guerrero ◽

Koro de la Caba

Keyword(s):

Citric Acid ◽

Morphological Changes ◽

Barrier Properties ◽

Cross Linking ◽

Fish Gelatin ◽

Film Properties ◽

Pharmaceutical Applications ◽

Gelatin Films ◽

Esterification Reactions ◽

Acid Esterification

The aim of this work was to assess the effect of fish gelatin–citric acid nucleophilic substitution and agar–citric acid esterification reactions on the properties of agar/fish gelatin films. Since temperature is an important cross-linking parameter, films were treated at 90 °C and 105 °C and film properties were compared to those of non-cured films. It was observed that temperature favored the aforementioned reactions, which induced physical and morphological changes. In this regard, darker films with a rougher surface were obtained for the films with a higher cross-linking degree. While mechanical properties were slightly modified, the barrier properties were enhanced due to the reactions that occurred. Therefore, these agar/fish gelatin films cross-linked through two different reactions can be considered to be promising materials as active films for different purposes, such as active packaging or pharmaceutical applications.

Download Full-text

Effect of pH on the Production of Acetylmethyl-Carbinol Plus Diacetyl in Milk by the Citric Acid Fermenting Streptococci

Journal of Dairy Science ◽

10.3168/jds.s0022-0302(38)95637-1 ◽

1938 ◽

Vol 21 (4) ◽

pp. 213-218 ◽

Cited By ~ 15

Author(s):

M.B. Michaelian ◽

W.H. Hoecker ◽

B.W. Hammer

Keyword(s):

Citric Acid ◽

Effect Of Ph

Download Full-text

Comparative study of thermoplastic liner materials with regard to mechanical and permeation barrier properties before and after cyclic thermal aging

Materials Testing ◽

10.1515/mt-2020-0051 ◽

2021 ◽

Vol 63 (4) ◽

pp. 311-316

Author(s):

Simon Backens ◽

Jan Siering ◽

Stefan Schmidt ◽

Nikolai Glück ◽

Wilko Flügge

Keyword(s):

Thermal Aging ◽

Barrier Properties ◽

Tensile Tests ◽

Polyamide 6 ◽

Pressure Vessels ◽

Cross Linking ◽

Polyamide 12 ◽

Type Iv ◽

Before And After ◽

Permeation Properties

Abstract Lightweight pressure vessels of type IV for hydrogen storage consist of a thermoplastic inner liner, commonly from polyethylene or polyamide. The liner is the permeation barrier against the compressed gas and must prevent the formation of cracks, also after temperature changes, for example after refueling processes. In the present work high-density polyethylene, cross-linked polyethylene, polyamide 6 and polyamide 12 were characterized by tensile tests, single notch impact tests and permeations measurements before and after a cyclic thermal aging process. The aging only lead to slight changes of mechanical properties due to post-crystallization, but to a significant decrease of permeation properties. This decrease was contributed to weakened, amorphous regions where chain splitting occurred. Considerable differences in properties resulted from different peroxide cross-linking times of polyethylene at the same temperature. A longer holding time at 200 °C led to an improvement in impact strength by a factor of more than three. However, the permeation properties decreased by about 50 %, indicating that peroxide cross-linking in the melt inhibited the formation of crystalline regions.

Download Full-text

Effects of cross-linking by MgCl2 as an initiator on the properties of EVOH

Journal of Thermoplastic Composite Materials ◽

10.1177/0892705720913313 ◽

2020 ◽

pp. 089270572091331

Author(s):

Bin Wang ◽

Chong Lu ◽

Jing Hu ◽

Weixin Lu

Keyword(s):

Mechanical Test ◽

Barrier Properties ◽

Thermomechanical Properties ◽

Cross Linking ◽

Resonance Spectroscopy ◽

Test Results ◽

Ethylene Vinyl Alcohol ◽

Ftir Spectrometry ◽

Stretching Vibration ◽

C Nmr

Ethylene vinyl alcohol (EVOH) with excellent barrier properties has insufficient thermomechanical properties. The introduction of magnesium chloride (MgCl2) as an initiator in EVOH blends improved its properties by cross-linking. Torque behavior and gel experiment analysis indicated that a cross-linking in EVOH was formed. The cross-linking mechanism was confirmed through 13C nuclear magnetic resonance spectroscopy (13C NMR) and Fourier-transform infrared (FTIR) spectrometry. In 13C NMR spectra, the splitting peaks of CH carbon and CH2 carbon tended to disappear, and the stretching vibration peak of –C=C– was observed in the FTIR spectra. The formation of hydrogen bond between MgCl2 and EVOH destroyed the intramolecular and intermolecular hydrogen bonds of EVOH, which contributed to the dehydration of –OH to form –C=C–, and –C=C– was the basis for a cross-linking reaction. The thermal analysis of blends demonstrated that the melting temperature and crystallization temperature decreased, and the crystallinity gradually disappeared when the MgCl2 content increased. Glass transition temperature significantly increased as the intermolecular force enhanced. Thermogravimetric analysis showed that a cross-linked structure could improve the thermostability of EVOH with an increase in the MgCl2 content. Mechanical test results revealed a remarkable increase in the tensile strength of EVOH as the MgCl2 content increased.

Download Full-text

Cross-linking of cellulose and poly(ethylene glycol) with citric acid

Reactive and Functional Polymers ◽

10.1016/j.reactfunctpolym.2015.03.007 ◽

2015 ◽

Vol 90 ◽

pp. 21-24 ◽

Cited By ~ 32

Author(s):

Pamela de Cuadro ◽

Tiina Belt ◽

Katri S. Kontturi ◽

Mehedi Reza ◽

Eero Kontturi ◽

...

Keyword(s):

Citric Acid ◽

Ethylene Glycol ◽

Cross Linking ◽

Poly Ethylene Glycol ◽

Poly Ethylene

Download Full-text

UV Radiation Induced Cross-Linking of Whey Protein Isolate-Based Films

International Journal of Polymer Science ◽

10.1155/2017/1846031 ◽

2017 ◽

Vol 2017 ◽

pp. 1-6 ◽

Cited By ~ 7

Author(s):

Markus Schmid ◽

Tobias Konrad Prinz ◽

Kerstin Müller ◽

Andreas Haas

Keyword(s):

Whey Protein ◽

Uv Radiation ◽

Reference Sample ◽

Barrier Properties ◽

Protein Isolate ◽

Cross Linking ◽

Protein Films ◽

Disordered Protein ◽

Radiation Induced ◽

The Cross

Casted whey protein films exposed to ultraviolet irradiation were analyzed for their cross-linking properties and mechanical and barrier performance. Expected mechanical and barrier improvements are discussed with regard to quantification of the cross-linking in the UV-treated whey protein films. Swelling tests were used to determine the degree of swelling, degree of cross-linking, and cross-linking density. When the UV radiation dosage was raised, a significant increase of the tensile strength as well as an increase in Young’s modulus was observed. No significant changes in water vapor and oxygen barrier properties between the UV-treated films and an untreated reference sample could be observed. The cross-linking density and the degree of cross-linking significantly increased due to UV radiation. Combined results indicate a disordered protein network in cast films showing locally free volume and therefore only minor mechanical and barrier improvements.

Download Full-text