Injection molded specimens

Table 1. Mechanical Properties of Injection-Molded Specimens of Main Classes of Styrene-Based Plastics ...

Tensile and flexural properties were studied with an Instron 4204 testing machine. Tensile tests were performed on the drawn strands at a test speed of 3 mm/ min, while three-point-bending tests (ISO 178) at a speed of 5 mm/min were applied to the injection molded specimens. Charpy impact strength was measured of the unnotched samples with a Zwick 5102 pendulum-type testing machine using a span of 70 mm. The specimens (4 X 10 X 112 mm) used for three-point-bending tests were also used for the impact tests. It should be noted that neither the tensile tests for the strands nor the impact tests were standard tests. The samples were conditioned for 88 h at 23°C (50% r.h,) before testing. 

Table 3 Flexural and Impact Properties of Injection Molded Specimens...

Anisotropic materials have different properties in different directions (1-7). 1-Aamples include fibers, wood, oriented amorphous polymers, injection-molded specimens, fiber-filled composites, single crystals, and crystalline polymers in which the crystalline phase is not randomly oriented. Thus anisotropic materials are really much more common than isotropic ones. But if the anisotropy is small, it is often neglected with possible serious consequences. Anisoiropic materials have far more than two independent clastic moduli— generally, a minimum of five or six. The exact number of independent moduli depends on the symmetry in the system (1-7). Anisotropic materials will also have different contractions in different directions and hence a set of Poisson s ratios rather than one. 

Many researchers have reported the structure-thermal property correlations in LCPs from substituted hydroquinones (HQs) and dicarboxylic acids. Lenz and co-workers have investigated the liquid crystallinity of the polyarylates obtained from substituted HQs and terephthalic acid (TA) [6-10], substituted HQs and l,10-bis(phenoxy)decane-4,4/-dicarboxylic acid [8], and substituted HQs and a,oo-bis(phenoxy)alkane-4,4/-dicarboxylic acid [11], Kricherdorf and Schwarz [12] and Osman [13] reported the liquid crystallinity of the polyarylates obtained from substituted HQs and 1,4-cyclohexanedicarboxylic acid, while Krigbaum el al. [14], Heitz and co-workers [15] and Kricherdorf and Engelhardt [16] investigated the liquid crystallinity of the polyarylates synthesized from substituted HQs and substituted TAs. In addition, Jackson reported the liquid crystallinity and the moduli of fibers and injection molded specimens of the polyarylates... 

A Toyo Boldwin Tensilon UTM-4-200 machine was used for these measurements. Determinations were performed according to ASTM D790 by using injection molded specimens with a thickness of 1/32 in. 

The morphologies of the tensile-fractured as-spun fibers and the flexural-fractured injection molded specimens were studied by scanning electron microscopy (SEM). 

The heat distortion temperatures (HDTs) of the injection molded specimens were determined under a load of 1.82 MPa according to ASTM D-648. 

HIGH-PERFORMANCE LIQUID CRYSTAL POLYESTERS 4.2 MODULI OF INJECTION MOLDED SPECIMENS... 

Because as-spun fibers of Me-HQ/Cl-PEC showed a higher modulus than those of Ph-HQ/Cl-PEC, the flexural modulus of injection molded specimens of Me-HQ/Cl-PEC exhibited a higher flexural modulus than those of Ph-HQ/Cl-PEC due to the liquid crystalline state. Although flexural-fractured injection molded specimens of Me-HQ/Cl-PEC exhibited highly oriented fibrils, Ph-HQ/ Cl-PEC no longer displayed fibrils because of the lack of liquid crystallinity. 

Figure 19.7 SEM images of flexural-fractured injection molded specimens of (a) Me-HQ/BB (31 GPa Tg, 175°C) (20x) [19], and (b) Me-HQ/Cl-PEC (15GPa Tg, 129°C) (30x) [31]. (a) From Inoue, T. and Tabata, N., Mol. Cryst. Liq. Cryst., 254, 417-428 (1994), and reproduced with permission of Gordon and Breach (Taylor and Francis) Publishers, (b) From Inoue, T., Tabata, N. and Yamanaka, T., Polym. J., 28, 424-431 (1996), and reproduced with permission of The Society of Polymer Science, Japan...

Figure 19.8 F-values of as-spun fibers and injection molded specimens [19]...

Accordingly, we have evaluated the flexural modulus of injection molded specimens of CP-HQ/BB having higher F-values than those of Me-HQ/BB polyarylates. The flexural modulus of injection molded specimens of Me-HQ/BB... 

As-spun fibers of Ph-HQ/HQ/BB with m/n = 50/502 exhibited a much higher modulus (100 GPa) than Ph-HQ/BB (40GPa) due to the increased F-value and rigidity of the polymer chain. Injection molded specimens of Ph-HQ/HQ/BB with m/n = 50/50 exhibited a much higher modulus than those of Ph-HQ/BB due to the increased rigidity and packing density of the polymer chain upon copolymerization with HQ. However, the F-value of injection molded specimens of Ph-HQ/HQ/BB (m/n = 50/50) was not much higher than those of Ph-HQ/BB, as shown in Table 19.4. 

Thus, both the rigidity and packing density of the polymer chain seem to be more influential factors than the F-values in achieving a high modulus of injection molded specimens. Figure 19.10 shows the variation of the flexural moduli as a function of the F-values for various substituted-HQs/BB and substituted HQs/BB modified with DHB, HQ, 2,6-dihydroxynaphthalene (DHN), NDA, Cl-PEC and TA [31,32], We could find no relationship between them. 

Thus, the influential factors in obtaining high moduli for injection molded specimens are as follows (1) the stability of the liquid crystalline state, (2) the rigidity of the polymer chain, and (3) the packing density of the polymer chain. 

Injection-molded specimen 4 mm, barrier values 100 pm blown films [3] Measured using standard test method ASTM D 3985 Compliance with European Commission Directive 2002/72/EC Compliance with European Standard EN 13432... 

Fig. 6 Stiffness of injection-molded specimen from Ecoflex /PLA compounds with varying PLA content, according to ISO 527...

Fig. 15 Evolution of the plastic energy, Gpiast) of a non-nudeated and of a -nucleated PP in between - 60 and 120 °C a puncture tests, b Charpy tests. Tests performed on injection molded specimens...

Fig. 18 Evolution of the a stress intensity factor, Kc, and the b energy release rate, Gc, for a low flowable and a medium flowable non-nucleated and /S-modified PP. The legend is the same for both parts of the figure. Injection molded specimens tested at 1 ms-1 in three-point bending [78] and compact tension [77] configuration...

Most HIPS fail in the uniaxial loading of a cantilever impact (Izod) test only if the test specimens have been notched beforehand. In the notched impact test, the stress direction in injection molded specimens is the same as the preferred orientation direction. This increases the measured impact toughness and the flexural impact test and, therefore, serves primarily for comparing the toughness of different products. 

The degrees of orientation for the crystallites in the injection-molded specimens of PECs were determined from the azimuthal breadth at half-maximum intensity in the strongest equatorial reflection by X-ray diffraction. Figure 6 showed the degrees of crystallite orientation of the as-molded and the annealed specimens. 

The ductility of phenoxy resins resembles that of metals. They are transparent and also characterized by low mold shrinkage, good dimensional stability, and moderately good resistance to temperature and corrosion. Phenoxy resins are soluble in methyl ethyl ketone and have been used for coatings and adhesives. A typical injection-molded specimen has a tensile strength of 9000 psi, heat distortion point 86.6C at 264 psi load, and d 1.18. 

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