Insight into roles of different types of additives on mechanical and crystalline properties of polylactic acid

The production of degradable packaging materials is a task that can be no longer postponed. Moreover, high amounts of agricultural wastes are landfilled without any recycling. In this research, the possibility to formulate particulate composites made of biopolymers filled with coffee waste with acceptable physical and mechanical characteristics that will degrade is investigated. The addition of this agricultural waste, by reducing the requested amount of biopolymer, can decrease the overall price of the material presently the main limiting factor to the use of biopolymers in the packaging industry. Silverskin, the integument of coffee beans discarded during the roasting process, after a milling step, is added up to a 30 wt% either to polylactic acid (PLA) or to a blend of PLA and polybutylene succinate. The filler can be homogeneously dispersed in both systems. The data shows that the silverskin filler increases the elastic modulus but decreases the tensile strength of the material and helps the development of crystal phase in the matrix. The thermal stability and the hydrophobicity of the materials stay almost unchanged on filler addition. Moreover, data shows that the addition of silverskin increases the materials susceptibility to microbial attack.

Section: Isothermal Crystallizationsupporting

confidence: 69%

An investigation on the possible use of coffee silverskin in PLA/PBS composites

Ghazvini

Ormondroyd

Curling

et al. 2022

“…It is seen from Table 2 that the crystallinities increase significantly from 6.53% for neat PLA to 22.59% and 30.69% respectively after incorporating talc with 1 and 2 wt% into PLA, which presents a clear rule in improving the crystallization capacity of PLA with increasing addition of talc. The reason can be ascribed that talc, as a nucleating agent, can promote the crystallization of uncrosslinked and short‐chain PLA matrix 27 . However, the talc content has little effect on the T g and T m for PLA.…”

Section: Resultsmentioning

confidence: 99%

“…A vacant aluminum pan was applied as the reference. The crystallinity ( χ c ) was calculated by the below formula 13,19,22,23,26 :

χ c (%) = \frac{∆ H m - ∆ H cc}{∆ H 0 \times X PLA} \times 100 %

where Δ H m and Δ H cc were the measured melting and cold crystallization enthalpies after removing thermal history, Δ H 0 was the melting enthalpy of totally crystallized PLA (93.6 J/g), 16,27,28 and X PLA was the mass fraction of PLA in the composites.…”

Section: Methodsmentioning

confidence: 99%

“…The reason can be ascribed that talc, as a nucleating agent, can promote the crystallization of uncrosslinked and short-chain PLA matrix. 27 However, the talc content has little effect on the T g and T m for PLA.…”

Section: Crystallization and Melting Behaviorsmentioning

confidence: 98%

“…where ΔH m and ΔH cc were the measured melting and cold crystallization enthalpies after removing thermal history, ΔH 0 was the melting enthalpy of totally crystallized PLA (93.6 J/g), 16,27,28 and X PLA was the mass fraction of PLA in the composites.…”

Section: Differential Scanning Calorimetry Analysismentioning

confidence: 99%

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Roles of physical filling and chemical crosslinking on the physico‐mechanical properties of polylactic acid

Hao¹,

Tian²,

Chen³

et al. 2022

Self Cite

Polylactic acid (PLA) modified materials were prepared with physical filling and chemical crosslinking methods by melt extrusion respectively in this work, and the mechanical, rheological, crystalline, and heat resistance properties were investigated. It is found that filling with talc as the nucleating agent enhanced the crystallization capacity of PLA evidently. When 2 wt% talc was added into the PLA matrix, the crystallinity increased to 30.69% from 6.53% for neat PLA, enhancing by more than 3.6 times. Meanwhile heat resistance of talc filled PLA was improved significantly after annealing, increasing the heat deflection temperature from below 55 C for neat PLA to about 130 C for 2 wt % talc filled PLA. Molecular chains entanglement and spatial structures formation due to crosslinking reactions played key roles in tailoring the tensile, rheological properties and melt strengths of PLA materials. The elongation at break of the modified PLA materials increased by 149% and 126% separately after the crosslinking reactions with and without talc. The melt flow index decreased to 1.70 g/10 min after crosslinking from 11.79 g/10 min of neat PLA, indicating that crosslinking reactions exert significant effects on improving melt strength of PLA.

Fabrication of high‐expansion, fully degradable polylactic acid‐based foam with exponent oil/water separation

Hua

Chen

et al. 2022

Polylactic acid (PLA) foam is widely regarded as an effective substitute for petroleum‐based foams. However, the fabrication of high‐expansive, lightweight, highly hydrophobic foams for oil/water separation remains a challenge. Here, an innovative method was developed to improve the foaming ability of PLA by introducing silane modified alkaline lignin (m‐LA), and a lightweight PLA foam with a high expansion ratio, high porosity, and high hydrophobic performance was successfully developed. The crystallization behavior, rheological properties, pore morphology, and oil/water separation performance of foams were evaluated. The results show that m‐LA not only improves the crystalline properties of PLA, but also plays an important nucleation role during the foaming. m‐LA increased the foaming ratio of PLA to 40.17 times, and reduced the apparent density of the foam to only 0.0303 g cm−3. The PLA foam has exponent hydrophobicity. The water contact angle is up to 130.0°, and the adsorption capacity of various organic solvents is 5.17–12.44 g g−1, because the surface energy of LA is reduced by silane modification. This study provides a new insight into the development of environment‐friendly PLA foams for oil/water separation applications.