02701nas a2200253   4500008004100000022001400041245011900055210006900174260009300243300001200336490000700348520178100355100001602136700001502152700002202167700001902189700001902208700001802227700001402245700001702259700002302276700002102299856012702320       2016                        eng d  a0930-777X00aEffect of plug temperature on the strain and thickness distribution ofcomponents made by plug assist thermoforming0 aEffect of plug temperature on the strain and thickness distribut  aKOLBERGERSTRASSE 22, POSTFACH 86 04 20, D-81679 MUNICH, GERMANYbCARL HANSER VERLAGcMAY  a166-1780 v313 a<p>Plug temperature is a key parameter affecting the thickness distribution of thermoplastic components made by plug assist thermoforming. For a specified pair of plug and plastic sheet, the variation in plug temperature can alter the coefficient of friction (COF) between the pair. We show here how the temperature dependence of COF influences the nature and extent of biaxial stretching of the sheet and consequently the thickness distribution of the thermoformed component. In the present study, high impact polystyrene (HIPS) sheets were thermoformed into axisymmetric cups using a plug-assist process in which the aluminum plug temperature (T-plug) was varied from ambient to above the glass transition temperature of HIPS (similar to 100 degrees C). Biaxial strain maps on the surfaces of the formed cups were measured and quantified using Grid Strain Analysis (GSA). Thickness distributions of the cups were also measured. Temperature dependent COF between HIPS and aluminum was determined independently using a rotational rheometer. The measured COF was low for T &lt; 100 degrees C, whereas it increased appreciably at and above 100 degrees C. We conclude that when T-plug &lt; 100 degrees C the HIPS sheet slips on the plug during forming, and this results in biaxial stretching of the base and walls of the formed cup. In contrast for T-plug &gt; 100 degrees C, a significant reduction in the magnitude of slip is expected. Here the sheet is gripped at the clamp and by the plug during forming which causes reduced biaxial stretching of the base and increased uniaxial stretching of the walls of the cup. Simulations of plug-assist thermoforming using a temperature dependent COF showed qualitative agreement with the GSA data thereby supporting our inferences.</p>1 aMarathe, D.1 aRokade, D.1 aAzad, Lal, Busher1 aJadhav, Kishor1 aMahajan, Sunil1 aAhmad, Zubair1 aGupta, S.1 aKulkarni, S.1 aJuvekar, Vinay, A.1 aLele, Ashish, K.  uhttps://library.ncl.res.in/content/effect-plug-temperature-strain-and-thickness-distribution-ofcomponents-made-plug-assist02400nas a2200229   4500008004100000022001400041245011100055210006900166260000800235300001200243490000700255520165800262100001601920700001501936700001601951700001401967700001401981700001701995700001502012700001302027856013002040       2019                        eng d  a0930-777X00aStudy of rheology and plug assist thermoforming of linear and branched pp homopolymer and impact copolymer0 aStudy of rheology and plug assist thermoforming of linear and br  cJUL  a339-3550 v343 a<p>Polypropylene (PP) is one of the fastest growing thermoplastic polymers in the world, second only to polyethylene. This is primarily due to its excellent balance of physical and chemical properties at a lower cost. PP however possesses low melt strength on account of its linear structure and hence is not easily amenable to processing techniques that involve free surface stretching deformations like thermoforming, blow molding and extrusion film casting. One way to enhance the melt strength of PP is to incorporate long chain branches in its molecular architecture. The present study focuses on the impact of rheology of linear and branched PP on their thermoforming characteristics. Two grades each of linear and long chain branched (LCB) PP homopolymer and impact copolymer (ICP) were used. It was observed that the LCB-PP homopolymer and LCB-ICP showed higher flow activation energy, reduced value of loss tangent and nearly equal frequency dependence of storage and loss moduli in shear rheology. Also, a strong strain hardening behavior was displayed in extensional rheology by the LCB grades. Plug assist thermoforming experiments were carried out to assess the effect of long chain branching on surface strain and thickness distribution for axisymmetric cups of two draw ratios. Biaxial surface strain maps of the formed cups were quantified using Grid Strain Analysis (GSA). Thermoformed cups made from LCB-PP homopolymer and LCB-impact copolymer showed lower surface strain and overall higher thickness as compared to cups made from their linear counterparts, which is in accordance with what might be expected from their rheology.</p>
1 aMarathe, D.1 aShelar, S.1 aMahajan, S.1 aAhmad, Z.1 aGupta, S.1 aKulkarni, S.1 aJuvekar, V1 aLele, A.  uhttps://library.ncl.res.in/content/study-rheology-and-plug-assist-thermoforming-linear-and-branched-pp-homopolymer-and-impact