Molding quenched

Extrusion Resins. Extmsion of VDC—VC copolymers is the main fabrication technique for filaments, films, rods, and tubing or pipe, and involves the same concerns for thermal degradation, streamlined flow, and noncatalytic materials of constmction as described for injection-molding resins (84,122). The plastic leaves the extmsion die in a completely amorphous condition and is maintained in this state by quenching in a water bath to about 10°C, thereby inhibiting recrystallization. In this state, the plastic is soft, weak, and pHable. If it is allowed to remain at room temperature, it hardens gradually and recrystallizes partially at a slow rate with a random crystal arrangement. Heat treatment can be used to recrystallize at controlled rates. 

Sample Preparation. Samples for mechanical studies were made by compression molding the polymers at 150°C between Teflon sheets for 15 minutes followed by rapid quenching to room temperature in air. These will be referred to as PQ (press-quenched or simply quenched) samples. The thickness of the PQ samples was around 10 mils (0.25 mm). The thermal history of all of the PQ samples (HBIB, HIBI, and LDPE) were essentially the same. They were used within one week after they were pressed. Samples for morphology, SALS and SEM studies were prepared from toluene solutions. These films were cast on a Teflon sheet at 80 C from a 1% (by weight) solution in toluene. These films were about 5 mils in thickness. When the polymer films had solidified (after 5 hrs), they were stored in a vacuum oven at 80°C for two days to remove residual solvent. These samples will be designated by TOL (solution cast from toluene). 

Schuster et al. s latest effort [61]—a clear PET system of the lumophore-spacer-receptor format—breaks free from this quenching mold just like their 1993 case [57], Sensor 17 is capable of binding (through the S atom to Cu2+ or... 

Mixed Polymers. A mixture of 5 parts of polyethylene and 95 parts of expandable polystyrene is extruded and converted to quenched pellets. The pellets are expanded and converted into molded foams with improved resistance to solvents and water vapor transmission (29). There is a polyethylene skin on the surface. 

The samples were desiccated in a vacuum oven at 110°C for 24 hr. They were then compression molded on a Pasadena press at 280°C and 30,000 psi for 1 min. They were then immediately quenched in the ice-water mixture and melted again in the press without pressure for another minute. They were then immediately quenched in the ice-water mixture. A set of these amorphous samples was used in the determination of the Tg by DSC. Other samples were crystallized in a fluidized bed at 150°, 130°, 110°, and 90°C for 15, 30, 60, 120, 180, 240, 300, 600, 900, and 1,800 seconds, following which they were quenched again. 

Crystallization at 52° and 60 °C was performed between polished steel plates in an air oven following compression molding in a laboratory press. The filament specimen used in the quenching experiments was fabricated by (1) inverting a capillary tube into the HMS powder, (2) evacuating the capillary and sample in a vacuum oven, and (3) admitting air pressure after the sample melted to force the sample into the evacuated capillary tube. Note in Figure 1 that this produces a uniform. — 1 mm diameter unoriented specimen that is easily quenched. 

Thin-fllm samples of specific Isothermal cure histories were prepared for dynamic tensile testing on the Rheovibron by compression molding 0.6 to 0.7 mm thick samples at a pressure of 14 MPa. The samples were air quenched after various times at constant cure temperature. The thin-fllms were then mounted In the Rheovibron and the temperature Increased from room temperature to approximately 31 0 C at 2 C/m1n In a dry nitrogen atmosphere. 

Materials and Processing. Copolyesters of poly(ethylene terephtha-late) (PET) and para-oxybenzoic acid (FOB) were supplied by the Tennessee Eastman Corporation. Past work Indicates the copolyesters form thermotropic liquid crystalline phases at compositions containing more than 30 mole% POB (26,27,28). The composition of the copolyester studied here contains 60 mole% POB. Quiescent liquid crystalline films were made by compression molding the copolyester at 210, 230, 255, and 285 C, and followed by a quench Into Ice water, ambient air, or cooled In the press with the power off. Film thicknesses ranged between 0.05-0.15 mm. Another sa(q>le of the 40/60 PET/POB copolyester was melted at 270 °C In a Mettler hot stage, manually sheared between glass slides, and then ambient air cooled. 

Figure 4 Typical Iso-lntenslty Contour Patterns oC Compression Molded 40/60 PET/POB Copolyester A) 255 c, Press Cooled B) 285 C, Ice Water Quenched.

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