Yes / Long chain branches (LCB) are successfully grafted to linear poly(lactic acid) (PLA) using functional group reactions with pentaerythritol triacrylate (PETA) and tetraethylthiuram disulfide (TETDS). Results show a high branching degree of PLA (∼49.5%) can be effectively obtained with adding only 1 wt % PETA, contributing remarkably to enhancing strain hardening. The density of the nuclei formed during nonisothermal crystallization for LCB-PLA samples is markedly increased contrasted with PLA, resulting in significantly enhancing crystallinity from 13.3% to 41%, the onset crystallization temperature (∼20 °C), and the crystallization rate. Interestingly, compared with mini-injection molding, the elevated wall shear rates (and corresponding shear stresses) prove to be beneficial to the creation of special crystalline morphologies (β-crystal form) and oriented structures under microinjection molding conditions, resulting in the improvement of tensile strength by ∼45 MPa. / Chinese Scholarship Council

No / A comprehensive study into the performance of 4 injection molding machines is reported, using identical mold, polymer, and processing conditions. Start-up dynamics and process repeatability were directly compared across machine technologies. One servohydraulic, one proportional hydraulic and two servoelectric machines were used in the study, ranging in age from 14 years to 1 year old at the time of the study. Experiments were carried out at identical set molding conditions for a run of 400 parts and part quality and process parameters monitored. Results showed a significant start up period in each case, correlating strongly to mold temperature. Age of machine proved to be the most significant factor in determining process repeatability; modern machines having significantly lower variation than older ones. Differences between the operating characteristics of hydraulic and electric machines were detected, control of screw position in hydraulic machines being less repeatable, although this had a minor effect on part repeatability. Electric machines were found to use up to 4 times less energy than their hydraulic counterparts and operate more efficiently.

Order was given for the prodiction of 20 000 pieces of fixing washers. In this case was chosen injection moulding technology. Based on the research, a structural design of the mold was prepared together with the drawing documentation. From the range of materials, it was chosen polypropilene MOSTEN GB218, which is suitable for the given produstion. The simulation verified the reliability and quality of production. The parameters of injection moulding were determined by calculations, and the machine J180ADS – 180U was selected base of them. In the economic evaluation, the total costs for the production of the entire series were established on Nc=19626,43€.

Yes / An ultrasound sensor system has been applied to the mould of both the water and gas assisted injection moulding processes. The mould has a cavity wall mounted pressure sensor and instrumentation to monitor the injection moulding machine. Two ultrasound sensors are used to monitor the arrival of the fluid (gas or water) bubble tip through the detection of reflected ultrasound energy from the fluid polymer boundary and the fluid bubble tip velocity through the polymer melt is estimated. The polymer contact with the cavity wall is observed through the reflected ultrasound energy from that boundary. A theoretically based estimation of the residual wall thickness is made using the ultrasound reflection from the fluid (gas or water) polymer boundary whilst the samples are still inside the mould and a good correlation with a physical measurement is observed.

Published Article / This paper discusses the results obtained from studies on the performance of different cooling layouts. The conventional method of cooling makes use of straight-line cooling channels. This simple method of cooling does not possess the capability of uniformly cooling down the part produced. In contrast, conformal cooling is a technique that makes use of cooling channels in an injection moulding tool that closely follows the geometry of the part to be produced. The paper presents some experiences gained in a comparative case study of conventional cooling vs conformal cooling using simulation, followed by an experimental validation and statistical analysis of the results.

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In this study, one of the plastic automotive parts, Air Duct, manufactured through blow moulding process is reviewed and investigated with a practical process point of view using structural mechanics approach. First, current blow moulding process was examined to find governing factors of the process which can be improved or adjusted for better quality control of finished product. Secondly, numerical analysis was conducted on the post-mould process in order to predict the deformation in the final products with properly assumed initial and boundary conditions. The simulation results showed that the degree of warpage under current blow moulding process could be predicted at a reasonable accuracy. It was also discovered that the distortions of the holes are strongly dependent on it location and surrounding, and the current cooling method should be improved to improve the quality. Based on the simulation results and literature survey, a better post-mould cooling method was suggested. In addition, the problem in cooling system was identified, and redesigning scheme was recommended.