نشریه صنعت لاستیک ایران
پیاپی 97 (بهار 1399)

This article is a review of the production method, advantages and application of recycled reclaim rubber. The most used rubber in the world is in the tire industry, whose raw materials contain the synthetic and natural rubbers. The most important reasons for recycling rubber are the natural rubber shortage, environmental problems, and pollution removal. In addition, the recycled rubbers are economically viable and create employment opportunities. The using of recycled reclaim rubber increases the blend mixing speed, decreases the process temperature and shrinkage, and also enhances the dimensional stability of the products. The reclaimed rubber provides higher curing speed, better adhesion and aging, and also enhances resistance to atmospheric conditions in the blend. Due to the mentioned advantages, the recycled rubber can be also used in other industries, e.g. cable sleeving, conveyors, roof insulation, pipes, etc

The purpose of this paper is to investigate the physical and mechanical properties of styrene-butadiene rubber/acrylonitrile butadiene rubber blends, SBR / NBR, with and without compatibilizer and clay nanoparticles. One of the ways to enhance and improve the properties of rubbers is blending, which is used to produce new products with improved properties, as opposed to each of the components. NBR and SBR are both commonly used rubbers, NBR’s mechanical properties is weaker than SBR, however SBR have higher abrasion resistance. SBR is a non-polar and non-saturated rubber which cannot be masticated easily, however NBR is polar and has good strength against solvents than SBR. The blend of these two elastomers can have many applications in industry, but because of the incompatibility of these two elastomers, the mechanical properties of the resultant blend is poor. It has been observed that the addition of a compatibilizer improves mechanical properties, including tensile strength, elongation at break which is due to the increased adhesion between the phases by decreasing the interfacial energy. In this paper, the effect of adding different compatibilizers on the properties of the SBR/NBR blends has been investigated. In the end, the effect of nano-clay as a stabilizer and reinforcing filler on the mechanical properties of the blend has been studied.

Generally, the useful life of a rubber component is governed by its susceptibility to failure by either mechanical or chemical deterioration. There are well established tests to address the failure properties of elastomers – fracture mechanism to investigate mechanical durability and also accelerated aging tests for chemical degradation. This paper is presented to experimentally estimate the life span of the rubber blend comprising NR and SBR in a ratio of 3:1 at accelerated ageing conditions. The specimens are subjected to ageing at different temperatures mainly at 90ºC, 100 ºC, 120 ºC and 150 ºC. The changes estimated at these temperatures were then understood with the help of the concept of Arrhenius theory and were compared to the rubber sample at ordinary conditions and the retention in physical properties was assessed. So, the retention of these mentioned properties decrease with increase in temperature as well as time. As result, the minimum value for life span of compound was 2.6 years for 55% retention and 3 years for 60% retention.

It is important to study the kinetics of rubber cooking in order to know the speed and time of cooking the mixture, as well as phenomena such as fragmentation and reversal. The rupture of the rubber compound during storage and before the main cooking operation causes major problems. The phenomenon of reversal also occurs in some tires that are prone to the destruction of sulfur bonds, and ultimately reduces the quality of the part produced. In this paper, after the general introduction of the cooking curve, which is necessary to determine the cooking parameters, how to measure the constant speed of the cooking reaction that depends on the reaction temperature and also the activation energy to start this reaction using oscilloscope disk )ODR( rheometers, Animated disc or die-casting )MDR( and rubber process analyzer )RPA( as well as Differential Scale Thermometer )DSC( are examined by referring to various researches.

This research is aimed at investigating the institutional investors and the value of cash flow on the stock returns of Petrochemical, Rubber & Chemical Companies in Tehran Stock Exchange. The statistical sample includes 14 companies that are members of the capital market in Tehran. During the period 2011 to 2017, the research variables were investigated. In order to test the hypotheses, the least squares regression model was used with consolidated data at 95% confidence level. The results of the first hypothesis show that institutional investors and the value of cash flow on stock returns in affiliated companies in Tehran Stock Exchange have a positive and significant effect. The results of the second hypothesis indicate that institutional investors do not have a positive and significant effect on stock returns in companies admitted in this field in Tehran Stock Exchange. Finally, the results of the third hypothesis at 95% confidence level indicate that the value of cash flow on stock returns in affiliated companies in Tehran Stock Exchange does not have a positive and significant effect, but if the confidence level is 90% The value of cash flow on stock returns in affiliated companies in Tehran Stock Exchange has a positive and significant effect.

In large organizations, it is vital to support entrepreneurial behaviors at all levels of hierarchy in order to grow performance and gain competitive advantage. On the other hand, trust is important because managers seek to understand how effective collaboration can be done in organizations and communication skills are behaviors. There are lessons learned and acquired that are essential to effective living that include awareness and creating the conditions needed to grow such behaviors. This study is quantitative in terms of purpose, and in terms of data collection. PLS and SPSS software were used for analysis. Therefore, to evaluate the reliability of the research measurement model, factor loadings, Cronbach's alpha coefficients and composite reliability, convergent validity and divergent validity were used. The results show that the correlational relationships between variables have been confirmed and based on the present study it can be suggested that an organization can succeed by having employees and managers with communication skills and entrepreneurial behavior that can ultimately promote organizational trust. Create an organizational environment.

Change is the most stable feature that can be introduced to the current business world. As the pace of change in science and technology accelerates, businesses and organizations become more complex, and along with these developments, the management of organizations becomes more complex. Today, it is not possible to manage organizations in the traditional way, because it is not easy to manage human beings, who are the main assets of organizations, and the leaders of organizations, especially human resources officials, need the necessary knowledge and skills. To gain important for this and to use them effectively. Therefore, the success of any organization depends on focusing the organization's attention on the unique talents of its employees and turning these talents into a sustainable function. Implementing knowledge management in the organization, as a process of creating and using knowledge to improve the organization's performance in terms of efficiency, information management, knowledge and experience in the organization, can be an effective solution in the process of responding to environmental changes. Also, changes in the external environment and rapid response to diverse customer needs force organizations to show resilience and change, and many efforts are made to increase organizational speed and flexibility. For this reason, many management scholars consider agility to be the key to the success of the organization in the dynamic and unpredictable environment of the present age. Hence, the effectiveness of human resource management is certainly related to investing in human capital as well as minimizing strategic costs. Human resource management, including training, skills and expertise of employees, is different from other departments of the organization.

In the current century, due to technological developments, especially the development of the production systems, the manufacturing systems have been faced with different complexities including their processes and activities i.e. organizational assets especially human resources are facing by various risks including safety risks. Hence, identification of risks followed by the provision of preventive measures to reduce and prevent the occurrence of accidental incidents is significantly required. For this purpose, this research is going to identify and prioritize the items that are inconsistent with engineering and safety principles in industries through the usage of 5S standard as an efficient and effective technique in optimization and elimination of inconsistencies in terms of engineering principles of industries, under five principles initiated by “S” as “sorting out”, “set in order/systematize”, “sweep/shine”, “standardize”, and “sustain”, as well as the safety risk assessment as a separate (sixth) principle applied in this technique. In this respect, in order to study the efficiency of this technique, field studies and safety risk assessment have been performed in the Barez Industrial group as one of the biggest tire manufacturing companies in the country. Hence, at first, a checklist was designed based on the ISO 45001 and 5S principles. Then, the checklist was evaluated by experts for two indicators of functionality and the current status of the manufacturing system. Finally, with consideration of the results, some preventive mechanisms have been proposed in order to identify the actions with high risks.