Abstract
An experimental investigation of injection molding was conducted to assess the high infrared radiation (IR) transmittance with an opaque state (low visibility ray (VR) transmittance) necessary for IR system lenses as a target high-density polyethylene (HDPE) IR transmission material. In our earlier investigation, experimental investigations of injection molding and injection press molding were conducted using the mold cavity of a disk-shaped finished mirror-like surface. For high mold temperature and long cooling time, the increased core-layer thickness improved the IR transmittance. Simultaneously, the VR transmittance decreased because the crystallinity became higher. Furthermore, when injection press molding was done, the VR transmittance decreased because the crystallinity increased. Using a 0.5-mm-thick mold cavity with disk shapes having different surface roughness, an injection molding experiment was conducted for this study while changing only the mold temperature of 20 to 80°C. Results show that when the mold surface roughness became high, the surface roughness of molded parts became high, too. Thereby the IR and VR transmittance were decreased. However, when the mold temperature was high, the influences of the so-called skin-core structure and crystallinity were stronger than the influence of the surface roughness of molded parts. The IR transmittance increased because of the decrease of the skin layer. Furthermore, the VR transmittance decreased because of a simultaneous rise of the crystallinity. The minimum value of obtained VR transmittance was 9.3% at mold temperature of 80°C using a mold of the highest surface roughness. This molded part reached an opaque state. Furthermore, a higher IR transmittance of 64.9% was obtained. When injection molding was conducted using a mold of a mirror-like surface with the same conditions as those in this investigation in our earlier investigation, the obtained IR and VR transmittances were 65.4% and 0.6%, respectively. Consequently, when the mold temperature was high, a few differences were found with transmittance of the molded parts using the mold of the mirror-like surface. Results showed that no difficulty arises when a mold having higher surface roughness is used at a higher mold temperature.
References
Abdul Manaf, A. R., Yan, J., “Press Molding of a Si–HDPE Hybrid Lens Substrate and Evaluation of its Infrared Optical Properties”, Precis. Eng., 43, 429–438 (2016) 10.1016/j.precisioneng.2015.09.007Search in Google Scholar
Cao, W., Wang, K., Zhang, Q., Du, R. and Fu, Q., “The Hierarchy Structure and Orientation of High Density Polyethylene Obtained via Dynamic Packing Injection Molding”, Polymer, 47, 6857–6867 (2006) 10.1016/j.polymer.2006.07.037Search in Google Scholar
Combessis, A., Mazel, C., Maugin, M. and Flandin, L., “Optical Density as a Probe of Carbon Nanotubes Dispersion in Polymers” J. Appl. Polym. Sci., 130, 1778–1786 (2013) 10.1002/app.39333Search in Google Scholar
Erismann, F., Fong, H., Graef, G. L. and Risbud, S. H., “IR Optical Properties of ZnS/ZnSe-modified High-Density Polyethylene”, J. Appl. Polym. Sci., 65, 2727–2732 (1997) 10.1002/(SICI)1097-4628(19970926)65:13<2727::AID-APP14>3.0.CO;2-USearch in Google Scholar
Fujiyama, M., Wakino, T., “Molecular Orientation in Injection-Molded Polypropylene Copolymers with Ethylene” Int. Polym. Proc., 7, 97–105 (1992) 10.3139/217.920097Search in Google Scholar
Giboz, J., Spoelstra, A. B., Portale, G., Copponnex, T. H., Meijer, E., Peters, G. W. and Mele, P., “On the Origin of the “Core-Free” Morphology in Microinjection-Molded HDPE”, J. Polym. Sci. Part B: Polym. Phys., 49, 1470–1478 (2011) 10.1002/polb.22332Search in Google Scholar
Guo, C., Liu, F. H., Wu, X., Liu, H. and Zhanf, J., “Morphological Evolution of HDPE Parts in the Microinjection Molding: Comparison with Conventional Injection Molding”, J. Appl. Polym. Sci., 126, 452–462 (2012) 10.1002/app.36698Search in Google Scholar
Hnatkova, E., Dvorak, Z., “Effect of the Skin-Core Morphology on the Mechanical Properties of Injection-Moulded Parts”, Mater. Technol., 50, 195–198 (2016) 10.17222/mit.2014.151Search in Google Scholar
Kamal, M. R., Kalyon, D. M. and Dealy, J. M., “An Integrated Experimental Study of the Injection Molding Behavior of some Polyethylene Resins”, Polym. Eng. Sci., 20, 1117–1125 (1980) 10.1002/pen.760201702Search in Google Scholar
Kaneda, R., Takahashi, T., Takiguchi, M., Hijikata, M. and Ito, H., “Optical Properties of HDPE in Injection Molding and Injection Press Molding for IR System Lenses”, Int. Polym. Proc., 31, 385–392 (2016) 10.3139/217.3261Search in Google Scholar
Kantz, M. R., NewmanJr., H. D. and Stigale, F. H., “The Skin-Core Morphology and Structure–Property Relationships in Injection Molded Polypropylene”, J. Appl. Polym. Sci., 16, 1249–1260 (1972) 10.1002/app.1972.070160516Search in Google Scholar
Kikutani, T., Ito, H.: Introduction to Higher-Order Structure Analysis of Plastic Molded Articles (in Japanese), Nikkan Kogyo Shimbun, Tokyo, Japan, p. 91 (2006)Search in Google Scholar
Kuttner, P., “Surface Structure, Veiling Glare, and Image Quality of Optical Elements in the 3 to 10 μm Spectral Region”, Opt. Eng., 23, 137–140 (1984) 10.1117/12.7973401Search in Google Scholar
Lin, X., Rose, F. C., Ren, D., Wang, K. and Coates, P., “Shear-Induced Crystallization Morphology and Mechanical Property of High Density Polyethylene in Micro-Injection Molding”, J. Polym. Res., 20, 122 (2013) 10.1007/s10965-013-0122-8Search in Google Scholar
Osswald, T. A., Turng, L. S. and Gramann, P. J., (Eds.): Injection Molding Handbook, Hanser Publishers, Munich, p. 37 (2002)Search in Google Scholar
Tan, V., Kamal, M. R., “Morphological Zones and Orientation in Injection-Molded Polyethylene”, J. Appl. Polym. Sci., 22, 2341–2355 (1978) 10.1002/app.1978.070220824Search in Google Scholar
Tohyama, S., “Optical Components in Infrared Region” (in Japanese), JSPE, 56, 1967–1970 (1990) 10.2493/jjspe.56.1967Search in Google Scholar
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