Molding temperature samples

Figure 27 shows that the release rate of CBP from the polymer decreased with increasing injection-molding temperatures. Samples with decreased levels of phthalic anhydride and increased levels of the phthalate half ester erode at slower rates presumably because the phthalic acid (pKai = 2.9 and pKa2 = 5.5) is a stronger acid than its alkyl half ester (estimated pKa = 3.6) and because the concentration of acidic groups is reduced by the esterification reaction. 

The standard injection molding machine used had a screw diameter of 30 mm and the aspect ratio of 23.70. The barrel temperature profile was 270, 280, 290, and 295°C. The mold temperature was about 90°C. The injection molded tensile samples were processed according to the CAMPUS specification (Computer Aided Materials Preselection by Uniform Standards) [24] and DIN 53455 Form 3. To obtain the different flow conditions, four groups of samples were injection molded by varying melt... 

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%). 

The mold and sample were placed in the press also preheated to 185°C and the cure cycle started immediately. Press temperature and pressure were microprocessor-controlled for consistent cure cycles. The cure cycle consisted of an initial 30 minute hold at 185°C with 1300 psi of pressure followed by 45 minutes at 221°C with 850 psi pressure and finally 15 minutes at 260°C with 300 psi pressure. The mold was removed from the press immediately following the completion of the final step and the sample removed from the mold while still hot. 

Sample application of the radial flow method. In this sample application, we are to determine the maximum clamping force and injection pressure required to mold an ABS suitcase shell with a filling time, tf=2.5 s. For the calculation we will use the dimensions and geometry schematically depicted in Fig. 8.49, an injection temperature of 227°C (500 K), a mold temperature of 27°C (300 K) and the material properties given in Table 8.8. 

Typical data are presented in Table I for samples of varying composition from 0 to 30% EPDM. All data in the table refer to samples injection molded at 1200 psi with one of three mold temperatures, 20°, 50°, or 87°C and under test temperatures that ranged from —30° up to 25°C. 

Samples with smaller spherulites are typical of the lower mold temperatures and show high impact strengths. 

Casting The silicone-rubber molds and premixed resin were heated to 150°C prior to casting. After the Eporal was totally dissolved, the resin was deaerated in a vacuum bell jar, reheated to 150 C, and poured into the preheated molds. The samples were cured for 1 h at 150 C, followed by 5 h at 177°C then the oven was turned off and the samples were allowed to cool slowly to room temperature. 

Fig. 43. Effect of cooling temperature from molding temperature on the bending moment-displacement curves of a notched PA 6 sample...

Dynamic mechanical experiments were performed on compression molded bars which had been molded from powders. Compression molding of the samples produced specimens adequate for solid state evaluation but not sufficient for physical property evaluation. Samples were molded using a standard Nabash press and a molding temperature of 300 C. 

Samples were purified by swelling in a Soxhlet extractor followed by drying in vacuum. Disks were compression molded at 250°C for 5 minutes followed by air quenching of the mold. Two samples were subsequently annealed at 80° in vacuum for 36 hours followed by slow-cooling to the test temperature 24°. UET48-1... 

Sample Identification. Given the number of samples and compositions, a general code was created as explained in Table II. In this table, the polyol type is identified by molecular weight and ethylene oxide content. Thus 40/15 refers to a polyol with M = 4000 and 15% (w/w) of ethylene oxide end capping agent. The last two labels in Table 2 indicate mold temperature and catalyst content. 

Differential Scanning Calorimetry. DSC scans for the M-B-23/25-48 series are shown in Figure 10. At low catalyst concentrations, there are two prominent endotherms at ca. 215°C and 225°C. As catalyst content increases, a new broad endotherm appears at ca. 190°C. These endotherms are characteristic of all polyol systems polymerized at high catalyst concentrations and/or high mold temperatures (Figure 11). Multiple endotherms in MDI/BDO polymers have been previously reported by other investigators (e.g. ref. 4, 14, 16, 17). Overall heats of fusion are a measure of crystallinity and crystal perfection and size and were higher (24 J/g) for samples with low catalyst content. 

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. 

In this paper we examine moisture sorption in an epoxy molding compound formulation used for semiconductor encapsulation. In particular, we will be concerned with moisture uptake as a function of relative humidity. The effects of temperature, sample thickness, and processing history will be systematically examined for a single commercially important material. 

Figure 17. Hardening rate of injection-molded samples of copolyether esters. Melt temperature is 240°C mold temperature is 30°C 58% 4GT/PTMEG-T (A), 56% 2GT/PTMEG-T (B)...

The Equations 5.5 (or 5.2) to 5.7 describe the process and allow the calculation of the final value of the state of cure obtained in the mold when the sample is spherical in shape. Calculation is made by using the above three equations, when the process of heating and cure starts from the temperature of injection to the mold temperature for the rubber sample. The total time necessary for the process of molding injection is thus the time t, in addition to the time necessary for the rubber to be cured in the mold, called t . However, it should be said already that the stage of heating in the reservoir for the nth material is done simultaneously during the stage in the mold of the (n-l)th rubber previously injected... 

Figure 5.9, where the state of cure-time histories are drawn at the center of the spherical rubber sample when the mold temperature is 170°C for various values of the injection temperature T (20, 80, 100, 120°C). The radius of the sphere is 2 cm. 

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