淀粉纳米晶对天然胶乳性能的影响

将淀粉纳米晶作为天然胶乳的补强剂,研究其对天然胶乳的胶体性能及硫化胶膜的物机性能、耐水性和耐溶剂的影响。研究结果表明:将淀粉纳米晶加入天然胶乳后,胶乳的粘度变化不大,机械稳定度提高;硫化胶膜的物机性能明显提高,耐溶剂性提高,而耐水性降低。     

去蛋白质天然胶乳的配制

该文描述了一种将蛋白酶加到天然胶乳中。经熟成后离心脱除蛋白的方法。用此脱蛋白胶乳制成的乳胶手套柔软性极佳。     

Reinforcement of natural rubber latex film by ultrafine calcium carbonate

Using ultrafine calcium carbonate to reinforce natural rubber latex film, the effect of its content on latex properties such as surface tension, viscosity, mechanical stability, and heat stability and the physical properties of latex film before and after aging such as tear strength, modulus, and tensile strength were investigated. The results showed that the surface tension of natural rubber latex reinforced by ultrafine calcium carbonate only changed slightly; when the content of calcium carbonate was less than 20%, the change of viscosity was not obvious, but when the content was greater than 20%, the viscosity significantly lowered. Ultrafine calcium carbonate could effectively improve the tear strength, tensile strength, and modulus of the natural rubber latex film. The modulus increased with the increment of the calcium carbonate. When the content of calcium carbonate was less than 15%, the tear strength and tensile strength increased with the increments of calcium carbonate, but when the content was greater than 15%, the above‐mentioned properties decreased with the increment of calcium carbonate. By comprehensive consideration, the best reinforcing effect was obtained at a content of 15% ultrafine calcium carbonate. The particle diameters of calcium carbonate and their distribution in the calcium carbonate emulsion and in the rubber film were analyzed with SEM and a laser particle size tester, which showed that the distribution of calcium carbonate in the latex film was even and that it could effectively reinforce natural rubber latex film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 982–985, 2003     

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。     

砖红壤/天然胶乳复合胶膜的制备与性能研究

研究了砖红壤对天然胶乳的补强作用。将砖红壤原土中的细粒子制成悬浮液,加入预硫化天然胶乳中,制备砖红壤/天然胶乳复合胶膜,并分析胶膜的结构特性、力学性能和交联密度等。结果表明,砖红壤粒子在橡胶相中分散均匀,砖红壤细粒子对天然胶乳具有优异的补强效果,硫化胶膜的拉伸强度和撕裂强度均有大幅度的提高,这是由于砖红壤的加入能够促进橡胶的硫化,砖红壤中的氧化铁能够与橡胶分子链中的不饱和双键结合,提高了砖红壤在橡胶相中的分散性,使二者形成良好的界面结合。     

天然胶乳的氢化

以水合肼、双氧水和硼酸为催化体系,对天然胶乳进行非贵金属催化的原位母体加氢.并用核磁共振氢谱对氢化天然胶乳的结构进行表征.结果表明,氢化度随着硼酸用量的增加而增大,当硼酸/碳碳双键(摩尔比)达到0.25时,天然胶乳的加氢度接近60%;     

Studies on the curing behaviour and mechanical properties of styrene/methyl methacrylate grafted deproteinized natural rubber latex

The graft copolymerization of styrene/methyl methacrylate (MMA) onto deproteinized natural rubber (DPNR) latex was carried out using ammonium peroxy disulfate (N₂H₈O₈S₂) as the initiator. The presence of the grafted polystyrene (PS) and polymethyl methacrylate (PMMA) on the rubber backbone was confirmed by FTIR spectroscopy. The effects of monomer concentrations on curing characteristics and mechanical properties were studied. It was found that the cure time and scorch time were increased with increasing monomer concentration whereas the torque_max–min value was slightly decreased. It was also noted that the increase in the monomer concentration resulted in stiffer rubber with increased modulus and reduced elongation at break.     

Acetoacetoxy functionalized natural rubber latex capable of forming cross-linkable film under ambient conditions

This work demonstrates that natural rubber (NR) latex particles containing acetoacetoxy (AcAc) groups are able to undergo cross-linking upon film formation at ambient temperature by reaction with glutaraldehyde (GTA). Natural rubber latex grafted with poly(acetoacetoxyethyl methacrylate) (NR-g-PAAEM) was synthesized by seeded emulsion polymerization, using benzoyl peroxide (BPO) as an initiator in free radical polymerization. The degree of grafting of PAAEM in the graft copolymers was evaluated by ¹H NMR technique. Transmission electron microscope (TEM) was used for investigation the particle morphology of the grafted NR latex. Since the AcAc groups are intentionally attached to the NR particles providing sites of cross-linking at ambient temperature, the cross-linking ability of these sites by reaction with GTA was then investigated. The results revealed that the latex film of NR-g-PAAEM with the addition of GTA had a much higher tensile strength in comparison with the film without GTA. The surface morphology of the NR-g-PAAEM latex film formed in the absence and presence of the GTA cross-linker was also investigated using atomic force microscopy (AFM). By GTA addition into the NR-g-PAAEM latex before film formation, an increase in the root-mean-square (RMS) roughness of the surface of the latex film was observed. Moreover, it was also observed that the NR-g-PAAEM films with the addition of GTA had higher activation energy for thermal degradation than that without the cross-linker. This confirms that the cross-linking reaction took place in the NR-g-PAAEM latex film as a result of its reaction with the GTA.     

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     

The utilisation of latex reclaim rubber in natural rubber

Scrap latex products contain rubber hydrocarbon of very high quality, that is only slightly crosslinked. A novel economic technique for converting such latex waste into a processible material is developed. This paper reports the effect of adding this latex reclaim to natural rubber. It is shown that latex reclaim can replace raw natural rubber up to about 50 wt.-% without affecting mechanical properties.     

Beta dielectric dispersion in natural rubber latex

The dielectric dispersion of natural rubber latex has been investigated over a frequency range of 0.1–100 MHz and at six temperatures from 20° to 70°C. A computer analysis of the dispersion data showed that the Cole–Cole structural equation gave a better fit than the Debye. The large values of the Cole-Cole α spread parameter suggest heterogeneity of structure in rubber latex. The latex viscosity and the relaxation time were both found to be influenced by changes in temperature. Application of the Arrhenius temperature equation to the data yielded a mean activation enthalpy of 32.6 ± 2.8 kJ/mol for the relaxation process.     

Nanocapsules embedded in natural rubber latex gloves

To prepare medical gloves containing disinfectant agent, poly(methyl acrylate) (PMA) with _w of 550 K was synthesized via the iniferter technique and then used for encapsulating disinfectant agent, i.e., chlorhexidine digluconate (CHD), droplets. The CHD‐PMA nanocapsules suspended in a sodium dodecyl sulfate aqueous solution having 93% encapsulation efficiency were successfully embedded between the outermost and inner layers of γ‐radiation vulcanized natural rubber (RVNR) latex films by the coagulant dipping process. A RVNR/CHD‐PMA nanocapsules/RVNR three‐layer structure was revealed by the contact angle measurement, ATR‐FTIR and SEM. Both the tensile strength and elongation at break of the three‐layer film were also measured. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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。     

环保型促进剂二苄基二硫代氨基甲酸锌对天然胶乳硫化胶膜性能的影响

选择二苄基二硫代氨基甲酸锌(ZBDC)、二异丙基黄原聚硫、二硫化四苄基秋兰姆作为天然胶乳(NRL)的硫化促进剂,采用正交试验确定了NBL的硫化配方及最佳工艺,对比了促进剂ZBDC及传统促进剂二乙基二硫代氨基甲酸锌(ZDC)对NRL硫化胶膜性能的影响,考察了贮存时间对NRL硫化程度及硫化NRL黏度、机械稳定性的影响。结果表明,硫化NRL的最佳配方及工艺:促进剂ZBDC、硫黄、氧化锌用量分别为0.75,1.25,0.50份,硫化温度为70℃,硫化时间为2.5 h;随着促进剂ZBDC用量的增加,NRL硫化胶膜的交联密度逐渐增大,而300%定伸应力、500%定伸应力、700%定伸应力、拉伸强度均呈现先增大后减小的趋势;当促进剂ZBDC与ZDC并用时,硫化胶膜的300%定伸应力、500%定伸应力、700%定伸应力和交联密度都达到了最大值,但拉伸强度和撕裂强度比采用最优方案制得硫化胶膜小;随着促进剂ZBDC用量的增加,NRL硫化胶膜的耐老化性能先提高后又下降;无论ZDC与ZBDC并用还是单独使用,硫化胶膜的耐老化性能都较优;随着贮存时间的延长,无论是使用环保型促进剂ZBDC还是使用促进剂ZDC,NRL的硫化程度均增加,硫化NRL的黏度均逐渐增大,而机械稳定性先稍有提高后下降。     

Study on hot air aging and thermooxidative degradation of peroxide prevulcanized natural rubber latex film

The air‐aging process at 120°C and the thermooxidative degradation of peroxide prevulcanized natural rubber latex (PPVL) film were studied with FTIR and thermal gravity (TG) and differential thermal gravity (DTG) analysis, respectively. The result of FTIR shows that the ? OH and ? COOH absorption of the rubber molecules at IR spectrum 3600–3200 cm^?1, the ? C?O absorption at 1708 cm^?1, and the ? C? OH absorption of alcohol at 1105 and 1060 cm^?1 increased continuously with extension of the aging time, but the ? CH₃ absorption of saturated hydrocarbon at 2966 and 2868 cm^?1, the ? CH₃ absorption at 1447 and 1378 cm^?1, and the C?C absorption at 835 cm^?1 decreased gradually. The result of TG‐DTG shows that the thermal degradation reaction of PPVL film in air atmosphere is a two‐stage reaction. The reaction order (n) of the first stage of thermooxidation reaction is 1.5; the activation energy of reaction (E) increases linearly with the increment of the heating rate, and the apparent activation energy (E₀) is 191.6 kJ mol^?1. The temperature at 5% weight loss (T_0.05), the temperature at maximum rate of weight loss (T_p), and the temperature at final weight loss (T_f) in the first stage of degradation reaction move toward the high temperature side as the heating rate quickened. The weight loss rate increases significantly with increment of heating rate; the correlation between the weight loss rate (α_p) of DTG peak and the heating rate is not obvious. The weight loss rate in the first stage (α_f1) rises as the heating rate increases. The final weight loss rate in second stage (α_f2) has no reference to heating rate; the weight loss rate of the rubber film is 99.9% at that time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3196–3200, 2004     

纳米氧化锌对天然胶乳膜干燥及硫化性能影响研究

采用失重法和溶胀法研究了普通氧化锌和纳米氧化锌活化的天然胶乳膜的干燥动力学,以及干燥过程中胶乳膜交联密度变化.结果表明:天然胶乳厚胶膜在成膜后仍含有大量水分并且去除困难.纳米氧化锌活化胶膜的干燥速率明显高于普通氧化锌胶膜.干燥温度对干燥过程影响显著,干燥时间随干燥温度升高明显降低.随着干燥的进行,2种氧化锌活化的胶乳膜的交联密度均迅速上升,在相同条件下,纳米氧化锌活化胶乳膜交联密度均比普通氧化锌的大.纳米氧化锌对天然胶乳膜的干燥及硫化过程均有促进作用.     

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     

New evidence of the surface morphology of deproteinized natural rubber particles

Summary A new evidence of the morphology of deproteinized natural rubber (DPNR) latex particles, i.e., γ-radiation vulcanized-deproteinized NR (RV-DPNR) and deproteinized-γ-radiation vulcanized NR (DP-RVNR), was obtained by transmission electron microscopy (TEM). Micrographs of the rubber particles embedding in polystyrene, prepared by using a phase transfer/ bulk polymerization process, revealed the destruction of membrane layer surrounded the DPNR particles crosslinked by γ-ray (DP-RVNR). Received: 30 July 1998/Revised version: 17 September 1998/Accepted: 14 October 1998