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Fast crystallizing alumina ceramic fiber filled polymer compositions

IP.com Disclosure Number: IPCOM000220991D
Publication Date: 2012-Aug-20
Document File: 9 page(s) / 114K

Publishing Venue

The IP.com Prior Art Database

Abstract

Alumina has been commonly used as a nucleating agent in semi-crystalline polymers to accelerate crystallization. However, due to the low (~1) aspect ratio of the alumina particles, the resulting compositions do not exhibit highly improved stiffness which may necessitate the use of additional reinforcing fillers, such as glass fibers. The use of additional fillers increases material and production costs. We describe the use of high aspect ratio alumina fibers in polymers which simultaneously act as nucleating and reinforcing agents and thus, eliminate the necessity of using multiple fillers.

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Fast crystallizing alumina ceramic fiber filled polymer compositions

Introduction

Alumina has been commonly used as a nucleating agent in semi-crystalline polymers to accelerate crystallization. However, due to the low (~1) aspect ratio of the alumina particles, the resulting compositions do not exhibit highly improved stiffness which may necessitate the use of additional reinforcing fillers, such as glass fibers. The use of additional fillers increases material and production costs. We describe the use of high aspect ratio alumina fibers in polymers which simultaneously act as nucleating and reinforcing agents and thus, eliminate the necessity of using multiple fillers.

The slow rate of crystallization from the melt of various semi-crystalline polymers, such as poly(ethylene terephthalate) (PET), has been known and it has been designated as one of the primary limitations of PET, as discussed in Modern Polyesters (edited by J. Scheirs and T. E. Long, Wiley, New York, 2003, page 515). Nucleating agents have been commonly introduced to polymers to increase the rate of crystallization during melt processing. Alumina, among other ceramics, has been a common and widely used nucleating agent. However, alumina filled, fast crystallizing polymers do not exhibit a very high stiffness. Although we do not wish to be bound by a theory, the relatively low extents of improvements in stiffness in the presence of alumina is thought to be originating from low (~1) aspect ratio of nearly spherical alumina particles. Hence, to obtain very stiff, yet fast crystallizing alumina filled polymer compositions, introduction of additional, reinforcing fibrous filler, such as glass fiber, is usually required. However, the use of additional fillers increases material and production costs. Hence, using a single filler, such as a ceramic fiber, which would act both as a nucleating agent and a reinforcing filler would be useful.

Examples

Example 1

Materials:

Table 1. Materials used in this work. Abbreviations: PET: Poly(ethylene terephtalate), PBT: poly(butylene terephtalate), PTT: poly(trimethylene terephtalate),

Material Grade

Alumina Fiber NextelTM 610 (4500D Rov DI Water Sized) 3M Company

PET Eastapak 7352

PBT Valox 195 PTT

Note that the aluminafibers are bare without the presence of any sizing and are used in the as received form. No further treatment or surface modification (such as the application of a coupling agent or sizing) was performed.

Sample Preparation:

Alumina fibers, PET, PBT, and PTT were dried at least for 12 hours in an oven at 95oC prior to melt compounding. Samples were prepared as follows:

The samples were prepared in a Brabender internal mixer. The temperature of the internal mixer was set to 295oC. The ingredients were mixed at 70 rpm for 5 minutes. The resin was introduced to the mixer first and the chopped fiber roving (each of ~10 cm length) was introduced to the mixer upon melting of the resin.

Vendor

Eastman Chemical

SABIC

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