Progress 07/01/24 to 06/30/25
Outputs
Target Audience:Target audience reached included the scientific community and industry including: -faculty and students at Lehigh University, the University of Massachusetts Lowell, and Ben Gurion University -staff scientists at USDA ARS -at least three industrial entities interested in nutrient-containing mulch film manufacturing, includingHarrell's Inc,Joachim P. Roesler, PhD,President,New Polymer Systems, Inc.,Jefferson Stauffer from Mettzler Foret Products,Paul Albee from CJ Biomaterials Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Graduate students and a postdoc were trained on manufacturing of stable nitrogen fertilizer materials, composite film formulation, extrusion and property testing. Additionally, one graduate student was trained on performing experiments on mineralization rates. How have the results been disseminated to communities of interest?We made a conscious effort to commuicate with theindustrial entities interested in nutrient-containing mulch film manufacturing, includingHarrell's Inc,Joachim P. Roesler, PhD,President,New Polymer Systems, Inc.,Jefferson Stauffer from Mettzler Foret Products,Paul Albee from CJ Biomaterials What do you plan to do during the next reporting period to accomplish the goals?We will further primarily focus onObjectives within Aim 1.Scale-up engineered urea co-crystals for formulation and synthesis of the composite mulch films with three types of known biodegradable polymers including Ecovio, Mater Bi and PBHV, in comparison with conventional LDPE mulch films. The structure, physical and chemical properties of the resulting composite mulch materials will be evaluated and their production as films will be demonstrated. Both Lehigh and Massachusetts Lowell are working on this in tandem and year 1 resulted in many successful laboratory thin films manufactured as well as extruded on a large scale..
Impacts
What was accomplished under these goals?
In years 1 and 2 of the project we focus primarily on the Objectives within Aim 1,e.g. engineering of the composite materials and their characterization.For the selection of most promising nutrient compounds to work with in mulch films, a set of cocrystals prepared by Lehigh was analyzed using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Six urea cocrystals with calcium sulfate, calcium nitrate, calcium phosphate, magnesium sulfate, magnesium nitrate, and magnesium phosphate were analyzed. TGA analysis was conducted using a Mettler Toledo instrument, heating in air at 10 C/min from room temperature to 600 C. Each compound shows multiple weight loss steps, likely due to the decomposition of different components of the cocrystals. The urea begins to degrade around 132C, which is near the melting temperature of the first polymer of interest in the mulch film work. The urea cocrystals with calcium sulfate, calcium nitrate, and magnesium nitrate show the highest temperature tolerance before they begin to degrade. Both phosphate cocrystals show the lowest thermal stability, which render them ineligible unless a polymer with a lower processing temperature is identified. The team met with collaborator CJ Biomaterials to select another suitable grade of bioplastic with rapid degradation properties and low melting temperature for an alternative to the Ecovio. The grade PHACT CA1270P was selected. Testing on this grade will be conducted in the near future. Thermal properties of the Ecovio were measured, and the polymer was compounded with the urea cocrystal with calcium sulfate (UrCaSO). Compounding was first verified in a Brabender batch mixer with batch size 30 g. Compounding was conducted at 170 C with 10%, 20%, and 30% UrCaSO in Ecovio, with mixing at 50 rpm for 10 minutes. Theoretical C:N ratios for these compounds ranged from ~40 to 3. Thermal properties of the batch mixed blends were measured using TGA and DSC. The weight loss associated with UrCaSO release is visible around 250 ?C. It appears that the UrCaSO is already degraded in the 10 wt% sample, since there is not a visible early weight loss in that blend. The residual mass above 550 ?C is likely ash content since the samples were heated in a nitrogen atmosphere.This data was obtained after erasing thermal history in the DSC with a first heating and cooling cycle (10 ?C/min). All samples show a broad melting peak centered around 120 ?C that is characteristic of the majority PBAT component of the polymer, and a sharper, small melting peak around 150 ?C that represents the minority PLA phase. Thermal analysis of continuous mixer compounded materials was also performed. A similar weight loss as seen in batch mixed blends around 250 ?C indicates the UrCaSO weight loading, and the broad melting of PBAT plus sharper melting of PLA are seen in the DSC. In the 20 wt% and 30 wt% blends the PLA peak is sharper, which may be due to an interaction with the cocrystal additive. A second compounding trial was completed using 10% UrCaSO in Ecovio with a Farrell Pomini low intensity continuous mixer. This machine was chosen due to its low residence time and gentle shear profile, with the aim of minimizing damage and overheating of the components. A total of 4.77 kg Ecovio with 7.5% UrCaSO was compounded at a rate of 15 kg/hr. The mixer speed was 300 rpm, extruder speed was 40 rpm, processing temperature was 160 °C with a 165 °C die?. The Ecovio was fed at 230.8 g/min? and UrCaSO was fed at 17.467g/min. Figure 4 shows the pellets as prepared. The material is soft and compliant with some voids that indicate some off gassing of ammonia from the UrCaSO may have occurred. Additionally, colleagues at Ben Gurion have already performed some work under objectives within Aim 2. They measured cumulative mineralization rates over 200 days of laboratory incubation of soil, soil+CaSO4*4urea cocrystal and soil+urea with and without various types of plastics, e.g. PE, ECOVIO, PBAT and PLA.Cumulative CO2 (µg C g dry soil-1) from soil amended with different plastic types and supplemented with either urea co-crystals or free urea were measured. Within each nitrogen treatment, statistical differences between plastic types were indicated by symbols (** p = 0.01 - 0.05; * p = 0.05 - 0.1), while significant differences in plastic type across nitrogen treatments is indicated by letters (p < 0.05).Cumulative flux calculations were integrated using R-package "pracma" using time specific averages (n = 5 in the initial 34 days, and n = 3 after day 34.) and the standard errors propagated as per standard error propagation of addition and multiplication of values. Significant differences were determined using pairwise Welch's tests in R. Main findings were as follows: In the absence of urea co-crystals and free urea, mineralization rates did not differ significantly. In contrast, mineralization rates exhibited plastic-specific, statistically significant increases when supplemented with either urea co-crystals or free urea. Neither urea co-crystals nor free urea affected mineralization rates of the biodegradable plastics ECOVIO, PBAT or PLA. In contrast, soils amended with PE (non-biodegradable) and supplied with either urea formulation exhibited significantly higher CO? mineralization than control soils, with significance observed only in the urea-treated groups. Soil without plastic amendments exhibited a marked increase in CO? mineralization rates when amended with free urea, whereas urea co-crystals had no detectable effect under the same conditions. This contrast implies that the co-crystal formulation limits microbial access to urea's carbon and nitrogen, whereas free urea, due to its rapid hydrolysis and inherent carbon content, readily fuels microbial respiration and drives higher CO? release.
Publications
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