SPE Library

Forced and starve feeding are well known feeding methods to input material into a co-rotating twin screw extruder. Polymers in powder form and materials such as talc and mica are a challenge to introduce into the extruder. The geometry of the intake zone screw elements and the side-feed zone screw elements decide the conveying ability and the intake capacity of the extruder. The problem of lower intake capacity is solved by the use of Single Flight Shovel (SFV) Triple Flight Shovel (TFV) and Regular Flight Shovel (RFV) classified as 'FV' type elements (Patent Pending). The screw flights are designed to plough through the material similar to the working of a snowplough. Increase in intake capacity compared to Erdmenger-type and Schubkanten-type screw elements is discussed.

Forced and starve feeding are well known feeding methods to input material into a co-rotating twin screw extruder. Polymers in powder form and materials such as talc and mica are a challenge to introduce into the extruder. The geometry of the intake zone screw elements and the side-feed zone screw elements decide the conveying ability and the intake capacity of the extruder. The problem of lower intake capacity is solved by the use of Single Flight Shovel (SFV), Triple Flight Shovel (TFV) and Regular Flight Shovel (RFV) classified as 'FV' type elements (Patent Pending). The screw flights are designed to plough through the material similar to the working of a snowplough. Increase in intake capacity compared to Erdmenger-type and Schubkanten-type screw elements is discussed.

Increase in screw speed results in increased localized shear rates in co-rotating twin-screw extruders due to higher radial and meta-radial shear. This results in shear non-uniformity which in-turn results in degradation of shear sensitive material. Shear rates induced by kneading elements with different geometries are studied in the axial (longitudinal) radial and meta-radial shear planes. Elements with fractional lobed geometry having unequal tip angles show greater shear uniformity minimizing excessive shear in small regions. A careful study of the geometries of kneading elements and their shear distribution is provided for practical use in compounding application.

Increase in screw speed results in increased localized shear rates in co-rotating twin-screw extruders due to higher radial and meta-radial shear. This results in shear non-uniformity which in-turn results in degradation of shear sensitive material. Shear rates induced by kneading elements with different geometries are studied in the axial (longitudinal), radial and meta-radial shear planes. Elements with fractional lobed geometry having unequal tip angles show greater shear uniformity minimizing excessive shear in small regions. A careful study of the geometries of kneading elements and their shear distribution is provided for practical use in compounding application.

In-situ compatibilization of immiscible blends of PEN and thermotropic LCP was achieved by the ultrasonically-aided extrusion process. Ultrasonically treated PEN underwent degradation. In PEN/LCP blends, LCP acted as a nucleating agent. Ultrasonically induced copolymer formation was detected by MALDI-TOF mass spectrometry in the blends. Ultrasonic treatment of 90/10 PEN/LCP blends improved interfacial adhesion in fibers spun at intermediate draw down ratios (DDR), improving their ductility. The lack of improvement in the mechanical properties of fibers spun at high DDR after ultrasonic treatment was attributed to the disturbance of interfacial copolymer by high elongational stresses.

This paper investigates the effects of clay on the mechanical properties of injection molded high-density polyethylene (HDPE)/clay nanocomposite foams that contained a very small amount of clay in the range of 0.1 to 1 wt%. Nanocomposite compounds were prepared by a melt blending masterbatch process and injection molded by using an advanced structural foam molding machine inwhich N2 was used for foams as a physical blowing agent.The results suggest that the addition of clay increased the flexural strength and modulus of both solid and foam nanocomposites as its contents were increased. The results also indicate that the foam nanocomposites always exhibited lower flexural properties but higher notched Izod impact strength than solid nanocomposites at each given clay amount.

Effective cooling channel design in the mould is important because it not only affects cycle time but also quality of the injection moulded plastic part. A good cooling system design can reduce cycle time and achieve dimensional stability of the part which will consequently produce better quality part. This paper describes a new square sectioned conformal cooling channel system for injection moulding. Both simulation and experimental verification have been done with these new cooling channels system. Comparative analysis has been done for an industrial part, a plastic bowl, with conventional cooling channels using the Moldflow simulation software. Experimental verification has been done for a test plastic part with mini injection moulding machine. Comparative results are presented based on temperature distribution on mould surface, cooling time or freezing time of the plastic part and hardness number of the plastic part. Results provide a uniform temperature distribution and hardness number with reduced freezing time of the plastic part.

Injection moldable thermoplastic polyetherimidepolyester carbonate miscible blends with Tgƒ??s rangingfrom 142ƒ??218oC were developed for applicationsrequiring practical impact and melt flow property capabilities greater than those currently achieved with Polyetherimide. The resin blends demonstrate significant improvement in room temperature ductility and high speed impact resistance with total energy required for sample fracture increased as high as 98% depending on blend ratio. The addition of polyester carbonate in the resin blend increased the melt flow rate 10x as compared to unblended polyetherimide therefore resulting in meltprocessing temperatures to 290-370 oC and moldtemperatures of 80-150 oC with actual processingconditions dependent on blend composition. The injection molding processability of the resins and their material properties are presented and compared to polyetherimide.

In recent years, the development of recycling methods for waste PET bottles has generated much interest due to environmental and waste management concerns. Therefore, in this study, recycled PET (RPET) was considered instead of PS or PVC to prepare shrink films for labeling purposes. However, the labels would still have to be removed from the bottles prior to recycling due to color incompatibility. For this reason, the tear properties of the RPET labels, especially at the heat sealed regions, are elucidated and correlated to film crystallinity and molecular orientation.

In recent years, the development of recycling methods for waste PET bottles has generated much interest due to environmental and waste management concerns. Therefore, in this study, recycled PET (RPET) was considered instead of PS or PVC to prepare shrink films for labeling purposes. However, the labels would still have to be removed from the bottles prior to recycling due to color incompatibility. For this reason, the tear properties of the RPET labels, especially at the heat sealed regions, are elucidated and correlated to film crystallinity and molecular orientation.

Wood Plastic Composites (WPC) require improvements in properties such as strength, which will help WPC find applications in areas where it is now deemed unsuitable. Compression molding provides a quick method for preparing test specimen. During extrusion a substantial amount of wood fibers get aligned in the direction of flow, whereas, in compression molding these are generally randomly oriented in two dimensions. A properly designed mold ensures greater uni-directional alignment of fibers so that test specimens have greater similarity of fiber orientation with extruded profiles. In this paper, a compression molding system, designed to provide greater one dimension extensional flow is discussed.

To maintain the constant temperature for the plastic inside the hot-runner manifold is an important quality control in mass-production injection-molding process with hot-runner design. Without the constant and uniform temperature distribution, the molded parts wonƒ??t have good yield percentage. As such, this work takes CAD model and the temperature of heater to simulate the temperature distribution of hot-runner manifold. The results show very good agreement with the experimental verification and can be utilized to improve the heater design and efficiency, as such the temperature distribution of manifold can be further optimized.

To maintain the constant temperature for the plastic inside the hot-runner manifold is an important quality control in mass-production injection-molding process with hot-runner design. Without the constant and uniform temperature distribution, the molded parts won’t have good yield percentage. As such, this work takes CAD model and the temperature of heater to simulate the temperature distribution of hot-runner manifold. The results show very good agreement with the experimental verification and can be utilized to improve the heater design and efficiency, as such the temperature distribution of manifold can be further optimized.

In the study a gas-assisted heating system was established and its efficiency evaluated. Relevant parameters including the variable geometry for gas entrance (Circular and Divergent channel) gas temperature and gas flow rate as well as the mold surface coating of ZrO2 were varied for heating efficiency consideration. The results show that the maximum heating rate and temperature reached 33oC/s and 245.3oC when air temperature was 500oC at a flow rate of 400 L/min. It was also found that the divergent entrance channel obtains better temperature uniformity. Finally a case study of molding biochips with a micro channel showed replication accuracy increases of up to 22%.

In the study, a gas-assisted heating system was established and its efficiency evaluated. Relevant parameters, including the variable geometry for gas entrance (Circular and Divergent channel), gas temperature, and gas flow rate, as well as the mold surface coating of ZrO2, were varied for heating efficiency consideration. The results show that the maximum heating rate and temperature reached 33oC/s and 245.3oC when air temperature was 500oC at a flow rate of 400 L/min. It was also found that the divergent entrance channel obtains better temperature uniformity. Finally, a case study of molding biochips with a micro channel showed replication accuracy increases of up to 22%.

It is known that the ultra high speed injection molding is a proper solution for molding thin-wall parts.This study investigates the effect of processing conditions including melt temperature, mold temperature, injection speed on mechanical strength of molded ABS parts. Both single gate and double gates tensile test specimens were molded with and without weldlines. It was found that higher melt temperature and mold temperature as well as faster injection speed would increase tensile strength.Faster injection speed will also influence part mechanical properties, particularly in Young's modulus will increase of 15%, due to flow-induced molecular orientation along melt flow direction.

Using layered silicates in polymer processing developed rapidly over the last decade. Depending on the particle structure in the polymer a significantly higher level of reinforcement can be achieved. Characterization of nanocomposites is usually done with optical, mechanical and light scattering methods, which are offline and require very time consuming sample preparation and tests. In contrast, implementing in-line near infrared spectroscopy in a twin screw compounder enables real-time material characterization during compounding and provides a powerful instrument for quality control and optimization of the compounding process in terms of increased and constant quality.

CAE technology can anticipate the injection conditions before real injection molding begins.However, the parameter settings of the software require modification for ultra high-speed injection molding. In this study, we tested the flow length and used Moldflow Plastic Insight (MPI) to demonstrate the experiment using injection speeds of 100 mm/s to 1100 mm/s. The model is a spiral shape with a thickness of 0.4 mm and a width of 6 mm. We found that HTC value of software affects seriously flow length above injection speed of 700 mm/s, because this value relates to the heat transfer.The trend of flow length in the experiment is the same as in the simulation, but at injection speeds above 700 mm/s, the margin of error becomes large, about 21.7% for 900 mm/s, and 19.3% for 1100 mm/s. Clearly, the parameter settings for ultra high-speed injection molding require special adjustment.

The mold rapid heating-cooling technology is applied to the thin-walled co-injection molding, to produce high-quality electronic products. In case of thin-walled co-injection molding, the flash is often generated when molten polymer flows into small gap at parting line in mold with high injection pressure or under unbalanced clamp force condition. In this study, we investigate the effect of processing conditions on flash generation using injection molding CAE. We found that the phenomenon problems can be caused from structural clamping of moving plate in co-injection molding machine. The predicted flash shape was compared with experimental result.

Ultra high speed injection molding plays a more significant role in molding thin-wall part in recent 3C products. Systematic studies on the proper molding window of Secure Digital (SD) card housing of 0.25 mm thick using ultra high speed injection molding have not yet been reported. In this study a proper molding window for SD card housing using ABS and HDPE by varying mold temperatures from 30 ? to 100 ? and injection speeds from 100 mm/sec to 1200 mm/sec was investigated in details. Molded dimension and weight were measured experimentally. It was found that higher mold temperature and faster injection speed are two critical molding parameters that leading to good moldablilty for SD card housing.