جستجوی مقالات مرتبط با کلیدواژه "بوتادی ان" در نشریات گروه "مهندسی شیمی، نفت و پلیمر"

Hypothesis: Substitution of carbon black by surface-modified silica in tire tread compound formulation often brings a lower friction coefficient and inadequate vehicle safety. Through modifying polymer-filler interactions, silane chain length is capable of altering viscoelastic properties. The connection between tribological properties and viscoelastic dissipation can be regarded as an important factor to control the frictional behavior of tire tread compounds. It has always been speculated that silane chain length dictates the properties of silane-treated silica filled rubbers through two possible reinforcing mechanisms namely: entropic interaction and/or mechanical engagement. In this contribution, the existence and severity of each mechanism is realized by excluding mechanical contributions of reinforcement from that of entropic interactions by surface-energy theories.
Two aliphatic silanes of short (trimethoxy(propyl)silane) and long chain (hexadecyl trimethoxysilane) with spacer length of 3 and 16 carbons are grafted onto the silica surface. The surface energy of the resulting powders is controlled by controlling the density of silane grafting. The rubber matrix constitutes a solution styrene butadiene rubber (S-SBR) and the compounds have been prepared by means of an internal mixer and a two-roll mill. The surface characteristics of silica as well as the morphological, mechanical and tribological properties of the resulting rubber composites are characterized and compared with a conventional bi-functional silane commonly used for this tread compound.
Findings: For systems in which the surface energy and thus energetic contributions of polymer-filler interaction are controlled to be equivalent for both short- and long-chain silane treated silica, no variations either in dynamic or tribological properties are detected, indicating that no mechanical engagement associated with interlocking of long chain silanes is available. At the same time, entropic interactions played a significant role in final dynamic and tribological properties of the composites. It is also observed that friction coefficient is correlated with loss modulus of the compound better than the loss factor.

The particle size distribution (PSD) is one of the most important parameters of emulsion polymerization latexes. This parameter affected the rheological and optical properties, adhesion, film formation and mechanical strength of latexes. Therefore, the modeling of PSD is of utmost importance in terms of application and mechanistic studies. Dynamic evolution of PSD is described by a set of population balance equations which involved various phenomena such as nucleation, growth, and coagulation. The extensive application and especially annually massive production of poly(butylacrylate) and polybutadiene produced by emulsion polymerization, highlights the significant of modeling these processes, which could resulted in better mechanistic knowledge and tailor-made polymer materials. In this paper, a mechanistic model based on population balance equations is developed for butyl acrylate and butadiene emulsion polymerization in a batch reactor. This model is used to predict the evolution of particle size distribution and the finite volume method as a precise technique is used for discritizing PBEs. The simulation results compared with the measured values during the evolution of conversion and average particle diameter for different initial surfactant concentrations.