A complex medical instrument exterior shell was chosen as a studying object to investigate the influence of relative low (<10 MPa) gas counter pressure process on microcellular injection molding process. The gas counter pressure microcellular injection mould and related experiments were designed. The relative low gas counter pressure under which the melt can foam was mainly considered to improve the surface quality of molded parts without significantly prolonging production cycle. The effects of the gas counter pressure parameters on the surface quality, cell morphology, and cell density of microcellular parts were studied. A critical melt flow front pressure to effectively eliminate surface swirl marks of microcellular injection molded part was proposed. The mechanism of the influence of gas counter pressure process on foaming behavior of melt in filling process was analyzed. The reasonable gas counter pressure parameters to improve surface quality of products without significantly increasing molding cycle were obtained. By using the obtained reasonable gas counter pressure parameters, a sound microcellular injection molded product was injected finally.
Okamoto K. Microcellular processing. Hanser: Munich, 2003.
4.
KramschusterACavittRErmerD. Effect of processing conditions on shrinkage and warpage and morphology of injection moulded parts using microcellular injection moulding. Plast Rubber Compos2006; 35: 198–209.
5.
YoonJDKimJHChaSW. The effect of control factors and the effect of CaCO3 on the microcellular foam morphology. Polym Plast Technol Eng2005; 44: 805–814.
6.
HwangSSHsuPPChiangCW. Shrinkage study of textile roller molded by conventional/microcellular injection-molding process. Int Commun Heat Mass Transf2008; 35: 735–743.
7.
HuangHXWangJK. Equipment development and experimental investigation on the cellular structure of microcellular injection molded parts. Polym Test2008; 27: 513–519.
8.
BledzkiAKFarukO. Influence of different endothermic foaming agents on microcellular injection moulded wood fibre reinforced pp composites. Cellul Polym2006; 25: 143–158.
9.
BledzkiAKFarukO. Effects of the chemical foaming agents, injection parameters, and melt-flow index on the microstructure and mechanical properties of microcellular injection-molded wood-fiber/polypropylene composites. J Appl Polym Sci2005; 97: 1090–1096.
10.
PengJTurngLSPengXF. A new microcellular injection molding process for polycarbonate using water as the physical blowing agent. Polym Eng Sci2012; 52: 1464–1473.
11.
YuanMTurngLS. Microstructure and mechanical properties of microcellular injection molded polyamide-6 nanocomposites. Polym2005; 46: 7273–7292.
12.
ChandraAGongSQYuanMJ. Microstructure and crystallography in microcellular injection-molded polyamide-6 nanocomposite and neat resin. Polym Eng Sci2005; 45: 52–61.
13.
KharbasHNelsonPYuanMJ. Effects of nano-fillers and process conditions on the microstructure and mechanical properties of microcellular injection molded polyamide nanocomposites. Polym Compos2003; 24: 655–671.
14.
WuHWintermantelEHaugenHJ. The effects of mold design on the pore morphology of polymers produced with mucell technology. J Cellul Plast2010; 46: 519–530.
15.
RizviSJABhatnagarN. Optimization of microcellular injection molding parameters. Int Polym Process2009; 24: 399–405.
16.
TurngLSKharbasH. Effect of process conditions on the weld-line strength and microstructure of microcellular injection molded parts. Polym Eng Sci2003; 43: 157–168.
17.
FengJJBerteloCA. Prediction of bubble growth and size distribution in polymer foaming based on a new heterogeneous nucleation model. J Rheol2004; 48: 439–462.
18.
YanYZuY. Numerical simulation of bubbles deformation, flow, and coalescence in a microchannel under pseudo-nucleation conditions. Heat Transfer Eng2011; 32: 1182–1190.
19.
ChaSWYoonJD. The relationship of mold temperatures and swirl marks on the surface of microcellular plastics. Polym-Plast Technol Eng2005; 44: 795–803.
20.
GuoMCSantoniAHeuzeyMC. Occurrence of surface defects in TPO injected foam parts. J Cellul Plast2007; 43: 273–296.
21.
LeeJTurngLSDoughertyE. A novel method for improving the surface quality of microcellular injection molded parts. Polymer2011; 52: 1436–1446.
22.
TurngLSKharbasH. Development of a hybrid solid-microcellular co-injection molding process. Int Polym Process2004; 19: 77–86.
23.
ChenHLChienRDChenSC. Using thermally insulated polymer film for mold temperature control to improve surface quality of microcellular injection molded parts. Int Commun Heat Mass Transf2008; 35: 991–994.
24.
BledzkiAKKuhnJKirschlingH. Microcellular injection molding of PP and PC-ABS with precision mold opening and gas counterpressure. Cellul Polym2008; 27: 91–100.
25.
KotzevGDjoumaliiskySKrastevaM. Effect of sample configuration on the morphology of foamed LDPE/PP blends injection molded by a gas counterpressure process. Macromol Mater Eng2007; 292: 769–779.
26.
ChenSCHsuPSHwangSS. The effects of gas counter pressure and mold temperature variation on the surface quality and morphology of the microcellular polystyrene foams. J Appl Polym Sci2013; 127: 4769–4776.
27.
ChenSCHsuPSLinYW. Establishment of gas counter pressure technology and its application to improve the surface quality of microcellular injection molded parts. Int Polym Process2011; 26: 275–282.
28.
ColtonJSSuhNP. Nucleation of microcellular foam:theory and practice. Polym Eng Sci1987; 27: 500–503.
HwangSSLiuSPHsuPP. Morphology, mechanical, thermal and rheological behavior of microcellular injection molded TPO-clay nanocomposites prepared by kneader. Int Commun Heat Mass Transf2011; 38: 597–606.
31.
ChenSCLiaoWHChienRD. Structure and mechanical properties of polystyrene foams made through microcellular injection molding via control mechanisms of gas counter pressure and mold temperature. Int Commun Heat Mass Transf2012; 39: 1125–1131.
