Effects of Lactoalbumin Addition to Vulcanized Rubber Determined by RPA2000
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We investigated the effect of lactoalbumin on the processing properties of vulcanized rubber by adding lactoalbumin protein. We found that G’ and G’’ of vulcanized rubber were increased and tan was decreased by adding lactoalbumin. The addition of lactoalbumin can improve the processing properties of natural rubber.Abstract Considerable data on the vulcanization characteristics of molecular fractions of ordinary (unpurified) natural rubber are available. There is, on the other hand, little information of any systematic work on the vulcanization of purified rubber and of its fractions. Pummerer and Pahl vulcanized the sol and gel fractions obtained from purified Hevea rubber, and also the purified whole rubber. But apart from a statement that whole rubber vulcanized much faster than the two fractions obtained from it, no details have been published. Vulcanization of purified whole rubber and of its sol and gel fractions was studied also by Smith and Holt. They concluded that the difference which they observed in the stress-strain behavior of the fractions and whole rubber was due to differences in the rubber which persisted through vulcanization. The present paper deals with a study of the vulcanization characteristics of different fractions of purified rubber prepared by a method described in a previous paper. Also, for comparative purposes a similar study was made of the corresponding fractions of unpurified rubber. As the difference in molecular weight of some of the fractions obtained by the above method was rather small, a grouping of the fractions was made as follows :
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Graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) are widely used in rubber fillers due to their good mechanical properties and thermal conductivity. In order to increase the vulcanization efficiency and improve the physical properties of natural rubber, a GO/MWCNTs rubber composite was prepared by mixing graphene oxide and multi-walled carbon nanotubes with rubber in different proportions. Through testing the physical properties of the rubber compound and the vulcanized rubber, it is concluded that there is a synergistic effect between MWCNTs filler and GO filler, and different ratios of GO and MWCNTs have different effects on the performance of the rubber compound. When MWCNTs filler is added quantitatively at 6wt%, with the increase of GO content: the maximum torque MH of the vulcanized rubber and the crosslinking density ΔM value increased; the scorch time tc10 and the normal vulcanization time tc90 decreased first, and tc90 rose slightly after 3wt%. When the content of GO and MWCNTs are 3wt% and 6wt%, the improvement of vulcanization efficiency is most obvious; when the two are added at 6wt% at the same time, the thermal conductivity of the compound and the vulcanized rubber are increased by 25.1% and 23.3% respectively; the 100% of the vulcanized rubber is fixed. Tensile stress and 300% constant elongation stress have a rising trend, and slightly decrease after 3wt%; Taken together, when GO and MWCNTs are added at 3wt% and 6wt%, respectively, the filler particles have the best reinforcement effect on the rubber. Its good thermal conductivity enhances the uniformity of the vulcanization reaction and realizes energy saving and consumption reduction in the vulcanization process.
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Abstract The results of characterization of the natural rubber vulcanizates are consistent with the results of characterization of the sulfidic products from 2-methylpent-2-ene. In both the model olefin system and the rubber system the initially formed crosslinks are polysulfidic but these are subsequently reduced to di- and monosulfidic crosslinks as the cure time is increased. Similar amounts of zinc sulfide are formed during the sulfuration of 2-methylpent-2-ene and during the vulcanization of natural rubber. The efficiency of sulfur utilization for crosslinking in natural rubber is approximately half that in comparable sulfurations of 2-methylpent-2-ene, i.e. approximately twice as many sulfur atoms are needed to obtain a chemical crosslink in natural rubber as are needed to obtain a crosslink in 2-methylpent-2-ene. This is presumed to be a consequence of the intra-molecular sulfuration that occurs in natural rubber. There is no evidence to indicate the presence of vicinal crosslinks in the natural rubber vulcanizates. Hence in agreement with the views of other workers it is concluded that the crosslinks present in accelerated sulfur vulcanizates of natural rubber are tetrafunctional and dialkenyl. The results of the characterization of the polybutadiene vulcanizates are not fully supported by the results of the model olefin studies. In the vulcanization of polybutadiene the initially formed crosslinks are polysulfidic. As vulcanization proceeds, the chemical complexity of the network increases. After long reaction times, however, no significant amount of monosulfidic crosslinks are present in the network and very little of the reacted sulfur is present in the form of zinc sulfide. Nitrogen analyses of the polybutadiene vulcanizates showed that a substantial fraction of the accelerator, equivalent to 80–90% of the available 2-thiobenzothiazole groups, become combined in the network during vulcanization. It is proposed that the combination of accelerator with polybutadiene prevents the desulfuration of dialkenyl polysulfides to dialkenyl monosulfides (the normally observed pathway of accelerated sulfuration of natural rubber) and allows vicinal crosslinking to proceed. Some support for this proposal is that vicinal crosslinks and a substantial amount of nitrogenous product are formed during the accelerated sulfuration of cyclohexene. The findings of Gregg and Katrenick on the MBTS accelerated sulfuration of cis-cis-1,5-cyclooctadiene are also consistent with this proposal. The nitrogen analyses of the polybutadiene vulcanizates indicate that very little of the accelerator is permanently combined in the network during the initial stages of network formation. Hence by comparison with the observed pattern of sulfuration of hex-3-ene, where it was shown that negligible amounts of nitrogenous product are present, it is proposed that dialkenyl (tetrafunctional) polysulfidic crosslinks are initially introduced into the polybutadiene network. The polysulfidic crosslinks then presumably undergo desulfuration reactions leading to dialkenyl crosslinks of reduced sulfur chain length until the desulfurating agent is, in effect, removed from the system by the 2-thio-benzothiazole groups becoming combined in the network. Once most of these groups have combined, after ca. 60 min. at 140° C, the desulfuration reactions are probably less important than the reactions leading to vicinal crosslinking, and it is likely that a well cured-polybutadiene vulcanizate contains a substantial fraction of vicinal crosslinks.
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High-dispersed nano-ZnO were used for alternating ordinary ZnO in the vulcanization process of nature rubber. The properties of vulcanized natural rubber including the mechanical properties and anti-aging properties were investigated in this paper. The results showed that high-dispersed nano-ZnO made natural rubber the scorched time longer, the degrees of cross-linking higher and anti-aging properties remarkably stronger, compared with 99.5 % of ordinary ZnO under the same vulcanization conditions. Specially, when 0.8 dosages of high-dispersed nano-ZnO being used, the mechanical properties and anti-aging ability of natural rubber were best and better than that of 5 dosages of 99.5 % of ordinary ZnO in traditional formula. The reasons may be that high-dispersed nano-ZnO were completely resolved in rubber and can fully be contacted with the double bond of rubber molecules and the surface of sulfur so that they increased the efficiency of rubber vulcanization to improve the properties of natural rubber.
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Бұл зерттеужұмысындaКaно моделітурaлы жәнеоғaн қaтыстытолықмәліметберілгенжәнеуниверситетстуденттерінебaғыттaлғaн қолдaнбaлы (кейстік)зерттеужүргізілген.АхметЯссaуи университетініңстуденттеріүшін Кaно моделіқолдaнылғaн, олaрдың жоғaры білімберусaпaсынa қоятынмaңыздытaлaптaры, яғнисaпaлық қaжеттіліктері,олaрдың мaңыздылығытурaлы жәнесaпaлық қaжеттіліктерінеқaтыстыөз университетінқaлaй бaғaлaйтындығытурaлы сұрaқтaр қойылғaн. Осы зерттеудіңмaқсaты АхметЯсaуи университетіндетуризмменеджментіжәнеқaржы бaкaлaвриaт бaғдaрлaмaлaрыныңсaпaсынa қaтыстыстуденттердіңқaжеттіліктерінaнықтaу, студенттердіңқaнaғaттaну, қaнaғaттaнбaу дәрежелерінбелгілеу,білімберусaпaсын aнықтaу мен жетілдіружолдaрын тaлдaу болыптaбылaды. Осы мaқсaтқaжетуүшін, ең aлдыменКaно сaуaлнaмaсы түзіліп,116 студенткеқолдaнылдыжәнебілімберугежәнеоның сaпaсынa қaтыстыстуденттердіңтaлaптaры мен қaжеттіліктерітоптықжұмыстaрaрқылыaнықтaлды. Екіншіден,бұл aнықтaлғaн тaлaптaр мен қaжеттіліктерКaно бaғaлaу кестесіменжіктелді.Осылaйшa, сaпa тaлaптaры төрт сaнaтқa бөлінді:болуытиіс, бір өлшемді,тaртымдыжәнебейтaрaп.Соңындa,қaнaғaттaну мен қaнaғaттaнбaудың мәндеріесептелдіжәнестуденттердіңқaнaғaттaну мен қaнaғaттaнбaу деңгейлерінжоғaрылaту мен төмендетудеосытaлaптaр мен қaжеттіліктердіңрөліaйқын aнықтaлды.Түйінсөздер:сaпa, сaпaлық қaжеттіліктер,білімберусaпaсы, Кaно моделі.
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This chapter deals with the mechanisms and factors involved in the adhesion between unvulcanized rubber to vulcanized rubber and partially vulcanized rubber to vulcanized rubber. In the first case, the adhesion between the two symmetric or asymmetric rubber layers is dictated by the magnitude of the diffusing rubber chains across the interface mostly from the unvulcanized rubber layers. The diffusion of the elastomer chains from the unvulcanized portion into the vulcanized portion and subsequent crosslinking will help to stitch and repair the damaged vulcanized rubber layer. There are research papers which describe adhesion between vulcanized rubber and partially vulcanized rubber and adhesion between vulcanized rubber and unvulcanized rubber. The adhesion strength between surface-modified vulcanized EPDM rubber and unmodified natural rubber was studied by the 180° peel test.
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Abstract In their summary of the aging of vulcanized rubber, Porritt and Scott state that three factors are responsible for the changes in mechanical properties of vulcanized rubber during aging, viz.: (a) oxidation of the rubber; (b) after-vulcanization; (c) some colloidal change of the rubber, sometimes termed aggregation. Of these factors, oxidation is by far the most important because it is responsible for the decrease in mechanical properties, which leads to the general deterioration of rubber from a technical standpoint. It was Marzetti who proved that the decrease of mechanical properties in accelerated aging is due to oxidation. Later, Kohman confirmed this in a more concise way and showed that even such small amounts as 0.5% of oxygen absorbed by vulcanized rubber are sufficient to decrease tensile properties to 50% of their original value. When studying aging, three ways of tackling this problem are possible, viz.: (1) Investigations of the mechanical properties, either under normal conditions, or under special conditions such as elevated temperature or high speed. (2) Determination of oxidation products, which are formed during oxidation of the rubber. (3) Direct determination of the amount of oxygen which is absorbed by the rubber. It is clear that any of these methods may be combined with accelerated aging tests.
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The preparation of synthetic rubber with tensile strength identical to that of natural rubber is a long-standing unsolved problem in chemistry despite extensive related research. Here, we prepare synthetic rubber with tensile strength identical to that of natural rubber as a result of our discovery that natural rubber is a naturally occurring nanocomposite with proteins and lipids. The synthetic rubber is prepared by chemically attaching nanoparticles onto microparticles of synthetic cis-1,4-polyisoprene dispersed in water as a colloidal dispersion, followed by drying to form an "island-nanomatrix structure" similar to that of natural rubber. The stress at break of synthetic cis-1,4-polyisoprene increases dramatically from 0.1 to 3.9 MPa. The cis-1,4-polyisoprene with an island-nanomatrix structure exhibits almost the same mechanical properties as natural rubber. In addition, the synthetic cis-1,4-polyisoprene with an island-nanomatrix structure is vulcanized in the conventional manner using sulfur, zinc oxide, a vulcanization accelerator, and stearic acid at 150 °C and 15 MPa for an optimal vulcanization time after mechanical mixing. The stress at break of the resulting vulcanized cis-1,4-polyisoprene with an island-nanomatrix structure is 35.2 MPa, which is higher than that of vulcanized natural rubber. The preparation of synthetic rubber with mechanical properties identical to those of natural rubber is achieved by the formation of an island-nanomatrix structure in the synthetic rubber and is demonstrated by the mechanical properties of the vulcanized synthetic rubber being identical to those of vulcanized natural rubber.
Synthetic rubber
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