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Temperature molding conditions

The mass fraction crystallinity of molded PHB samples is typically around 60%. As shown in Table 3, PHB resembles isotactic polypropylene (iPP) with respect to melting temperature (175-180°C), Young s modulus (3.5-4 GPa) and the tensile strength (40 MPa). In addition, the crystallinity of iPP is approximately 65% [18]. Accordingly, the fracture behavior of PHB may be anticipated to be tough at room temperature. Molded PHB samples do indeed show ductile behavior, but over a period of several days at ambient conditions, they slowly become more brittle [82, 85, 86]. Consequently, the elongation to break of the ultimate PHB (3-8%) is markedly lower than that of iPP (400%). [Pg.268]

Heat pipes are used to perform several important heat-transfer roles in the chemical and closely allied industries. Examples include heat recovery, the isotherm alizing of processes, and spot cooling in the molding of plastics. In its simplest form the heat pipe possesses the property of extremely high thermal conductance, often several hundred times that of metals. As a result, the heat pipe can produce nearly isothermal conditions making an almost ideal heat-transfer element. In another form the heat pipe can provide positive, rapid, and precise control of temperature under conditions that vary with respect to time. [Pg.511]

Photo 1. Cellulose sample used. Top A part of molded film from the cellulose— PMMA composite, PC—3. Molding conditions temperature 300°C time, 2 min pressure, 50 kg/cm . Bottom under a microscope. [Pg.327]

Photo 2. Lauroylated wood, meals, a and a sheet prepared from the lauroylated wood meals by compression molding, b. Molding conditions temperature, 140°C time, 2 min pressure, 150 kg/cm2. [Pg.343]

Once the process has been optimized, plastic conditions should be recorded such as fill time, peak pressure at fill, cavity pressure,184 melt temperature, mold temperature, melt flow rates, and gate seal time. Record all basic machines setpoints on the setup sheet such as the transfer time (fill time) and weight, overall cycle time, and total shot weight, part weight, % runner, etc. [Pg.202]

For practical estimates and deductions of approximate relationships for determining the temperature-time conditions for reactoplast treatment, we may use a simplified model of the thermal field, namely by assuming that that the temperature of the material in each of the zones, the mold included, is constant for the entire period of the presence of a portion of the material in a specific zone. [Pg.55]

In recent years, HR foams have been prepared by using almost the same molding conditions as cold-molded foams, i.e., low mold temperature using the MDI-TDI blend formulation. However, in the development stage of HR foam, only TDI-based formulations were used, which required hot-mold conditions. For these reasons HR foams are not exactly equal to cold-cure foams. However, in recent years, HR foams have been produced by blends of MDI and TDI. The resulting foam systems can be molded at the same molding conditions as those for cold-molded foam systems. [Pg.59]

All samples show a sharp decrease in Mw at 0.02-0.03% DBTDL. Judging from the results of the M-B-20/30-60 series, an increase in mold temperature allows for larger decreases in catalyst composition without major effect on the molecular weight. Information like this is valuable 1n establishing optimum levels of catalyst or molding conditions. [Pg.42]

The polyarylsulfone thermoplastic exhibits essentially the same heat resistance of the polyarylstdfone based on bis-(4-chlorophenyl)sulfone and 2,2-bis(4-hydroxyphenyl)pro-pane, along with the added plus of a lower melt viscosity at equivalent processing temperatures. The flow improvement is demonstrated by comparison with Brabender data, injection-molding conditions, and melt-viscosity data. [Pg.142]

The significant improvement in flow properties of resin IV vs. V is evident from the data. First, the torque from Brabender mixing indicates that resin IV is an easier-flowing material (Table II). The lower torque values for IV indicate the necessity of a lower-energy input to mix the polymer melt. This lower rotational force therefore indicates the polymer melt has a lower melt viscosity. Secondly, injection-molding conditions demonstrate the improved processability of resin IV (Table III) in comparison with resin V. At the same injection cylinder temperatures, the injection pressure for the tensile bar and Izod/heat distortion bar molds is lowered by 300 psi and 250 psi, respectively. [Pg.147]

Although the dynamic mechanical properties and the stress-strain behavior iV of block copolymers have been studied extensively, very little creep data are available on these materials (1-17). A number of block copolymers are now commercially available as thermoplastic elastomers to replace crosslinked rubber formulations and other plastics (16). For applications in which the finished object must bear loads for extended periods of time, it is important to know how these new materials compare with conventional crosslinked rubbers and more rigid plastics in dimensional stability or creep behavior. The creep of five commercial block polymers was measured as a function of temperature and molding conditions. Four of the polymers had crystalline hard blocks, and one had a glassy polystyrene hard block. The soft blocks were various kinds of elastomeric materials. The creep of the block polymers was also compared with that of a normal, crosslinked natural rubber and crystalline poly(tetra-methylene terephthalate) (PTMT). [Pg.273]

Specimens of each material were prepared under two very different molding conditions slow-cooled and quench-cooled. Hytrels 6355 and 5555 were compression-molded at 270°C quench-cooled specimens were then plunged into ice water whereas slow-cooled specimens were cooled to 200°C over 10 min and then cooled from 200°C to room temperature in about another 10 min. [Pg.275]


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Temperature conditions

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