Influence of a Melt Flow on Generation of Functionally Graded Structure in Bulk Polymeric Materials under Uniaxial Thermal Gradient

Abstract

A mechanism for the generation of the compositional gradient along the long axis for poly(ε‐caprolactone) (PCL)/poly(ethylene oxide) (PEO) blend under uniaxial thermal gradient was proposed by observations of the convection of polymer using graphite powder as a visual probe. The convection under the thermal gradient promoted the transfer of PCL into the liquid phase from the interface of PEO crystallites. The convex downward shape of the solid–liquid interface indicates the generation of the compositional gradient along the radial direction. By dissolution of PEO, a porous scaffold with a porosity gradient structure along the longitudinal direction was fabricated.magnified image

Density Graded Polyethylene Foams Produced by Compression Moulding Using a Chemical Blowing Agent

“…A quick look at the pictures can give some information about foam structure homogeneity with respect to symmetric and asymmetric cases. The first row (samples 13,16,17) presents the effect of mould temperature difference (asymmetric samples) at fixed CBA content (1%) and moulding time (6 min). It is clear that cell size and cell density are changing with position across thickness.…”

“…The first one is to impose a blowing agent concentration inside the part before foaming [15][16]. The second option is to impose a temperature gradient inside the mould [17][18] while foaming the part. Since cell nucleation, growth and stabilization are functions of temperature and blowing agent concentration, as well as pressure, a variation with position of any of these parameters will induce a different local morphology.…”

Effect of annealing on self-organized gradient film obtained from poly(3-[tris(trimethylsilyloxy)silyl] propyl methacrylate-co-methyl methacrylate)/poly(methyl methacrylate-co-n-butyl acrylate) blend latexes

“…FGMs are of interest to the study of orchestrated responsive behaviors, aerospace materials, and photoelectric and nuclear energy conversion materials [3][4][5][6]. Despite that FGMs are well known in the field of ceramics, metals, and other inorganic materials [7], functional gradient polymeric materials (FGPMs) have been extensively used because of their excellent properties, such as optical properties and mechanical stress relaxation [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

“…The gradation inside the material can be the result of a position‐dependent chemical composition, microstructure, or atomic order . The easiest way to produce FGM is by imposing a temperature gradient inside the mold to generate symmetric or asymmetric samples, leading to improved mechanical properties or stability compared with uniform (homogeneous) materials made under constant/uniform temperature and pressure.…”