Compression-molded blends

Abis et al. [32] also obtained evidence on compression molded blends of sPS/ SEBS of the occurrence of a phase compatibility between the components arising from the solubility of the polystyrene end-block of SEBS with the amorphous phase of sPS. In fact, although immiscible, a very fine dispersion and adhesion of the rubber particles is observed on SEM. However, contrary to the previous case, no improvement in the mechanical properties of sPS measured by tensile tests is observed, probably owing to the poorer performances of thermo-compressed samples than injection molded samples [38,39]. 

A compatible blend should have good processing properties along with a smooth surface and cross-section. If needed, further tests on mechanical properties should be carried out on testing samples made from 2-mm films produced by compression molding. 

Jiang and Zhu (2000) and Qiu and Zhu (2001) have reported the fabrication of multilayered devices composed of stacks of compression-molded disks of alternating compositions. One type of disk is either P(SA-EG) or P[SA-co-TMAgly)-Z>-EG] and the other is a pH-sensitive, protein-loaded blend of, for example, poly(methacrylic acid) and polyethoxazoline. The release of model proteins, myoglobin, bovine serum albumin, and FITC-dextran, and compounds such as brilliant blue have been studied and pulsatile release profiles have been demonstrated (Jiang and Zhu, 2000 Qiu and Zhu, 2001). 

Preparation of Samples for Flammability Testing. Samples of the phosphorus containing terepolymers and of the polymer blends were converted to film by compression molding on a Carver Laboratory Press with electrically heated platens. The films were prepared at 250°C and 20,000 lb. pressure, using a 10 mil thick frame mold. Samples (2" x 1/4") were cut from this film for flammability testing. 

Solution blends of 20-25% by weight were formed in DM Ac, with conventional dry spinning and film casting techniques used to produce blend fiber and film, respectively. Blend powders were prepared by precipitating the dope with a non-solvent (water). All materials were extensively washed in methanol or water to reduce residual solvent to less than 1 wt %. Neat resin tensile bars and plaques were compression molded from both powder and fiber. 

The graft polymers were diluted with an SAN copolymer to 20 and 30 wt % substrate. The dry blends were mixed on a two-roll mill for a maximum of 5 minutes (165° 175°C) without added lubricants. Compression-molded samples from the milled slabs were evaluated for impact and tensile strength. Figure 5 is a schematization of this procedure. 

Fig. 26 Micro structure of (PPE/PS)/SAN blend systems following compression-molding, as observed by transmission electron microscopy (PPE/PS - dark, SAN - bright)...

Another application of PTFE dispersions is the preparation of a variety of compositions with other materials, such as mineral fillers, other polymers in powdered form by co-coagulation. The dispersion of the other component is blended with the PTFE dispersion and the blend is then coagulated. The resulting composition can be processed by extrusion with lubricants (see processing of fine powders) or by compression molding.16... 

It was then blended at -8g C with unlabeled PVAc, and compression molded at 9000 psi at 30 C. The sample was rapidly raised to lh6 C and monitored. By the time the first spectrum was obtained ( 8 minutes) all segments had been desorbed and replaced by overcoated, unlabeled polymer, i.e., the labeled polymer had diffused from the surface into the bulk polymer. Although this seemed at first to be surprising, when one considers that the... 

Polymers and blends were worked up by evaporating the cyclohexane solvent and massing the polymer on a 140°C roll mill. Films were then prepared by compression molding (5 min at 200°C) or, in one set of experiments, by extrusion through a slit die. Dynamic viscoelastic meas-... 

Preparation of the Samples. Blends of different composition were prepared by freeze drying dioxane solutions. Sheets were compression molded at 249°C and cut into samples of desired dimensions. Rectangular samples were used for the stress-relaxation measurements and dumbbellshaped samples were used for the tensile stress-strain experiments. The compositions by weight of the PC-PST blends studied are as follows 95/5, 90/10, 80/20, 75/25, 50/50, and 25/75. 

The polymers used and some of their physical properties are listed in Table I. Polymers were mixed and blended on a two-roll mill at 450 K. Samples were compression molded at 450 K for 7 min and cooled in the press with tap water for 5 min. ASTM D412 6.35-mm (Va in.) dumbbells were cut parallel to the mill grain from sheets having 1.9-mm (75 mils) thickness. Instron tensile tests were carried out at least 48 hr after molding. Pull rate was 50.8 cm/min (20 in./min). 

Jin et al. (26) used melt blending to fabricate MWCNT-PMMA composites with different CNT loadings varying from 0 to 26 wt%. They used a laboratory mixing molder to disperse MWCNT in PMMA at 200°C followed by compression molding at 210°C. Their TEM studies revealed good dispersion even at high MWCNT concentration. The composites showed enhanced mechanical and thermal properties. 

We have tested the following polymers polycarbonate (PC), poly-carbonate/4% polyethylene blend (PC/PE), poly (ethylene terephthal-ate) (PET), ABS, and impact modified polystyrene (HIPS). All materials except PC were compression molded into nominal Vs-inch sheets. The PC used was an Vs-inch extruded sheet heat-treated in a manner previously described (22). These PC specimens were considered to be... 

Preparation of Blends of Grafted Polymers. The individual 360-, 2000- and 5000-A polymers were worked up, compounded, and compression molded into sheets. Blends of the three particle size polymers were made according to the following proportions based on percent rubber. The total rubber content in the blends remained at 15%. 

The above blends were mixed in powder form prior to compounding on the roll mills. The resultant compounds were compression molded into sheets and were delivered along with the single particle size compounds to AMMRC for ballistic impact evaluation. 

Material. Optically clear films (about 5 mils thick) of three SA (saturated acrylic) plastics (3) that contained 25, 33, and 50% of an acrylic graft rubber (referred to as SA-1, SA-2, and SA-3) were compression molded. The acrylic graft rubber latices were latex blended with a resin latex composed primarily of methyl methacrylate, and the blend was coagulated. The compositions of these three polymers are as follows SA-1, 79/17/4 wt %—methyl methacrylate/butyl acrylate/styrene SA-2, 72/23/5 wt %—methyl methacrylate/butyl acrylate/styrene SA-3, 59/34/7 wt %—methyl methacrylate/butyl acrylate/styrene. All three graft rubbers contained low levels of a crosslinking comonomer (less than 1.0 wt %). 

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