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    امروز  پنج شنبه - ۳ بهمن - ۱۳۹۸  
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مرجع پلیمر در بازار ایران: اوره فرمالدئید از پر مصرفترین رزینهای گروه آمینه می‌باشد. رزینهای آمینه پلیمرهایی ترموست تولید می گردندکه شامل اوره وملامین فرمالدئید هستند که از واکنش فرمالدئید و ترکیبات گروه -NH2 می‌باشد. اوره فرمالدئید محصول افزایشی اوره و فرمالدئید است. ساختار عمومی اوره فرمالدئید پیچیده است. زنجیرهای اوره فرمالدئید در زمان پخت بدلیل ایجاد پیوندهای جانبی به شکل غیر محلول در می آید و شبکه های سه بعدی ایجاد ...

The applicability and service time of polymer details working in various media are limited by the degradation of their physical and mechanical properties. From the structural point of view the weakest places strongly affected by ageing are the surface and boundary regions of the crystallites. If a material is subjected to high-strain deformation, it deforms permanently (plastic deformation) and ultimately fails. For sufficiently low stresses and strains, the polymeric material behaves as a linear elastic solid. The point where the behaviour starts to be non-linear is called the proportional limit. The local maximum in the stress-strain curve is called the yield point and indicates the permanent deformation. The corresponding stress and elongation are called ...

PolymPart: Viscosity for non-Newtonian polymers is a combination of increasing temperature and shear rate, as described by the following relationship: η = mγn-1 where viscosity (η) equals consistency index (m) times the shear rate (γ) to the power law index (n) minus 1. Generally, only rheology experts discuss the effects of the consistency index. The consistency index, or viscosity change with increasing temperature, is largely dependent on the energy input to the polymer by shear from the screw rotation. That is, as the shearing raises the polymer temperature by viscous dissipation or conversion of mechanical power to temperature, the viscosity additionally decreases due to the higher temperature and adds to the shear thinning. The ...


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