Effects of molecular weight on selected physical properties of polyaromatic ether-ketones

Polyaromatic ether-ketones with various inherent viscosities were prepared and their thermal properties and stress–strain relationships were studied. It was found that the polymer should have an inherent viscosity greater than 0.8 in order to give flexible films, but there was no difference in thermal and stress–strain properties among polymers with viscosities greater than 0.8. Values of 110 MPa and 13% are considered to be the standard values of tensile strength and elongation, respectively, for these polyaromatic ether-ketones. The crosslinking effects on these properties were also studied, using polymers containing 1 and 5 mol % of crosslinkable biphenylene units, but no significant changes in the properties due to crosslinking were observed.     

Property Modification via Crosslinking in CBDO-Based Copolyterephthalates

The work discussed herein focuses on the examination of the effects of crosslinking CBDO containing copolyterephthalates. A series of copolyterephthalates containing the aliphatic CBDO monomer along with aromatic diols was examined. These materials incorporate CBDO, bisphenol A, phloroglucinol, and terephthaloyl chloride and were made using standard solution polymerization techniques. The phloroglucinol, a trifunctional aromatic alcohol, was used as the crosslinking agent. The series of materials examined included both linear and crosslinked systems. The percent incorporations of the selected monomers, CBDO, bisphenol A, phloroglucinol, and terephthaloyl chloride, was varied to create a homologous series of polymers. Each polymer material was characterized for both thermal and mechanical performance.     

Methacrylate monomer as an alternative to styrene in typical polyester–styrene copolymers

This study presents the research on the influence of crosslinking monomers [styrene and diethylene glycol dimethacrylate (DEGDMA)] on the properties of unsaturated polyester resins (UPRs). Syntheses of the unsaturated polyesters (UPs) modified with benzyl alcohol were carried out. Then, each polyester was used in preparation of five resin solutions with different amounts of crosslinking monomers acting as reactive diluents. These diluents improve the processability of UPs reducing their viscosities. They also take part in crosslinking of resins during copolymerization process. The properties of the prepared UPRs systems were investigated before and after the curing process. The measurements of their viscosity, reactivity, mechanical properties, thermal stability (thermogravimetry), and dynamic mechanical analysis were performed. Resins where DEGDMA was used as reactive diluent were characterized by the largest viscosities in comparison to styrene ones. The type of the used monomer influenced also degree of the resin crosslinking. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47735.     

Tuning the mechanical properties of UV coatings towards hard and flexible systems

The standard resins of radiation-curable coatings provide either hard or flexible coatings dependent on the type of chemistry used. Whereas aromatic epoxide acrylates usually give hard and brittle coatings, urethane acrylates are known for their flexibility. Since the radiation curable systems should not contain solvents, the desired low viscosity for the specific application is adjusted with reactive monomers. This normally prevents the use of flexible high-molecular-weight polymers. On the other hand, the viscosity of dispersions is determined by the solid content only and not by the molecular weight of the polymers used. Thus, waterbased UV-curable coatings are one strategy out of this dilemma in order to combine the flexibility of higher-molecular-weight polymers with the hardness of highly crosslinked acrylates. The mechanical data of conventional and waterbased UV coatings are discussed in dependency on glass transition temperature and elastically effective chain length between crosslinks.     

Photocross-linked polymers based on plant-derived monomers for potential application in optical 3D printing

Photocross linking of the resins composed of plant-derived monomers, acrylated epoxidized soybean oil (AESO), myrcene (MYR) and vanillin dimethacrylate (VDM) or divinylbenzene (DVB, for comparison), was performed using 2,2-dimethoxy-2-phenylacetophenone as photoinitiator. Photocross-linking rate and properties of the crosslinked polymers depended on the resin compositions. The higher amount of MYR caused not only the better homogenization and lower viscosity of the resin but also the reduction of polymerization rate and the worse mechanical and thermal properties of the resulting polymers. The higher amount of aromatic component (VDM or DVB) improved mechanical and thermal properties of polymers. Moreover, the use of VDM instead of DVB in the system led to the higher photocross-linking rate and higher yield of insoluble fraction. The resin composed of only plant-derived monomers AESO/MYR/VDM, molar ratio 1:1:3, showed characteristics comparable to those of commercial petroleum-derived photoresins and was selected as a potential renewable photoresin for application in optical 3D printing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48708.     

Solvent-Cast 3D Printing of Biodegradable Polymer Scaffolds

3D printing is a popular fabrication technique because of its ability to produce complex architectures. Melt-based 3D printing is widely used for thermoplastic polymers like poly(caprolactone) (PCL), poly(lactic acid) (PLA), and poly(lactic-co-glycolic acid) (PLGA) because of their low processing temperatures. However, traditional melt-based techniques require processing temperatures and pressures high enough to achieve continuous flow, limiting the type of polymer that can be printed. Solvent-cast printing (SCP) offers an alternative approach to print a wider range of polymers. Polymers are dissolved in a volatile solvent that evaporates during deposition to produce a solid polymer filament. SCP, therefore, requires optimizing polymer concentration in the ink, print pressure, and print speed to achieve desired print fidelity. Here, capillary flow analysis shows how print pressure affects the process-apparent viscosity of PCL, PLA, and PLGA inks. Ink viscosity is also measured using rheology, which is used to link a specific ink viscosity to a predicted set of print pressure and print speed for all three polymers. These results demonstrate how this approach can be used to accelerate optimization by significantly reducing the number of parameter combinations. This strategy can be applied to other polymers to expand the library of polymers printable with SCP.     

Synthesis and characterization of cross‐linkable poly(phthalazinone ether ketone)s

A novel class of crosslinkable poly(phthalazinone ether ketone)s with relative high molecular‐weight and good solubility were successfully synthesized by the copolymerization of bisphthalazinone containing monomer, 3,3′‐diallyl‐4,4′‐dihydroxybiphenyl and 4,4′‐di‐ fluorobenzophenone. The synthesized polymers with inherent viscosities in the range of 0.42 to 0.75 dL/g can form flexible and transparent membranes by casting from their solution. The crosslinking reaction of these polymers can be carried out by thermally curing of the virgin polymers in or without the presence of crosslinking agent. The experimental results demonstrated that the crosslinking reaction also occurred to some extent during the polymerization. The crosslinked polymers exhibited equivalent glass transition temperature (T_g) at lower crosslinking density, and showed higher T_g than virgin polymers at higher crosslinking density. The crosslinked high‐temperature polymer can be used as the base material for high temperature adhesive, coating, enamel material, and composite matrices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Microstructure,Thermal and Mechanical Behavior of 3D Printed Acrylonitrile Styrene Acrylate

Fused deposition modeling (FDM) is one of the most popular additive manufacturing techniques for polymers. Despite the numerous works on the printability of various types of polymers, there is a lack in understanding the role of the microstructure on the mechanical performance of printed parts. This work aims at addressing this particular point for the case of a polymer that did not receive much attention, namely acrylonitrile styrene acrylate or ASA. This study emphasizes on the effect of the printing temperature on thermal and mechanical performance of printed ASA using differential scanning calorimetry, infra‐red measurements, mechanical testing, X‐ray micro‐tomography, and finite element computation. The experimental results demonstrate a narrow window of printability of ASA based on the thermal response of this polymer during the laying down process. In addition, both experimental and numerical results show an evident loss in the performance that represents one third of the performance of the raw material. Despite this loss, the limited amount of generated porosity and the level of tensile strength of ASA make it a good choice as a feedstock material for FDM compared to other polymers such as acrylonitrile butadiene styrene.     

Synthesis and properties of copolypyromellitimides

Copolyamic acids with different proportions of diamine component were prepared by polymerizing different molar ratios of diamines—benzidine (B)/4,4′-diaminodiphenyl ether (E) and p-phenylene diamine (P)/4,4′-diaminodiphenyl methane (M)—with pyromellitic dianhydride (PMDA) in dimethylacetamide (DMAc) at room temperature. Diamine component can be arranged in regular sequence through various reaction processes, such as alternating, block, and partial block copolymers. In addition, it can also be arranged in random sequence to obtain random copolymers. Thermal cyclodehydration of polyamic acids results in the corresponding polyimides. Polymers are characterized by viscosity, thermal stability, crystallinity, and mechanical strength. It was found that an increase in the proportion of more flexible diamine component (such as E and M) incorporated in polymer chain results in copolyimides with better mechanical strength and causes a fall in viscosity of copolyamic acids and a decrease in thermal stability and crystallinity of copolyimides. Within the copolymers of the same composition, the thermal stability, crystallinity, and mechanical strength of ordered polymers are superior to those of random polymers. The results of viscosity measurements imply that the anhydride-terminated prepolymer is easily destroyed by water in the solution, so that the ultimate viscosities of alternating and block copolyamic acids are inferior to those of random ones, but this phenomenon can be improved through the preparation of the partial block copolymers.     

Mechanical and Dynamic Mechanical Properties of Photocrosslinked Norbornene-Thiol Copolymer Films

A number of novel organic norbornene and norbornene siloxane polymer precursors have been synthesized as part of an on-going research project to produce a non-acrylate, UV-curable adhesive system. These precursors (monomers or oligomers) are di-, tri- and tetra-functional. The crosslinking agent is a multifunctional thiol.

The organic norbornene systems, formulated to stoichiometry, have been characterized using thermal, static and dynamic mechanical analysis. We have found that norbornene ester systems have a range of physical properties, with tensile moduli ranging from 820-2300 MPa (118-350 kpsi), tensile strengths of 17-61 MPa (2.5-8.8 kpsi) and elongations of 4-100%. Glass transition temperatures range from 30-71°C for samples cured at room temperature with a dose of 620 mJ/cm².

Norbornene siloxanes crosslinked with thiol siloxanes have been formulated with increasing levels of a high surface area reinforcing agent. Tensile properties of filled films show that filler loading to 30 wt% significantly increases peak stress and elongation to break above that of 25 wt% filler. The addition of filler did not appear to increase the T_g of the films in this series monotonically. Increased levels of filler were found to produce films with a broadened cold crystallization range and an increased melting temperature.     

Development of semitransparent wood‐polymer composites

A new material has been developed consisting of pieces of wood embedded within a matrix of acrylic polymer, resulting in a transparent or semitransparent wood‐based product. This material presents quite appealing aesthetic features, thereby opening new possibilities for decorative applications. Because acrylic and methacrylic monomers are in the liquid state at room temperature, it is possible to introduce wood (in the current case, walnut wood) into a mixture of acrylic (hydroxypropyl acrylate) and/or methacrylic monomers (methyl methacrylate and 2‐hydroxyethyl methacrylate) along with a plasticizer (dioctyl phthalate) in the presence of a chemical initiator (benzoyl peroxide). A transparent polymeric matrix with dispersed wood is then obtained through bulk free‐radical polymerization. Introducing this reaction mixture along with pieces of wood into a mold results in a wood‐polymer composite. A 2^4?1 experimental fractional factorial design was implemented to study the importance of the composition of these materials on several relevant properties. The sheets produced were characterized by tensile testing, dynamic mechanical thermal analysis, thermal gravimetric analysis, and heat deflection temperature. The models obtained for predicting each property pointed to valuable insights regarding the influential constituents. In particular, our results suggested that monomers to be used in future applications of this material should be selected in terms of their cost and the desired flexibility for the final product, not in terms of their polarity. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Studies on the synthesis and properties of novel phospholipid analogous polymers

Two kinds of phospholipid analogous compounds, methacrylate monomers ( 4a–b ) and acrylamide monomers ( 5a–b ), were prepared and polymerized with a radical initiator in water at room temperature. The viscosity behavior of these charged polymers were investigated in the presence or absence of inorganic salts, and the found inherent viscosity [η] of amide polymer ( poly7a ) is higher than those of ester polymers ( poly6a1 and poly6b ). On the other hand, the radical copolymerization of monomer 5b with acrylamide ( AAm ) was also carried out in water. Based on the x-ray analyses, it is proposed that some of the obtained polymers show ordered bilayer structures in condensed phase. Furthermore, the thermal properties were studied by DSC and TG-DTA measurements. © 1996 John Wiley & Sons, Inc.     

Single‐Point Determination of Intrinsic Viscosity of Semirigid Thermotropic Copolyesters in Phenol/1,1,2,2‐Tetrachloroethane

A series of semirigid thermotropic copolyesters with different compositions were prepared from p‐hydroxybenzoic acid (HBA), hydroquinone (HQ), terephthalic acid (TPA) and poly(ethylene terephthalate) (PET) by acidolysis reaction and following polycondensation. Fourteen procedures of calculation of the intrinsic viscosities from a single viscosity measurement for polymer solutions, including three proposed ones, have been applied for the copolyesters in phenol/1,1,2,2‐tetrachloroethane (60/40, v/v) at 30°C. It is found that various forms of the Huggins and Kraemer equations, used singly or in a combined form, yield intrinsic viscosities in good agreement with those extrapolated values obtained in the usual manner from multipoint viscosity measurements over a wide range of concentrations.     

Development of a rapid crosslinking preceramic polymer system

A low-viscosity, fast crosslinking preceramic polymer system was developed as a base for liquid state processing. The system consists of a water-crosslinkable silicone polymer, a latent water source for in situ water generation, and a tin catalyst. While the silicone polymer and the water source can be mixed in any proportion, the catalyst must be added separately to achieve crosslinking at room temperature within a short time. By pyrolysis in inert atmosphere at 1000 °C the system was shown to have a high ceramic yield of ∼54 wt.%. The base system is compatible with alkanes, which makes it suitable for viscosity control when the system is filler-loaded for tailoring of properties. Due to its low viscosity one possible use of the system is in inkjet printing. Further since the crosslinking is rapid it can also be used in the layer by layer manufacturing of ceramic parts.     

Transmission and Mechanical Properties of Optical Adhesives

The optical, mechanical and durability performance of selected epoxy, polyester, UV-curable acrylic, cyanoacrylate and silicone adhesives were evaluated and measured for bonding applications of optically transparent glasses in the visible and infra-red regions of the electromagnetic spectra.

From the initially selected adhesives only the UV-curable modified acrylic, two-component silicone and room temperature cured epoxy, were found to be of high performance characteristics, having good transmission properties and enhanced endurance in a combination of heat and humidity and following thermal cycling.

Sodium chloride substrates served as adherends for the transmission characterization of the optical adhesives, due to their high transmission properties in the 0.4-10 m μ spectral range. A modified lap shear specimen was designed for studying the mechanical properties and failure mechanisms of the adhesives and their durability in a humid and not environment. Finally, a two-piece glass doublet was used for investigating the optomechanical characteristics of the optical adhesive following environmental conditioning and thermal shock cycling.

Due to the inherent C-C bond, polymer adhesives are limited in utility, as far as transparency is concerned, close to 3.5 μm and in most of the 8-12 μm spectral range.     

The fabrication of SiBCN ceramic components from preceramic polymers by digital light processing (DLP) 3D printing technology

We present a novel method to fabricate SiBCN ceramic components with complex shapes from preceramic polymers by using digital light processing (DLP) 3D printing technology in this research work. The photocurable precursor for 3D printing was prepared by blending high ceramic yield polyborosilazane with photosensitive acrylate monomers. The material formulation and printing parameters were optimized to fabricate complicated SiBCN ceramic components with high precision. The printed SiBCN ceramic materials were pyrolyzed at different temperatures, and retained their fine features after pyrolysis. Their microstructures were characterized by FTIR, XRD and TEM respectively. Furthermore, the thermal stability and mechanical properties of the SiBCN ceramic samples were investigated and discussed in detail. The 3D printed SiBCN ceramic material exhibited excellent thermal stability and resistance to high temperature oxidation up to 1500?°C.     

Synthesis and curing behavior of macrocycle‐terminated poly(aryl ether ketone)s

BACKGROUND: The introduction of poly(ether ether ketone)‐based carbon‐fiber composites accelerated the application of poly(ether ether ketone)s in advanced composite materials. In order to improve the compatibility and processability with reinforced components, polymers with low melt viscosity are preferable. RESULTS: Novel fully aromatic macrocycle‐terminated poly(aryl ether ketone)s (MCPAEKs) were prepared by condensation of macrocyclic aryl ether ketone dimers containing hydroxyphenyl groups and fluorine end‐capped poly(aryl ether ketone) oligomers. Compared with liner poly(aryl ether ketone)s, MCPAEKs showed much lower melt viscosities at low temperature. In the presence of caesium fluoride, the crosslinking reaction of MCPAEKs afforded fully aromatic thermoset poly(aryl ether ketone)s by ring‐opening reaction. CONCLUSION: The MCPAEKs exhibited high thermal stability due to their wholly aromatic structures. After crosslinking, the glass transition temperatures and complex melt viscosities of the polymers were increased greatly. Although there was some residual cesium fluoride or phenoxides produced by ring‐opening reaction, the thermoset poly(aryl ether ketone)s obtained had good thermal stability with temperatures at 5% weight loss above 475 °C. Copyright © 2009 Society of Chemical Industry     

马来酸酐改性超支化聚酯及在紫外光固化涂层中的应用

以马来酸酐改性末端为羟基的超支化聚酯,得到链段中含大量不饱和双键的超支化马来酸酯,分析表征了不同改性度的超支化马来酸酯黏度、热稳定性及Tg的变化。以超支化马来酸酯为预聚物应用于紫外光固化涂层,考察了改性度对光固化膜附着力、冲击强度、柔韧性、硬度及耐溶剂性能的影响。实验表明,超支化马来酸酯是一种低黏度、热稳定性好、Tg易调节的高分子材料。当改性度为80%时,光固化涂层性能最佳,其光固化时间可达3 s,膜附着力为1级,耐冲击强度为4.8 N.m,柔韧性>7 cm,硬度达5H,同时具有优良的耐溶剂性能。     

含钆漆酚基聚合物的合成及表征

由漆酚和漆酚苯胺醛缩聚物分别与三氯化钆反应合成含钆漆酚基聚合物〔漆酚钆聚合物 (PUG)和漆酚苯胺钆聚合物 (PUAG)〕。用IR、XPS、DMTA和DSC -TG对产物进行表征。结果表明 ,与Gd(Ⅲ )发生配位反应的是漆酚基聚合物中酚羟基氧原子 ;漆酚基聚合物与Gd(Ⅲ )反应后 ,其侧链进一步交联聚合形成具有较高模量和良好热稳定性的含钆漆酚基聚合物 ,PUAG的耐热性比PUG的好。