Processing of cenosphere/HDPE syntactic foams using an industrial scale polymer injection molding machine

Abstract

Rapid production of high quality components is the key to cost reduction industrial applications.The present work is the first attempt of manufacturing syntactic foams, hollow particle filled lightweight composites, using an industrial scale injection molding machine. High density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the cost of the component. The pressure and temperature used in injection molding process are optimized to minimize fracture of cenospheres and obtain complete mixing of cenospheres with HDPE. The optimized parameters are used for manufacturing syntactic foams with 20, 40 and 60 wt.% cenospheres. With increasing cenosphere content, density and strength reduce and modulus increases. Surface modification of constituents results in rise in strength with increasing filler content. A theoretical model based on a differential scheme is used to estimate the properties of cenospheres by conducting parametric studies because of inherent difficulties in direct measurement of cenosphere properties. The potential for using the optimized injection molding process is demonstrated by casting several industrial components.

Effect of cenosphere surface treatment and blending method on the tensile properties of thermoplastic matrix syntactic foams

“…Figure (a) presents a representative micrograph of a syntactic foam containing untreated HDPE and cenospheres from a preliminary study on untreated constituents. Uniform dispersion of hollow cenospheres in the matrix is observed in this micrograph demonstrating the feasibility of using PIM for developing syntactic foam composites . However, lack of interfacial bonding between cenospheres and HDPE is visible in Figure (b).…”

“… A representative failed specimen of (a) virgin and (b) functionalized HDPE. [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.…”

“…This effective value for η encapsulates information about the loss in reinforcing capability of cenospheres due to defects in the particle wall as well as due to the imperfect interfacial bonding. The rule of mixtures approach for determining the properties of the ceramic wall is described in a previous work and yields the elastic modulus and Poisson's ratio of 157.4 and 0.185 GPa, respectively. Using these parameters, the measured modulus of the matrix, and assuming the Poisson's ratio of HDPE to be 0.425, the model is fitted to the experimental data for each material type with the radius ratio as the free parameter.…”

“…Tensile test samples are cast using PIM confirming to ASTM D 638‐10 standard. Injection temperature and pressure are maintained at 160°C and 30 kg cm −2 as per the earlier optimization study …”

“…The present work is focused on synthesis of cenosphere/HDPE syntactic foams using an industrial scale plastic injection molding (PIM) machine to reduce the production time and cost. Optimization of injection molding temperature and pressure parameters was conducted in a previous work . Using these optimized parameters, syntactic foams are fabricated using surface treated cenospheres and functionalized HDPE matrix.…”