天然胶乳的挥发脂肪酸值与电导率关系的探索

通过改变挥发脂肪酸含量、无机盐浓度、外界温度，探索天然胶乳的挥发脂肪酸值与电导率的关系。     

磷脂对浓缩天然胶乳机械稳定性的影响

在天然胶乳中添加磷脂,研究磷脂对天然胶乳机械稳定性的影响,结果表明,随着磷脂用量和氨含量的增加,天然胶乳的机械稳定度逐渐升高。气相色谱-质谱联用仪(GC-MS)分析表明,磷脂在碱性条件下水解产生亚油酸、棕榈酸、油酸、反油酸、硬脂酸、α-亚麻酸等长链脂肪酸,进一步与氨水反应形成脂肪酸铵,并吸附在橡胶烃粒子表面,提高了天然胶乳的机械稳定性。随着碱度的升高和水解时间的延长,磷脂水解产物的化学组成和含量存在一定差异。     

Novel nonammonia preservative for concentrated natural rubber latex

A derivative of sym‐triazine (HTT) was chosen as a new nonammonia preservative for concentrated natural rubber latex (CNRL) in place of NH₃–TT/zinc oxide (ZnO). The preservation effects of the HTT for CNRL, drying characteristics, mechanical properties, and cytotoxicity of the vulcanized natural rubber (NR) film were investigated. The results show that the CNRL was preserved steadily for more than 6 months with 0.3% HTT, and the volatile fatty acid number, viscosity, and mechanical stability of CNRL all met the requirements of ISO 2004:2010(E). The drying characteristics of the vulcanized NR film preserved by HTT retained no change compared with those of the film preserved by NH₃–TT/ZnO. The tensile strength and elongation at break of the vulcanized NR film preserved by HTT were 32.17 MPa and 853.80%, respectively; these were very similar to those of the film preserved by NH₃–TT/ZnO, whereas the tear strength reached 68.43 kN/m, and this was much higher than that by NH₃–TT/ZnO. The results of the cytotoxicity and dermal irritation tests prove that HTT is not especially harmful to humans. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41749.     

天然胶乳补强技术的进展

主要介绍了胶乳的炭黑补强、有机树脂补强和无机纳米粒子补强等补强技术的进展，分析了这几种补强技术对天然胶乳的补强效果。     

Modified graphite filled natural rubber composites with good thermal conductivity

The rubber composites with good thermal conductivity contribute to heat dissipation of tires. Graphite filled natural rubber composites were developed in this study to provide good thermal conductivity. Graphite was coated with polyacrylate polymerized by monomers including methyl methacrylate, n-butyl acrylate and acrylic acid. The ratios between a filler and acrylate polymerization emulsion and those between monomers were varied. Eight types of surface modification formulas were experimentally investigated. Modification formula can affect coating results and composite properties greatly. The best coating type was achieved by a ratio of 1:1 between methyl methacrylate and n-butyl acrylate. The coating of graphite was thermal y stable in a running tire. Filled with modified graphite, the tire thermal conductivity reached up to 0.517–0.569 W·m-1·K-1. In addition, the mechanical performance was improved with increased crosslink density, extended scorch time and short vulcanization time.     

The effects of potassium and rubidium hydroxide on the alkali-silica reaction

Expansion of mortar specimens prepared with an aggregate of mylonite from the Santa Rosa mylonite zone in southern California was studied to investigate the effect of different alkali ions on the alkali-silica reaction in concrete. The expansion tests indicate that mortar has a greater expansion when subjected to a sodium hydroxide bath than in a sodium-potassium-rubidium hydroxide bath. Electron probe microanalysis (EPMA) of mortar bars at early ages show that rubidium ions, used as tracer, were present throughout the sample by the third day of exposure. The analysis also shows a high concentration of rubidium in silica gel from mortar bars exposed to bath solutions containing rubidium. The results suggest that expansion of mortar bars using ASTM C 1260 does not depend on the diffusion of alkali ions. The results indicate that the expansion of alkali-silica gel depends on the type of alkali ions present. Alkali-silica gel containing rubidium shows a lower concentration of calcium, suggesting competition for the same sites.     

Electrical conductivity and mechanical properties of polyaniline/natural rubber composite fibers

Electrically conducting elastomer fibers based on natural rubber (NR) and up to 10% w/w polyaniline (PANI) in its emeraldine base (EB) form were fabricated by a wet spinning process. The resulting fibers at various PANI contents were doped by immersion in aqueous HCl solution, which converted the PANI to the electrically conductive emeraldine salt (ES) form. The morphology of the composite fibers was studied by scanning electron microscopy (SEM). PANI particles were inhomogeneously distributed in the NR matrix. The electrical conductivity of the fibers increased with the increasing PANI‐ES content and leveled off at a value of around 10^?3 S/cm at PANI‐ES concentration of 5% w/w. The fibers retained most of their elasticity upon doping, while the tenacity was somewhat reduced. Gratifyingly, the electrical conductivity of the new elastomer fibers was preserved upon elongational deformation, even if strains as large as 600% were applied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

胶乳法氯化天然橡胶干燥历程中脱氯化氢反应动力学

新型工艺胶乳法氯化天然橡胶(CNR)产品在干燥过程中会有HCl脱出,其脱出量对CNR的制备、性能等有一定的影响。采用电导法可连续测定CNR在干燥历程中脱HCl量及速率,这是研究CNR在低温下热降解行为的有效方法。用改进工艺的"胶乳法"制备出湿的CNR,并在一定温度下通入氮气进行干燥,在此历程中会发生脱氯化氢反应,其反应过程可分为诱导期、恒速期和低速期。文中使用Friedman法分析该过程在恒速期、低速期的反应动力学参数,其脱氯化氢反应分别为0级反应、1级反应,活化能分别为26.65,36.79 kJ/mol。在80℃以下对产品进行加热(或干燥),虽有少量HCl脱出,但并不会对产品质量造成影响。所以干燥温度应以低于80℃为宜。     

BCT-2无氨保存剂对浓缩天然胶乳保存效果及其性能的影响

研究了水溶性杀菌剂BCT-2保存浓缩天然胶乳的效果及对预硫化胶乳粘度、成膜特性、硫化胶膜干燥特性及力学性能的影响。结果表明,浓缩天然胶乳保存6个月以上的挥发性脂肪酸值最高为0. 048,要比GB/T 8289—2016的0. 06低,粘度和p H值也都符合应用的要求。预硫化胶乳的粘度在放置前6 d没有太大变化,不影响预硫化胶乳的基本性能,且成膜性能好;与传统高氨保存的硫化胶膜相比,BCT-2保存的硫化胶膜干燥时间短,干燥速率常数提高了5～6倍; BCT-2保存的硫化胶膜的拉伸强度变化不大,而撕裂强度为49. 31 k N/m。     

Oil resistance and physical properties of in situ epoxidized natural rubber from high ammonia concentrated latex

Epoxidized natural rubber (ENR) was prepared via in situ epoxidation from high ammonia concentrated natural rubber latex with formic acid and hydrogen peroxide in the presence of a surfactant at 50°C for 4, 8, and 12 h. The obtained ENRs containing 20, 45, and 65 mol % of expoxide groups were denoted ENR20, ENR45, and ENR65, respectively. The differential scanning calorimetric study revealed that they exhibited higher glass transition temperatures than that of natural rubber (?62.4°C), at ?38.2°C for ENR20, ?27.8°C for ENR45, and ?19.7°C for ENR 65. It was clearly seen that their glass transition temperatures increased as the amount of epoxide groups increased. The prepared ENRs were compounded and vulcanized to prepare test specimens for determination of oil resistance and various physical properties. It was found that the swelling of ENRs in oils was substantially less than that of natural rubber. The oil resistance of ENR65 was comparable to that of nitrile rubber, commonly used as oil resistant rubber. ENR65 also showed higher hardness than other ENRs. Contrarily, ENR20 possessed superior tensile strength and compression set when compared with other ENRs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3948–3955, 2006     

BCT-2无氨保存剂对浓缩天然胶乳保存效果及其性能的影响

研究了水溶性杀菌剂BCT-2保存浓缩天然胶乳的效果及对预硫化胶乳粘度、成膜特性、硫化胶膜干燥特性及力学性能的影响。结果表明,浓缩天然胶乳保存6个月以上的挥发性脂肪酸值最高为0. 048,要比GB/T 8289—2016的0. 06低,粘度和p H值也都符合应用的要求。预硫化胶乳的粘度在放置前6 d没有太大变化,不影响预硫化胶乳的基本性能,且成膜性能好;与传统高氨保存的硫化胶膜相比,BCT-2保存的硫化胶膜干燥时间短,干燥速率常数提高了5～6倍; BCT-2保存的硫化胶膜的拉伸强度变化不大,而撕裂强度为49. 31 k N/m。     

Noncatalytic hydrogenation of natural rubber latex

Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene‐based elastomers. Natural rubber latex (NRL) could be hydrogenated to a strictly alternating ethylene–propylene copolymer using diimide generated in an in situ system. The diimide generated using the in situ technique for hydrogenation of NRL was accomplished by thermolysis of p‐toluenesulfonyl hydrazide (TSH). A molar ratio of TSH to double bonds equal to 2 : 1 was found to be the optimum ratio to provide a high percentage of hydrogenation. 95% Degree of saturation of NRL was achieved in o‐xylene. Hydrogenated products are characterized by FTIR and NMR spectroscopy. The thermal stability of hydrogenated rubber was improved as shown from the results of thermogravimetric analysis. From the differential scanning calorimetry measurement, the glass transition temperature of the hydrogenated product did not appear to change. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2885–2895, 2007     

Diimide hydrogenation of natural rubber latex

Hydrogenation is one important method of chemical modification, which improves the physical, chemical and thermal properties of diene‐based elastomers. Natural rubber latex (NRL) could be hydrogenated to a strictly alternating ethylene‐propylene copolymer using a diimide reduction system. The diimide reduction technique of NRL was accomplished by using hydrazine hydrate/hydrogen peroxide and Cu²⁺ as catalyst. The hydrogenated products are characterized by FTIR and NMR spectroscopy. It has been found that cupric acetate is a highly active catalyst for the reaction and the addition of a controlled amount of gelatin demonstrated a beneficial effect on the degree of hydrogenation, whereas, sodium dodecyl sulfate (SDS) acted as a stabilizer of the latex particle in the reaction system and reduced the degree of hydrogenation. In the presence of SDS, a longer reaction time and a higher amount of hydrazine hydrate was required for hydrogenation of NRL. Gel formation during hydrogenation does not significantly affect the degree of hydrogenation. Gel inhibitors such as hydroquinone also decrease the degree of hydrogenation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of magnesium and phosphate ions on the stability of concentrated natural rubber latex and the properties of natural rubber latex–dipped products

The presence of Mg²⁺ ions was found to be a major cause of destabilization of natural rubber (NR) latex. On the other hand, the addition of excess PO ions to remove Mg²⁺ ions could adversely affect the physical properties of dipped products made of NR latex. A series of concentrated latex samples were treated with varying amounts of Mg²⁺ and PO ions. Changes with time in the characteristics of the treated latex samples such as mechanical stability time, volatile fatty acid number, and chemical stability time and in the physical properties of the dipped products such as aged and unaged tensile properties were monitored. The latex batch with a PO ion concentration of 30 ppm was found to produce the best‐quality latex and dipped products. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3120–3124, 2006     

聚丙烯酸酯改性石墨及其对天然橡胶导热性能的影响

采用聚丙烯酸酯改性石墨,然后将其填充到天然橡胶中,研究了改性石墨对复合材料导热性能和力学性能的影响。结果表明,石墨经聚丙烯酸酯改性后降低了自身的聚集作用,同时由于其被包覆,受力时更不易分层滑移;表面粗糙度的提高及有机基团的增多使得石墨与橡胶间的结合作用增强,同时促成了更多导热网链和"桥接"导热通道的形成,从而提高了其填充天然橡胶的热导率和力学性能。石墨在改性时软硬段单体的配比影响其包覆效果,进而影响其填充天然橡胶的导热和力学性能;当石墨与改性单体的质量比为10/1、软硬段单体的质量比接近1/1时,所改性石墨填充天然橡胶的热导率较高,综合力学性能较好。     

Thermal degradations of chlorinated natural rubber from latex and chlorinated natural rubber from solution

The thermal degradations of chlorinated natural rubbers from latex (CNR‐L) and from solution (CNR‐S) under nitrogen atmosphere were studied with thermogravimetric analysis (TGA). The thermal degradations of CNR‐L and CNR‐S are one‐step reaction. The shapes of the thermogravimetric and derivative thermogravimetric curves are similar. The degradation temperatures of CNR‐L and CNR‐S increase linearly with the increment of heating rates. The heating rate hardly affects the thermal degradation rates of CNR‐L and CNR‐S at the various degradation stages. The thermal degradations of CNR‐S and CNR‐L are dehydrochlonation reactions. The reaction activation energy (E) of CNR, at the first stage, is around 100 kJ/mol. After that, E remains relatively steady (80–140 kJ/mol). At the last stage, E rises rapidly (130–270 kJ/mol). The variation tendency of frequency factor (A) is similar to that of E. As the initial degradation temperature T₀ of CNR‐L is 10.9°C lower than that of CNR‐S, the thermal stability of CNR‐S is better than that of CNR‐L, which may be caused by the difference of molecular structure between CNR‐L and CNR‐S, as FTIR results indicate that there are more ? OH, ? C?O and ? COO? groups in the CNR‐L molecular chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermal conductivity of natural rubber nanocomposites with hybrid fillers

Natural rubber nanocomposites filled with hybrid fillers of multi-walled carbon nanotubes(CNTs) and carbon black(CB) were prepared. CNTs were ultrasonically modified in mixture of hydrogen peroxide(H_2O_2) and distilled water(H_2O). The functional groups on the surface of CNTs, changes in nanotube structure and morphology were characterized by Fourier transform infrared spectroscopy(FT-IR), Raman Spectroscopy, and transmission electron microscopy(TEM). It shows that hydroxyl(OH·) is successfully introduced. The surface defects of modified CNTs were obviously higher than those of original CNTs, and the degree of agglomeration was greatly reduced. Thermal conductivity of the composites was tested by protection heat flow meter method. Compared with unmodified CNTs/CB filling system, the thermal conductivity of hybrid composites is improved by an average of 5.8% with 1.5 phr(phr is parts per hundred rubber) of hydroxyl CNTs and 40 phr of CB filled. A three-dimensional heat conduction network composed of hydroxyl CNTs and CB, as observed by TEM, contributes to the good properties. Thermal conductivity of the hybrid composites increases as temperature rises. The mechanical properties of hybrid composites are also good with hydroxyl CNTs filled nanocomposites; the tensile strength, 100% and 300% tensile stress are improved by 10.1%, 22.4% and 26.2% respectively.     

Development of biodegradable natural rubber latex composites by employing corn derivative bio-fillers

This study aims to investigate the viability of employing corn-based fillers (powdered corn grain [CG], corn flour [CF] and cornstarch [CS]) to improve the biodegradability of natural rubber latex (NRL) composites by varying filler loading from 0 to 50 phr. Notable variation in both physical and mechanical properties were observed for the different filler types, with CG-filled NRL demonstrating the better adhesion with NRL. Thus, CG-filled composites were selected for investigation of biodegradability. Increased CG loading in NRL compounds enhanced biodegradation; with over 70% degradation observed for 50 phr CG loading upon 15 weeks of soil burial. However, the trade-off between mechanical properties and biodegradability limits the CG loading in the NRL matrix to 20 phr for manufacturing NRL-based products. It was observed that NRL with CG filler loading of 20 phr conforms to the ASTM D3578 standard for manufacturing rubber gloves; with 50% biodegradation upon 15 weeks of soil burial.     

Use of sodium and potassium butyl xanthate as accelerator for room temperature prevulcanization of natural rubber latex

Sodium and potassium butyl xanthates (Nabxt and Kbxt) were prepared in the laboratory. Characterization of these xanthates were done using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (¹H NMR) spectroscopy, thermogravimetric analysis (TGA), and differential thermal analysis (DTA) techniques. These xanthates were used as accelerators for the prevulcanization of natural rubber latex (NRL) at room temperature. Optimization of prevulcanization time was done. Films were casted from these prevulcanized NRL. Tensile properties of latex vulcanisates were measured and potassium butyl xanthate gave superior properties to the NRL films compared with sodium butyl xanthate. Effect of thermal ageing on tensile properties of these prevulcanized NRL films was also investigated and these properties were found to be improved after thermal ageing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

环氧化天然胶乳/天然胶乳并用提高探空气球胶膜气密性的研究

为了提高探空气球的气密性,采用25%,40%和50%3种不同环氧化程度的环氧化天然胶料(ENRL)与天然胶料(NRL)并用制备硫化胶膜,研究了ENRL环氧化程度和用量对硫化胶膜气密性、物理力学性能以及并用胶乳的黏度、稳定性的影响。结果表明,并用胶乳硫化胶膜的气密性会随着ENRL环氧化程度和用量的提高而提高,相应的气球体积保持率也会大大提高;此外,并用胶乳热稳定性良好,但ENRL用量和环氧化程度较高时机械稳定性较差,黏度值也较高;ENRL用量较低时,能在一定程度上提高硫化胶膜的拉伸强度、撕裂强度和定伸应力;ENRL用量较高时会明显降低胶膜硬度,断裂伸长率也会有所提高。