Solvents for thermoporosimetry analysis of natural rubber networks

Thermoporosimetry is known as an analytical method to investigate network structures in swollen elastomers. Despite this interesting potential capability, only few investigations are published in literature which apply different solvents on differently crosslinked natural rubber samples. The choice of the solvent is critical as it strongly influences the separation of confined and bulk solvent transition signal, the confined solvent signal intensity and the peak width representing the pore size resolution. No critical comparison has been done in these investigations regarding the solvent choice related to peak separation, pore size resolution or signal intensity. Furthermore, no critical assessment is available relating thermoporosimetry results to solvent parameters to identify an optimal solvent regarding the mentioned criteria. This argument motivated the present investigation to identify the most appropriate solvents for the analysis of natural rubber compounds by thermoporosimetry. Different types of solvents (aliphatic, aromatic, non‐polar, and polar) were selected and benchmarked against each other. It was concluded that n‐heptane was identified as the best solvent for these investigations. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43998.     

Preparation and characterization of polyamide 6/liquid natural rubber blends

This study presents a new approach to toughen Polyamide 6 (PA6) by using a low‐molecular weight liquid natural rubber (LNR). The LNR is prepared by mastication of pale latex crepe in the presence of 0.5 phr Peptizol 7. The PA6/LNR blend samples are characterized in terms melt flow index, hardness, abrasion resistance, impact strength, flexural strength, tensile strength, and thermal properties. The impact strength of PA6 increases by about 67% upon addition of 10% LNR. The percolation model is applied to study of brittle to ductile transition. The percolation threshold for the brittle to ductile transition of the blend was found to be 14.5 wt % LNR, corresponding to the critical volume fraction of the stress volume, V_sc = 0.58, which is consistent with the calculated value of ≈ π/6. The PA6/LNR blends exhibit cavitation and matrix shear yielding, which would be the main contribution to the increases impact strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39750.     

差示扫描量热仪在橡胶配方研究中的应用

叙述了差示扫描热量热仪（DSC）在橡胶组分分析，橡胶配合剂的选择，橡胶的质量评价等橡胶配方中的应用。     

Physical properties of natural rubber/organoclay nanocomposites compatibilized with epoxidized natural rubber

Onium ion‐modified montmorillonite (organoclay) was melt compounded with natural rubber (NR) in an internal mixer and cured by using a conventional sulfuric system. Epoxidized natural rubber with 50 mol % epoxidation (ENR 50) was used in 10 parts per hundred rubber (phr) as a compatibilizer. The effect of organoclay with different filler loading up to 10 phr was studied. Cure characteristics were determined by a Monsanto MDR2000 rheometer, whereas the tensile, compression, and tear properties of the nanocomposites were measured according to the related ASTM standards. While the torque maximum and torque minimum increased slightly, both scorch time and cure time reduced with the incorporation of organoclay. The tensile strength, elongation at break, and tear properties went through a maximum (at about 2 phr) as a function of the organoclay content. As expected, the hardness, moduli at 100% (M100) and 300% elongations (M300) increased continuously with increasing organoclay loading. The compression set decreased with incorporation of organoclay. The dispersion of the organoclay in the NR stocks was investigated by X‐ray diffraction and transmission electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1083–1092, 2006     

A study about the structure of vulcanized natural rubber/styrene butadiene rubber blends and the glass transition behavior

A study of the thermal behavior of cured elastomeric blends of natural rubber (NR) and styrene butadiene rubber (SBR) prepared by solution blending in toluene is presented. Binary blends with different compositions of NR/SBR were produced using a conventional cure system based on sulfur and TBBS (n-t-butyl-2-benzothiazole sulfonamide as accelerator. The compounds were vulcanized at 433 K up to an optimum time of cure determined by rheometric tests. From swelling tests, the crosslink densities of the compounds were obtained and compared with those obtained in similar blends prepared by mechanical mixing. The results were analyzed in terms of the disentangling of the chain structures of the SBR and NR phases and the achieved cure state of the blend. Using differential scanning calorimetry, the glass transition temperature T_g of each blend was measured. In most compounds, the value of T_g corresponding to each phase of the blend was determined, but in some blends a single value of T_g was obtained. The variation of T_g with the composition and cure level in each phase was analyzed. On the other hand, a physical mixture of two equal parts of NR and SBR vulcanized was measured and the results were compared to those of the NR50/SBR50 cured blend. Besides, to analyze the influence of the network structure, pure NR and SBR unvulcanized samples were measured. On the basis of all the obtained results, the influence of the interphase formed in the blend between SBR and NR phases is discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

PET树脂的DSC研究

使用差示扫描式量热法(DSC)研究了6种不同产地的 PET 树脂的热力学性质.着重比较和讨论了它们的结晶性能以及试样热历史对树脂结晶性能的影响.并由此对树脂的可纺性进行了探讨.     

Confinement effects at nanoscale in natural rubber composites: Influence on macroscopic properties

The study of molecular level interactions in elastomer composites has got very scant attention even though a large number of studies are going on in this topic. This work embodies the understanding of confinement effects in natural rubber (NR)/ ZnO composites from micro to nano length scales, and their influence on macroscopic properties of the composites. The interactions between fillers and matrix are characterized from the Donth's approach, which allows estimating the cooperativity size N_α at the glass transition, N_α being directly related to the filler-matrix interactions. The improved properties of NR-nano ZnO composites can be attributed to microstructural and morphological changes due to nano ZnO in the NR matrix. A correlation between N_α, the constrained volume C_v and the thickness of immobilized polymer chains χ_m at the glass transition has also been established. Thus, this work proves that the Donth's approach is a powerful probe to estimate the enhance of mechanical properties in nanocomposites from calorimetric investigations.     

Effect of electron-beam irradiation on the thermal vulcanization of a natural rubber compound

The influence of electron-beam irradiation on the thermal vulcanization curing kinetics of a natural rubber compound was investigated by means of rheometric tests [moving die rheometry (MDR)] and differential scanning calorimetry (DSC). Differences in the storage moduli of compounds with different radiation doses were observed and assigned to a plasticizer effect by the zinc stearate mainly formed in the mixing stages; this compound migrated to the interphase region. This fact was confirmed by Fourier transform infrared spectroscopy. From the measurements performed by MDR and DSC testing, the induction time (t_o) was analyzed in the frame of the Claxton–Liska model, whereas the kinetic behavior of the nonirradiated and pre-irradiated compounds were satisfactorily fitted with the Isayev–Deng and Kamal–Ryan models. Additionally, both curing characterization techniques corroborated the fact that the pre-irradiated rubber compound showed an earlier t _o and a lower activation energy in comparison with the nonirradiated compound. These facts were attributed to the effect of irradiation on the free sulfur content present in the rubber compound, which promoted more activated precursor species to crosslink with rubber. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47216.     

Epoxidized natural rubber toughened poly(lactic acid)/halloysite nanocomposites with high activation energy of water diffusion

Poly(lactic acid)/halloysite nanotube (PLA/HNT) nanocomposites were prepared using melt compounding followed by compression molding. Epoxidized natural rubber (ENR) was used to toughen the PLA nanocomposites. The properties of PLA/HNT nanocomposites were characterized by impact tests, thermal analysis (DSC), morphological analysis (FESEM, TEM), and Fourier transform infrared spectroscopy (FTIR). Water absorption tests were performed at three immersion temperature (30, 40, 50°C). The maximum water absorption (M_m), diffusion coefficient (D), and the activation energy of water diffusion (E_a) were determined. The impact strength of PLA/HNT6 nanocomposites was increased significantly to ～296% by the addition of 15 wt % ENR. The incorporation of HNT and ENR increase its nucleation effect and assist in the crystallization process of PLA. The HNT has good affinity with PLA and ENR, which was revealed by TEM and FTIR. The M_m of PLA was increased in the presence of HNT and ENR. Nevertheless, the D value and the E_a of the PLA nanocomposites were found to be affected by the HNT and ENR contents. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42850.     

Effects of methylene diphenyl diisocyanate on the physical,mechanical, and vulcanization properties of nitrile rubber

In this research, methylene diphenyl diisocyanate (MDI) was added to an acrylonitrile–butadiene rubber (NBR) compound as an additive, and its effects on the vulcanization of the rubber investigated. For this purpose, MDI was added at different concentrations (5, 10, and 20 phr) to the rubber compound. The rubber properties, including the rheometry and tensile strength, were investigated. Differential scanning calorimetry and swelling tests were used to assess the vulcanization mechanism and chemical reactions in the presence of MDI. Finally, Fourier transform infrared spectroscopy analysis was used to study the chemical structure of the NBR–MDI cured compounds. We found that MDI played a more important role than the additive in the NBR compound. It acted as a covulcanizing agent along with the sulfur groups. The 10 phr MDI content was found to be the optimum content for achieving the best NBR–MDI properties. This content increased the crosslinking density of the compound and decreased the swelling of NBR in toluene. We also found that MDI adsorbed the accelerator agents and sulfur groups, so it decreased the rate of vulcanization, especially at early ages. Furthermore, it reacted with NBR and produced strong urea (i.e., NH? CO? NH) and thiourethane groups (i.e., S? CO? NH), and this increased NBR's structural strength. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45200.     

Comparative d.s.c. studies of the crystallization of natural rubber and its synthetic analogues

A comparative d.s.c. crystallization study has shown that deproteinized natural rubber (DPNR) undergoes crystallization much more readily than synthetic analogues of 99% cis-1,4 purity. Acetone extracted DPNR is closer in behaviour to the synthetic materials whereas, the latter, when doped with 1% w/w stearic acid or rubber extract approach the crystallization character of DPNR. The differences in crystallization behaviour are thus largely, but not entirely, due to the presence of nucleating impurities in the natural product. Secondary rate effects may also be caused by slight differences in polymer microstructure or variation in molecular weight distribution. The maximum extent of crystallinity observed under the most favourable conditions approaches 40% for the DPNR samples as determined from the observed heat of fusion of the crystalline regions.     

Relations between Wallace plasticity and Mw for natural rubber

Wallace plasticity and the weight‐average molar mass (M_w) were measured on natural rubber samples of different origins. A sigmoidal model describes the relations between Wallace plasticity and M_w (0.872 > r² > 0.992) for given families of samples. The families of samples analyzed differed through their clonal origin, collection method (cup lumps or latex), and type of processing (CV or non‐CV). This study showed that two samples of natural rubber can be identical in terms of plasticity, but very different in terms of the average polyisoprene chain length or M_w. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3078–3087, 1999     

Ozonolysis of model olefins—Efficiency of antiozonants

In this study, the efficiency of several potential long lasting antiozonants was studied by ozonolysis of model olefins. 2‐Methyl‐2‐pentene was selected as a model for natural rubber (NR) and 5‐phenyl‐2‐hexene as a model for styrene butadiene rubber (SBR). A comparison was made between the efficiency of conventional antiozonants like N‐(1,3 dimethylbutyl)‐N′‐phenyl‐p‐phenylene diamine (6PPD), N‐isopropyl‐N′‐phenyl‐p‐phenylene diamine (IPPD), and a mixture of diaryl p‐phenylene diamines (Wingstay 100) and some newly synthesized antiozonants. The stearic acid salt of 6PPD (PPD‐C18), 2,4,6‐tris(4‐(phenylamino)phenyl)‐1,3–5‐triazinane (ADPAT), and 4‐pyrole diphenylamine (PDPA) showed a higher efficiency than the conventional antiozonants in both NR as well as SBR model system. Special attention was paid to the carboxylic acid salts of 6PPD such as PPD‐C18, which has shown good long‐term protection of passenger tire sidewall compounds. It was demonstrated that by varying the chain length, C7, C18, and C22, of the carboxylic acid part of the 6PPD salts, the ozone protection was not influenced under the selected test conditions. The 6PPD salts made from strong acids like succinic acid (SA) and methyl sulfonic acid (MSA) appeared to be less efficient than PPD‐C18. It was also investigated whether the reactions between ozone and the double bonds of the model rubber could be measured online by a spectroscopic technique. It was demonstrated that near infrared spectroscopy is a suitable technique to study these reactions. FT Raman looked also a promising technique because of the high response factor of double bonds. However, the addition of p‐phenylene diamines (PPDAs) to the sample solution resulted in a strong discoloration (dark brown) and therefore in a high fluorescence background signal. This technique can therefore not be used for the evaluation of staining antiozonants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 100: 853–866, 2006     

DSC测试条件对淀粉糊化测试结果的影响

利用差示扫描量热仪(DSC)研究了测试条件对淀粉糊化测试结果的影响,为淀粉糊化研究提供了参考.对DSC测试条件(平衡时间、样品量、升温速率、淀粉颗粒粒径、含水量)进行筛选,优化了测试条件.对优化测试条件进行重复性实验,得到t0、tp、△H的RSD分别为0.2％、0.26％、0.15％.结果表明该测试方法精密度高,重复性好.     

Role of lignin filler in stabilization of natural rubber–based composites

The stabilizing effect of a natural filler, sulfur‐free lignin, on the thermal degradation of natural rubber (NR) was examined. Lignin was incorporated into NR in amounts of 10–30 phr (parts per hundred parts of rubber). It was shown that the lignin preparation used improved the physicomechanical properties of the rubber vulcanizates. Thermogravimetric analysis and differential scanning calorimetry were used to study the thermal degradation of unfilled and lignin‐filled vulcanized natural rubber. Measurements were carried out under atmospheric conditions. It was revealed that lignin used as filler increased the resistance of NR vulcanizates to thermooxidative degradation in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1226–1231, 2007     

超细二氧化错的差示扫描量热法分析及物相表征

通过对由超临界干燥制得的超细ZrO₂及Y₂O₃含的ZrO₂超细的热分析和物相表征发现, 由超临界干燥法制得的ZrO₂含水量极微, 但含有较多的有机物, 这些有机物需在空气中在约450℃方可除去。ZrO₂及Y₂O₃-ZrO₂在差示扫描量热曲线上400~500℃间出现的放热峰对应其由无定型向四方晶系的转化。和惰性气氛相比, 空气气氛有利于这一晶化过程。在ZrO₂中添加微量Y₂O₃有利于稳定ZrO₂的四方晶系。     

丝胶-双醛普鲁兰糖复合物改性天然橡胶膜的研究

利用丝胶-双醛普鲁兰糖（SS-dia—PU）复合物补强天然橡胶（NR）,旨在改善其致密性,减小橡胶薄膜的孔径,以达到提高橡胶薄膜阻隔性能的目的。采用扫描电镜、粒径分析、差示扫描量热分析及乙醇透过性实验,对改性薄膜的相关性质进行了袁征。结果表明,当SS-dia-PU的固含量不超过0．3％（质量分数）时,可以改善NR膜的性能。     

BOPP专用料的DSC非等温行为研究

采用差示扫描量热仪研究了两种双向拉伸聚丙烯（BOPP）薄膜专用料在非等温条件下的熔融结晶特性。结果表明：BOPP非等温结晶过程中,随着冷却速率的增加,结晶峰温度降低,过冷度增加,总结晶时间和结晶最快时间缩短,结晶峰半高峰宽增大;在两种BOPP料中,B容易结晶,A的光学性能好。     

Characterization of recycled styrene butadiene rubber ground tire rubber: Combining X‐ray fluorescence,differential scanning calorimetry,and dynamical thermal analysis for quality control

Appraisal of the main rubber characterization techniques for styrene butadiene rubber (SBR) was performed on standard SBR samples as well as recycled ground tire rubber (GTR) from an industrial tire recycling facility, containing a blend of SBR and natural rubber. The aim of the work was to provide additional information relevant to quality control in the field of rubber recycling. Benchmark characterization of industrial samples by inductively coupled plasma optical emission spectrometry, atomic absorption spectrometry, solid‐state proton nuclear magnetic resonance, and elemental (CHNS) analysis are reported. X‐ray fluorescence spectrometry is shown to be rapid and quantitative for determining the zinc content in an industrial context. Thermogravimetric analysis, already used to determine carbon black and inorganic material content in rubbers and GTR, is recommended for determination of monomer weight ratios of SBR sources not containing other rubbers, but not for GTR. Differential scanning calorimetry (DSC) measurements of the glass‐transition show that changes in monomer ratio affect glass‐transition temperature values, and therefore, DSC can be used to detect changes in rubber composition from batch to batch. These results show that DSC and X‐ray fluorescence spectroscopy characterization techniques can be used for GTR and may lead to more thorough and rapid quality control procedures of these complex samples. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42692.     

应用DSC研究醋酸纤维生产中的混酸相变行为

应用差示扫描量热仪(DSC)测量了不同组分浓度下混酸的结晶点、熔融点及熔融焓,分析了不同组分浓度对混酸的结晶与熔融行为的影响。研究的结果为生产工艺改进提供了理论及数据支持。