Polymer Weight Loss Research Articles

Isolation and characterization of bio-prospecting gut strains Bacillus safensis CGK192 and Bacillus australimaris CGK221 for plastic (HDPE) degradation.

The present work reports the application of novel gut strains Bacillus safensis CGK192 (Accession No. OM658336) and Bacillus australimaris CGK221 (Accession No. OM658338) in the biological degradation of synthetic polymer i.e., high-density polyethylene (HDPE). The biodegradation assay based on polymer weight loss was conducted under laboratory conditions for a period of 90days along with regular evaluation of bacterial biomass in terms of total protein content and viable cells (CFU/cm2). Notably, both strains achieved significant weight reduction for HDPE films without any physical or chemical pretreatment in comparison to control. Hydrophobicity and biosurfactant characterization were also done in order to assess strains ability to form bacterial biofilm over the polymer surface. The post-degradation characterization of HDPE was also performed to confirm degradation using analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electronic microscopy (FE-SEM) coupled with energy dispersive X-ray (EDX), and Gas chromatography-mass spectrometry (GC-MS). Interestingly strain CGK221 was found to be more efficient in forming biofilm over polymer surface as indicated by lower half-life (i.e., 0.00032day-1) and higher carbonyl index in comparison to strain CGK192. The findings reflect the ability of our strains to develop biofilm and introduce an oxygenic functional group into the polymer surface, thereby making it more susceptible to degradation.

Biodegradation of Nitrile Gloves as Sole Carbon Source of Pseudomonas aeruginosa in Liquid Culture.

Nitrile gloves have become a significant environmental pollutant after the COVID-19 pandemic due to their single-use design. This study examines the capability of P. aeruginosa to use nitrile gloves as its sole carbon energy source. Biodegradation was determined by P. aeruginosa adapting to increasing nitrile glove concentrations at 1%, 3%, and 5% (w/v). The growth kinetics of P. aeruginosa were evaluated, as well as the polymer weight loss. Topographic changes on the glove surfaces were examined using SEM, and FT-IR was used to evaluate the biodegradation products of the nitrile gloves. Following the establishment of a biofilm on the glove surface, the nitrile toxicity was minimized via biodegradation. The result of the average weight loss of nitrile gloves was 2.25%. FT-IR analysis revealed the presence of aldehydes and aliphatic amines associated with biodegradation. SEM showed P. aeruginosa immersed in the EPS matrix, causing the formation of cracks, scales, protrusions, and the presence of semi-spherical particles. We conclude that P. aeruginosa has the capability to use nitrile gloves as its sole carbon source, even up to 5%, through biofilm formation, demonstrating the potential of P. aeruginosa for the degradation of nitrile gloves.

Synthesis, characterization, thermal stability, and in vitro and in vivo degradation study of polycaprolactone and polyglycolide block copolymers

Biodegradable polymer materials are attractive in various biomedical applications. Herein, we report a block aliphatic copolymer, polycaprolactone-block-polyglycolide (PCL-b-PGA, denoted as PCLGA), and explored the polymer composition effect on the thermal and degradation behaviors. Three copolymers with different PCL/PGA weight ratios were obtained by a two-step ring opening polymerization. The chemical structures and compositions of copolymers were studied by NMR and FT-IR. The thermal behaviors were investigated by DSC and TGA. The in vitro degradation in phosphate buffer saline and in vivo degradation as an implant in rats were evaluated and the hygroscopic rate and polymer weight loss changes were monitored in an eight-week period. PCLGA with a higher PCL composition showed a slower degradation in vitro and in vivo. These PCLGAs with different degradation rates could be used as biomedical implants for potential application in drug delivery and tissue repair.

Термическая стабильность полиуретанового покрытия, полученного с использованием дифенилолпропана

Thermal stability of polyurethane varnish coating prepared by using diphenylolpropane, polyetherpolyol and polyisocyanate with an equimolar ratio of isocyanate and hydroxyl groups was assessed in the air. The polyurethane weight loss thermogram shows three temperature regions: I – (217-275)°С, II – (275-380)°С, and III – above 380°С. For interpreting thermogram of the polyurethane under study the model substances simulating the urethane groups of a polymer were synthesized. The substance containing the urethane group formed by phenolic hydroxyl of diphenylolpropane was shown to demonstrate relatively low thermal stability and gets broken down into isocyanate and bisphenol. Decomposition of the substance containing the urethane group formed by alcoholic hydroxyl occurs at the higher temperature. The data obtained allow interpreting the occurrence of thermal decomposition step I in TGA curve by structural changes in the blocks formed by diphenylolpropane and polyisocyanate being the least stable when exposed to elevated temperatures. The next step can be attributed to decomposition of more thermostable urethane groups formed by functional groups of oligooxypropylenetriol and polyisocyanate. Transition to the step III accompanied by severe sample weight loss due to decomposition of urethane groups is explained by thermal oxidation of oligoether units of polymer. Based on the data obtained the conclusion was made that the presence of urethane groups formed by phenolic hydroxyl of diphenylolpropane in polymer structure results in the decreased thermooxidative decomposition onset temperature of polymer. At the same time, a deceleration of thermooxidative processes due to the stabilizing effect of diphenylolpropane released at the beginning of thermal decomposition of polyurethane is observed in a high-temperature region. The proposed polyurethane coating is inferior to commercial counterparts in thermal decomposition onset temperature but superior to them in the temperature corresponding to a 50% polymer weight loss.

Biodegradation of poly(ε-caprolactone) in natural water environments

Abstract The environmental degradation of poly(ε-caprolactone)[PCL] in natural fresh water (pond) and in The Baltic Sea is presented in this paper. The characteristic parameters of both environments were measured during experiment and their influence on the biodegradation of the samples was discussed. The loss of weight and changes of surface morphology of polymer samples were tested during the period of incubation. The poly(ε-caprolactone) was more biodegradable in natural sea water than in pond. PCL samples were completely assimilated over the period of six weeks incubation in The Baltic Sea water, but after forty two weeks incubation in natural fresh water the polymer weight loss was about 39%. The results have confirmed that the investigated polymers are susceptible to an enzymatic attack of microorganisms, but their activity depends on environments.

Investigation of filled polymer weight loss upon irradiation in vacuum

A computational and experimental investigation of the influence of the filler particle distribution on the polymer composite material weight loss in vacuum upon irradiation with electrons is performed. The model of the radiolysis product migration in materials under investigation is proposed for numerical analysis of the experimental data. It is shown that the weight loss rates of model materials upon irradiation at fluences not exceeding the threshold values depend on the type of filler distribution.

Instrumental Physical Analysis of Microwaved Glycerol Citrate Foams

Solid glycerol citrate polyester polymeric foams generated by microwave heating were further cured in a conventional oven at 100 °C for 0, 6, 24, 48, or 72 h and their physical properties were tested. Curing glycerol citrate polyesters resulted in decreased moisture content (MC), altered color, increased hydrated polymer weight loss (HWL), and increased polymer oven weight loss (OWL). Polyester polymer samples were evaluated for firmness and springiness employing a texture analyzer (Model TA/TX2i). Oven curing increased polymer firmness and springiness. For example, firmness and springiness in 48 h cured samples increased 202 and 143%, respectively, when compared to uncured controls. High correlations were found comparing OWL, MC, HWL, firmness, and springiness. Compression molded samples obtained from ground cured and non-cured polymers were evaluated for tensile strength, elongation and Young’s modulus using the Instron universal test machine (Model 4201). Curing promoted higher tensile strengths and elongation but did not affect Young’s modulus values. High correlations were found between springiness, firmness, tensile strength, and elongation. The texture analyzer was shown to have merit in the preliminary evaluation of the glycerol citrate polyester polymers.

In vitro and in vivo degradation of poly(D, L‐lactide‐co‐glycolide)/amorphous calcium phosphate copolymer coated on metal stents

The purpose of this study was to optimize a novel biodegradable polymer for drug eluting stent (DES) applications. Degradation profiles of different poly(D,L-lactide-co-glycolide)/amorphous calcium phosphate (PLGA/ACP) composites coated on stents were studied both in vitro and in vivo for three months. For the in vitro study, stents were immersed into the phosphate buffered saline (37 °C, pH 7.4) with constant shaking. The polymer weight loss was measured weekly and morphological changes were analyzed. The results demonstrated that approximately 60% of polymer was degraded within the three-month period and there was no significant difference between the different PLGA/ACP composites. However, the composite of 50% PLGA (65/35) with 50% ACP showed a slightly faster degradation rate than other composites. Morphologically, all stent surfaces changed from a micro-porous before degradation to a corrugated solid micro-net-like structure at two months post degradation. Based on in vitro results, 65% PLGA (65/35) with 35% ACP) coated stents were selected and implanted into rat aortas (n = 12) for the in vivo study. Microscopic observation showed that no composite was found on any of the implanted stents at 12 weeks post implantation, which indicated the selected PLGA/ACP composite is desired for DES applications.

Structured Drug-eluting Bioresorbable Films: Microstructure and Release Profile

Bioresorbable drug-eluting films can be used in many biomedical applications. Examples for such applications include biodegradable medical support devices which combine mechanical support with drug release and antibiotic-eluting film coatings for prevention of bacterial infections associated with orthopedic implants or during gingival healing. In the current study, bioresorbable drug-loaded polymer films are prepared by solution processing. Two film structures are studied: A polymer film with large drug crystals located on its surface (A-type) and a polymer film with small drug particles and crystals distributed within the bulk (B-type). The basic mode of drug dispersion/location in the film (A or B-type) is found to be determined mainly by the process of film formation and depends mainly on the solvent evaporation rate, whereas the drug's hydrophilicity has a minor effect on this structuring process. Most release profiles from A-type films exhibit a burst effect of approximately 30% and a second release stage that occurs at an approximately constant rate and is determined mainly by the polymer weight loss rate. An extremely high burst release is exhibited only by a very hydrophilic drug. The matrix (monolithic) nature of the B-type film enables release profiles that are determined mainly by the host polymer's degradation profile, with a very low burst effect in most of the studied systems. In addition to the drug location/ dispersion in the film, the host polymer and drug type also strongly affect the drug's release profile from the film. It has been demonstrated that appropriate selection of the process parameters and film components (polymer and drug) can yield film structures with desirable drug release behaviors. This can lead to the engineering of new bioresorbable drug-eluting film-based implants for various applications.

Surface changes in polyhydroxyalkanoate films during biodegradation and biofouling

AbstractBACKGROUND: Despite the recognition that microbial biofilms play a role in environmental degradation of bioplastics, few studies investigate the relationship between bioplastic biodegradation and microbial colonisation. We have developed protocols based on a combination of confocal laser scanning microscopy and contact angle goniometry to qualitatively and quantitatively map surface changes due to biofilm formation and biopolymer degradation of solvent cast poly(3‐hydroxyalkanoate) films in an accelerated in vitro biodegradation system.RESULTS: A significant regression relationship between biofilm formation and polymer biodegradation (R2 = 0.96) was primarily conducted by cells loosely attached to the film surfaces (R2 = 0.95), rather than the strongly attached biofilm (R2 = 0.78). During biodegradation the surface rugosity of poly(3‐hydroxybutyrate) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] increased by factors of 1.5 and 1.76, respectively. In contrast, poly(3‐hydroxyoctanoate) films showed little microbial attachment, negligible weight loss and insignificant changes in surface rugosity.CONCLUSION: A statistically significant link is established between polymer weight loss and biofilm formation. Our results suggest that this degradation is primarily conducted by cells loosely attached to the polymer rather than those strongly attached. Biofilm formation and its type are dependent upon numerous factors; the flat undifferentiated biofilms observed in this study produce a gradual increase in surface rugosity, observed as an increase in waviness. Copyright © 2008 Society of Chemical Industry

Reflexive Interfaces of Poly(trimethylene carbonate)-Based Polymers: Enzymatic Degradation and Selective Adsorption

A reflexive interface was designed and prepared based on poly(trimethylene carbonate) (PTMC), which was polymerized from the hydroxyl groups of cholesterol or poly(ethylene glycol) monomethyl ether (mPEG) by conventional ring-opening polymerization techniques. Resulting polymer coatings were analyzed in terms of surface wettability and polymer weight loss during degradation using contact angle and quartz crystal microbalance measurements. The adsorption of hydrophilic and hydrophobic dyes on the membrane was evaluated by UV−vis spectrometry and was found to be largely dependent on the polarity of the terminal unit such as the cholesterol or mPEG segment. For example, mPEG (Mn = 5000 g/mol)−PTMC membranes, abundant with surface mPEG segments, demonstrated quick, spontaneous surface enrichment in water. In terms of results, surface wettability increased and enzymatic degradation decreased due to a lack of enzymatic accessibility. Moreover, such membranes could adsorb hydrophobic dyes from aqueous solutions, demonstrating interfacial stabilization by mPEG segments. Resulting polymers could be interesting candidates for commercial applications and of specific interest in biomedical applications.

Development of a chlorine-resistant polyamide reverse osmosis membrane

The chlorine resistance of polyamides synthesized using various diamines and acid chlorides was investigated. The retention ratio of molecular weight and the polymer weight loss after the immersion in chlorine solution were used as the evaluation for chlorine resistance. The influence of the diamine chemical structures on the chlorine resistance is discussed. After screening 17 diamines, N,N'-dimethyl-m-phenylenediamine (N,N'-DMMPD) was selected in the preparation of the reverse osmosis polyamide membrane. The membrane prepared from N,N'-DMMPD and 1,3,5-benzenetricarbonyl trichloride (TMC) showed much higher chlorine resistance than commercial polyamide and cellulose acetate RO membranes. The use of mixture of TMC and isophthaloyl dichloride (IPC) in the preparation of the polyamide membrane brought about further improvement in the chlorine resistance. The solute rejection hardly changed after the immersion in aqueous sodium hypochlorite solution (200 ppm) at 40°C for 96 h.

Clinical relevance of trans 1,4-polyisoprene aging degradation on the longevity of root canal treatment

This in vivo study investigated the time of degradation of root filling material (trans 1,4-polyisoprene) retrieved from endodontically treated teeth and correlated the occurrence of degradation with the longevity of endodontics. Thirty-six root-filled teeth with different filling times (2 to 30 years) and with and without periapical lesions were selected. All teeth presented clinical indication for root canal retreatment. The association among filling time, presence of periapical lesion and root filling material degradation was investigated. Root filling samples were retrieved from the root canals using a Hedströ m file without solvent. The trans 1,4-polyisoprene was isolated by root filling solubilization in chloroform followed by filtration and centrifugation. GPC and FT-IR were the analytical techniques utilized. Degradation of trans 1,4-polyisoprene occurred with time, as a slow process. It is an oxidative process, and production of carboxyl and hydroxyl groups in the residual polymer were observed. Statistically significant decrease of molar mass was observed after 5 (p=0.0001) and 15 (p=0.01) years in teeth with and without periapical lesion, respectively. Bacteria participated in polymer degradation. Gutta-percha aging was proven an important factor for the long-term success of endodontic treatment. The findings of the present study showed that, after 15 years, polymer weight loss may decrease the capacity of the filling mass to seal the root canal space and prevent re-infection, thus compromising significantly the longevity of root canal therapy.

In vivo aging of gutta‐percha dental cone

AbstractGutta‐percha cone is the most widely used material for root canal filling. The in vivo aging of this cone focus on the degradation of its main organic component, trans‐1,4‐polyisoprene, was studied. Aged cones (25 samples) from 2 to 30 years of root canal filling were extracted from different patients in the occasion of retreatment by mechanical way. The information about the aging time was given by the patients. Gel‐permeation chromatography (GPC) and infrared spectroscopy (FTIR) were the analytical techniques used. Polyisoprene degrades with time of aging, but in a slow process. Decrease in polymer molar mass from 5.7 × 105 to 1.7 × 105 g/mol was observed in polyisoprene from cone after 30 years of root canal filling and inside a noninfected tooth. In tooth with caries and periodontal infection, the decrease in molar mass is higher (4.6 × 104 g/mol in cone with 10 years of aging). The production of carbonyl and hydroxyl groups in the aged material indicates that the process is oxidative, even in closed teeth. In these cases, the oxygen could be provided from tissue fluid. The degradation mechanism is complex and depends on many factors, besides time of root canal filling. The dental problem caused by the aging could be the production and migration of cytotoxic substances to periodontal ligament and the reduction on the canal sealing property due to the polymer weight loss. Both of them could contribute to the root canal treatment failure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:4082–4088, 2006

Open windrow composting of polymers: an investigation into the rate of degradation of polyethylene

The compostability of degradable polymers under open windrow composting conditions is explored within this paper. Areas for consideration were the use of, and impacts of, degradable polyethylene (PE) sacks on the composting process and the quality of the finished compost product. These factors were investigated through polymer weight loss over the composting process, the amount of polymer residue and chemical contaminants in the finished compost product, the windrow temperature profiles and a bioassay to establish plant growth and germination levels using the final compost product. This trial also included a comparative study of the weight loss under composting conditions of two different types of ‘degradable’ polymer sacks currently on the European market: PE and a starch based product. Statistical analysis of the windrow temperature profiles has led to the development of a model, which can help to predict the expected trends in the temperature profiles of open compost windrows where the organic waste is kerbside collected using a degradable PE sack.

The interaction mechanism between microorganisms and substrate in the biodegradation of polycaprolactone

AbstractThe present work concerns the interplay of the degradation mechanism and the nature of the interaction between microorganisms and substrate. The biodegradation of polycaprolactone films by a pure strain of microorganisms isolated from an industrial composting unit for household refuse was studied in minimal medium with the polymer as sole carbon source. In conditions where the polymer surface is colonized and a biofilm is formed (under a low stirring rate), polymer weight loss is limited, whereas total degradation is observed when stirring conditions prevent biofilm formation. In the first case, holes are observed in the degraded film and a polysaccharide responsible for microorganism adhesion was identified by FTIR. SEM observation of the polymer surface as a function of the degradation time suggests that the crystalline and amorphous phase are degraded at about the same rate in the first case, whereas the amorphous phase is preferentially degraded in the latter. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1334–1340, 2002

Protein release from poly(ortho ester) extruded rods

Poly(ortho ester) rods containing 15 wt% FITC-BSA were prepared by extruding an intimate mixture of finely powdered polymer and protein at a temperature where protein activity is retained. After an induction period, linear in vitro release kinetics were obtained with concomitant polymer weight loss.

Changes in chemical and thermal properties of the tri-block copolymer poly(l-lactide-b-1,5-dioxepan-2-one-b-l-lactide) during hydrolytic degradation

Hydrolysis of the novel tri-block copolymer poly(l-lactide-b-1,5-dioxepan-2-one-b-l-lactide) of different compositions has been studied in buffered salt solution at 37°C and pH 7.4. Specifically, polymer weight loss, composition changes, molecular weight changes, thermal properties and release of lactic acid and 3-(2-hydroxyethyl)-propanoic acid have been detected. The degradation was found to start immediately after the sample was immersed into the aqueous buffer solution. The rate of degradation was influenced only by the original molecular weight, the copolymer composition had no significant effect. The heat of fusion and Tg increased with degradation time due to an increased amount of l-lactide (l-LA) in the polymer matrix. The GC–MS analysis showed that up to 70% of the theoretical amount of 3-(2-hydroxyethyl)-propanoic acid and 10–20% of lactic acid was released after 23weeks of degradation.

Renewable Long-Chain Fatty Acids for Production of Biodegradable Medium-Chain-Length Polyhydroxyalkanoates (mcl-PHAs) at Laboratory and Pilot Plant Scales

Several types of mcl-PHAs were produced by Pseudomonas putida KT2442 at pilot and laboratory scales from renewable long-chain fatty acids (LCFAs) and octanoic acid. These and other mcl-PHAs are now available in sufficient amounts to carry out application and processing studies. We have isolated and purified these polymers in preparative amounts of 10−500 g by solvent recovery and selective enzymolysis. The molecular weights of mcl-PHA copolymers produced from LCFAs were generally similar to those found for octanoic acid based material, but the polydispersity was higher and the degree of polymerization was lower. The polymers showed thermal properties common for amorphous or semicrystalline thermoplastic elastomers above their Tg, which decreased with increasing average pendant chain length. PHAs derived from LCFAs, which contained 3−12 new hydroxyacid comonomers compared to PHA produced from oleic acid, were amorphous, did not crystallize, and showed liquid properties at room temperature. As the number of comonomers and thus the degree of disorder increased in these PHAs, the polymers became more viscous and tacky. PHAs derived from octanoic acid and oleic acid were not affected by the production scale in terms of composition and physical properties. Although different production process control strategies used at lab and pilot scale did influence the process productivity, the substrate yield was not affected by the process control type applied and was always close to the theoretical PHA yield to be expected for fatty acid utilization through the β-oxidation pathway. Isolation and GC−MS analysis of the methanolyzed trimethylsilyl- (TMSI-) derivatives allowed the identification of a large number of previously unknown 3-hydroxy acid PHA components. All purified polymers were subjected to in vitro aerobic biodegradation using a compost isolate. The extent of mineralization varied from 15 to 60% of the theoretical biochemical oxygen demand (ThBOD). The polymer weight loss after 32 days ranged from 40 to 90% for the different mcl-PHAs.

Hydrolysis and Erosion Studies of Autocatalyzed Poly(ortho esters) Containing Lactoyl−Lactyl Acid Dimers

Poly(ortho esters) based on 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,10-decanediol, and 1,10-decanediol dilactate were prepared and their hydrolysis in phosphate buffer at 37 °C and pH 7.4 was determined as a function of time. Specifically, kinetics of polymer weight loss, polymer molecular weight changes, release of lactic acid and release of propionic acid were determined. A significant decrease in molecular weight occurred within about 20 days. Weight loss and evolution of hydrolysis product occurred after an induction period that decreased with increasing content of the lactoyl-lactyl segment in the polymer. After the induction period, a concomitant rate of weight loss and release of hydrolysis products was noted. The rate increased with increasing content of the lactoyl-lactide segment. After a certain time period, size-exclusion chromatography revealed the formation of peak at an apparent molecular mass of about 550 Da. The compounds under the peak were analyzed by electrospray ionization/ mass spectrometry (ESI/MS) and found to consist of a multiplicity of lower molecular weight polymer hydrolysis fragments. On the basis of expected hydrolysis products, it was possible to assign a structure to most molecular weight peaks in the ESI/MS spectrum. The data were found to be consistent with a hydrolysis that takes place predominantly in the surface layers of the solid polymer.