Addition Of Chain Extender Research Articles

Castor oil-based polyurethane adhesives: Effect of cross-linker on the bond strength

Adhesives are important for binding diverse materials, promoting structural integrity and functional versatility in countless daily life applications. An enormous obstacle remains in the development of polyurethane (PU) adhesives exhibiting excellent bonding strength. Designing a chain extender with appropriate molecular structures is critical to improving the bonding strength of polyurethane-based adhesives. In this work, polyurethane-based adhesive was prepared using castor-oil-based polyol and diisocyanate. The bonding strength of the adhesive was improved by adding chain extenders such as N, N-bis(2-hydroxyethyl) thiophene-2,5-dicarboxamide (ETP) and N, N-Bis(2-hydroxyethyl)-terephthalamide (ETAM). The modified adhesive showed high bonding strength after the addition of chain extenders due to the presence of the dicarboxamide group, which served as a center for hydrogen bonding. The bonding strength of PU adhesive increased to 7.22 and 9.68 MPa from 5.0 MPa after the addition of 7.5 wt% of ETP and 5.0 wt% of ETAM, respectively. The bonding strength of the adhesives was tested on both wood (oak) and metal (stainless steel) coupons. The bonding strength of 9.68 MPa on oak wood and 6.73 MPa on stainless steel coupon was observed for the 5.0 wt% of ETAM-based PU adhesive. The bonding failure was observed to be due to wood failure. The reason behind the good bonding is noncovalent bonds which are formed between the functional group of the PU molecular chain and the surface of the substrate. In addition, no major changes in FT-IR after keeping these adhesives in different solvents were observed. Good crosslinking is also confirmed by studying the gelling and swelling data of the adhesives.

Effects of di- and trifunctional chain extenders on the properties of flexible cold-cure polyurethane foams

In this study, effects of di- and trifunctional chain extenders including ethylene glycol (MEG), ethanolamine (MEA), diethanolamine (DEA), and glycerin (GLY) were investigated. 0.3, 0.6, and 0.9 php (parts per hundred parts of polyol mixture) of the chain extenders were added to the polyol formulation. Then, foam parts were produced by molding. The reaction profile, free rise density (FD), and mechanical properties of the specimens were tested regarding ASTM D7487 test methods. First of all, reaction profiles were affected by the chemical nature of the chain extenders. MEA and DEA which have a primary and secondary amine unit, respectively, accelerated both the polymerization and blow reactions and resulted in faster cream (CT), gel (GT), and end-of-rise time (RT) values. On the other hand, MEG also accelerated GT, but retarded CT. Finally, GLY retarded CT, GT, and RT of foam samples. FD of all samples were almost the same with a slight decrease by increasing the amount of chain extenders. Besides, force-to-crush (FTC) as a measure of closed- or open-cell structure, was investigated. Results showed that incorporating di- and trifunctional chain extenders led to a remarkable increase in FTC values. The influence was more profound with amine-based chain extenders. The effects of chain extenders on the mechanical properties were also studied according to the ASTM D3574. In the compression set test, using difunctional chain extenders up to 0.6 php, improved the performance. But higher amounts reversed the trend. On the other hand, trifunctional chain extenders declined the compression set properties of the foam. The addition of chain extenders dwindled the tensile and tear properties of the foams. However, the reduction was less with difunctional chain extenders.

The Efficiency Evaluation of the Reactive Extrusion Process for Polyethylene Terephthalate (PET). Monitoring of the Industrial Foil Manufacturing Process by In-Line Rheological Measurements

The main topic of the presented work is the evaluation of the in-line viscometer (VIS) operation installed on the industrial line for polyethylene terephthalate (PET) foil production. The tests were performed during the regular operation of the machine, which results from the need to maintain production continuity. Polymer viscosity control is of particular importance in the production of degradable materials and recycled polymers. The processing of PET film is, therefore, a particularly difficult issue due to the presence of both of these problems at the same time. The conducted research had a two-pronged character: assessment of the correct operation of the viscosity measurement system and testing of the effectiveness of reactive additives during the extrusion process. Measurements were carried out with the use of several types of input materials, including recycled blends. The key tests were carried out with the addition of viscosity modifiers. Measurements conducted during the extrusion process confirmed the effectiveness and high sensitivity of the in-line system (VIS), while clear changes in the polymer flow characteristics were observed only after the addition of chain extenders. The in-line measurements revealed that the addition of 1% of the reactive compound increased the viscosity from the initial 150 Pa∙s to over 350 Pa∙s. The most significant increase in viscosity for the additive based on pyromellitic dianhydride (PMDA) confirms the effectiveness of the reactive extrusion method and the suitability of the used measuring. During further analysis, the obtained films were also tested. The results showed no negative effects of the reactive extrusion on the mechanical performance of the foil; however, for recycled materials, the average values of tensile strength and elongation at break have deteriorated. A positive aspect of the use of reactive additives was the greater uniformity of mechanical properties. For some materials, there was a significant increase in the haze factor (transparency), which should be considered a disadvantage.

Enhancement of the compatibility, mechanical properties, and heat resistance of poly(butylene succinate-co-terephthalate)/poly(butylene succinate) blends by the addition of chain extender and nucleating agent

Enhancement of the compatibility, mechanical properties, and heat resistance of poly(butylene succinate-co-terephthalate)/poly(butylene succinate) blends by the addition of chain extender and nucleating agent

Property improvement of processed PLA/PBAT using chain extenders

The polymer blend of poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT), commercially named Ecovio, is a biodegradable plastic with a high level of strength and toughness. Despite the development of biodegradable plastics with improved characteristics and greater applicability, their cost remains prohibitively high preventing their widespread use. One approach to reducing production costs is recycling manufactured waste plastics. However, in this process, the properties of plastic are typically changed due to chain scissions during thermal reprocessing. Using an additive such as a chain extender is thought to reconnect cleaved polymer chains. Therefore, the purpose of this research is to investigate the influences of two chain extenders, multifunctional epoxide and multifunctional imide, on the mechanical properties and thermal properties as well as the melt flow rate of Ecovio. Materials were processed and blended using a twin-screw extruder and formed into film samples via the blow film extrusion process. The findings revealed that the addition of chain extenders resulted in a higher viscosity of Ecovio. In the thermal properties test, it was found that the use of chain extenders resulted in shifts in the glass transition, crystallization, melting temperature, and thermal stability of Ecovio. Finally, the result of mechanical properties test illustrated that Young’s modulus and tensile strength of thermal processed Ecovio were changed and improved by blending with virgin Ecovio and chain extenders.

From polymeric waste to potential industrial product: Modification of recycled polycarbonate

The aim of this study is to investigate the effects of simultaneous addition of chain extender and impact strength modifier on tribological, mechanical, thermomechanical and morphological properties of recycled polycarbonate (r-PC). Mechanical properties of the samples were evaluated by using essential work of fracture method and tensile tests. Tribological properties were investigated by means of adhesive wear test. Thermomechanical properties were investigated by using dynamic mechanical analysis. As a result of the study, different types of samples were obtained, which simultaneously contained chain extender and impact strength modifier and exhibit improved fracture toughness, adhesive wear performance, storage modulus and not deteriorated tensile strength compared to neat r-PC. Thus, in this study, a solution alternative for both the expanding of the usage area of r-PC and waste management of it has been presented.

Enhancement of the Processability and Properties of Nylon 6 by Blending with Polyketone

Polyketones (PKs) having strong hydrogen bonding properties and a chain extender are used as additives in the melt processing of nylon 6 (PA6). Their effect on the chain structure and properties of PA6 is studied to enhance the processability of PA6 in melt processing. The addition of the chain extender to PA6 increases the melt viscosity by forming branches on the backbone. The addition of PKs results in an additional increase in viscosity through the hydrogen bonding between N–H of PA6 and C=O of PK. The change in the N–H bond FT-IR peak of PA6 and the swelling data of the PA6/PK blend containing a chain extender, styrene maleic anhydride copolymer (ADR), suggest that incorporation of chain extender and PK in the melt processing of PA6 results in physical crosslinks through hydrogen bonding between the branched PA6 formed by the addition of chain extender and PK chains. This change in the chain structure of PA6 not only increases the melt strength of PA6 but also increases randomness resulting in decreased crystallinity.

Statistical Design of Biocarbon Reinforced Sustainable Composites from Blends of Polyphthalamide (PPA) and Polyamide 4,10 (PA410).

A full factorial design with four factors (the ratio of polyphthalamide (PPA) and polyamide 4,10 (PA410) in the polymer matrix, content percent of biocarbon (BioC), the temperature at which it was pyrolyzed and the presence of a chain extender (CE)), each factor with two levels (high and low), was carried out to optimize the mechanical properties of the resulting composites. After applying a linear model, changes in tensile strength, elongation at break and impact energy were not statistically significant within the considered material space, while the ones in the flexural modulus, the tensile modulus, density and heat deflection temperature (HDT) were. The two most influential factors were the content of BioC and its pyrolysis temperature, followed by the content of PPA. The affinity of PPA with a high-temperature biocarbon and the affinity of PA410 with a lower-temperature biocarbon, appear to explain the mechanical properties of the resulting composites. The study also revealed that the addition of CE hindered the mechanical properties. By maximizing the flexural modulus, tensile modulus and HDT, while minimizing the density, the optimal composite predicted is an 80 [PPA:PA410 (25:75)] wt% polymer composite, with 20 wt% of a BioC, pyrolyzed at a calculated 823 °C.

Development of Toughened Flax Fiber Reinforced Composites. Modification of Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) Blends by Reactive Extrusion Process.

The presented study focuses on the development of flax fiber (FF) reinforced composites prepared with the use of poly(lactic acid)/poly(butylene adipate-co-terephthalate)—PLA/PBAT blend system. This type of modification was aimed to increase impact properties of PLA-based composites, which are usually characterized by high brittleness. The PLA/PBAT blends preparation was carried out using melt blending technique, while part of the samples was prepared by reactive extrusion process with the addition of chain extender (CE) in the form of epoxy-functionalized oligomer. The properties of unreinforced blends was evaluated using injection molded samples. The composite samples were prepared by compression molding technique, while flax fibers reinforcement was in the form of plain fabric. The properties of the laminated sheets were investigated during mechanical test measurements (tensile, flexural, impact). Differential scanning calorimetry (DSC) analysis was used to determine the thermal properties, while dynamic mechanical thermal analysis (DMTA) and heat deflection temperature (HDT) measurements were conducted in order to measure the thermomechanical properties. Research procedure was supplemented with structure evaluation using scanning electron microscopy (SEM) analysis. The comparative study reveals that the properties of PLA/PBAT-based composites were more favorable, especially in the context of impact resistance improvement. However, for CE modified samples also the modulus and strength was improved. Structural observations after the impact tests confirmed the presence of the plastic deformation of PLA/PBAT matrix, which confirmed the favorable properties of the developed materials. The use of PBAT phase as the impact modifier strongly reduced the PLA brittleness, while the reactive extrusion process improves the fiber-matrix interactions leading to higher stiffness and strength.

Viscosity improvement of recycled poly (ethylene terephthalate) from waste bottles by adding antioxidants and chain-extender

This research work is focused on the viscosity improvement of recycled poly(ethylene terephthalate) (rPET) from waste bottles by adding antioxidants and multi-functional reactive polymer (Joncry ADR 4468, chain extender). The achieve the objective of this work the investigated was broken into two parts. The first part studied the effect of rPET viscosity after adding various types of antioxidants and stabilizer such as Irgafos®168, Tinuvin® 770, Irganox®1010. The second part observed the effect of viscosity after it was blended with chain extender at 0, 0.2, 0.4, 0.6 and 0.8 pph. rPET was then dried in the oven at 120 oC for 12 hrs, to deplete the moisture. Then, the dried rPET (mixed with the chemicals above) was extruded into a compound using a twin screw extruder. The shear viscosity of the extruded compound was then measured using a rotational rheometer at 270 oC. The results revealed that the addition of chain extender increased the shear viscosity and the tensile strength at break of rPET. Therefore, the chain extender interacted with chains, which could change the structure to be the longer chains, branching or network structures. These structures are entangled and interrupt the movement of the molecular chains. It can be concluded that the viscosity of rPET can be improved by adding a chain extender at 0.6 pph, and the antioxidants of Irgafos®168, Tinuvin®770 and Irganox®1010 at 0.2, 0.1 and 0.5 pph, respectively.

Effect of chain extender and light stabilizer on the weathering resistance of PBAT/PLA blend films prepared by extrusion blowing

Biodegradable poly (butylene adipate‑co‑terephthalate)/polylactic acid (PBAT/PLA) films were prepared by melt blending and blowing technology under the presence of a chain extender and two different light stabilizers. A comparison of the infrared spectra of the film with and without these additives before and after the weathering tests showed that the addition of chain extender and light stabilizer improved the polymer weathering resistance significantly. Without PLA, PBAT underwent serious chain scissions and crosslinking during the weathering. PBAT/PLA film chain scissions were weakened as the PLA content increased. After 200 h of the weathering, the machine direction (MD) tensile strength as well as MD and transverse direction (TD) elongation at break of both PBAT and PBAT/PLA films decreased, while their TD tensile strength changed only slightly. The film with the 85:15 PBAT:PLA ratio containing 1.5 phr of chain extender showed much better flexibility without any changes to its tensile strength. The addition of 0.6 phr of light stabilizer (Chimassorb2020 or Irganox 1010) to this blend showed significantly improved weathering resistance. Better weathering improvement was observed when Chimassorb2020 was added. The tensile strength of PBAT/PLA/ADR/ Chimassorb2020 sample in the machine and transverse directions decreased by 8.4 and 28%, respectively, after 200 h of weathering.

Evaluation of Polyurethane Elastomers for Encapsulation of Hydroacoustic Transducers

AbstractHydroacoustic transducers are devices capable of converting mechanical energy from acoustic waves into electrical energy, and vice versa, through piezoelectric elements connected to electronics that need to be protected from contact with the water. This tightness is provided by the encapsulation of the transducers with elastomers. The use of fillers and chain extenders are known to promote a barrier for water diffusion, but it would inevitably change the other properties of the elastomer. Thus, this work aims to evaluate the effects of filler and chain extender addition on the properties of polyurethane elastomers (PUR) for this application. Thermogravimetric, thermomechanical, glass‐rubber transition temperature, hardness, and dielectric loss analyses are performed. It is observed an increase in the dielectric loss, hardness, and thermal stability with the addition of mineral fillers and carbon black. The addition of chain extender promoted a greater hardness in the final elastomer, but has no measurable effects on the dielectric loss, and decreased the thermal and dimension stability with temperature. Glass‐rubber transition temperatures remain in the range from –78 to –80 °C, which is in the acceptable range for the application as encapsulants.

Development of Eco-Sustainable PBAT-Based Blown Films and Performance Analysis for Food Packaging Applications.

In this work, eco-sustainable blown films with improved performance, suitable for flexible packaging applications requiring high ductility, were developed and characterized. Films were made by blending two bioplastics with complementary properties—the ductile and flexible poly(butylene-adipate-co-terephthalate) (PBAT) and the rigid and brittle poly(lactic acid) (PLA)—at a 60/40 mass ratio. With the aim of improving the blends’ performance, the effects of two types of PLA, differing for viscosity and stereoregularity, and the addition of a commercial polymer chain extender (Joncryl®), were analyzed. The use of the PLA with a viscosity ratio closer to PBAT and lower stereoregularity led to a finer morphology and better interfacial adhesion between the phases, and the addition of the chain extender further reduced the size of the dispersed phase domains, with beneficial effects on the mechanical response of the produced films. The best system composition, made by the blend of PBAT, amorphous PLA, and the compatibilizer, proved to have improved mechanical properties, with a good balance between stiffness and ductility and also good transparency and sealability, which are desirable features for flexible packaging applications.

Reactive Compatibilization of Multi-Hydroxy Functional Compound Based on Polyoxymethylene/Thermoplastic Polyether Elastomer Blends

Polyoxymethylene/thermoplastic polyether elastomer composites were prepared by using the chain extender based on styrene, methyl methacrylate and glycidyl methacrylate copolymer as the reaction compatibilizer. The composites were fabricated by melt extrusion, and the content of thermoplastic polyether elastomer varied from 0 to 25 phr, while the amount of the chain extender was 0.2, 0.4, and finally 0.6 phr at thermoplastic polyether elastomer content 15 phr. The reactive compatibilization and the properties of the blends were studied. It was found that the viscosity of the blends increased gradually, and the notch impact strength did not change significantly after the addition of chain extender, but the tensile modulus increased significantly.

Toughening mechanism of long chain branched polyamide 6

Polyamide 6 (PA6) materials with different degrees of long chain branching (LCB) were prepared via extrusion through varying the addition of chain extender. The LCB degree was quantitatively determined by using a rheological method based on macromolecular dynamic models. The topological structures of long-chain branching and crosslinked network were effectively distinguished through rheological percolation analysis so that modified PA6 with ultra-high LCB level was obtained. The XRD analysis indicated that LCB modification favored the generation of the γ-form, and the γ-form content of LCB-PA6 increased with increasing degree of LCB, which could provide a reasonable explanation for the high Izod impact strength of ultra-high LCB-PA6. Another reason for the great enhancement of impact toughness was the strong interfacial interaction between LCB molecules and virgin PA6 matrix. A large number of fibrillar ligaments and cavities during crack propagation were observed in the SEM analysis.

Recycled poly(lactic acid)–based 3D printed sustainable biocomposites: a comparative study with injection molding

With the objective of giving a new economic life to postindustrial waste poly(lactic acid) (PLA), biocomposites based on recycled PLA were manufactured using conventional melt blending, and the strands produced were successfully used for three-dimensional (3D) printing of American Society for Testing and Materials (ASTM) samples by means of the fused deposition molding (FDM) method. This article further discusses the processing advantages and challenges associated with void formation, anisotropic behavior, and the quality of the 3D printed (3DP) samples in comparison with injection-molded (IM) counterparts. The blends were manufactured containing 30 wt % of recycled PLA in a matrix of virgin PLA. Similarly, blends were also prepared with addition of an epoxy-based chain extender (CE) and as well as with the CE and a reinforcing phase of microcrystalline cellulose (MCC). One of the limitations of recycled PLA in FDM-based 3D printing is its high melt flow due to the reduced molecular weight after recycling, which results in excessive material flow during extrusion, and hence limits its application in FDM-based 3D printing. Consequently, the main effect of the CE, Joncryl, was to control the Melt Flow Index (MFI) of the biocomposites containing the recycled PLA. The addition of CE also resulted in improvement of the impact strength of 3DP samples. In general, the CE in combination with the natural fibers (MCC) allowed the incorporation of postindustrial PLA. Data suggest that more recycled PLA may be incorporated by using this blend combination. In general, owing to the void formation, 3DP samples presented lower values of density (lightweight) and mechanical properties as compared with IM samples. However, the tensile strength, modulus and Izod impact strength of 3DP biocomposites were increased by up to 88%, 127%, and 11%, respectively, by the addition of 5 wt % MCC, as compared with 3DP samples based on postindustrial PLA without additives.

Silicone Chain Extender for Recycled Polyethylene-terephthalate with Higher Flexibility

To decrease the modulus and increase the mechanical properties of recycled PET by introducing the flexible segments, the recycled polyethylene-terephthalate (PET) was modified by the chain extender produced with 2, 4, 6, 8-tetramethyl-2, 4, 6, 8-tetra (2, 3-epoxypropoxy) propylcyclotetrasiloxane by the hydrosilylation reaction. Different percentages of chain extender were used in order to investigate the effect of chain extender content on the modulus of PET. The dynamic mechanical analysis was performed on PET samples, which showed that Tg of PET was firstly raised by the addition of chain extender and then decreased. Small amplitude shearing test performed on PET samples confirmed that the addition of the flexible segments could remarkably decrease the modulus of PET, which would be helpful for the extrusion process. The entanglements from branches were also influenced by the addition of extender.

Crystallization kinetics of chain extended poly(L-lactide)s having different molecular structures

Poly(l-lactide)s (PLLAs) with different chain structures were prepared by reactive melt processing and using Joncryl ADR as chain extender. Results of gel permeation chromatography (GPC) revealed that chain extended PLLAs had high molecular weights and two differentiated molecular weight distributions. Linear rheology was sensitive to the obtained molecular structures and revealed as the increase on the amount of chain extender gradually led to a decrease of the loss factor in the whole frequency region and to an increase of melt viscosity and both storage and loss moduli. In addition, the entanglement density increased significantly with addition of chain extender and had a significant influence on crystallization kinetics. Correlation of molecular weight, viscosity and entanglements changed the crystallinity and crystallization kinetics of chain extended PLLAs in both isothermal and non-isothermal crystallizations. Specifically, samples prepared from 1 wt-% of Joncryl (PLLA1R) revealed the highest nucleation and the fastest crystallization rate.

Microcellular foaming behaviors of chain extended poly (butylene succinate)/polyhedral oligomeric silsesquioxane composite induced by isothermal crystallization

Currently, the fabrication of microcellular semi-crystalline polymer foams using supercritical CO2 as a blowing agent had attracted worldwide interest. In this paper, a novel and facile isothermal crystallization induction method was proposed to prepare biodegradable microcellular semi-crystalline poly (butylene succinate) (PBS) foams by supercritical CO2. In order to improve melt viscoelasticity and increase cell nucleation number, chain extender (CE) and polyhedral oligomeric silsesquioxane (POSS) were introduced into PBS through melt blending method. Differential scanning calorimetry results showed that with the addition of CE and POSS, the crystallization temperature of various PBS samples increased and their crystallinity kept unchanged almost. Compared with those of pure PBS, the complex viscosity and storage modulus of chain extended PBS (CPBS), PBS/POSS and CPBS/POSS increased. The effect of chain extension, POSS addition and induction time on the foaming performance of various PBS samples was studied systematically. Microcellular CPBS/POSS foam was successfully fabricated at the induction time of 18 min and foaming temperature of 90 °C, in which the cell size and volume expansion ratio could reach 6.80 ± 1.21 μm and 7.48 ± 0.03 times, respectively. Finally, the formation mechanism of various PBS foams by isothermal crystallization induction method was presented and the thermal conductivity of various PBS foams was investigated.

Effects of chain extender and uniaxial stretching on the properties of PLA/PPC/mica composites

Poly(lactic acid) (PLA)/poly(propylene carbonate) (PPC)/mica composites with different amount of chain extender (CE) were melt compounded and then processed via two routes (compression molding and uniaxial stretching) into sheets and films. The tensile, thermal, and oxygen barrier properties of all the samples were investigated. Tensile test showed that the tensile strength and elongation at break of all films were much higher than that of all sheets, especially for PLA/PPC/mica with 0.9‐wt% CE composite (CM3(CE)0.9) film. The crystallinity of all films increased significantly after uniaxial stretching of sheet samples. The Fourier transform infrared spectroscopy (FTIR) results proved the chemical reactions occurred between PLA/PPC and CE. Scanning electron microscope (SEM) analysis revealed that compatibility and interfacial adhesion of all samples were improved after adding mica and CE, and they were further enhanced after uniaxial stretching. The addition of CE was not favorable to improve the oxygen barrier performance of PLA/PPC/mica sheet samples. However, the oxygen barrier performance of film samples was significantly improved after uniaxial stretching. In particular, the CM3(CE)0.9 film had the lowest oxygen permeability coefficient (1.4 × 10−15 cm3·cm/(cm2·s·Pa)), and this was the best oxygen barrier properties reported in the literature for PLA‐based composites, which was comparable with PA film. This study demonstrated the high efficiency of uniaxial stretching on improvement of properties of composites, which would promote the application of biodegradable polymers in oxygen sensitive food packaging.