Direct Injection Moulding Research Articles

Structure and mechanical properties of polysulfone‐based in situ composites

AbstractComposites based on the polysulfone of bisfenol A (PSF) and a liquid‐crystalline copolyester (Rodrun 5000) were obtained by two processing methods, (1) direct injection moulding (DI) and (2) extrusion followed by injection moulding (PI), across the whole composition range. The blends were immiscible and showed two pure amorphous phases. The inferior mechanical properties of PI blends, and their more difficult processing, meant that the PI procedure is not suitable in these blends. The generally linear relationship of the Young's modulus of the DI blends is due to the counteracting effects of the large orientation of the skin and its low thickness. The improvement in notched impact strength of PSF on the addition of small amounts of LCP indicated an important reduction in its notch sensibility. The tensile strength behaviour was close to linearity, with the exception of the 20/80 blend in which it was synergistic. This had been seen in previous thermoplastic/LCP blends, and depicts a behaviour reminiscent of rubber‐toughened blends. Copyright © 2004 Society of Chemical Industry

Structure and properties of amorphous polyamide/liquid crystalline polyester blends

AbstractAmorphous polyamide (AP)/liquid crystalline polyester (VA) blends were obtained by extrusion‐injection molding (EI) throughout the whole composition range. The phase behavior, chemical nature and morphology of the blends were studied, and the mechanical properties discussed and compared with those of the 10 and 30% VA blends obtained by direct injection molding (DI). The blends showed two almost pure slightly reacted amorphous phases. The apparently higher reaction level of the EI blends, although small, led to a more homogeneous, fine and fibrillated morphology, attributed to a lower interfacial tension. Significant synergisms in the modulus of elasticity (up to 25%) and in the tensile strength (up to 40%) were seen in EI blends. The similar values of both specific volume and orientation in the blends and in the pure components suggest that the contribution to the modulus of the dispersed VA rigid particles is greater than that due to the proportion of VA in the blend. The 10% VA DI blend showed a similar behavior in these two properties, indicating that the DI procedure is preferred, provided that only stress‐related properties are sought. At 30% VA content, the moduli of elasticity were similar by the two molding processes, but the clearly lower tensile strength and lower ductility of the easier DI procedure, means that the more complex, but more effective, EI procedure is the one of choice for high performance materials.

Structure and mechanical properties of blends of an amorphous polyamide and a liquid crystalline polymer

AbstractThe structure and the mechanical properties of blends of an amorphous polyamide (PA) and a thermotropic copoly(ester‐amide) (VB) obtained both by direct injection molding (DI) and also by extrusion and subsequent injection molding (EI) have been studied. Besides the usual fibrillar morphology of the skin, fibrillation was also observed in the core of most of the blends. The important synergisms in the modulus of elasticity (20% positive deviations in both blends with 30% and 40% VB contents) and also in the tensile strength (30% and 55% positive deviations in the EI blends at the same compositions) were obtained without the presence of compatibilizer.

Synergistic mechanical behaviour in new polyamide 6/poly(amino-ether) blends

New polyamide 6 (PA)/poly(amino-ether) (Blox) blends were obtained by direct injection moulding covering the full composition range. The blends comprised an almost pure PA phase and a Blox-rich phase in which significant amounts of PA were miscibilized. A very positive mechanical response was obtained, as synergisms were observed both in Young's modulus/yield stress and in elongation at break. The combined effects of the observed partial miscibility, and the very small dispersed phase size, are stated as the main factors responsible for the mechanical behaviour.

Blends of a thermotropic copolyester and a thermotropic copoly(ester–amide): structure and mechanical properties

Rodrun 5000/Vectra B950 blends were obtained by direct injection moulding at two injections rates. The blends were partially miscible and unreacted under the processing conditions used. Higher orientations and properties were obtained at the lower injection rate due to the higher overall orientation obtained. The produced orientation and the negative volume of mixing of the blends led to a range of LCP materials with intermediate modulus and tensile strength and slightly higher ductility.

Phase Structure, Processability, and Mechanical Properties of Rodrun Liquid Crystalline 5000/Rodrun Liquid Crystalline 3000 Blends

New liquid crystalline materials with low processing temperature, whilst maintaining the mechanical properties characteristic of the liquid crystalline polymers, were sought by blending Rodrun 5000 and Rodrun 3000. After direct injection moulding, the solid blends appeared as miscible. The crystallization from the melt was hindered by the presence of the other component, but the minimum processing temperature of Rodrun 5000 clearly decreased as a consequence of the presence of Rodrun 3000. This decrease was not at the cost of a decrease in the overall mechanical properties. It should be noted that, unlike in thermoplastics blends, in liquid crystal polymer (LCP) blends the miscibility level influences the modulus values. Immiscibility leads to clear positive synergisms in the values of the modulus of elasticity and also in the tensile strength, that are not seen in miscible LCP blends.

Compatibilization of PP/Vectra B “in situ” composites by means of an ionomer

Ionomer addition has been investigated as a compatibilizer for the immiscible polypropylene (PP)/Vectra B 950 (VB). Both modified and unmodified blends as a reference, with VB contents up to 30% were obtained by direct injection moulding. The crystallinity of PP/VB was barely influenced by the presence of the ionomer. The compatibilization leads to the presence of thinner fibres that broke during testing. Compatibilization reduced toughness, but at VB contents of 15wt% or more, both the modulus of elasticity and the tensile strength significantly increased with respect to the uncompatibilized blends. The properties of both compatibilized and uncompatibilized blends, as a whole, were similar in the case of PP modified by either maleic anhydride or ionomer addition. However, favourable experimental conditions such as thinner specimens or higher compatibilizer content were used in the case of maleic anhydride modified PP. This indicates a more important positive effect on compatibilization by means of ionomer addition.

Fracture Mechanisms and Residual Strength of FRPA made with Direct Injection Molding Method by Means of Acoustic Emission Technique

Fracture Mechanisms and Residual Strength of FRPA made with Direct Injection Molding Method by Means of Acoustic Emission Technique

‘Nanovel’ process for powders for direct injection moulding application : G.Schulz. (Nanovel AG, Germany.)

‘Nanovel’ process for powders for direct injection moulding application : G.Schulz. (Nanovel AG, Germany.)

Morphology and mechanical characteristics of compatibilized polyamide 6-liquid crystalline polymer composites

The blend behaviour of polyamide 6 (PA6) and thermotropic liquid crystalline polymer (LCP) compatibilized with maleic anhydride grafted polypropylene (MAP) was studied by means of scanning electron microscopy (SEM), drop weight Charpy impact test, static tensile and dynamic mechanical measurements. The blending was performed via direct injection moulding of PA6(MAP) with LCP pellets at 285°C. Tensile measurements indicated that the tensile strength and modulus increase with increasing LCP content and the mechanical properties are above predictions of the rule of mixtures. This was correlated with the formation of LCP fibrils with large aspect ratios in both skin and core sections of the PA6(MAP)/LCP blends. Charpy impact test showed that the impact fracture toughness decreases significantly with the addition of small amounts of LCP content. However, the impact toughness appeared to increase as the LCP content is above 30 wt%. This was attributed to the enhanced fibrillation of the LCP dispersed phase at higher concentration. © 1997 Elsevier Science Ltd.

Acrylonitrile–butadiene–styrene-toughened polysulphone of bisphenol A blends: influence of processing temperature and composition

Polysulphone of bisphenol A (PSU)/acrylonitrile–butadiene–styrene (ABS) blends have been obtained by direct injection moulding at different temperatures and for compositions in the PSU-rich range. Direct injection moulding provided a mixing level similar to that of kneading. The blends were almost fully immiscible with the exception of the polybutadiene (PBD) phase where some PSU appeared to be present. Only a very small amount of ABS was required to greatly improve the tracking index of PSU. The mechanical properties, however, were those of a compatible material, and did not depend on the injection temperature. Moreover, with the exception of the ductility, they were in fairly good proportion to the blend composition, and provided the most balanced set of properties at an ABS content near 5%.

Development of tough matrix/brittle dispersed phase blends: PSU/SAN blends

Blends consisting of a tough matrix/brittle dispersed phase 75 25 polysulfone of bisphenol A (PSU)/styrene-acrylonitrile copolymer (SAN) were obtained both by kneading followed by compression moulding, and by direct injection moulding. The compression moulded blends showed very poor ductility due to the coarsening of the fine dispersed phase obtained by kneading. The directly injection moulded blends, however, showed almost additive ductility values between those of the two pure components but poor impact strength. This was mainly due to the different morphology obtained, this being fine and homogeneous in tensile specimens and heterogeneous in the impact ones.

Phase and mechanical characterization of poly(ether imide)/polyarylate injection moulded blends

Poly(ether imide) (PEI)/polyarylate (PAr) blends were prepared throughout the composition range by direct injection moulding (IM) at 300 and 340 °C. The homogeneity and miscibility level obtained were comparable to that usually obtained by kneading. Whatever the moulding temperature, the 90 10 and 80 20 blends, although with a higher T g than usual, appeared miscible by both DSC and SEM. The blends of other compositions were partially miscible. Unexpectedly, the mechanical properties were close or even above those predicted by the additivity rule for both miscible and partially miscible compositions. This took place not only in the case of the Young's modulus or yield stress, but also in the case of a property as sensitive to immiscibility as ductility. Leaving aside orientation effects, it was concluded that full miscibility is not necessary for synergism in break properties to be obtained.

Mechanical property enhancement of glass fibre-reinforced polyamide composite made by direct injection moulding process

The direct injection moulding process—in which composite parts are moulded directly from a dry blend of the resin and reinforcement, eliminating the preliminary melt-compounding process—is more effective in enhancing the mechanical properties of composite parts with high glass fibre loading than the conventional two-step process. By applying a complex theory of composites, the tensile strength of composites were calculated at suitable combinations of fibre—matrix interface adhesion τ and glass fibre tensile strength λ f, so that the calculated tensile strength corresponds to the measured tensile strength of the moulded parts. The enhanced tensile strengh of composites moulded by the direct injection process is attributed to the longer glass fibres remaining in the parts; moreover, the reduced deterioration of the glass fibres associated with the process may also have an effect.

Development of High Strength Composite Parts by Direct Injection Molding

Development of High Strength Composite Parts by Direct Injection Molding