Industrial SBR Process: Computer Simulation Study for Online Estimation of Steady‐State Variables Using Neural Networks

This work investigates the industrial production of styrene‐butadiene rubber in a continuous reactor train, and proposes a soft sensor for online monitoring of several processes and polymer quality variables in each reactor. The soft sensor includes two independent artificial neural networks (ANN). The first ANN estimates monomer conversion, solid content, polymer production, average particle diameter, and average copolymer composition; the second ANN estimates average molecular weights and average branching degrees. The required ANN inputs are: (i) the reagent feed rates into the first reactor and (ii) the reaction heat rate in each reactor. The proposed ANN‐based soft sensor proved robust to several measurement errors, and is suitable for online estimation and closed‐loop control strategies.

     

Preparation,Structure, and Properties of Starch/Rubber Composites Prepared by Co-Coagulating Rubber Latex and Starch Paste

Summary: Several rubber/starch composites in which the starch particles are in an amorphous state and are smaller than 1 μm, prepared by directly mixing and co-coagulating rubber latex and starch paste, exhibit higher hardness, stress at 100%, tensile strength, and tear strength relative to the corresponding rubber/starch composites prepared by direct blending.

TEM micrograph of starch/SBR composite.     

丁苯橡胶的阳离子环化

应用一氯二乙基铝和苄基氯催化剂体系进行了丁苯橡胶的阳离子环化反应。研究了反应温度、苄基氯／一氯二乙基铝比例、溶剂、原胶浓度对环化的影响。发现通过控制苄基氯／一氯二乙基铝比,可在高温（１２０℃）、高原胶浓度（２～４％ｗ／ｖ）下进行丁苯橡胶的环化,制得特性粘度较原胶有大幅度降低,可溶性无凝胶的环化丁苯胶。通过对红外光谱、＾１Ｈ－ＮＭＲ谱初步解析,证实了环化反应的发生。     

Gas transport in vulcanized natural rubber‐cellulose. II. Composites

This work reports the transport of carbon dioxide, oxygen, and nitrogen in amorphous membranes of vulcanized natural rubber reinforced with regenerated cellulose. The values of the permeability coefficient of carbon dioxide, oxygen, and nitrogen in the composites with 25% of cellulose, measured at 25 °C and 15 cmHg of pressure, are roughly one‐third of those measured in the same conditions for these gases in natural rubber. The isotherms representing the variation of both the permeability and diffusion coefficients of the gases with pressure present a relatively sharp increase in the region of low pressures, attributed to changes in the free volume. The analysis of the permeability characteristics of the membranes in terms of the free‐volume theory suggests that gas transport is severely hindered in both the cellulose phase and the cellulose–rubber interphase of the composites. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 393–402, 2000     

Styrene‐butadiene copolymers with different butadiene microstructure: Mechanical,swelling, and orientational properties

Results of equilibrium stress‐strain and swelling experiments are reported for styrene‐butadiene copolymers of varying butadiene microstructure. The orientation of polymer chains was investigated under uniaxial elongation by birefringence and infrared dichroism spectroscopies which probe orientation on a segmental scale. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2449–2456, 2000     

A 3D printable and self-healing polydimethylsiloxane elastomer

Silicone elastomers are broadly used in various fields because of their unique properties, such as flexibility, durable dielectric insulation, and excellent stability in hash environments. As a result, three-dimensional (3D) printing of silicone elastomers is frequently required to construct personalized structures. However, existing 3D-printing of silicone elastomers are less accurate, difficult to maintain shape, or require doping modification with thixotropic agents. Moreover, common 3D-printable silicone elastomers do not have self-healing capability, so they have to be discarded upon damaging. Herein, by introducing hydrogen bonds to improve the shape retention ability and induce network reversibility, we have developed a self-healing polydimethylsiloxane elastomer, which can be readily 3D-printed by fused deposition modeling (FDM) technology. We believe that this new silicone elastomer would be useful in the field of biomedical materials, flexible electronics, medical inserts, soft robots and so on.     

Microstructural model for prediction of stress–strain curves of amorphous and semicrystalline elastomers

A fundamental microstructural model was developed to calculate the stress–strain curves of rubbery amorphous polymers and of semicrystalline polymers with a rubbery amorphous phase by numerical simulations. The rubbery amorphous phase was treated by using a version of the theory of rubber elasticity with finite extensibility. Physical entanglements and chemical crosslinks were both allowed. Slippage was implemented by a Monte Carlo algorithm controlled by kinetic parameters such as the activation energy and activation volume for slippage. The crystalline phase was treated in a very idealized manner, including a crude representation of tie chains but not taking the internal structure of the crystallites into account. A two-dimensional embodiment of the model was implemented into software. For amorphous polymers, while lacking truly quantitative accuracy, the model showed sufficiently good agreement with the experimental trends to be used as a qualitative or semiquantitative predictive tool, and it is currently being used in this manner. The more complex semicrystalline version was less accurate and will need to be improved in future work. Most of the limitations of the semicrystalline version could be ascribed unambiguously to specific simplifications made in the software implementation to reduce the amount of computer time required for the calculations. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2715–2739, 1997     

Non-covalent Surface Interactions between Silicone and Biological Macromolecules Yield Bioreactive Substances

While most organometallics enter the en- vironment through their industrial release, silicones are organometallic compounds purposefully introduced in high volume directly into healthy humans. A chemically centered study of the behavior of silicones in the biological environment reveals numerous de- gradative reactions and surface interactions that can produce bioreactive substances. Data from a variety of disciplines suggest that the preponderance of evidence supports the argument that silicone is a toxic organometallic. © 1997 by John Wiley & Sons, Ltd.     

Surface modification of chlorobutyl rubber by plasma polymerization

Radio frequency (r.f.) plasma polymerization of vinylidene fluoride (CH₂CF₂) has been used to modify the surface properties of chlorobutyl rubber. FTIR-ATR spectra of the treated rubbers and transmission spectra of plasma polymer films on NaCl windows indicated that as power increased the F/H ratio decreased. SIMS tests supported the FTIR results, and showed that the decrease in the F/H ratio was due to a decrease in the amount of F and an increase in the amount of H in the plasma polymer. Sliding friction measurements showed a reduction in the coefficient of friction (μ) from 3.7 for the untreated rubber to values ranging between 0.4 and 1.9 for the plasma-treated rubbers. There did not appear to be any correlation between the coefficient of friction and plasma power or monomer flow rate, and the average coefficient of friction for the plasma-treated samples was 0.9, which was lower than a commercially used silicone oil treatment (μ = 1.1–1.3). Repetitive sliding friction tests showed that the plasma- and silicone oil treated-chlorobutyl rubbers had the similar lubricating lifetimes. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1651–1660, 1997