5-7 OCTOBER

ISFR

2011

167

TOLEDO (SPAIN)RHEOLOGICAL MODELIZATION OF ABS+PC RECYCLED BLENDS FOR INJECTIONMOLDING
M.A. Sellés 1, S. Sánchez-Caballero2, F. Parres1, J.E. Crespo1, R. Navarro1
1Instituto de Tecnologia de Materiales, Universitat Politècnica de València, Spain
2Instituto de Diseño para la Fabricación, Universitat Politècnica de València, Spaine-mail:maselles@dimm.upv.esAbstract
Acrylonitrile-butadiene-styrene copolymer (ABS) is a very broadly used material across various industries; however, inorder to improve its manufacturability, it is generally blended with polycarbonate. ABS is a rubber-modified copolymer ofstyrene and acrylonitrile. The development of ABS also has undergone several notable changes that have been carriedout because of need for improved the manufacturability. Polycarbonate (PC) is an engineering thermoplastic material withthree key characteristic properties that make it useful in many applications: toughness, transparency, and heat
resistance. However, PC is not easily processed. Generally, if attempting to make a more processable PC, the toughness
decreases, making it inadequate for engineering applications.
When these materials are recycled, the general characteristics of the ABS and the PC demean, but they fit perfectly inindustrial purposes. In the present work it is carried out a study of the rheological behaviour of the blends of ABS andrecycled PC, and its influence in the injection process. The aim is to present a model of the rheological behaviour,
validating the pattern with the obtained data of the different rehearsals carried out in a capillary rheometer.
It is difficult, due to their high cost, that a small company has a rheometer in their facilities to be able to find the curves ofviscosity of their materials. As a result of the presented modelization, they will be able to obtain these curves only from aseries of points measured in a MFI (Melt Flow Index).

Keywords: ABS, PC, Recycled, Modelization, Injection Molding

1. Introduction

2. Materials and Methods

In order to avoid the limitations and, thus, to characterize
the recycled material for evaluation in subsequent
phases, a model for rheological evaluation of materials isproposed in this document, which is based on thefollowing aspects:

We have used 3 types of blends, all formed by mixing
recycled ABS and PC, but with a different percentage.
The first mix is composed by simply recycled ABS. The
second is a blend of ABS and a 5% CP, and finally, thethird has a 10% blend of PC.

- Evaluation of the rheological characteristics of potential
starting materials.
- Determination of material behavior model based on thestudy of flow rate ranges.
- Correction of model, based on the recycled blend
composition.

Using the standard test for determining the rate of bulk
material flow and volume, we have established the MFI
index of the different mixtures, using a viscometer.
Results are shown in Table 1.

This rheological behavior modelization serves also as an
aid to small companies in the sense that it is difficult(given the relatively high cost that would be theacquisition of a capillary rheometer) to accurately identify
the rheological behavior of the recycled material [1]. In
this way, if characteristics of ABS and PC blends areknown, and with the help of this model, a company could
determine the material behavior in a specific section ofthe viscosity curve [2].

Table 1. Melt Flow Index for the three mixtures
Mixtures
123MFI
52 gr / 10 min
58 gr / 10 min
63 gr / 10 min

3. Results
With the three blends, tests were performed in a capillaryrheometer. 90 tests were conducted (5 tests x 2temperatures x 3 x 3 nozzles).
The variables used for each experiment were thosereflected in Table 2:interiores libro.indd 167

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6th International Symposium on Feedstock Recycling of Polymeric Materials

Table 2. Variables used for experiments
MaterialABS
ABS + 5% PC
ABS + 10%PC

Temperature
220 ºC240 ºCNozzle (L/D)
102030It has been also evaluated different types ofmathematical models, choosing the Cross-WLF, which
offer as a result the material viscosity in terms of physicalconditions to which it is subjected.
Moreover, the dependence parameters that directly
influence the viscosity of the material are [3,4]:
1. Temperature of the material during the process, Tm[K].
2. Shear rate at which the material is undergoing theprocess, [1 / s].
3. The pressure at which the material is subjected during
the process, p [Pa].

4. Conclusions
It is important to note that the model fits reality veryaccurately, as has been corroborated. The approach
may be perfectly good for many applications.
In addition, from tests performed and subsequentgraphical representation, it has been clearly observed in
the viscosity curves how the addition of recycled
polycarbonate ABS provides a lower viscosity. Thisquality greatly improves the processability.

References[1] Macosko C.W. Rheology principles, Measurements,and Applications. ISBN 0471185752 –VCH Publishers,
Inc, New York 1994.
[2] Ruifeng L. Rheological properties of recycled
Polycarbonate and ABS melts. XIIIth International
Congress on Rheology. 2000. Vol.1 p216-218[3] Rohn C.L. Analytical polymer rheology: structure,processing, property, relationships. ISBN 156990149X –Hanser 1994
[4] Pham, Wecle, Ceraso, Rheology Enhancement in
PC/ABS Blends, Advanced Materials, 2000, 12, nº 23

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