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     

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。     

Effect of temperature on sulfur prevulcanization of natural rubber latex

Sulfur prevulcanization of natural rubber latex was conducted at 60, 70, 80, and 90°C for different periods. The extent of crosslinking was assessed. Tensile properties, water absorption, leaching, and stress-relaxation characteristics of the films were also evaluated. The volume fraction of rubber (Vr), which is a measure of crosslink density of the films, showed a maximum when prevulcanization was conducted at 80°C for 2 h or at 90°C for 1 h. At lower temperatures, the rate of reaction was slow. At each temperature, tensile strength and elongation at break decreased when the prevulcanization time increased, whereas the modulus increased up to a maximum crosslinking and thereafter decreased. Water absorption and leaching were more rapid in prevulcanized film than in postvulcanized film. The rate of stress relaxation slightly increased as the extent of prevulcanization increased. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1913–1920, 1997     

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     

热裂解气相色谱法测定天然胶乳中的干胶含量

研究热裂解气相色谱法测定天然胶乳中的干胶含量。试验结果表明,干胶含量与裂解主要产物峰面积呈现良好的线性关系,采用标准曲线法测定天然胶乳中的干胶含量,重复测定的相对标准偏差为0.14%,与国标法的平均相对误差为1.51%,定量分析结果准确,操作简便。     

Mechanical properties of thermoplastic elastomeric blends of chitosan and natural rubber latex

Thermoplastic chitosan/natural rubber blends (Cs/NR) were prepared from natural rubber latex and chitosan by solution casting technique. The blends were characterized by mechanical analysis (stress–strain) and the mechanical properties were found to vary with chitosan/natural rubber ratios. Experimental values were compared with different theoretical models. Effect of thermal aging on mechanical properties was also investigated. Dicumyl peroxide was used as the crosslinking agent. The effect of crosslinking on mechanical properties of Cs/NR has also been studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

改性氨基硅溶胶/天然乳胶膜材料的制备、结构及性能

采用阳离子乳化剂聚二烯丙基二甲基氯化铵(PDDA)对氨基硅溶胶进行改性制备改性氨基硅溶胶(MSS),然后将其与天然乳胶(NRL)进行杂凝聚制得MSS/NRL膜材料,分析了MSS,MSS/NRL膜材料的结构、粒径、Zeta电位及形态,考察了MSS/NRL膜材料的力学性能及耐紫外老化性能。结果表明,MSS与NRL共混后粒径较NRL增大;氨基硅溶胶经PDDA改性后呈弱正电性,能在杂凝聚共混环境下与带负电荷的乳胶粒子形成多层次核-壳结构;随着MSS添加量的增加,MSS/NRL膜材料的拉伸强度呈先增后减的趋势,当MSS质量分数为0.35%时,膜材料的拉伸强度达到21.98 MPa的最大值,扯断伸长率达到750%;MSS/NRL薄膜的耐紫外老化性能在老化12 h以后较NRL薄膜提高10%以上。     

Study on preparation of chlorinated natural rubber from latex and its thermal stability

The effects of pH value of reaction system, reaction time, and reaction temperature on the chlorination reaction in the preparation of chlorinated natural rubber (CNR) from natural rubber latex were discussed. It has been found from the thermal analysis that the thermal degradation of CNR in nitrogen is a one-step reaction, and 30% carbonide with a stable structure remained at 360 to 700°C; whereas the thermo-oxidative degradation of CNR in air is a multistep reaction, and the thermal degradation ratio reaches to 100% at 560°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2863–2867, 1999     

Preparation and thermal stability of brominated natural rubber from latex

The effects of pH value of reaction system, reaction time, reaction temperature, bromine concentration, and amount of potassium persulfate on the bromination reaction in the preparation of brominated natural rubber (BNR) from natural rubber latex were discussed. It has been found from the thermal analysis, that is, the thermal degradation of BNR in nitrogen is a two‐step reaction, and 16% carbonide with a stable structure remained at 470–650°C. The thermo‐oxidative degradation of BNR in air is also a two‐step reaction, and the percentage of degraded BNR reaches to nearly 100% at 600°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

三氯溴甲烷改性天然胶乳的研究

用三氯溴甲烷改性天然胶乳，研究了反应时间、反应温度、三氯溴甲烷的用量等对改性胶乳的硫化胶膜物理机械性能的影响，利用DSC对产物进行了分析。结果表明，反应时间为10h，反应温度在35℃时，所得胶膜物理机械性能较好；随着三氯溴甲烷用量的增加，改性天然胶乳的硫化胶膜物理机械性能下降：三氯溴甲烷改性天然胶乳的玻璃化温度高于未改性天然胶乳。     

用改性天然胶乳进行合成纤维橡胶基布浸胶处理的研究

介绍用环氧化改性天然胶乳进行涤纶、尼龙及维棉、涤棉等橡胶基布表面浸胶处理,并对处理布在制品中与橡胶的层间附着性能进行评价.     

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     

弱酸铵盐保存天然鲜胶乳的研究

通过对弱酸铵盐性质的分析，探索弱酸铵盐对鲜天然胶乳的保存效果及其性能的影响。实验结果表明，浓度越高的碳酸铵盐溶液的保存体系，其缓冲能力越大．越能很好地中和细菌代谢产生的脂肪酸．以防止天然胶乳的迅速凝固，保存效果越好。综合考虑经济和社会效益，碳酸铵可作为天然胶乳的保存剂，最佳质量分数为1．8％，其硫化胶力学性能得到部分改善，可以代替传统的氨水保存剂，降低污染，提高经济效益，改善工厂作业环境。     

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。     

Preparation of carbon black/natural rubber latex masterbatch in bead form

Carbon black/natural rubber latex masterbatch in the form of spherical beads was prepared according to the acid-precipitation method. High-loading carbon black (40 phr) was incorporated in natural rubber with the aid of a nonionic surfactant (Nonidet P40). Shearing the beads in an internal mixer provided good integration of carbon black in the rubber matrix and hence the high bound rubber content. Results confirmed the contribution of chemical interaction to the bound rubber content. By an oxidation process, the size of modified carbon black was reduced, whereas the large agglomeration took place in the case of partially graphitized carbon black. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 489–498, 2001     

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     

Processability characteristics and physico‐mechanical properties of natural rubber modified with rubber seed oil and epoxidized rubber seed oil

The processability characteristics and physico‐mechanical properties of natural rubber (NR) modified with raw rubber seed oil and epoxidized rubber seed oil have been studied. The modified mixes showed higher scorch time and lower cure rate, crosslink density, and ultimate state of cure compared to an unmodified mix. The thermal stability of the vulcanizates was practically unaffected by the modification. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1413–1418, 2000     

Effects of Sm3+/PMAA on mechanical and thermal properties of natural rubber latex film

Samarium carbonate [Sm₂(CO₃)₃] was taken as the source of Sm³⁺, and methyl acrylic acid (MAA) was employed as the precursor to prepare polymethacrylic acid (PMAA). The mixture of Sm₂(CO₃)₃ and PMAA was marked as “SmP.” The SmP prepared under different conditions was added to natural rubber (NR) latex to prepare NR/SmP films. The influence of the polymerization temperature of MAA and the amount of SmP on the mechanical properties and structure of NR/SmP films were analyzed. The results show that polymerization temperature has significant effect on the mechanical properties of NR/SmP film; lower temperature is benefit to improve modulus and rigidity, whereas higher temperature helps maintain good elasticity. Compared with neat NR, addition of 5-phr Sm₂(CO₃)₃ results in a 30%–37% increase of tensile strength. Furthermore, the glass transition temperature (T_g) can also be increased by the addition of SmP; and the tan δ curves of all samples exhibit only one transition peak and indicate no phase separation between SmP and NR matrix. The influence of SmP on the structure and morphology of NR was explored by Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy analysis; and the results show that SmP can be dispersed uniformly in the NR latex when loading of Sm₂(CO₃)₃ is lower than 20 phr.     

新型“胶乳法”氯化天然橡胶的研制

采用新型的"胶乳法"工艺制备氯化天然橡胶(CNR),不仅相对于传统的"溶液法"具有污染少、工艺简单、投资小、成本低等突出优点,而且解决了原"胶乳法"氯化过程橡胶分子交联严重的问题,是CNR的发展方向。介绍了该方法的反应机理、工艺流程、反应历程以及影响氯化反应的因素。研究结果表明:对现行工艺下低浓度胶乳法的氯化反应,可采用经验式预测不同相对反应时间的含氯量。根据氯含量随相对时间的变化规律,可以把反应过程分为2个阶段:高速期和低速期。在CNR氯化反应的第2阶段,反应温度的升高有利于氯含量提高,但温度过高,能量耗费过大,加上要考虑到反应的宏观动力学等因素,CNR氯化的第2阶段反应温度以343.15~353.15 K为宜。第2阶段表面活性剂平平加O的质量分数大于3%,天然胶乳的质量分数小于1%时,引发剂质量分数以0.5%~1%为宜。     

天然橡胶胶乳热稳定性测定方法

论述了几种天然橡胶胶乳热稳定性测定方法的特点及其在应用上存在的问题,指出了进一步研究胶乳热稳定性测定方法的必要性