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Filler Blends for Improving Thermoplastic Olefin Low-Temperature Impact/Stiffness Balance

IP.com Disclosure Number: IPCOM000244377D
Publication Date: 2015-Dec-07
Document File: 6 page(s) / 30K

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The IP.com Prior Art Database

Related People

Tonson Abraham: AUTHOR [+5]

Abstract

EMForce BioTM (needle-shaped, precipitated calcium carbonate, median particle length =1.25 µm) has been shown to improve both notched izod impact strength and low-temperature multi-axial impact ductility of TPOs over the corresponding talc (1.0µm median particle size) filled compounds. However, EMForce Bio is less reinforcing than talc, and compound stiffness is reduced. Increasing the EMForce loading over talc in a TPO formulation can produce equivalent stiffness compounds. In this case, the low-temperature ductility of the more dense TPO with the higher loading of EMForce is still improved over that of the less dense TPO filled with a lower level of talc. Note that both talc and EMForce Bio have the same specific gravity (2.7). However, the increased density of the EMForce Bio containing TPO makes this material unacceptable for the production of automotive plastic parts where "light weighting" of parts is mandated. In comparison with talc reinforced TPOs, EMForce Bio reinforced products also allow increased product melt flow and scratch resistance.

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Filler Blends for Improving Thermoplastic Olefin Low-Temperature Impact/Stiffness Balance

ABSTRACT: EMForce BioTM (needle-shaped, precipitated calcium carbonate, median particle length =1.25 µm) has been shown to improve both notched izod impact strength and low-temperature multi-axial impact ductility of TPOs over the corresponding talc (1.0µm median particle size) filled compounds.  However, EMForce Bio is less reinforcing than talc, and compound stiffness is reduced.  Increasing the EMForce loading over talc in a TPO formulation can produce equivalent stiffness compounds.  In this case, the low-temperature ductility of the more dense TPO with the higher loading of EMForce is still improved over that of the less dense TPO filled with a lower level of talc.  Note that both talc and EMForce Bio have the same specific gravity (2.7).  However, the increased density of the EMForce Bio containing TPO makes this material unacceptable for the production of automotive plastic parts where “light weighting” of parts is mandated.  In comparison with talc reinforced TPOs, EMForce Bio reinforced products also allow increased product melt flow and scratch resistance.

It is been found that the TPO stiffness loss observed in an EMForce Bio reinforced product as compared to the equivalent talc reinforced product, can be considerably reduced when a small portion of EmForce Bio in the original formulation is replaced with talc.  Largely retained in the mixed filler containing TPO is the excellent low-temperature ductility, and increased product melt flow and scratch resistance, of the TPO reinforced only with EMForce Bio.

Talc is known to nucleate the crystallization of PP.  Hence the increase in TPO stiffness by the addition of a small amount of talc to an EMForce Bio reinforced TPO is expected.  However, the retention of TPO low-temperature ductility is unexpected as conventional nucleating agents increase TPO stiffness at the expense of greatly reduced impact strength.  Data is presented to support the latter concept.

The use of EMForce Bio and filler (talc, nano-talc, Halloysite, magnesium oxysulfate whiskers) blends as reinforcement in any TPO composition is demonstrated.

BACKGROUND, SAMPLE DATA AND PERFORMANCE

Isotactic polypropylene (PP) would be ideal for use in automobile interior and exterior applications due to low cost, low density, and high stiffness, except for the poor low temperature impact resistance of this material.  The low temperature impact resistance of PP is improved by melt compounding with polyolefinic elastomers, at the expense of reduced compound stiffness.  Reinforcing fillers are included in the melt compounding process in order to increase compound stiffness and thus achieve the desired thermoplastic olefin (TPO) low-temperature impact/stiffness balance. 

Conventional reinforcing fillers such as talc have a detrimental effect on TPO impact resistance owing to the presence of a small fraction of large particles,...