Designing Green Plasticizers: Linear Alkyl Diol Dibenzoate Plasticizers and a Thermally Reversible Plasticizer.

Hanno Erythropel,Richard Leask,Aurélie Börmann,Milan Maric,Jim Nicell

doi:10.3390/polym10060646

Abstract

Several linear alkyl diol dibenzoate compounds, ranging from C3 to C6 in central diol length, were evaluated for their plasticizing effectiveness in blends with poly(vinyl chloride) (PVC). The results were compared to blends of PVC/di(2-ethylhexyl) phthalate (DEHP), the most commonly used commercial plasticizer. DEHP has come under scrutiny, due to its suspected endocrine-disrupting behaviour, and the proposed diol dibenzoates have previously been shown to have the potential to be green, safe candidates for DEHP replacement. The thermal and mechanical properties of PVC/dibenzoate blends were determined, and include glass transition temperature (Tg), the elongation at break, maximum stress, apparent moduli, torsional modulus, and surface hardness. The C3, C5, and C6 dibenzoates performed as well as or better than DEHP, with the exception of torsional modulus, further supporting their use as green plasticizers. For blends with 1,4-butanediol dibenzoate, differential scanning calorimetry and torsional temperature sweeps suggested that the compound partly crystallizes within PVC blends over the course of two days, thereby losing the ability to effectively plasticize PVC. However, upon heating to temperatures above 60 °C, effective plasticization was again observed. 1,4-Butanediol dibenzoate is thereby a reversible heat-activated plasticizer or processing aid with excellent plasticizer properties at mildly elevated temperatures.

Highlights

Poly(vinyl chloride) (PVC) is one of the “big 6” polymers [1], with worldwide production capacities above 5 × 107 tonnes per year [2]
This study demonstrates that three diol dibenzoate compounds with alkyl central linker lengths of C3, C5, and C6 (Figure 2) are as effective, or more effective than the commercial plasticizer di(2-ethylhexyl) phthalate (DEHP), of C3, C5, and C6 (Figure 2) are as effective, or more effective than the commercial plasticizer DEHP, as demonstrated by glass transition temperature, torsional modulus, tensile strength, and surface as demonstrated by glass transition temperature, torsional modulus, tensile strength, and surface hardness measurements
The proposed diol dibenzoate compounds could be good green candidates to replace phthalates, given previous work that identified their rapid biodegradation by candidates to replace phthalates, given previous work that identified their rapid biodegradation by soil soil bacteria [21,24,30]

Summary

Introduction

Poly(vinyl chloride) (PVC) is one of the “big 6” polymers [1], with worldwide production capacities above 5 × 107 tonnes per year [2]. The difficulty in processing pure PVC is remedied through the use of several additives, including plasticizers, heat stabilizers, internal and external lubricants, processing aids, and others [2]. These additives are not chemically bound to PVC, leading to the possibility of their leaching from the blend over time [3]. Plasticizers are of particular importance for PVC, to which they are commonly added in concentrations up to 30–40% by weight [4], in order to render the material soft and “plastic” by breaking up PVC chain–chain interactions [5].

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Discussion

Conclusion