Erratum-The Diffusion of Radioactively Tagged n-hexadecane and n-dodecane through Rubbery Polymers. Effects of Temperature, Cross-linking, and Chemical Structure

1968 ◽  
Vol 1 (4) ◽  
pp. 374-374 ◽  
Author(s):  
Stephen P. Chen ◽  
John D. Ferry
Keyword(s):  
Chemical Structure ◽  
Cross Linking ◽  
Rubbery Polymers ◽  
Effects Of Temperature

scholarly journals Characterization of polydimethylsiloxane rubber upon photochemical, thermal, salt-fog ageings and exposure to acid vapours

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
F. Delor-Jestin ◽  
N. S. Tomer ◽  
R.P. Singh ◽  
J. Lacoste
Keyword(s):  
Ir Spectroscopy ◽  
Chemical Structure ◽  
Mesh Size ◽  
Cross Linking ◽  
Scanning Calorimetry ◽  
New Knowledge ◽  
Salt Fog ◽  
Complementary Analysis ◽  
Thermal Stability Of

AbstractThe changes in the chemical structure and the physical properties of a filled crosslinked polydimethylsiloxane rubber were monitored as a function of various ageing factors. The variables included photochemical, thermal, salt-fog ageings and exposure to acid vapours. Unaged and aged samples were studied by IR spectroscopy, hardness measurements, Differential Scanning Calorimetry (DSC) and thermogravimetric analysis (TGA) coupled with IR spectroscopy. No significant oxidation was detected after all ageings, except for nitric acid treatment. The presence of aluminium trihydrate was clearly identified as responsible for the observed chemical changes. Then an important vulnerability of this filled silicone rubber towards the cross-linking reactions provoked by usual ageings was also detected. The DSC-thermoporosimetry measurements of the mesh size distribution gave a comparison of cross-linking densities for each ageing. The complementary analysis with TGAIR allowed us to differenciate the thermal stability of the formulation after various ageings and to acquire new knowledge about thermal decomposition.

scholarly journals Preparation and pH Controlled Release of Fe3O4/Anthocyanin Magnetic Biocomposites

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2077
Author(s):  
Xizhi Jiang ◽  
Qingbao Guan ◽  
Min Feng ◽  
Mengyang Wang ◽  
Nina Yan ◽  
...  
Keyword(s):  
Smooth Surface ◽  
Chemical Structure ◽  
Magnetic Nanoparticle ◽  
Cross Linking ◽  
Pharmacological Properties ◽  
X Ray ◽  
Drug Storage ◽  
Acidic Conditions ◽  
Average Size ◽  
Fe3o4 Magnetic Nanoparticle

Anthocyanins are a class of antioxidants extracted from plants, with a variety of biochemical and pharmacological properties. However, the wide and effective applications of anthocyanins have been limited by their relatively low stability and bioavailability. In order to expand the application of anthocyanins, Fe3O4/anthocyanin magnetic biocomposite was fabricated for the storage and release of anthocyanin in this work. The magnetic biocomposite of Fe3O4 magnetic nanoparticle-loaded anthocyanin was prepared through physical intermolecular adsorption or covalent cross-linking. Scanning electron microscopy (SEM), Dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and thermal analysis were used to characterize the biocomposite. In addition, the anthocyanin releasing experiments were performed. The optimized condition for the Fe3O4/anthocyanin magnetic biocomposite preparation was determined to be at 60 °C for 20 h in weak alkaline solution. The smooth surface of biocomposite from SEM suggested that anthocyanin was coated on the surface of the Fe3O4 particles successfully. The average size of the Fe3O4/anthocyanin magnetic biocomposite was about 222 nm. Under acidic conditions, the magnetic biocomposite solids could be repeatable released anthocyanin, with the same chemical structure as the anthocyanin before compounding. Therefore, anthocyanin can be effectively adsorbed and released by this magnetic biocomposite. Overall, this work shows that Fe3O4/anthocyanin magnetic biocomposite has great potential for future applications as a drug storage and delivery nanoplatform that is adaptable to medical, food and sensing.

scholarly journals Influence of the chemical structure of cross-linking agents on properties of thermally reversible networks

2016 ◽  
Vol 88 (12) ◽  
pp. 1103-1116 ◽  
Author(s):  
Lorenzo Massimo Polgar ◽  
Robin R.J. Cerpentier ◽  
Gijs H. Vermeij ◽  
Francesco Picchioni ◽  
Martin van Duin
Keyword(s):  
Chemical Structure ◽  
Chemical Conversion ◽  
Rubber Matrix ◽  
Cross Linking ◽  
Cross Link ◽  
Molar Amount ◽  
Link Density ◽  
Cross Link Density ◽  
Cross Linker ◽  
The Cross

Abstract It is well-known that the properties of cross-linked rubbers are strongly affected by the cross-link density. In this work it is shown that for thermoreversibly cross-linked elastomers, the type and length of the cross-linker also have a significant effect. A homologous series of diamine and bismaleimide cross-linkers was used to cross-link maleic-anhydride-grafted EPM irreversibly and furan-modified EPM thermoreversibly, respectively. Bismaleimide cross-linkers with a polarity close to that of EPM and a relatively low melting point have a better solubility in the rubber matrix, which results in higher chemical conversion and, thus, higher cross-link densities at the same molar amount of cross-linker. Samples cross-linked with different spacers (aromatic and aliphatic spacers of different lengths) were compared at the same cross-link density to interpret the effects on the material properties. The rigid character of the short aliphatic and the aromatic cross-linkers accounts for the observed increase in hardness, Young´s modulus and tensile strength with respect to the longer, more flexible aliphatic cross-linkers. In conclusion, the structure of the cross-linking agent can be considered as an alternative variable in tuning the rubber properties, especially for thermoreversibly cross-linked rubber.

Studies of the Vulcanization of Rubber

1952 ◽  
Vol 25 (2) ◽  
pp. 209-229 ◽  
Author(s):  
Shu Kambara ◽  
Kumakazu Ohkita
Keyword(s):  
Organic Compounds ◽  
Chemical Structure ◽  
Room Temperature ◽  
Great Influence ◽  
Cross Linking ◽  
Oxidizing Agent ◽  
Vulcanized Rubber ◽  
Cross Linkage ◽  
Bridge Type ◽  
The Difference

Abstract In this study much information about the method of distinguishing the state in which sulfur is combined in simple organic compounds consisting of carbon, hydrogen, and sulfur was obtained, and a new theory of vulcanization was postulated as a result of its application to vulcanized rubber. When activated sulfur reacts with rubber, it first adds to the double bonds, forming thioketones, which in turn, as a characteristic of these radicals, combine with each other, with the formation of a thioether structure. This transformation of thioketone into thioether takes place, not only during vulcanization, but also gradually after vulcanization. Because of the presence of thioketone, treatment of vulcanized rubber with hydrazine, forms a new network, that is, a ketoazine cross-linkage. Combined sulfur of the thioketone type was determined by an oxidizing agent, and as the difference of this value and total combined sulfur a method of determining bridge type of combined sulfur has been proposed. By this method, it was found that, even in ebonite, about one-third of the combined sulfur is the thioketone type, and that the bridge type is only about two-thirds of the total. The thioketone type of combined sulfur in soft vulcanized rubber is transformed gradually into the thioether type of cross-linkage when allowed to stand at room temperature, and this transformation is accelerated when the temperature is raised. In the case of hard rubber, this phenomenon is also observable, but the rate of this transformation is much slower compared to the former. This tendency is the same in the case of ketoazine cross-linking when rubber vulcanizates are treated with hydrazine. From these facts, it seems that the distribution of the thioketone radicals is not uniform, and the magnitude of the probability for collision of these radicals to form cross-linkages has a great influence on the properties of rubber after vulcanization. That is, the property of the vulcanizate is greatly affected by the fact whether the thioketone radicals in the vulcanizates are comparatively uniformly distributed or whether they exist in sectional groups or in colonies. The authors are the first to advance this postulate concerning the chemical structure of vulcanized rubber and its transformation. We believe that when the study is extended, using this postulation, problems such as aging and the differences in the properties of vulcanized rubber accelerated with various accelerators will become clear. Moreover, we believe that it will be of interest to physicists studying rubber elasticity to suggest this idea of colony of cross-linkages. We are now carrying on researches on these problems, and we shall report on them later.

Preparation and Properties of Glutaraldehyde Cross-Linked Silk Sericin Films

2017 ◽  
Vol 748 ◽  
pp. 148-152 ◽  
Author(s):  
Fang Yu Zhan ◽  
Kun Yan Wang ◽  
Miao Miao Niu
Keyword(s):  
Thermal Decomposition ◽  
Chemical Structure ◽  
Decomposition Temperature ◽  
Swelling Behavior ◽  
Cross Linking ◽  
Swelling Ratio ◽  
Thermal Decomposition Temperature ◽  
Silk Sericin ◽  
Peak Intensity ◽  
The Cross

Glutaraldehyde cross-linked silk sericin films were successfully prepared. FTIR was applied to characterize the chemical structure of films. Compared to pure silk sericin, cross-linked silk sericin film with 3% glutaraldehyde was found a new peak at 1620 cm-1 and the peak intensity of cross-linked film decreased markedly, which indicating cross-linking reaction has been occurred. Thermal and swelling behavior of cross-linked films was investigated. The cross-linking reaction increased the thermal decomposition temperature. The swelling ratio of glutaraldehyde cross-linked silk sericin films went up with increasing glutaralehyde loading to 3wt%.

CHANGES OF CHEMICAL STRUCTURE AND MECHANICAL PROPERTY LEVELS DURING THERMO-OXIDATIVE AGING OF NBR

2013 ◽  
Vol 86 (4) ◽  
pp. 591-603 ◽  
Author(s):  
Jiaohong Zhao ◽  
Rui Yang ◽  
Rossana Iervolino ◽  
Stellario Barbera
Keyword(s):  
Mechanical Property ◽  
Thermal Aging ◽  
Chemical Structure ◽  
Structural Changes ◽  
Elevated Temperatures ◽  
Chain Scission ◽  
Bending Test ◽  
Cross Linking ◽  
Butadiene Rubber ◽  
Oxidative Aging

ABSTRACT The accelerated thermo-oxidative aging of acrylonitrile–butadiene rubber (NBR) was studied at elevated temperatures. The chemical structure characterized by attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) and pyrolysis gas chromatography–mass spectroscopy (PGC-MS) showed the loss of low-molecular-weight additives, such as antioxidants and paraffin, and the formation of carbonyl groups and unsaturated double bonds. The cross-linking degree characterized by NMR and a swelling test showed that aging is a competitive process of cross-linking and chain scission. Cross-linking dominated the thermal aging of NBR most of the time, whereas chain scission began to increase after a long time at high temperatures. The changes of mechanical property magnitudes during thermal aging of NBR were studied by using the recovery from bending test (RFB) and tensile test. By comparing the physical property results and the structural changes, their relationship is discussed.

scholarly journals Spruce Bark-Extracted Lignin and Tannin-Based Bioresin-Adhesives: Effect of Curing Temperatures on the Thermal Properties of the Resins

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3523
Author(s):  
Sunanda Sain ◽  
Leonidas Matsakas ◽  
Ulrika Rova ◽  
Paul Christakopoulos ◽  
Tommy Öman ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Properties ◽  
High Temperature ◽  
Chemical Structure ◽  
Hot Water ◽  
Cross Linking ◽  
Compression Moulding ◽  
Hot Water Extraction ◽  
Spruce Bark ◽  
Modified Lignin

In this study, formaldehyde-free bioresin adhesives were synthesised from lignin and tannin, which were obtained from softwood bark. The extraction was done via organosolv treatment and hot water extraction, respectively. A non-volatile, non-toxic aldehyde, glyoxal, was used as a substitute for formaldehyde in order to modify the chemical structure of both the lignin and tannin. The glyoxal modification reaction was confirmed by ATR–FTIR spectroscopy. Three different resin formulations were prepared using modified lignin along with the modified tannin. The thermal properties of the modified lignin, tannin, and the bioresins were assessed by DSC and TGA. When the bioresins were cured at a high temperature (200 ℃) by compression moulding, they exhibited higher thermal stability as well as an enhanced degree of cross-linking compared to the low temperature-cured bioresins. The thermal properties of the resins were strongly affected by the compositions of the resins as well as the curing temperatures.

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