Polylactic Acid Grade Research Articles

Biocomposite materials from natural rubber/polylactic acid blends reinforced rubberwood sawdust for producing children's toys

Biocomposite materials are prepared by blending natural rubber (NR) and polylactic acid (PLA) reinforced with rubberwood sawdust (RWS). This study aimed to investigate the effects of PLA grade, NR/PLA blend ratio, and RWS content on flexure, tension, hardness, and water absorption characteristics, including thermal stability. The RWS content significantly affected the physical and mechanical properties of the biocomposite materials. The increasing additions of RWS from 30 to 50 wt% increased the mechanical modulus, hardness, and water absorption but decreased the thermal stability of the biocomposites. Polymer blended with an NR/PLA ratio of 30/70 reinforced with 30 wt% RWS exhibited the highest mechanical strength, whereas a blend ratio of 40/60 was found to be reinforced with 40 wt% RWS. The polymer matrix blended with a higher PLA content resulted in superior biocomposite properties. Thus, the biocomposites with an NR/PLA ratio of 30/70 had better properties than those with a ratio of 40/60. Further, biocomposites with PLA grade of low melt flow rate (6 g/10 min) improved their properties more than that of a high melt flow rate (80 g/10 min). Therefore, the appropriate formulation of biocomposites for producing children's toys is a blend ratio of 30/70 with 2003D PLA grade of low melt flow rate and reinforcement with 30 wt% RWS. The tensile, flexural, and compressive forces of a toy boat prototype were 70.08, 104.9, and 124.8 N, respectively, while the specified standard is 69.0, 69.0, and 113.5 N, respectively, thus meeting the requirements of the American Society for Testing and Materials F963.

Poly-lactic acid self-reinforcing composites with improved toughness utilising solid-state drawn oriented tape

With the increasing white pollution problem and the enhancement of people’s awareness of environmental protection, the bio-based and biodegradable polymers have received unprecedented attention. Poly-lactic acid (PLA) is considered as one of the most potential alternatives to petroleum-based polymer materials. However, Due to its inherent brittleness and the difficulties of post-disposal and recycling caused by traditional processing methods, PLA has not been fully accepted by the market. To overcome the issues, self-reinforcing PLA composites (SRPLA) were prepared with different PLA grades as the matrix and the reinforcement respectively. High toughness SRPLA were prepared by hot pressing using PLA3052 casting films as the matrix and PLA6202 oriented tapes fabricated by solid state drawing as the reinforcement. In addition, the toughening mechanism was analyzed. Mechanical tests showed that the strength, modulus and elongation at break were increased by 124.3%, 114% and 145.2% respectively compared with pure PLA hot pressed film. Particularly, the tensile toughness of SRPLA is more than 200% that of pure PLA. The interface debonding and tape pullout were the main toughening mechanisms.

Life cycle assessment of advanced grade PLA product with novel end-of-life treatment through depolymerization

Using biobased plastics has the potential to avoid fossil resource depletion and fossil CO2 emissions. Polylactic acid (PLA) is a fast-growing bio-based plastic made from fermented sugars. Nowadays, PLA is used to replace fossil-based polymers in healthcare and single-use applications, such as for packaging applications. However, PLA offers a much broader application range with the targeted use of a combination of its stereoisomers; PL(L)A and PL(D)A. A variety of these advanced grades of PLA can be used for multiple purposes in durable consumer products such as furniture. Recycling complex, mixed material and advanced grades of PLA is currently limited, as mechanical recycling has limitations in recycling mixed PLA grades. Using a depolymerization technology, products of such advanced grades of PLA can be recycled to form high-quality recycled PLA. A cradle-to-grave life cycle assessment study was executed to evaluate the sustainability of high-end durable product (a rug) with mixtures of PLA grade and the novel depolymerization technology. The findings of the study showed a 70 % reduction in CO2-eq. emissions compared to a conventionally designed rug. However, an increase is indicated in the following environmental impact categories: land use, eutrophication, and environmental toxicity. Sensitivity analyses for collection rates showcased that design for collection and recycling are key to obtaining a more sustainable biobased products. Additionally, scenario analysis supported depolymerization for PLA as recycling technology with low CO2-eq. emissions. Based on the results of the LCA and additional scenario analysis, the use of PLA is encouraged to be used in more durable and lasting products, such as furniture, from an environmental perspective, provided that the products are designed for collection and high-quality recycling to ensure material circularity.

Understanding the PLA–Wood Adhesion Interface for the Development of PLA-Bonded Softwood Laminates

With polylactic acid (PLA) usage projected to increase in wood-based composite materials, a study comparing composite processing parameters with resulting PLA−wood adhesion and panel performance is warranted. In this study, PLA-softwood veneer laminates have been prepared and spatial chemical imaging via FTIR analysis was applied to identify PLA bondlines characterizing bondline thickness and the extent of PLA migration into the wood matrix. These PLA–wood adhesion interface characteristics have been compared with the performance of panels varying in pressing temperature, pressing time and PLA grades. For amorphous PLA, bondline thicknesses (60–120 μm) were similar, pressing at 140 °C or 160 °C, whereas with semi-crystalline PLA, the bondline thickness (340 μm) significantly reduced (155–240 μm) only when internal panel temperatures exceeded 140 °C during pressing. Internal temperatures also impacted PLA penetration, with greater PLA migration from bondlines evident with higher pressing temperatures and times with distinctions between PLA grades and bondline position. Performance testing revealed thinner PLA bondlines were associated with greater dry strength for both PLA grades. Cold-water soaking revealed laminated panels exhibit a range of wet-strength performance related to panel-pressing regimes with the semi-crystalline PLA pressed at 180 °C having similar tensile strength in dry and wet states. Moreover, an excellent correlation between wet-strength performance and bondline thickness and penetration values was evident for this PLA grade. Overall, study findings demonstrate PLA wood composite performance can be tuned through a combination of the PLA grade and the pressing regime employed.

Rethinking the paper cup — beginning with extrusion process optimization for compostability and recyclability

More than 50 billion disposable paper cups used for cold and hot beverages are sold within the United States each year. Most of the cups are coated with a thin layer of plastic — low density polyethylene (LDPE) — to prevent leaking and staining. While the paper in these cups is both recyclable and compostable, the LDPE coating is neither. In recycling a paper cup, the paper is separated from the plastic lining. The paper is sent to be recycled and the plastic lining is typically sent to landfill. In an industrial composting environment, the paper and lining can be composted together if the lining is made from compostable materials. Coating paper cups with a compostable performance material uniquely allows for used cups to be processed by either recycling or composting, thus creating multiple pathways for these products to flow through a circular economy. A segment of the paper converting industry frequently uses an extrusion grade of polylactic acid (PLA) for zero-waste venues and for municipalities with ordinances for local composting and food service items. The results among these early adopters reveal process inefficiencies that elevate manufacturing costs while increasing scrap and generally lowering output when using PLA for extrusion coating. NatureWorks and Sung An Machinery (SAM) North America researched the extrusion coating process utilizing the incumbent polymer (LDPE) and PLA. The trademarked Ingeo 1102 is a new, compostable, and bio-based PLA grade that is specifically designed for the extrusion coating process. The research team identified the optimum process parameters for new, dedicated PLA extrusion coating lines. The team also identified changes to existing LDPE extrusion lines that processors can make today to improve output. The key finding is that LDPE and PLA are significantly different polymers and that processing them on the same equipment without modification of systems and/or setpoints can be the root cause of inefficiencies. These polymers each have unique processing requirements with inverse responses. Fine tuning existing systems may improve over-all output for the biopolymer without capital investment, and this study showed an increase in line speed of 130% by making these adjustments. However, the researchers found that highest productivity can be achieved by specifying new systems for PLA. A line speed increase to more than 180% and a reduction in coat weight to 8.6 µm (10.6 g/m2 or 6.5 lb/3000 ft2) was achieved in this study. These results show that Ingeo 1102 could be used as a paper coating beyond cups.

A Comparison of the physical properties of two commercial 3D printing PLA grades

ABSTRACT As desktop three-dimensional (3D) printing has gained popularity over a wide range of settings, the use of polylactic acid (PLA) has increased commensurately due to the perceived positive safety and environmental qualities of the material. Though there are currently several manufacturers of PLA for fused filament fabrication (FFF) platforms, Ingeo grade 4043D (NatureWorks, LLC, Minnetonka, MN, USA) is widely used amongst the 3D printing community. The work presented here compares two grades of commercially available PLA that have been marketed to the 3D printing community. Here, the former ‘gold standard’, PLA Grade 4043D, is compared to the newer grade, 3D870. Mechanical properties, rheological characteristics, chemical qualities, and the ability to manipulate the crystallinity of the material were compared between the two. A detailed fracture surface analysis of tensile specimens was also performed that revealed distinct differences in crack propagation behaviour between the two materials in the annealed and non-annealed conditions.

Melt Rheology of Renewable Polymers and of New Materials Based on them as Tool in Controlling the 3D/4D Printability

The article presents results regarding the use of the melt flow index method (MFIM) in estimating the rheological properties of polylactic acid (PLA) and PLA-based materials, as tool in the selection of the operating conditions at their shaping into filaments and for 3D printing with thus obtained filaments. Based on the MFIM, the molecular weight of various PLA grade commonly used in melt processing techniques, including printing, were qualitatively compared. It was found that PLA for printing has the lowest molecular weight as compared with the PLA melt processed through injection, extrusion, thermoforming. It has been also shown that the MFIM can be used to verify the efficiency of drying, pre-treatment always needed to be done, before filaments obtaining and/or printing, especially in case of renewable polyesters. By simulating the printing at the indexer, via depositing successive layers, one over the other, it was possible to estimate the optimal flow conditions that ensure a good adhesion between the deposited layers. The estimation of the condition which ensure the needed adhesion between the deposited layers with the help of the MFIM was verified with good results on a grade of high loaded PLA achieved according to an original formulation.

Feasibility study of epoxy coated Poly Lactic Acid as a sustainable replacement for river sand

River sand is ruling construction industry due to its tremendous properties and composition. According to the statistics of World Industrial Silica Sand Demand, this need for sand will increase up to 123.4 millions of metric tons in 2025 in the United States and about 51 millions of metric tons in Asian countries. The increasing population has escalated the demand, in-parallel asking for an alternative material development from research community. The earlier study yielded a promising results on Polylactic acid as a replacement for river sand in steps of 0, 10, 30 and 50% inclusion in holding concrete matrix. Currently, the work focuses on reducing the degradation aspect of Polylactic acid, when it comes in contact with cement and aggregate. The work comprising of coating a Poly lactic acid with epoxy for better durability. Soil burial test was conducted from 0 to 50 days and weight of samples recorded. Further, the samples were subjected to Scanning Electron Microscopy study to check the water entrapment or air void filling by water droplets. After epoxy coating coupons were built to check any strength deterioration but results were quite convincing under simulation package ANSYS workbench along with experimental investigation. Compressive strength reduced by 43% in comparison to pristine PLA sample with previous work. As per Polylactic acid grade, a monomer and then polymer was built under the J-OCTA platform to extract the material properties, the same data were used in ANSYS Workbench for simulation. The results reveal that a good correlation with experimental and simulation for compressive strength of 21.7 MPa for the control mix of M30(based on previous work). In case of degradation study, the day-wise extracted reports reveal quite interesting facts, and with positive note, probably PLA in future can be considered as the most preferred material for replacement of river sand.

3D Printing of PLA/clay Nanocomposites: Influence of Printing Temperature on Printed Samples Properties.

In this study, the possibility of using a layered silicate-reinforced polylactic acid (PLA) in additive manufacturing applications was investigated. In particular, the aim of this work was to study the influence of printing temperature in the 3D printing process of PLA/clay nanocomposites. For this reason, two PLA grades (4032D and 2003D, D-isomer content 1.5 and 4, respectively) were melt-compounded by a twin screw extruder with a layered silicate (Cloisite 30B) at 4 wt %. Then, PLA and PLA/clay feedstock filaments (diameter 1.75 mm) were produced using a single screw extruder. Dog-bone and prismatic specimens were 3D printed using the FDM technique at three different temperatures, which were progressively increased from melting temperature (185–200–215 °C for PLA 4032D and 165–180–195 °C for PLA 2003D). PLA and PLA/clay specimens were characterized using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile tests. Moreover, the morphology of the 3D printed specimens was investigated using optical microscopy and contact angle measurements. The different polymer matrix and the resulting nanocomposite morphology strongly influenced 3D printed specimen properties. DMA on PLA/clay filaments reported an increase in storage modulus both at ambient temperature and above the glass transition temperature in comparison to neat PLA filaments. Furthermore, the presence of nanoclay increased thermal stability, as demonstrated by TGA, and acted as a nucleating agent, as observed from the DSC measurements. Finally, for 3D printed samples, when increasing printing temperature, a different behavior was observed for the two PLA grades and their nanocomposites. In particular, 3D printed nanocomposite samples exhibited higher elastic modulus than neat PLA specimens, but for PLA 4032D+C30B, elastic modulus increased at increasing printing temperature while for PLA 2003D+C30B slightly decreased. Such different behavior can be explained considering the different polymer macromolecular structure and the different nanocomposite morphology (exfoliated in PLA 4032D matrix and intercalated in PLA 2003D matrix).

Effect of polymer/organoclay composition on morphology and rheological properties of polylactide nanocomposites

In this work the relationships between system composition, polymer–organoclay interaction, morphology and rheological response, under shear, and elongational flow, of different melt compounded polylactic acid (PLA)/organoclay nanocomposites are investigated, with the aim to properly select the better organoclay for a well‐specified PLA grade and processing technology. Polylactide nanocomposites are prepared using two commercial polylactide grades (PLA 4032D and PLA 2003D) and two different organomodified montmorillonites (Cloisite 30B and Nanofil SE3010). FTIR analysis evidences the occurrence of stronger polymer/organoclay interactions for the system PLA4032D+C30B, resulting in a higher clay dispersion and exfoliation levels. Moreover, rheological tests at low shear rates show that, if PLA 2003D is used as polymer matrix (differing from PLA4032D by the presence of a high molecular weight tail), a better dispersed nanomorphology can be obtained with Nanofil SE3010, characterized by a double d‐spacing compared to Cloisite 30B, despite the higher polar character of this latter nanofiller. On the other hand, elongational rheological measurements evidence for NSE3010‐based hybrids a marked extensional thickening, whilst the stronger polar interactions between the phases in both the polylactide grades filled with C30B, determine increments in elongational viscosity, but inhibit the strain hardening behavior. POLYM. COMPOS., 36:1135–1144, 2015. © 2015 Society of Plastics Engineers

Effect of PLA grades and morphologies on hydrolytic degradation at composting temperature: Assessment of structural modification and kinetic parameters

The present work focuses on a study of the hydrolysis process of different commercial grades of polylactic acid (PLA). The aim was to evaluate the fundamental factors affecting hydrolysis in aqueous medium at 58 °C, namely the temperature indicated by the international standards for biodegradation during composting, and the kinetic constant of the reaction involved in such process. We analyzed samples of PLA with different d-isomer content, having amorphous and semi-crystalline structures. The hydrolysis process was followed, as function of the time, by means of different techniques: pH variation, variation of weight (%) of samples, crystallinity degree using DSC analysis, FTIR and WAXD investigation, molecular weights and molecular weight distribution by GPC analysis. The experimental data were used to describe the kinetic of hydrolysis phenomenon, assuming an autocatalytic mechanism.

Dynamic Mechanical Behaviour of Poly Ethylene Glycol Plasticized Polylacticacid

Polylacticacid (PLA), produced from annually renewable, natural resources is a potential candidate for the partial replacement of petroleum based polymers and also for its biodegradability. PLA is well known for its better mechanical, thermal property but unfortunately the brittleness and rigidity limit its applicability. For a great number of applications such as packaging, fibers, films, etc., it is of high interest to formulate new PLA grades with improved flexibility and better impact properties. In order to develop PLA-based biodegradable packaging, the physico-mechanical properties of commercially available PLA should be modified using plasticizers. For this, PLA was melt-mixed with poly ethylene glycol (PEG) of 600 molecular weights by twin screw extruder. The thermal properties of plasticized PLA were characterized by utilization of dynamic mechanical analysis. The result shows that with addition of plasticizer glass transition temperature (Tg) is decreased sharply and the storage modulus was also decreased.