Injection molding samples

An example is poly(bis(p-carboxyphenoxy)propane) (PCPP) which has been prepared as a copolymer with various levels of sebacic anhydride (SA). Injection molded samples of poly (anhydride) / dmg mixtures display 2ero-order kinetics in both polymer erosion and dmg release. Degradation of these polymers simply releases the dicarboxyhc acid monomers (54). Preliminary toxicological evaluations showed that the polymers and degradation products had acceptable biocompatibiUty and did not exhibit cytotoxicity or mutagenicity (55). 

Measured on extmded samples, all others measured on injection molded samples. 

Similar to prepared metallographic samples, the injection molded samples were cut along the flow direction, smoothed, and polished in order to expose their internal surface. After proper etching, the treated surfaces of the flank cross-section were photographed using a polarized light optical microscopy. Based on the color differences between the TLCP and matrix, volume fraction and aspect ratio of the TLCP fibers were measured [23]. 

The release behavior depends on both the choice of polymer and on the formulation procedure. The best results were obtained with injection-molded samples. For prototypical drugs like p-nitroaniline, the drug release pattern followed closely that of the polymer degradation over a period of 9 months for PCPP. The correlation between release and degradation was still maintained in the more hydrophilic PCPP-SA, 20 80, where both processes were completed in 2 weeks. Compression molding can also be used for these polymers, but the correlation between drug release and polymer degradation is not as... 

Figure 5 presents the results of tensile tests for the HPC/OSL blends prepared by solvent-casting and extrusion. All of the fabrication methods result in a tremendous increase in modulus up to a lignin content of ca. 15 wt.%. This can be attributed to the Tg elevation of the amorphous HPC/OSL phase leading to increasingly glassy response. Of particular interest is the tensile strength of these materials. As is shown, there is essentially no improvement in this parameter for the solvent cast blends, but a tremendous increase is observed for the injection molded blend. Qualitatively, this behavior is best modeled by the presence of oriented chains, or mesophase superstructure, dispersed in an amorphous matrix comprised of the compatible HPC/OSL component. The presence of this fibrous structure in the injection molded samples is confirmed by SEM analysis of the freeze-fracture surface (Figure 6). This structure is not present in the solvent cast blends, although evidence of globular domains remain in both of these blends appearing somewhat more coalesced in the pyridine cast material.

Measured on extruded samples, all others measured on injection molded samples. C To convert MPa to psi, multiply by 145. 

X-Ray Analysis. Wide angle x-ray patterns were photographically recorded with 30-minute exposures from selected areas of the injection-molded samples. 

Fig. 22 Evolution of the E-modulus and Izod notched impact strength of composites based on PP (MFR 4.2 dg min 1) and increasing amounts of talc. Injection molded samples tested according to ASTM D790. Data taken from Fujiyama [40]...

Fig. 38 Evolution of /u, the J-Integral accounting for the fracture toughness, and of the elongation at break, break> as a function of the long period, LP, (left) and the lateral size of /3-crystals, L300, (right). Tests have been performed at room temperature on injection molded samples at 1.5 m s-1 to determine /Icj and at 50 mm min 1 to measure ebreak-Mechanical and structural responses have been varied by varying the concentration of NU-100, the nucleating agent from 0 to 1300 ppm...

Fig. 26 Injection molded samples of higher-molecular-weight PS tested perpendicular to injection direction (PS 168N) with and without oil...

However, the kind of technique used to mold these blends seems to be important in determining their mechanical properties. In fact, mechanical tests carried on injection molded samples [37] show, with respect to compression molded samples, a significant enhancement of the energy to break for all samples (Tables 20.2 and 20.3). Moreover the addition of 10wt% of SEBS to an 80 20 wt% sPS/HDPE blend involves in the injection molded samples an increase in both the energy at break and the Izod impact strength, whereas in the thermo-compressed samples no improvement is observed. Differences between compression and injection molded samples are widely acknowledged [38] and... 

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]. 

In the following sections the fatigue lifetime results for fom polymers will be described. In aU cases, the samples were pre-notched at knit lines by using doublegated tensile bar injection molded samples. 

To a degree, the mechanical properties of copolyether esters depend upon the conditions under which the sample is allowed to crystallize. Polymers having 4GT hard segments crystallize very rapidly compared with some other terephthalate copolymers. This is apparent from the rate of hardness development of injection-molded samples. Figure 17 compares the hardness of injection moldings at a 57% 4GT/PTMEG-T copolymer with that of a 2GT copolymer at various times after ejection... 

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)...

Fig. 39 Photographs of an injection-molded sample (25 mm diameter and 1.1 mm thickness) of polymer blend comprising block copolymer 18 left injection-molded sample without polarizers middle sample with several inscribed holograms between crossed polarizers, right sample showing the first diffraction order of some of these holograms under illumination with white light. (Reproduced with permission from [67]. Copyright Wiley-VCH Verlag GmbH Co. KGaA)...

Stndying microbial degradation of 50% WPCs by brown-rot and white-rot fungi (G. trabeum and T. versicolor, respectively), it was found that the decay was more prononnced as the wood particle size increased [9]. The authors found that decay in the pine-based composites was more sensitive to particle size than that in the maple-based composites. It is noticeable from the above examples that for the same soil block test, ASTM 1413 or similar to it, the weight loss figures are quite different, and vary from fractions of a percent to qnite high numbers. Indeed, as it was shown, extended composite material samples are mnch more sensitive to soil block test compared to compression-molded and injection-molded sample. After 12 weeks,... 

The release behavior depended on the formulation procedure. The best results were obtained with injection-molded samples. The drug release pattern followed closely that of the polymer degradation over a period of... 

The SEM micrographs in Fig. 19.7 show the morphology of longitudinal sections of the blends that are subsequently etched with formic acid. Since the exposed surface is parallel to the flow direction of the injection-molded samples, the micrographs are likely to reveal some process-induced orientation in the morphology. 

Figure 10.27 illustrates the process whereby we can evaluate the recyclabihty of plastic waste. After initial crushing, injection-molded samples are analyzed simultaneously by different physico-chemical characterization techniques, such as dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) or RSR. These transformation/analysis cycles can repeat up to eight times, and we observe the evolution of the different characteristics at each stage. 

Due to the miscibility of these blends, injection molded samples of the blends are transparent even though the poly(aryl ether ketone) is opaque under normal injection molding conditions. However, with proper annealing, opacity due to crystallization of the poly(aryl ether ketone) can be accomplished. 

Figue 11-23. Tensile stress at break (tensile strength) ob of at-poly(styrenes) of narrow molar mass distribution and various number-average molar masses M . Measurements were made at 23°C and 50% relative humidity. Processing was by compression molding ( ) or injection molding (O ) Injection-molded samples are oriented. (After H. W. McCormick, F. M. Brower, and L. Kin.)... 

Preparation of liyection-Molded Plates. The injection-molded sample was made of polymer pellets which have a molecular weight of about 1X10 (Toshiba Co., IS-130-FII). The molding conditions of polymers having different compositions were almost the same and details are given in Table HI. The dimensions of the samples used as heat distortion test pieces were 127 mm X 12.5 mm X 3.2 mm. 

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