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Direct injection molding of hollow glass microspheres with thermoplastics to produce light weight plastic articles

IP.com Disclosure Number: IPCOM000233954D
Publication Date: 2014-Jan-03
Document File: 8 page(s) / 458K

Publishing Venue

The IP.com Prior Art Database

Abstract

Hollow glass microspheres (HGM’s) are low density fillers provide high strength to weight ratio for reducing the weight of plastic components used in automotive vehicles. The light weight plastics help to reduce carbon emissions and promote fuel savings. 3M Glass Bubbles IM16K can sustain higher compressive force resistance and provide new application opportunities for compounders and processors.

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Direct injection molding of hollow glass microspheres with thermoplastics to produce light weight plastic articles

Introduction:

Common filler used in thermoplastics industry include talc, glass fibers, wallsonite etc. Fillers often improve stiffness, modulus, reduce the coefficient of thermal expansion and acts as the reinforcing or non- reinforcing filler based on their aspect ratio. Glass bubbles has an aspect ratio of 1 and spherical shape, promotes isotropic properties, improved dimensional stability, reduce injection molding cycle time and act as a preferred light weight filler

Polypropylene impact copolymer is used as a base polymer matrix in combination with or without impact modifiers for manufacturing automotive plastic parts. Addition of glass bubbles between 5 and 7wt% to the thermoplastic matrix, provide light weight, improved flexural and tensile modulus, and reduce warpage and shrinkage in molded components.

Glass microspheres are made from a chemically stable soda-lime borosilicate glass and produced in nominal diameters from 9-microns to 70-microns with densities ranging from 0.15 to 0.60 g/cc. The compressive strength of glass microspheres lies between 250 psi to 30,000 psi. The presence of glass bubbles in unfilled polypropylene will cause shorter cooling time from melt due to reduced volumetric heat capacity with hollow glass microspheres.

Thermoplastics compounds with specified loading of glass bubbles and/or other filler (eg. mineral or glass) can be prepared via compounding in a co-rotating intermeshing twin screw extruder such as shown in Figure


1. Polymer resin is feed into an extruder hopper via a resin feeder and passed through a set of conveying and kneading blocks to ensure its complete melting before wetting pressure sensitive fillers such as glass bubbles and glass fibers are introduced downstream in the extruder via side stuffing ports. If the filler is clay or talc, it can be introduced in zone 1 together with the resin.

One can see from Figure 1 the process involved and there are several elements needed to prepare the compounded pellets in a twin screw extruder.


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Figure 1. Twin screw extruder set up for compounding various fillers

Experimental:

Table 1 : Experimental Materials

Materials used 

Description 

Polypropylene Impact  copolymer 

Relene B220 MN, 20 MI commercially supplied by  Reliance  Industries, India  

Soda lime borosilicate glass 

Glass bubble iM16K, 0.46 g/cc commercially supplied by 3M  

microspheres 

Paraffinic Oil 

IPOL RPO‐201 from Sah Petroleum limited 

Polyamide‐6,6 

Zytel 101L NC1010 fr  om DuPont 

Specimen Preparation:

     In order to achieve all that is shown in Figure 1 in a one step injection molding process, the following methodology is used

• Glass bubble powders can be bound to plastics pellets using very small percentages of binders such as mineral oil or paraffinic oil. The purpose of the binders is to pr...