Prediction Compounded rubber

Mathematical models of the internal mixing process for the on-line prediction of rubber compound viscosity and viscoelastic properties were developed on the basis of multiple linear regression and artificial neural networks. The models gave high levels of accuracy when applied to predicting the properties of SBR and NR/SBR/ polybutadiene compounds produced using mixers of three different sizes. 9 refs. 

ANALYSIS METHODS FOR THE PREDICTION OF RUBBER COMPOUND QUALITY FOR MIXING IN INTERNAL MIXERS... 

It is found that many nitro compounds fall into the group for which butyl rubber is an appropriate choice, so if a new nitro-containing compound had been synthesized and we wished to choose a glove to provide protection, inspection of the members of the class would suggest butyl rubber as a suitable candidate. In this application, we are using the observation of similarities within a class (the presence of many nitro compounds) as a predictive tool (best handled using butyl rubber gloves). 

Many types, such as pine tar, are distillates from pine tree farming in Scandinavia. Pine tar is a dark viscous liquid used at about 3-7 phr dosage level. It does not affect hardness levels to the same extent as the equal amount of petroleum oil. From the nature of its sources it can vary in acidity and thus has tended to be replaced by cheaper more predictable alternatives which are available from the residues of petroleum distillation. Tack improvement of rubber compounds is derived from the presence of colophony resin derivatives. 

The most relevant property of stereoregular polymers is their ability to crystallize. This fact became evident through the work of Natta and his school, as the result of the simultaneous development of new synthetic methods and of extensive stractural investigations. Previously, the presence of crystalline order had been ascertained only in a few natural polymers (cellulose, natural rubber, bal-ata, etc.) and in synthetic polymers devoid of stereogenic centers (polyethylene, polytetrafluoroethylene, polyamids, polyesters, etc.). After the pioneering work of Meyer and Mark (70), important theoretical and experimental contributions to the study of crystalline polymers were made by Bunn (159-161), who predicted the most probable chain conformation of linear polymers and determined the crystalline structure of several macromolecular compounds. 

From practical compounding experience, we would predict that a butadiene-acrylonitrile rubber will co-vulcanize across an interface with... 

These studies have dealt with materials suitable for fuel and feedstocks, the process for converting these materials to carbon black with predictable properties, the techniques for measuring and defining those properties, a better understanding of the effects of those carbon black properties on processing parameters of compounded goods, and the predictability of the performance properties of finished rubber goods. This presentation briefly considers the status of each of these areas of study relative to today s carbon blacks and tomorrow s rubber products. 

The use of thermodynamic data for predicting the reaction path can, for example, be applied for the thermal decomposition of aliphatic hydrocarbons. This example is more related to practical applications for petroleum products, but can explain the yield of certain compounds in secondary steps for the pyrolysis of polymers such as rubber. 

The compound predicted to have the second greatest potential for swelling nitrile rubber was 2-naphthol. Its optimized interaction with isobutyronitrile is shown in Figure 3. The position of the -OH group in 2-naphthol precludes the simultaneous occurrence of the phenolic hydrogen-nitrile interaction and the much weaker methyl-hydrogen aromatic pi-electron system interaction. 

Wan and Isayev (1996) examined a hybrid approach of control-volume finite-element and finite-difference modelling of injection moulding of rubber compounds. The effect of vulcanization on viscosity and yield stress during cavity filling is reported. On comparing two versions of the modified Cross viscosity models - with and without the effect of cure - the use of a viscosity model that accounts for the cure was found to improve the accuracy of the cavity-pressure-prediction models. When the modified Cross model was further extended to include the yield stress and was implemented in the simulation program a significant improvement in the prediction of cavity pressure was obtained in the case of low injection speed. 

From previous accelerated and real time ageing studies, it is known that rubber compounds exhibit complex property changes over time (1,2). Oftentimes, this can lead to less than desirable characteristics in the rubber, such as increased stiffness, embrittlement, poor abrasion characteristics, and others. In thin latex rubber products, it is common practice to under cure the rubber. As the product ages, certain properties will tend to improve for a while before starting a decline. For example, latex rubber condoms are stored in hermetically sealed packages, which limit exposure to oxygen, ozone and UV therefore, their ageing characteristics are more predictable and less pronounced than tires or footwear outsoles, since they can establish a three to five year shelf-life (3). 

Various processability tests are used to predict how well a rubber compound will process. However the process" can vary greatly. Table 1 shows the diverse categories of rubber processes and some of the quality characteristics and concerns associated with each process. The natures of these processes vary because of differences in applied shear rates, temperatures, residence times, etc. Changing a given compound property can improve performance in one or more of these processes but could hurt the performance in another process. This is why it is important to look at all processes in a manufacturing operation when implementing compound changes. 

Dick. John S.. and Pawlowski. Henry, Applications of the rubber process analyzer in predicting proces.sability and cured dynamic properties of rubber compounds, presented at the Denver. Colorado meeting. May 18 21. 199,3, p. 18. 

Small-scale laboratory tests for rubber are used in material and product specifications and for such activities as compound development, component design, factory quality control, and life prediction. Many of these tests have been shaped by the distinguishing features of rubber, rubber products, and their means of manufacture. Such features can conveniently be grouped as follows ... 

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