Mechanical properties of poly(ε‐caprolactone) and poly(lactic acid) blends

Abstract

The aim of this work was to better understand the performance of binary blends of biodegradable aliphatic polyesters to overcome some limitations of the pure polymers (e.g., brittleness, low stiffness, and low toughness). Binary blends of poly(e-caprolactone) (PCL) and poly(lactic acid) (PLA) were prepared by melt blending (in a twin-screw extruder) followed by injection molding. The compositions ranged from pure biodegradable polymers to 25 wt % increments. Morphological characterization was performed with scanning electron microscopy and differential scanning calorimetry. The initial modulus, stress and strain at yield, strain at break, and impact toughness of the biodegradable polymer blends were investigated. The properties were described by models assuming different interfacial behaviors (e.g., good adhesion and no adhesion between the dissimilar materials).The results indicated that PCL behaved as a polymeric plasticizer to PLA and improved the flexibility and ductility of the blends, giving the blends higher impact toughness. The strain at break was effectively improved by the addition of PCL to PLA, and this was followed by a decrease in the stress at break. The two biodegradable polymers were proved to be immiscible but nevertheless showed some degree of adhesion between the two phases. This was also quantified by the mechanical property prediction models, which, in conjunction with material property characterization, allowed unambiguous detection of the interfacial behavior of the polymer blends.

Processing and characterization of binary poly(hydroxybutyrate) (PHB) and poly(caprolactone) (PCL) blends with improved impact properties

“…The crystallinity degree of both PHB (X c, PHB ) and PCL (X c, PCL ) in the blends was calculated by following Eq. (1) where H m is the fusion enthalpy and H 0 is the enthalpy related to the corresponding 100 % crystallinity (theoretical value) polymer; these values were assumed as 146 J g -1 [1] for PHB and 156.8 J g -1 [3] for PCL. Finally, "w" represents the weight fraction of PHB and PCL in each PHB-PCL blend.…”

“…Rectangular samples sizing 40x10x4 mm 3 were subjected to a dynamic temperature program from -100 to 150 ºC at a constant heating rate of 2 ºC min -1 at a frequency of 1 Hz and constant deformation () of 0.1%.…”

“…An important fraction of these wastes are incinerated or poured into controlled landfills because of technical or economical reasons thus leading to important environmental problems such as waste removal from environment, soil contamination or toxic gas emissions coming from incineration processes. This acts as leading force to the study, development and use of biobased and/or biodegradable polymers characterized by low environmental impact [1][2][3].…”

Effect of halloysite on structure and properties of melt-drawn PCL/PLA microfibrillar composites

“…As a result, low yield stress, stiffness, and high ductile deformation under ambient conditions limit the range of PCL applications. The purpose of numerous modifications is, in particular, higher yield stress and modulus [1]; advantageous modifications are those preserving biodegradability, for instance blending with more rigid polyesters, mostly PLA [2][3][4][5].…”

Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers

“…On the other hand, PCL has a melting temperature around 60 ºC and a glass transition temperature well below room temperature, thus at room temperature it behaves as a tough plastic. Copolymers [13][14][15], blends [16] and composites [17] with PLLA and PCL have been developed in order to take advantage of the improved synergic properties offered by both polymers. Actually, for this integration strategy, copolymerization represents a better route in comparison with blending due to the immiscibility of the homopolymers [18].…”