Mechanical recycling of poly(lactic acid): Evaluation of a chain extender and a peroxide as additives for upgrading the recycled plastic.

Poly(lactic acid) (PLA) is a biobased polymer that represents one of the most interesting alternatives to fossil-fuel based polymers in food packaging applications. Most of the PLA used in food packaging is used only once and then discarded, even though the PLA types used in packaging have good properties and stability. Therefore, it seems reasonable to consider the possibility of recycling the used polymer through a mechanical recycling process. The main aims of this work are to study the effect of the mechanical recycling on the properties of PLA and the usefulness of different upgrading methods to obtain recycled PLA with improved properties. A commercial type of PLA was subjected to accelerated thermal, photochemical and hydrolytic aging and then reprocessed. During reprocessing, aged PLA was blended with virgin PLA and a commercial chain extender was added. Results point out that recycling causes the degradation of PLA, and negatively affects the thermal stability and mechanical properties. However, addition of virgin PLA, and the chain extender, led to an increase of up to 9% in the intrinsic viscosity and 8% in the Vickers hardness of the recycled material. These results suggest that mechanically recycled PLA with improved performance can be obtained, a fact which might improve the recyclability of PLA and thus the environmental impact of this material.

Download Full-text

The Preparation of Poly(lactic acid) via Chain Linked Hydroxy-Terminated Lactic Acid Prepolymer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.410.337 ◽

2011 ◽

Vol 410 ◽

pp. 337-340

Author(s):

Suek Songprateepkul ◽

Suriyan Rakmae ◽

C. Deeprasertkul ◽

Nitinat Suppakarn ◽

Pranee Chumsamrong

Keyword(s):

Molecular Weight ◽

Lactic Acid ◽

Average Molecular Weight ◽

Glass Tube ◽

Acid Value ◽

Chain Extender ◽

Hexamethylene Diisocyanate ◽

Poly Lactic Acid ◽

Weight Average Molecular Weight ◽

A Chain

In this work, hydroxyl-terminated lactic acid prepolymer was firstly prepared by adding diethylene glycol in the condensation of lactic acid. Molecular weight, acid value and structure of prepolymer were characterized. The results showed that the prepolymer was hydroxyl-terminated with weight average molecular weight (MW) of 10,000 g/mol. After that, the chain linking polymerization of the prepolymer was carried out in a glass tube at 160 °C for 1 h employing 1,6-hexamethylene diisocyanate (HMDI) as a chain extender. By varying the hydroxyl/isocyanate ratio, it was found that the OH/NCO ratio of 1:2 seemed to be the most suitable ratio which gave PLA with the maximum MW of 93,000 g/mol.

Download Full-text

Biodegradable Plastics Prepared from Poly(lactic acid), Poly(butylene succinate) and Microcrystalline Cellulose Extracted from Waste-Cotton Fabric with a Chain Extender

Journal of Polymers and the Environment ◽

10.1007/s10924-014-0689-0 ◽

2014 ◽

Vol 23 (1) ◽

pp. 114-125 ◽

Cited By ~ 25

Author(s):

Phasawat Chaiwutthinan ◽

Vimolvan Pimpan ◽

Saowaroj Chuayjuljit ◽

Thanawadee Leejarkpai

Keyword(s):

Lactic Acid ◽

Cotton Fabric ◽

Microcrystalline Cellulose ◽

Biodegradable Plastics ◽

Chain Extender ◽

Poly Lactic Acid ◽

Butylene Succinate ◽

A Chain

Download Full-text

Processing and characterization of poly(lactic acid) blended with polycarbonate and chain extender

Journal of Polymer Engineering ◽

10.1515/polyeng-2013-0309 ◽

2014 ◽

Vol 34 (7) ◽

pp. 665-672 ◽

Cited By ~ 7

Author(s):

Yottha Srithep ◽

Wuttipong Rungseesantivanon ◽

Bongkot Hararak ◽

Krisda Suchiva

Keyword(s):

Molecular Weight ◽

Lactic Acid ◽

Gel Permeation Chromatography ◽

Chain Extender ◽

Chain Extension ◽

Morphological Properties ◽

Poly Lactic Acid ◽

Scanning Calorimetry ◽

Commercial Applications ◽

A Chain

Abstract Currently, use of poly(lactic acid) (PLA) is limited for commercial applications because it has a low heat resistance. In this research, an increase of over 40°C heat distortion temperature (HDT) of PLA alloy was obtained by blending PLA with polycarbonate (PC) and a chain extender (CE). Molecular weight, thermal, mechanical and morphological properties of PLA and PC blend with different CE contents were investigated. Gel permeation chromatography (GPC) results showed that some PLA-PC copolymers were produced and the compatibility of the PLA phase and in the PC phase was improved via the chain extension reaction. In addition, the reaction induced by CE also affected the crystallization behaviors of PLA, as observed from differential scanning calorimetry (DSC) results and the enthalpy of melting of PLA decreased with increasing CE content. The combined effects of the CE increasing molecular weight, improving compatibility and limiting the crystallization behavior of PLA/PC alloy greatly improved the HDT.

Download Full-text