Investigation of the Effect of MM5935EF on Polylactic Acid Formulations (30-Nov-2011)

REPORT TITLE:

Investigation of the Effect of MM5935EF on Polylactic Acid Formulations

ABSTRACT:

A DOE was used to evaluate the effect of MM 5935EF on the melt strength and thermal properties of Polylactic Acid (PLA). When comparing MM 5935EF to a conventional fibrillating polytetrafluoroethylene (PTFE), the results demonstrate that both PTFE types are functionally equivalent.

INTRODUCTION

Polytetrafluoroethylene (PTFE) has been used to improve melt strength of various polymers. 3M has a family of additives that can be used for that purpose. The most recent addition to the family, MM5935EF, has the advantage of being easier to handle. Unlike conventional PTFE, it does not require cold storage to avoid premature fibrillation.

This study investigates the efficacy of this product when compared to conventional PTFE. More specifically, the comparative performance of both types of PTFE was evaluated in PLA, where melt strength has been reported to be insufficient for several applications. To this extent, we used a design of experiment (DOE) to prepare formulations comprising blends of PLA (Ingeo 4032D) with three types of additives. These additives were: Tributyl-O-Acetyl Citrate (equivalent to Citroflex A4, a plasticizer), talc (ABT 2500, a nucleator), and PTFE (a viscosity modifier and nucleator). Two types of fibrillating PTFE were used (TF 2021 and MM 5935). A fluoroplastic (FTP

- FX 5912) similar to the one found in MM5935EF was also used, thus ensuring an orthogonal design. The formulations are outlined in Table I.

Pub. No. US2005/0250/0250908A1 Pub. Date 11/10/2005 - Polymer Melt Additive Composition and Use Thereof. /Assignee-3M / Describes use of fibrillated-PTFE with a thermoplastic for added efficiency. Table 2 is PP example, noting storage modulus improvement from 2389 Mpa to 4760 Mpa. The goal of this work is to assess if the MM5935EF product offers any advantages in PLA over conventional PTFE, beyond the ease of handling that has been reported in US2005/0250/0250908A1.

MATERIALS AND METHOD

Sample Preparation

For all experiments shown here, Natureworks' Ingeo 4032D PLA resin was used. The plasticizer, Tributyl-O-Acetyl Citrate, was obtained from Tokyo Kasei Kogyo Co LTD, Tokyo, Japan. The nucleator, talc used (ABT 2500, was purchased from Specialty Minerals Inc, Bethlehem, PA). The fluoropolymers, 3M TF 2021 (fibrillating PTFE), MM5935EF (3M PTFE fluorothermoplastic blend), and FX 5912 (fluorothermoplastic), were obtained from 3M, Maplewood, MN.

The PLA pellets were dried in a forced air oven overnight at 60ºC before use. Samples (50g) were prepared by mixing PLA with plasticizer and/or nucleant in a Haake mixer equipped with a Rheomix 600 mixing bowl at 190ºC using a 2 minutes loading period (25 rpm) and a one minute rpm ramp to 75rpm, followed with mixing at 75rpm for 5 minutes. Five minute mixing time was sufficient to disperse the additives uniformly within the PLA resin. The polymer collected and coole...