Ceramic green and fired body with a uniform microstructure prepared using living characteristics of photo-curable cycloaliphatic epoxide: Applicability of cycloaliphatic epoxide in photo-polymerization-based 3D printing

In photopolymerization-based ceramic 3D printing, light cannot efficiently penetrate the opaque slurry, which is composed of particles and a photo-curable monomer. This can result in a difference of the crosslinking density within the layer, which can cause problems such as cracking and distortion. In this study, we used a photo cationic polymerizable cycloaliphatic epoxide as a photo-curable monomer to produce a green body with uniform crosslinking density by the living characteristics of photo cationic polymerized cycloaliphatic epoxide. The green body prepared with cycloaliphatic epoxide based ceramic slurry was subjected to an additional polymerization process, which involved heating at 150°C. Because of the living characteristics of the cycloaliphatic epoxide, a green body with a uniform crosslinking density was created and the fracture strength was improved. In addition, the green body exhibited good adhesion properties between layers. Finally, a sound fired body could be produced without any changes in shape after firing.     

Effect of particle size on mechanical properties of alumina ceramic processed by photosensitive binder jetting with powder spattering technique

As an Additive Manufacturing technique, Binder Jetting enables the fabrication of customized and complex ceramic parts. However, the insufficiency of powder packing in green parts restricts the final products’ densifications and strengths. To form a layer of ceramic green parts, Photosensitive Binder Jetting with powder spattering technique provides entrapment of ceramic powder by printing of photo-curable resin and recoating by releasing the powder through a vibrating mesh. This recoating technique enables the processing of fine alumina powders, the average particle sizes of which are 3 μm, 1.65 μm, and their mixtures. Apparent densities, porosities, mechanical properties, and microstructures of the sintered parts were investigated. The alumina sample with the apparent density of 3.70 g/cm³, the compressive strength of 94.87 MPa, the biaxial strength of 50.06 MPa, and the porosity of 41.01 % was attained by the mixture with 70:30 wt.% of the 3 μm and 1.65 μm powders respectively.     

The kinetics of vinyl acrylate photopolymerization

The photopolymerization of vinyl acrylate has been investigated using real-time FTIR. The acrylate and vinyl groups exhibit different polymerization kinetics with the acrylate functionality polymerizing at a much faster rate. Vinyl acrylate not only self-initiates its own free-radical polymerization, but also photoinitiates the polymerization of mono- and difunctional acrylates. Kinetic studies using a model monomer system indicate that it is essential for the acrylate and vinyl group to be part of the same molecule in order to function as an effective initiator for acrylate polymerization.     

Superior real time method to evaluate photo‐curing resin by means of rigid‐body pendulum rheometer

The objective of this article is to establish a new method in evaluating photo‐polymerization resin reaction behavior, and to use the trends resulting from past evaluation methods and those already known to prove the feasibility of this method. Another objective is to compare the data gathered using the differential photo calorimeter (DPC) method and RPT on different photo‐polymerization resin systems to illustrate that the application of RPT on photo‐polymerization resin studies is more suitable. Experiment results show that the trends through the real time method using oxide series acrylate research through rigid‐body Pendulum Rheometer, the photo‐curing behavior under the various parameters of monomer functionality, and photo‐initiator concentration can all be observed. Comparing the DPC and RPT methods on polyester acrylate series, when the oligomer of tetra‐functional polyester acrylate is added with a different ratio of the monomer of propoxylated neopentyl‐glycol di‐acrylate, DPC evaluation methods show that the differences in observation are minimal. However, when RPT was applied, not only were the differences in reaction speed observed, but also the differences in crosslinking and other data in the hardening process when the balanced time was achieved during the oscillations procedure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3402–3407, 2006     

Digital light processing of ceramic components from polysiloxanes

Additive manufacturing using photocurable polymers is one method to answer the increased demand of ceramic structures with complicated morphology by fabricating ceramic parts with high resolution and good surface quality. We introduce here a new method to fabricate SiOC ceramic structures by utilizing a simple physical blend between two different preceramic polysiloxanes, one providing photosensitive acrylate groups while the other one a high ceramic yield. Different blend ratios have been realized and respectively optimized concerning the printing additives and setting times to fabricate exact replications of highly complex polysiloxane structures by Digital Light Processing. After pyrolysis, a uniform, homogenous shrinkage was observed yielding dense, pore- as well as crack-free SiOC ceramics. By adjusting the ratio between the different polysiloxanes, parameters such as the ceramic yield, shrinkage, chemical composition and resolution after pyrolysis could be tailored in a wide range of values.     

SiC and SiOC ceramic articles produced by stereolithography of acrylate modified polycarbosilane systems

3D printed ceramic articles are receiving increased interest recently. Stereolithography (STL) is the method of choice where surface quality, high resolution and high aspect ratio architectures are concerned. Recently, we have developed a UV curable system consisting of allylhydridopolycarbosilane (AHPCS) and multifunctional acrylates. In our present work we investigate the photo-crosslinking mechanism and use selected formulations for the 3D printing of SiC rich ceramic articles using a desktop STL device. High resolution and complex shape articles are demonstrated. The versatile curing method can be used for the STL of practically most other vinyl/allyl modified preceramic polymers. The nano-porosity as well as SiOxCy composition can be tailored in a wide range for specific applications by the ratio of acrylate to AHPCS and by the type of acrylate and AHPCS used.     

自交联型丙烯酸酯树脂纸塑复合胶的制备与性能

以丙烯酸丁酯(BA)、酪酸乙烯酯(VAC)为主要原料,适当引入丙烯酸(AA)、丙烯酸羟丙酯(HPA)等活性功能单体,在半连续加料方式下通过种子乳液聚合法制备乳液型纸塑复合胶。探讨了单体选择及配比和功能单体、引发剂与乳化剂用量对乳胶性能的影响。最后对松香增粘作用进行了试验研究。     

Hyperbranched poly(methyl methacrylate)s prepared by miniemulsion polymerization and their (non)-Newtonian flow behaviors

Miniemulsion polymerization is most suitable for the targeted synthesis of vinyl copolymers than the conventional emulsion polymerization, because in miniemulsion polymerization each monomer nanodroplet is a nanoreactor, and the monomers in each droplet are in situ converted to the corresponding polymers. Soluble and hyperbranched poly(methyl methacrylate)s (PMMA) were prepared with quantitative monomer conversion and without gelation by the miniemulsion copolymerization with di- and tri-acrylate and mediated with 1-dodecyl thiol (DDT). DDT acted both as a gelation prohibitor and as a reactive cosurfactant. The PMMAs with varied “X” or “Ж” shaped branches, depending on the di- and tri-functional acrylate used as the branching agent, are characterized and interpreted in terms of the repeating units per part, parts and branches per macromolecule, average molecular weight, latex particle size and size distribution. Effects of topology changes of the branched PMMAs on the rheological behaviors are observed for the first time: from Newtonian flow for the densely branched PMMAs to the non-Newtonian flow with pronounced shear thickening for the PMMA samples with high-molecular-weight and longer parts.     

用顶空气相色谱法(HSGC)测定乳液中未反应的残余单体含量

采用顶空气相色谱法（HSGC）对各类合成树脂乳液中未反应的残余单体，如醋酸乙烯酯、丙烯腈、丙烯酸乙酯、甲基丙烯酸甲酯、苯乙烯、丙烯酸丁酯、丙烯酸异辛酯等的含量进行测定，以便用于检验和控制生产过程中聚合的程度以及确定最高未反应单体的含量。     

Influences of infiltrated resin on properties of printed electrodes on non-sintered ceramic films

Ceramic–resin hybrid substrate-based printed capacitors are fabricated for next generation ceramic packaging. The resin solution is infiltrated into the non-sintered ceramic powder beds by either inkjet printing or spin-coating. The amount of infiltrated resin and its spatial distribution throughout the films critically influence the dielectric loss factor, the adhesion strength, and the electrical conductivity of the electrodes. Although inkjet printing leads to non-uniform distribution of the resin, spin-coating is an effective means to uniformly infiltrate the resin solution. The resulting non-sintering ceramic–resin hybrid substrate-based printed capacitors demonstrate optimal properties comparable to their state-of-the-art low-temperature co-fired ceramic (LTCC) counterparts.     

Preparation of hyperbranched polymers by atom transfer radical polymerization

A cheap acrylic AB* monomer, 2‐(2‐chloroacetyloxy)‐isopropyl acrylate (CAIPA), was prepared from 2‐hydroxyisopropyl acrylate with chloroacetyl chloride in the presence of triethylamine. The self‐condensing vinyl polymerization by atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization, has yielded hyperbranched polymers. All the polymerization products were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR). CAIPA exhibited distinctive polymerization behavior that is similar to a classical step‐growth polymerization in the relationship of molecular weight to polymerization time, especially during the initial stage of the polymerization. However, a significant amount of monomer remained present throughout the polymerization, which is consistent with typical chain polymerization. Also, if a much longer polymerization time was used, the polymer became gel. As a result of the unequal reactivity of group A* and B*, the polymerization is different from an ideal self‐condensing vinyl polymerization: the branch structures of polymers prepared depend dramatically on the ratio of 2,2'‐bipyridyl to CAIPA. Hyperbranched polymers exhibit improved solubility in organic solvent, however, they have lower thermal stability than their linear analogs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2114–2123, 2002     

高固体分涂料用含羟基星形丙烯酸酯树脂的制备及性能

以占单体物质的量0.01%的低铜盐用量催化剂体系进行电子转移活化再生催化剂原子转移自由基聚合(ARGET ATRP), 制备了丙烯酸丁酯、甲基丙烯酸甲酯和丙烯酸羟丙酯为单体的线形和六臂星形共聚物。采用折光指数-激光-黏度三检测联用GPC, ¹H NMR和DSC对聚合物的分子结构、共聚组成和玻璃化转变行为进行了研究。将聚合物配制成涂料用树脂溶液, 流变行为研究表明星形聚合物溶液黏度最低。在高固含量时, 星形聚合物降低黏度的优势更明显。在适合喷涂施工的黏度下, 六臂星形共聚物比普通自由基聚合得到的商品化丙烯酸酯树脂的固含量可提高10%。采用异氰酸酯固化剂固化得到的漆膜性能测试表明, 星形聚合物对应清漆的表干时间很短, 同时力学性能达到良好水平。     

Graft polymers with macromonomers. I. Synthesis from methacrylate-terminated polystyrene

Pure graft polymers having uniform molecular weight polystyrene side chains were prepared by free radical copolymerization of methacrylate-terminated polystyrene macromonomers (MA-CROMER) with ethyl acrylate, butyl acrylate, or other suitable monomers. The MACROMER monomer was synthesized by living anionic polymerization under conditions that led to very narrow molecular weight distributions. Very effective end capping produced a material that was highly monofunctional. The graft copolymers were prepared by several techniques such as free radical solution polymerization, by aqueous suspension polymerization which produced beads, or by emulsion reactions which yielded stable latices. Polymerizations were reproducible. High conversion of the MACROMER monomer into pure graft polymers was achieved, and the product was contaminated with only a little homopolymer. The milled and molded phase-separated graft polymers had optical clarity and physical properties characteristic of polystyrene-reinforced triblock polymers. Compositions of 20-30% polystyrene were thermoplastic elastomers with good recovery. When polystyrene contents were increased, the graft products were strong, flexible thermoplastics with well defined yield strengths and increased permanent set. Copolymers of polystyrene macromers with acrylonitrile or vinyl chloride produced transparent polystyrene homopolymer-free graft polymer products having improved processing over polyacrylonitrile or poly(vinyl chloride) homopolymers.     

Synthesis of core-shell emulsion copolymer of poly(butyl acrylate)/α-methyl styrene-co-methyl acrylate,with application as processing aid of poly(vinyl chloride)

The core-shell grafting copolymer of α-methyl styrene-methyl acrylate on poly(butyl acrylate) was synthesized. The particle morphology of latex and core-shell grafting polymerization was investigated as a function of: (a) reaction temperature; (b) initiator concentration used in the secondary polymerization; (c) monomer to polymer ratio; (d) emulsifier concentration. The compatibility of this copolymer with poly(vinyl chloride) (PVC) was determined by the method of solubility parameter and scanning electron microscopy. The rheological behavior of the blend of this copolymer with PVC was investigated. The mechanical properties of the blend were determined. The results show that this copolymer can be used as processing aid for PVC. © 1994 John Wiley & Sons, Inc.     

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.     

环氧树脂改性醋-丙乳液胶粘剂的研究

为了提高醋-丙乳液胶粘剂的粘结强度、成膜性能、涂膜硬度和耐玷污性,将环氧树脂加入到聚合体系中,通过乳液聚合的方法制备出环氧树脂改性醋-丙乳液胶粘剂。采用正交实验方法分析讨论了不同的引发剂加入量、乳化剂加入量、丙烯酸丁酯加入量、环氧树脂加入量等因素对环氧树脂改性醋-丙乳液胶粘剂剥离强度的影响。从中优化出最佳聚合配方,采用...     

The miscibility of polyacrylates and polymethacrylates with PVC: In situ polymerization and the miscibility of poly(methyl acrylate) and poly(ethyl acrylate) with PVC

The in situ polymerization of vinyl chloride with various polyacrylates and polymethacrylates has been studied. The products were examined by dynamic mechanical analysis. Poly(methyl acrylate) and poly(ethyl acrylate) had previously produced two-phase blends with poly(vinyl chloride) (PVC) by solvent casting, but poly(ethyl acrylate) was shown to be miscible with PVC when blends were produced by in situ polymerization. Poly(methyl acrylate) and poly(octyl acrylate) were found to be immiscible with PVC whereas other polyacrylates and polymethacrylates with intermediate ester group concentrations were found to be miscible, confirming previous studies. The glass transition temperatures of the blends were measured and the deviations from the expected mean of the two base polymers were calculated as an indication of the strength of interaction between the polymers. The polymers having intermediate ester group concentrations showed the strongest interactions and the results correlated well with previously measured interaction parameters.     

Acrylonitrile-styrene-acrylate particles with different acrylonitrile contents for improving the toughness of poly(vinyl chloride) resin

Poly(butyl acrylate) grafted styrene and acrylonitrile copolymer (PBA-g-SAN, ASA) with core–shell structures were prepared by emulsion polymerization technology to improve the toughness of the poly(vinyl chloride) (PVC). The mechanical properties of the PVC/ASA blends were investigated. The notch impact strength of the PVC/ASA blend could reach 1200 J/m when the 13 phr ASA was added to the PVC. This was several times more than pure PVC resin. Scanning electron microscopy analysis results indicated that the improvement in impact strength of the PVC/ASA blend was attributed to shear yielding induced by ASA particles. Additionally, subtle changes in the ratio of monomers in the shell layer led to significant fluctuations in the mechanical properties of the composites. Dynamic mechanical analysis showed that the intermolecular interaction forces between ASA particles and PVC resins played a key role in improving the toughness of PVC/ASA blend.     

丙烯酸酯乳液增稠机理的研究

以丙烯酸丁酯、苯乙烯、醋酸乙烯、丙烯酸羟丙酯等为单体,采用种子乳液聚合法合成乳液,讨论了乳化剂的用量对乳液聚合的影响,并对乳液的增稠机理进行了研究.     

Near-visible stereolithography of a low shrinkage cationic/free-radical photopolymer blend and its nanocomposite

In this work, a newly prepared cationic/free-radical photopolymer, which consists of two epoxies and a tetrafunctional acrylate, is presented for the first time for a visible light stereolithography (SL), showing the advantages of both cationic and free-radical resins. An onium salt, commonly used as a cationic UV initiator, and a photosensitizer make the blend suitable for a near-visible (405 nm) SL. An increase in the polymerization rate and a drop in the induction period are observed for the newly prepared cationic/free-radical blend, compared with either only cationic systems or free-radical resins. This suggests that the combination of cationic and free-radical polymerizations in a single resin has a positive synergistic effect. The addition of silica nanoparticles to the blend provides a reinforcing and toughening effect. Indeed, the resin loaded with silica shows a 31% increase in the elastic modulus, compared with the unfilled resin. Regarding the values of tensile strength and elongation at break, they, respectively, grow by 47 and 15%, when the nanocomposite resin is compared with the neat resin. A very low volumetric shrinkage of 0.7% and a remarkable printing quality of objects obtained with this new photopolymer will enable the 3D printing of microrobots, bioengineering microdevices, and sensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48333.