PLA plasticizers

To improve the properties of PLA, plasticizers, special additives such as chain-extenders, polymer blends, and composites are commonly investigated. Martin and Averous (10) have studied the effects of various plasticizers on the properties of PLA. Pilla et al. (11-12) have investigated the effects of chain-extenders on the foaming properties of PLA. In addition, a vast number of studies have been conducted to enhance the properties of PLA by blending it with various polymers such as polyethylene oxide (PEO), polypropylene oxide (PPO), polyvinyl acetate, polyolefins, polystyrene, HIPS (high impact polystyrene), polyacetals, polycarbonate, and acrylonitrile butadiene styrene (ABS) (13-26). 

Fgerch Plast is an extruder of film and thermoforms packaging. Packaging is made from PS, CPET, APET, PP and PLA plastics. Principal end use sectors served are ready meals, fresh meat, cold food, snacks and disposables. 

Table 11.9 Thermal and mechanical properties of PLA plasticized with different citrate esters...

Table 5.3 gathers the main literature results on PLA plasticized with monomeric external plastieizers. It shows furthermore that different... 

Another interesting feature of PLA plasticizing can be observed in Figure 5.2, which plots s values against Tg. In the case of the poorly compatible plasticizer GMS, even though some decrease in Tg is reached, not... 

Figure 5.4 Stress-strain plots of initially amorphous neat PLA and amorphous PLA plasticized with 5 wt% and 7.5 wt% of PPG 400, PPG 1000 and PEG 600 (a) and for PLA plasticized with 10 wt% and 12.5 wt% of PPG 400, PPG 1000 and PEG 600 (b). Reprinted with permission from Kulinski et al., Biomacromolecules, 2006, 7, 2128. ...

Figure 5.5 Stress-strain plots of initially semiciystalline neat and plasticized PLA, plasticized at 5 wt%, 7.5 wt%, 10 wt% and 12.5 wt% of PEG 600 (top), PPG 400 (middle) and PPG 1000 (bottom).

Table 5.5 Overview of physical ageing behaviour of PLA/plasticizer compounds. 

Another study reported the PLA plasticization effect of oligomers of tributyl citrate with diethylene glycol produced via transesterification [18]. The HSP of these are expected to be similar to the other citrates, so it is no surprise to find that the bleeding of these plasticizers is still rather unsatisfactory. 

Labrecque et al. demonstrated good miscibility of PLA with different citrate esters at up to 20-30% by weight of plasticizer concentration, depending on the type of citrate employed [36]. Tensile strength and elongation at break of PLA plasticized with citrate esters are reported in Table 11.4, and show a marked effect of plasticizer at concentrations between 10% and 30%. 

TABLE 11.4 Thermal and Mechanical Properties of PLA Plasticized with Different Citrate Enters [36]... 

Epoxidizedsoybean oil (ESO) is produced via conversion of the double bonds of soybean oil with peracids or peroxides, resulting in more reactive oxirane or epoxide moieties, promoting chemical reactions [230-232]. ESO is normally used to plasticize and/or stabilize poly(vinyl chloride) (PVC), chlorinated rubber, and PVOH emulsions [231, 232]. The effects of ESO as a PLA plasticizer were reported elsewhere [230, 233, 234]. In summary, ESO lowered Tg, cold crystallization temperature Tm. enthalpy of cold crystallization (AHcc), tensile strength, and tensile... 

The degradation of polylactic acid (PLA) plastic films in Costa Rica soil and in a leaf composting environment was investigated [22]. The average soil temperature and moisture content in Costa Rica were 27°C and 80%, respectively. The average degradation rate of PLA plastic films in the soil of the banana field was 7657 A/ /week. PLA films required two weeks to disintegrate physically in leaf compost rows. 

Ho K.-L.G., Pometto III A.L., Gadea-Rivas A., Briceno, Rojas A. D radation of polylactic acid (PLA) plastic in Costa Rican soil and Iowa State University compost rows, J. Environ. Polym. Deg. 

The tendency for PLA plasticized with PEG to lose properties with time at ambient temperature is a major obstacle to its application as a biodegradable packaging material. Without plasticizer, PLA is stiff and brittle. Blending with low molecular weight PEG improves elongation at break and softness. The desired mechanical properties are achieved in quenched PLA/PEG blends with 30 wt% PEG However, the blends are not stable at ambient temperature and the attractive mechanical properties are lost over time. Crystallization and phase separation are possible aging processes. 

Blends of PLA plasticized with TbC-7 display phase separation already at a concentration of 15wt%, due to its higher molecular weight. Only a certain amount of plasticizer can be incorporated in PLA before becoming saturated and the higher the molecular weight of the plasticizer, the lower the saturation concentration. 

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