Mechanical Characterization of Rubber Latex-Based Carpets (Hevea bresiliensis): Influence of Rubber Latex Content and Fiber Fabrics (Cotton and Mosquito Nets) on Wear Resistance of Rubber Latex-Based Carpets

This work focuses on the development of carpets from sand, fabrics of cotton fiber and mosquito nets and rubber latex. Following a study on the choice of the best formulations, the quantity of rubber latex used for shaping varies between 14% and 18% (latex/sand + latex ratio) for the carpet with the fabric of mosquito nets and between 16% and 18% for the one made with the fabric of cotton fiber. Thus, with a mixture of sand, fiber fabrics (cotton and mosquito nets) and rubber latex, carpets were developed. In addition, the wear test carried out on these samples indicates that it is possible to produce carpets with the new material made of rubber sand and latex: SABLATEX At room temperature. Following the characterization test, it resorts to only 16% latex with cotton fiber fabric, allowing to have carpets with good mechanical characteristics.

STUDY ON THE PROPERTIES OF BLEND OF NATURAL RUBBER LATEX/METHYL METHACRYLATE GRAFTED RUBBER LATEX BY GAMMA RADIATION

Natural rubber latex （NRL） and methyl methacrylate （MMA） grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The tensile properties, swelling ratio and permanent set were measured. The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy. Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose. Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends. The decreasing trend of permanent set is high up to 5 kGy absorbed dose, and beyond that dose, it becomes almost flat.

Use of Alternative Binder: Influence of Latex Content on Physical and Mechanical Properties of Laterite Stabilized with Raw Rubber Latex

Raw rubber Latex contents, from 0% to 30% were used to stabilize lateritic samples to provide an alternative to cement stabilization. These samples were submitted to physical tests (water resistance test, absorption test) and mechanical tests (dry compressive strength test). The results indicate that samples made of latex content less than 15% dissolve completely into water. So it was impossible to make sample with these contents. Samples with 15% of raw rubber content or more are steady after water resistance test. The absorption rate of these samples decreases as the latex content increases. It goes from 14.45% for the samples at 15% to 5.87% for those at 30%. Therefore, the compressive strength test indicates that the resistance increases from 0.37 MPa for samples without latex to 3.15 MPa for those at 30% of latex content. Also, the rheological study shows that the samples pass from a brittle behaviour to a plastic behaviour when the latex content increases. The behaviour of the sample according to these different tests shows that this material can be used in several activity areas, such as construction, road building and sports area.

Modification of Natural Rubber Latex by Graft Copolymerization of 2-Ethylhexyl Acrylate and Methacrylic Acid

Natural rubber(NR)grafted with 2-ethylhexyl acrylate(2-EHA)and methacrylic acid(MAA,collectively NR-g-PEHA/MAA)was synthesized by emulsion polymerization.Tetraethylenepentamine and cumene hydroperoxide were used as redox initiators.The successful grafting of 2-EHA and MAA onto NR was confirmed by Fourier transform infrared spectroscopy.The morphology of the NR latex particles was observed by transmission electron microscopy.The effects of reaction temperature,initiator dosage,feeding mode,and hard monomer content on the mechanical properties of the modified NR film were investigated.Grafted polymer chains were unevenly wrapped on the outside of NR particles,and smaller particles were more easily grafted.Crosslinking was characterized using a toluene swelling method.Thermal stability and glass transition temperature were examined by differential scanning calorimetry and thermogravimetric analysis.The results showed that the thermal stability of NR-g-PEHA/MAA had been improved,and the glass transition temperature(Tg)was unchanged.

Reinforcement of natural rubber latex with silica modified by cerium oxide:preparation and properties

Variable masses of nano cerium oxide (CeO2) were added into nano silica (SiO2) to prepare the well-dispersed SiO2-CeO2 suspension (SiO2-CeO2), cetyltrimethyl ammonium bromide (CTAB) was used to adjust the compatibility of SiO2-CeO2 with rubber matrix, then SiO2-CeO2 modified by CTAB and curing formulas were mixed with fresh natural rubber (NR) latex to prepare NR/SiO2-CeO2 nanocomposites that contained 0–10 parts of CeO2 by a new emulsion compounding method. The morphologies, cure characteristics, mechanical properties and thermal-oxidative stability of NR/SiO2-CeO2 nanocomposites were investigated. The re-sults revealed that the presence of CeO2 in NR/SiO2-CeO2nanocomposites was favorable for enhancing the interaction between NR matrix and fillers, helped to get smaller SiO2-CeO2 particles with narrower particle size distribution, further improved the crosslink densities and mechanical properties of NR/SiO2-CeO2 nanocomposites vulcanizates. Meanwhile, the addition of CeO2 increased the active energy at least 4.66%, obviously improved the thermal-oxidative aging-inhibiting properties of NR/SiO2-CeO2 nanocomposites. Additionally, nanocomposites containing CeO2 promotedTg shift to high temperature direction, causing the nanocomposites featured higher tanδ at 0 oC and lower tanδ at 60 oC and exhibited comparable wet grip and lower rolling resistance when NR/SiO2-CeO2nano-composites were used in tire tread compound.

Permittivity models for determination of moisture content in Hevea Rubber Latex

The commercial open-ended coaxial probe(Agilent 85070E)is the most commonly used sensor to determine the permittivity of wet materials.This paper extends the usability and applicability of the sensor to the estimation of moisture content in Hevea Rubber Latex.The dielectric constant and loss factor were measured using the commercial probe whilst the moisture contents were obtained using the standard oven drying method.Comparison results were obtained between the different dielectric models to predict moisture content in latex.Both the dielectric constant and the loss factor of rubber latex linearly increased with moisture content at all selected frequencies.Calibration equations were established to relate both the dielectric constant and the loss factor with moisture content.These equations were used to predict moisture content in Hevea latex from measured values of the dielectric constant and the loss factor.The lowest mean relative error between actual and predicted moisture contents was 0.02 at 1 GHz when using the Cole-Cole dielectric constant calibration equation.

Preparation and Characterization of Natural Rubber/Silica Nanocomposites using Rule of Similarity in Latex

Rule of similarity and latex compounding techniques were combined for the first time to prepare natural rubber/nanosilica （NR/SiO2） nanocomposite with core-shell nanosilica-poly （methyl methacrylate） （SiO2-PMMA） particles and PMMA-modified natural rubber matrix （NR-PMMA）. The micro- structure of SiO2 and nanocomposites with different SiO2 contents was characterized by fourier transform infrared spectroscopy （FTIR）; the morphology of nanocomposites was investigated with scanning electron microscopy （SEM）; the tensile strength was characterized by tensile testing machine and the thermal stability of composites was studied by thermal gravimetric analysis. Results showed that PMMA chains have successfully grafted onto the surface of SiO2, and the core-shell SiO2-PMMA nanoparticles and NR-PMMA latex have been perfectly incorporated. SiO2-PMMA nanoparticles are evenly distributed over the NR matrix with an average size in the range of 60-100 nm at the low content （SiO2≤ 3 wt%）, while aggregations are apparently observed when 5 wt% SiO2 is loaded. In addition, NP/SiO2 composities possess a considerable improvement in ageing resistance compared with the pure NR. The tensile strength of composite increases from 6.99 to 12.72 MPa, reaching the highest value at a 0.5 wt% SiO2 loading, and then the figure decreases gradually because of the aggregation of SiO2 nanoparticles. It is anticipated that the reported process is to provide a simple and economic way for preparing NR composites.

搅拌工艺对高掺量丁苯乳液改性硫铝酸盐水泥性能的影响

研究了搅拌速度与搅拌时间对高掺量丁苯乳液改性硫铝酸盐水泥砂浆的匀质性、含气量、流变性能、早期强度等宏观性能的影响,采用TGA、BET等微观手段研究了硬化砂浆的水化程度和孔隙特征。结果表明:延长搅拌时间、提高搅拌速率均可改善砂浆的匀质性和力学强度。但以176 r/min搅拌时,延长搅拌时间会提高新拌砂浆含气量,增大硬化砂浆“凝胶孔”含量,抑制水泥前1 h的水化。以108 r/min搅拌时,延长搅拌时间则促进水泥前1 h的水化。延长搅拌时间和提升搅拌速率阻碍砂浆絮凝,破坏水泥颗粒桥接,显著降低结构构筑速率。延长搅拌时间,砂浆屈服应力和塑性黏度降低。优化搅拌工艺,有助于为充填层修补砂浆的搅拌规范制定提供重要参数。

鲜胶乳熟化时间对天然橡胶组成及性能的影响

采用复合保存剂HY/NH 3保存鲜胶乳1~5 d,定期取样凝固制备成天然生胶,以胶乳熟化时间为1 d的样品作对照样,探究鲜胶乳熟化时间对天然橡胶组成、性能的影响。分别采用红外光谱仪、核磁共振交联密度仪、拉力试验机等仪器对天然橡胶进行表征。结果表明,鲜胶乳熟化可以减少天然生胶中杂质、灰分、挥发物的含量,提高塑性保持率及交联密度;混炼胶的焦烧时间、正硫化时间、扭矩差值以及硫化胶的拉伸强度、撕裂强度、定伸应力等均有提高;胶乳熟化3 d制备的天然橡胶综合性能最好,其硫化胶的拉伸强度、撕裂强度分别达到20.47 MPa、30.38 kN/m,比对照样提高了3.5%和7.0%。

硫酮衍生物LS对天然胶乳保存效果的研究

天然胶乳很容易腐败变质,而当前的高氨保存体系存在严重的污染问题。本研究采用硫酮衍生物LS保存天然胶乳,研究保存剂LS对天然胶乳的保存效果。结果表明:LS保存的鲜胶乳挥发脂肪酸值(VFA No.)和黏度值均比较低,当LS用量为0.1%时,对鲜胶乳的保存效果优于0.25%氨;采用LS-氨复合保存制备低氨浓缩胶乳,当LS用量为0.01%~0.05%时可稳定保存浓缩胶乳达180d之久;所保存的低氨浓缩胶乳挥发脂肪酸值(VFANo.)较低,稳定性良好,各项指标均满足当前生产应用需求。此外,LS-氨复合保存低氨浓缩胶乳具有优异的理化性能和成膜性能,硫化胶膜的拉伸强度和撕裂强度普遍优于当前高氨保存浓缩胶乳。通过红外吸收光谱分析,LS-氨复合保存的低氨浓缩胶乳硫化胶膜的结构无明显变化;热分析结果表明,硫化胶膜热稳定性与高氨浓缩胶乳胶膜基本一致。此外,安全性分析结果表明,LS-氨复合保存低氨浓缩胶乳干胶膜不具有潜在毒性影响;同时无皮肤刺激性反应,安全性良好。硫酮衍生物LS对天然胶乳具有优异的保存效果,复合保存制备低氨浓缩胶乳性能良好,可用于多种纯胶制品的生产,同时使用成本低廉,具有广阔的应用前景。

天然胶乳/丁基胶乳并用胶乳的性能研究

采用完全随机化试验方法,研究天然胶乳/丁基胶乳并用比和硫化强化包用量(以干量计)对并用胶乳及其硫化胶膜性能的影响。结果表明:并用胶乳的粘度随着停放时间的延长而逐渐增大;并用胶乳硫化胶膜的气密性随着丁基胶乳占比的增大而呈提高趋势;当天然胶乳用量为100份、丁基胶乳用量为5.42份、硫化强化包用量为2.65份时,并用胶乳硫化胶膜的拉伸强度可达到24 MPa左右。

白炭黑补强天然胶乳胶膜性能的提升研究

采用白炭黑对天然胶乳胶膜补强,并通过正交试验研究硫黄、促进剂PX、碳酸锌、白炭黑用量对硫化胶膜物理性能的影响。结果表明:以硫化胶膜的拉伸强度为考察指标,4个因子的影响从大到小依次为促进剂PX、白炭黑、碳酸锌、硫黄,优化用量为促进剂PX0.9份、白炭黑1.11份、碳酸锌0.6份、硫黄1份,相应配方硫化胶膜的拉伸强度可达到31.37 MPa;以硫化胶膜的撕裂强度为考察指标,4个因子的影响从大到小依次为白炭黑、促进剂PX、硫黄、碳酸锌,优化用量为白炭黑1.31份、促进剂PX0.7份、硫黄1.25份、碳酸锌0.5份,相应配方硫化胶膜的撕裂强度可达到65 kN·m^(-1)。

植物激素调控橡胶树产排胶机制研究进展

巴西橡胶树(Hevea brasiliensis)是重要热带经济作物之一,其次生代谢产物天然橡胶(NR)是中国重要的工业原料及战略物资。植物激素对植物生长发育、萌发和环境应答等多方面均具有重要调控作用。本文详细介绍了乙烯、脱落酸、油菜素内酯和赤霉素4种植物激素在橡胶树生长发育、橡胶生物合成、产排胶和品质形成等关键环节中应用的研究进展,并展望4种激素在提高橡胶树产排胶机制研究中的应用前景,为支撑橡胶产业发展提供理论支撑。

鲜胶乳稀释浓度对酶凝固天然橡胶组成及性能的影响

采用碱性蛋白酶凝固稀释浓度为34%,25%,20%,17%的鲜胶乳,制备天然橡胶样品,探究鲜胶乳稀释浓度对酶凝固天然橡胶组成及性能的影响。分别采用无转子流变仪、橡胶加工分析仪、拉力试验机等仪器来表征天然橡胶的性能。结果表明,随着鲜胶乳稀释浓度的降低,天然生胶的塑性初值(P_(0))先升高后降低,而塑性保持率(PRI)则相反;其氮含量、丙酮溶物含量及分子链支化度逐渐降低;混炼胶的焦烧时间(t_(10))、正硫化时间(t_(90))分别增加了19.05%,5.62%,而扭矩差则逐渐降低;硫化胶的拉伸强度、撕裂强度、定伸应力等略有降低,而扯断伸长率略有增加。

双组分快速固化可剥离放射性去污剂性能调控及固化机理

针对现有的水系可剥离放射性去污剂成膜固化时间长的不足,以氯丁胶乳(CRL)作为主要成膜材料,采用无机盐组分溶液对CRL/PU(聚氨酯)复合乳液进行诱导破乳的方法,设计并制备了一种双组分快速固化可剥离放射性去污剂。考察了不同CRL/PU质量比、无机盐破乳剂的种类及含量对去污剂固化成膜时间和膜体力学性能的影响,获得了双组分快速固化可剥离去污剂最佳制备工艺,并对其快速固化机理进行了探讨,同时讨论了不同施工工艺对去污剂快速固化性能的影响,为相关涉核场所表面放射性污染物的快速去除提供了技术支撑。

水性环氧-SBR乳化沥青微表处混合料路用性能研究

以水性环氧树脂(WER)和丁苯(SBR)胶乳为乳化沥青改性剂,制备水性环氧-SBR乳化沥青(WESEA),采用蒸发残留物三大指标、旋转黏度、水煮法、湿轮磨耗试验、冻融循环试验、轮辙变形试验,探究水性环氧掺量对WESEA胶结料及其微表处混合料路用性能的影响。结果表明:WESEA胶结料高温性能、黏度与黏附性均随着水性环氧掺量增加而提升;当水性环氧掺量为10%时,WESEA微表处混合料1h湿轮磨耗值、6d湿轮磨耗值分别较SBR改性乳化沥青微表处混合料降低50.2%、44.0%,宽度变形率降低了41.8%;WESEA微表处混合料的耐磨性、抗水损能力以及抗车辙性能均优于SBR改性乳化沥青微表处混合料。

Incorporation of Clay into Natural Rubber (Hevea) for the Production of Tile Adhesive

Natural rubber latex is the white liquid in the form of the colloidal dispersion of rubber globules suspended in the aqueous liquid. Produced in large quantities in Ivory Coast, the local transformation of natural latex has so far remained insignificant, although some attempts have been made to use it in the manufacture of flexible facade briquettes for rounded walls. Thus, this study aims to incorporate clay as a filler in natural latex for use as an adhesive for tile installation. To do this, different proportions of clay paste were added to the natural latex and the resulting mixtures were used to make the sample and tile adhesive. From the analysis of the results obtained, it appears that the samples with a clay paste density of 0.8 and 1 absorb less water and shows good pull-out strength. The mixtures of 30% and 35% latex and 0.8 and 1 clay paste density respectively have pullout stresses greater than 1 N/mm2. According to NF EN 1348, these adhesives can therefore be used as tile adhesive.

高掺量丁苯乳液改性硫铝酸盐水泥的早期性能

研究了丁苯(SBR)乳液掺量对硫铝酸盐水泥流变性能、水化放热及水化产物的影响.结果表明,当SBR乳液掺量超过20%时,硫铝酸盐水泥净浆的固含量增大,聚合物加速聚集黏附,增加了净浆的屈服应力和塑性黏度,缩短了净浆的凝结时间并增大了浆体的水化放热,钙矾石随着SBR乳液掺量的增大逐渐增多,促进了硫铝酸盐水泥的早期水化进程.

碳纳米管与丁苯胶乳提升聚合物水泥砂浆力学和阻尼性能的研究

将碳纳米管(CNTs)均匀分散到羧基丁苯胶乳(XSBRL)中形成混合液,并制备聚合物改性水泥砂浆(CLMM)。通过静、动态力学性能试验及微观试验,探讨了碳纳米管与丁苯胶乳对CLMM的力学和阻尼性能提升的影响及机理。结果表明:与普通水泥砂浆相比,碳纳米管与丁苯胶乳复掺提升了CLMM的基本力学性能;损耗因子随频率和温度的变化而变化,且在20℃、1.5 Hz条件下,聚灰比和碳灰比分别为15%和0.05%时,损耗因子提升至普通水泥砂浆的14倍;均匀分散的碳纳米管-丁苯胶乳形成了三维网络结构,填充并优化了水泥砂浆基体的孔隙结构,可同时提升CLMM的力学和阻尼性能。

Structure and Properties of Self-assembled Narural Rubber/Multi-walled Carbon Nanotube Composites

Natural rubber （NR）/multi-walled carbon nanotube （MWCNTs） composites were prepared by combining self-assembly and latex compounding techniques.The acid-treated MWCNTs （H2SO4：HNO3=3：1,volume ratio） were self-assembled with poly （diallyldimethylammonium chloride） （PDDA） through electrostatic adhesion.In the second assembling,NR/MWCNTs composites were developed by mixing MWCNTs/PDDA solution with NR latex.The results show that MWCNTs are homogenously distributed throughout the NR matrix as single tube and present a great interfacial adhesion with NR phase when MWCNTs contents are less than 3 wt%.Moreover,the addition of the MWCNTs brings about the remarkable enhancement in tensile strength and crosslink density compared with the NR host,and the data peak at 2 wt% MWCNTs loadings.When more MWCNTs are loaded,aggregations of MWCNTs are gradually generated,and the tensile strength and crosslink both decrease to a certain extent.