Crack growth under dynamic loading in silanised silica filled rubber vulcanisates

Rubbers are widely used to manufacture industrial articles such as tyres, conveyor belts, hoses, and engine mounts. During flexing, these articles fail in service due to initiation and subsequent growth of cracks leading to catastrophic failure. The failure is due to either environmental ageing by ozone and oxygen or mechanical failure due to crack initiation and growth. The unexpected failure in service is due to mechanical crack growth and may cause danger to life and property. Therefore, rubber articles are designed for long durability and low fatigue damage. To achieve these requirements, reinforcing fillers such as colloidal carbon black and synthetic silica are added to raw rubbers. In recent years, silica has been replacing carbon black in many industrial rubber articles. Some studies have investigated crack growth behaviour in unfilled and carbon black filled rubbers. But limited data is available for crack growth behaviour in silica-filled rubber vulcanisates and their effects on the durability and service life of industrial rubber articles has remained uncertain. When partly soluble chemical curatives are mixed with raw rubber, they migrate to the rubber surface, which can be detrimental to the rubber properties. Two rubber compounds with different amounts of curatives were prepared by mixing natural rubber with a high loading of precipitated amorphous white silica nanofiller. The silica surfaces were pretreated with bis(3-triethoxysilylpropyl)-tetrasulphane (TESPT) coupling agent to chemically adhere silica to the rubber. The chemical bonding between the filler and rubber was optimised via the tetrasulphane groups of TESPT by adding accelerators and activators. The rubber compounds were cured and stored at ambient temperature for up to 65 days before they were tested. One compound showed extensive blooming as a function of storage time. The cyclic fatigue life of the rubber vulcanisates was subsequently measured at a constant strain amplitude and test frequency at ambient temperature using standard dumbbell test pieces. The crack length, c, was also measured as a function of the number of cycles, N, at a constant strain amplitude ranging from 15% to 40% using tensile strip test pieces and the crack growth rate, dc/dn, was then calculated. The rate was subsequently plotted against the tearing energy, T, to determine correlation between the two. In storage, the chemical curatives migrated to the rubber surface and formed bloom. Blooming of the chemical curatives had detrimental effects on the cyclic fatigue life, crack growth rate and internal structure of the rubber. Blooming reduced the cyclic fatigue life of the rubber vulcanisate by more than 100%. The migrated chemical curatives produced thin layers approximately 15-20 µm in size beneath the rubber surface. When the rubber was stressed repeatedly, cracks initiated in these layers and subsequently grew, causing the cyclic fatigue life of the vulcanisate to decrease. At a given value of the tearing energy, the rate of crack growth also increased due to the re-agglomeration of the chemical curatives within the rubber which produced regions of low resistance to crack development. There was evidence that migration of the chemical curatives to the rubber surface had significantly damaged the internal structure of the rubber, creating voids and cracks which weakened the rubber mechanically. Styrene-butadiene rubber (SBR) and polybutadiene rubber (BR) were mixed together (75:25 by mass) to produce two SBR/BR blends. The blends were reinforced with a precipitated amorphous white silica nanofiller the surfaces of which were pre-treated with TESPT. The rubbers were primarily cured by using sulphur in TESPT and the cure was optimised by adding non-sulphur donor and sulphur donor accelerators and zinc oxide. The hardness, Young s modulus, modulus at different strain amplitudes, tensile strength, elongation at break, stored energy density at break, tear strength, cyclic fatigue life, heat build-up, abrasion resistance, glass transition temperature, bound rubber, and tan δ of the cured blends were measured. The blend which was cured with the non-sulphur donor accelerator and zinc oxide had superior tensile strength, elongation at break, stored energy density at break and modulus at different strain amplitudes. It also possessed a lower heat build-up, a higher abrasion resistance and a higher tan δ at low temperatures to obtain high-skid resistance and ice and wet-grip. Optimising the chemical bonding between the rubber and filler reduced the amount of the chemical curatives by approximately 58% by weight for passenger car tyre tread. This helped to improve health and safety at work and reduce damage to the environment

Effect of Chop Length and Level of Molasses on Chemical Composition of Yellow Corn Stover Silage

This factorial study was carried out from 15/10/2020 to 31/6/2021 to investigate the effect of chop length (CL) and level of molasses (M) added at ensiling on chemical composition of yellow corn stover including leaves and stems. Those materials were chopped into 4 lengths, 5, 10, 15 and 20 mm and molasses was added as a source of soluble carbohydrates at 3 levels, 6, 8 and 10% of dry matter (DM). Urea was added to all samples at 2% to enhance nitrogen content. Samples of ensiled materials were packed in double plastic bags and preserved for 60 days. Results revealed that there was a significant (P˂0.01) increase in DM content with increasing CL and level of M, and a significant (P˂0.05) increase in crude protein (CP) content with increasing level of M. Ether extract content was significantly (P˂0.05) decreased with increasing CL but (P˂0.01) increased with increasing level of M. Regarding cell wall components, neutral and acid detergent fibers (NDF, ADF) and cellulose contents were significantly (P˂0.01) decreased in silage samples prepared at fine CL. Lower (P˂0.01) NDF and cellulose contents were associated with those prepared with addition of M at 10%. In general, it was concluded that better results were achieved when samples of yellow corn stover silages including leaves and stems were prepared at 5 mm of chop length and addition of molasses at 10%. &nbsp

Developing ethylene-propylene-diene rubber compounds for industrial applications using a sulfur-bearing silanized silica nanofiller

The loading of a sulfur-bearing silanized silica nanofiller in ethylene-propylene-diene rubber with 4.5 wt % of ethylidene norbornene diene content was increased progressively to 60 parts per hundred rubber by weight. The rubber compounds were cured via the tetrasulfane groups of the silane by adding sulfenamide accelerator and zinc oxide. The hardness, tensile strength, elongation at break, stored energy density at break, tear strength, Young’s modulus, M50-M300, compression set, cyclic fatigue life and bound rubber content of the rubber vulcanizates were measured. With the exception of the elongation at break and compression set which deteriorated, the remaining properties improved and the rate of cure, optimum cure time and crosslink density benefitted also when the loading of silica was increased in the rubber. The bound rubber content was unchanged and the cyclic fatigue life of the rubber vulcanizate enhanced considerably when silica was added. Optimizing the chemical bonding between the rubber and filler via the tetrasulfane groups of TESPT reduced the chemical curatives in the rubber. This was a major improvement in health, safety and environment

Use of Natural Antimicrobial Agents: A Safe Preservation Approach

Microorganism contamination at various stages of food chain is one of the major causes for food spoilage that ultimately leads to food waste, increasing food insecurity issues and substantial economic losses. Various synthetic chemical preservatives are being used to control microbial food spoilage and to extend product shelf life. Researchers and consumers are discouraging the use of synthetic preservatives due to their negative health impacts. Naturally occurring antimicrobials have gained attention among researchers and food manufacturer due to their safety and nontoxic status. Natural preservatives are easy to obtain from plants, animals and microbes. These naturally occurring antimicrobial agents can be isolated from indigenous sources using various advanced techniques. Natural preservatives such as nisin, essential oils, and natamycin have effective potential against spoilage and pathogenic microorganisms. The regulations regarding the use of these naturally occurring preservatives are not well defined in some developing countries. This chapter focuses on source and their potential role, antimicrobial mechanism in food preservation, and current knowledge on the subject

Continuing medical education and pharmaceutical industry

Continuing medical education providers\u27 (academia) and industrial relationship is drawing attention all over the world. To date, there are no national commercial support guidelines available in Pakistan to properly regulate cooperation between the two distinct entities. However, the fact is that the future of all continuing medical education depends on pharmaceutical support and the providers are heavily dependent on the pharmaceutical industry to remain in action. It should always be remembered that medical education and profession is regarded as a moral of enterprise based on a blind faith between the physician and the patient. The funding support by the industry should not bind or influence physician\u27s prescription for any reason. To be trusted, medicine must be free of all such dependency; it should be accountable only to the society it serves and to its own professional standards

Intimate partner violence against women: A comprehensive depiction of Pakistani literature

Background: Intimate partner violence against women is a significant problem in Pakistan associated with an alarming set of mental health issues.Aims: To identify the prevalence of intimate partner violence in Pakistan and the causes, health effects and coping strategies used by women.Methods: A comprehensive search based on the identified keywords was conducted using Google Scholar and PubMed. Relevant literature was also searched and included. Abstracts were then shortlisted using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, and 25 studies were selected. Quantitative studies on intimate partner violence were included in the review. The review comprises only reports published in English from 2008 to 2018.Results: The review accounts for the overall prevalence of violence and its various subtypes against women in Pakistan: psychological 31.3-83.6%, physical 10.0-98.5%, sexual 2.5-77.0%, physical and sexual combined 1.0-68.0% and any other type 6.9-90.0%.Conclusion: The evidence generated will help notify policy-makers and health officials about the determinants and effects of intimate partner violence, making it easier to address these issues and identify victims as early as possible. It also sheds light on the limitations of this study: tools used by the published studies not specifically designed for Pakistan and there is no standardized definition of violence against women. This calls for more studies to be conducted to help find a solution

Microbial biotransformation of beclomethasone dipropionate by Aspergillus niger

Na pesquisa presente o fármaco esteróide antiasmático dipropionato de beclometasona foi submetido à biotransformação microbiana pelo Aspergillus niger. O dipropionato de beclometasona foi transformado, pela primeira vez, em metabólitos variados por biotransformação microbiana. Novos metabólitos do fármaco produzidos podem agir como novas moléculas potenciais e podem substituir os fármacos antigos em questão de segurança, eficácia e mínima resistência. Eles foram purificados por cromatografia em camada delgada preparativa e as suas estruturas foram elucidadas usando técnicas espectroscópicas modernas, como 13C NMR, 1H NMR; HMQC; HMQC; COSY, NOESY e espectrometria de massas, por exemplo, EI-MS. Purificaram-se quatro metabólitos, denominados (i) 17-monopropionato de beclometasona; (ii) 21-monopropionato de beclometasona: (iii) beclometasona e (iv) 21-propionato de 9beta,11beta-epoxi-17,21-diidroxi-16beta-metilpregna-1,4-dieno-3,20-diona.In the present research, the steroidal anti-asthmatic drug beclomethasone dipropionate was subjected to microbial biotransformation by Aspergillus niger. Beclomethasone dipropionate was transformed into various metabolites first time from microbial transformation. New drug metabolites produced can act as new potential drug molecules and can replace the old drugs in terms of safety, efficacy, and least resistance. They were purified by preparative thin layer chromatography technique, and their structures were elucidated using modern spectroscopic techniques, such as 13C NMR, 1H NMR, HMQC, HMQC, COSY, and NOESY, and mass spectrometry, such as EI-MS. Four metabolites were purified: (i) beclomethasone 17-monopropionate, (ii) beclomethasone 21-monopropionate, (iii) beclomethasone, and (iv) 9beta,11beta-epoxy-17,21-dihydroxy-16beta-methylpregna-1,4-diene-3,20-dione 21-propionate

Quality outputs of physical education and sports sciences faculties from the point of view of some labour market institutions

The research problem lies in answering to the following question what is the quality outputs of physical education and sports sciences faculties from the point of view of some labour market institutions and the research goal is to identify the quality outputs of physical education and sports sciences faculties from the point of view of some labour market institutions and the researchers used the descriptive curriculum for the survey style because of its suitability to the research nature problem, the research community was the directors of the directorates of youth and sports and the managers and members of the representatives of the Olympic Committees in the provinces of the Middle Euphrates, where the research community reached (280) official, the research sample consisted of (220) official, it was divided into three groups in a random way, where the first group included a building sample, which reached (100) official, and the second group, which is the sample of the application, consisted of (90) official and the third group, which is the sample of the exploratory experiment consisted of (30) official. To achieve the research objectives and measuring variables, the researchers prepared the research tool by looking at some similar studies and previous related measures It was concluded that the quality outputs from the point of view of the beneficiary was below the desired level, through results analysis the results were not satisfactory about the quality of the qualitative level of graduates and the training programs of the institutions of society as well as consulting