Using an additive to control the electrospinning of fibres of poly(ε‐caprolactone)

Electrospinning is a route to polymer fibres with diameters considerably smaller than available from most fibre‐producing techniques. We explore the use of a low molecular weight compound as an effective control additive during the electrospinning of poly(ε‐caprolactone). This approach extends the control variables for the electrospinning of nanoscale fibres from the more usual ones such as the polymer molecular weight, solvent and concentration. We show that through the use of dual solvent systems, we can alter the impact of the additive on the electrospinning process so that finer as well as thicker fibres can be prepared under otherwise identical conditions. As well as the size of the fibres and the number of beads, the use of the additive allows us to alter the level of crystallinity as well as the level of preferred orientation of the poly(ε‐caprolactone) crystals. This approach, involving the use of a dual solvent and a low molar mass compound, offers considerable potential for application to other polymer systems. Copyright © 2010 Society of Chemical Industry     

Preparation and characterization of a Bacterial cellulose/Chitosan composite for potential biomedical application

Bacterial cellulose (BC)/Chitosan (Ch) composite has been successfully prepared by immersing wet BC pellicle in Ch solution followed by freeze-drying process. The morphology of BC/Ch composite was examined by scanning electron microscope (SEM) and compared with pristine BC. SEM images show that Ch molecules can penetrate into BC forming three-dimensional multilayered scaffold. The scaffold has very well interconnected porous network structure and large aspect surface. The composite was also characterized by Fourier transform infrared spectrum, X-ray diffraction, thermogravimetric analysis and tensile test. By incorporation of Ch into BC, crystallinity tends to decrease from 82% to 61%, and the thermal stability increases from 263 °C to 296 °C. At the same time, the mechanical properties of BC/Ch composite are maintained at certain levels between BC and Ch. The biocompatibility of composite was preliminarily evaluated by cell adhesion studies. The cells incubated with BC/Ch scaffolds for 48 h were capable of forming cell adhesion and proliferation. It showed much better biocompatibility than pure BC. Since the prepared BC/Ch scaffolds are bioactive and suitable for cell adhesion, these scaffolds can be used for wound dressing or tissue-engineering scaffolds.     

苎麻纤维增强聚碳酸亚丙酯复合材料的工艺与性能研究

采用苎麻纤维和聚碳酸亚丙酯制备了可降解复合材料,讨论了苎麻长度、含量对苎麻/聚碳酸亚丙酯复合材料机械性能的影响,并借助扫描电子显微镜对复合材料的冲击断口形貌进行了观察.结果表明:苎麻经碱液处理后,苎麻/聚碳酸亚丙酯复合材料的拉伸性能和冲击性能有了明显提高.     

Surface‐active amphiphilic poly[(2‐acrylamido‐2‐methylpropanesulfonic acid)‐co‐(N‐isopropylacrylamide)] nanoparticles as stabilizer in aqueous emulsion polymerization

This work reports the effect of nanogel solid particles on the surface and interfacial tension of water/air and water/styrene interfaces. Moreover, the work aimed to use nanogels as a stabilizer for miniemulsion aqueous polymerization. A series of amphiphilic crosslinked N‐isopropylacrylamide (NIPAm) and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) copolymer nanogels were synthesized based on an aqueous copolymerization batch method. Divinylbenzene and N,N‐methylene bisacrylamide were used as crosslinkers. The morphologies of the prepared nanogels were investigated using transmission and scanning electron microscopies. The lower critical transition temperatures were determined using differential scanning calorimetry. The surface tension of colloidal NIPAm/AMPS dispersions was measured as functions of surface age, temperature and the morphology of the NIPAm/AMPS nanogels. The NIPAm/AMPS nanogels reduced the surface tension of water to about 30.1 mN m^?1 at 298 K with a small increase at 313 K. Surface activities of these nanogels in water were determined by surface tension measurements. The NIPAm/AMPS dispersions had high surface activity and were used as a stabilizer to prepare a crosslinked poly(styrene‐co‐AMPS) microgel based on emulsion crosslinking polymerization. © 2013 Society of Chemical Industry     

Preparation of thermoresponsive poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) nanogels via inverse miniemulsion polymerization

Stimuli-responsive polymeric nanogels hold great potential in biological applications. In this work, thermoresponsive polymeric nanogels were conveniently prepared through inverse miniemulsion polymerization of two monomers with a good biocompatibility, N-vinylcaprolactam and 2-methoxyethyl acrylate. A macromolecular crosslinker, poly(ethylene glycol) dimethacrylate (PEGDMA), was used to achieve a better thermoresponsiveness, compared with low-molecular-weight crosslinkers. The prepared poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) (poly(NVCL-co-MEA)) nanogels could be well redispersed in aqueous systems, displaying a reversible thermoresponsive transition behavior. The influences of the synthesis parameters including the emulsifier content, PEGDMA content, and monomer composition on the particle properties of poly(NVCL-co-MEA) nanogels both in inverse emulsions and in aqueous dispersions were systematically investigated. Furthermore, the impacts of the monomer composition and PEGDMA content on the thermoresponsiveness of poly(NVCL-co-MEA) nanogels were also studied. Promisingly, the introduction of MEA monomeric units to the copolymer chains only slightly reduced the thermoresponsiveness of poly(NVCL-co-MEA) nanogels. This feature allows to improve the biocompatibility of polymeric nanogels by using MEA as the comonomer without need to compromise the thermoresponsiveness of nanogels. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48237.     

Use of modified poly(ϵ‐caprolactone) in the compatibilization of poly(ϵ‐caprolactone)/maize starch blends

In this work, the compatibilization of a poly(?‐caprolactone) with a number‐average molecular weight of 120,000 g/mol (PCL¹²⁰) and maize starch was investigated by the addition of a chemically modified poly(?‐caprolactone). Two types of blends were prepared by melt extrusion. In type A blends, low‐molecular‐weight compatibilizers were used: (1) a poly(?‐caprolactone) with a number‐average molecular weight of 10,000 g/mol that was reacted with maleic anhydride to obtain chains terminating in carboxylic groups and (2) low‐molecular‐weight poly(?‐caprolactone)s (number‐average molecular weights of 600 and 2000 g/mol) with one pendant carboxylic group within the chains. With these groups of blends, tensile testing and scanning electron microscopy demonstrated that the compatibilizers were generally effective in inducing a better dispersion for a 60/40 poly(?‐caprolactone)/maize starch blend with a compatibilizer, improving the mechanical properties in comparison with uncompatibilized blends. The blends with 30% starch were not improved by the addition of compatibilizer, and this may be related to the rheology of the blends during preparation. In type B blends, high‐molecular‐weight compatibilizers were prepared through the grafting of variable amounts of acrylic acid or maleic anhydride to PCL¹²⁰ chains. The best compatibilizer action was obtained with 0.7 wt % maleic anhydride grafted to PCL¹²⁰ because both the dispersion and mechanical properties were further improved in comparison with uncompatibilized blends and type A blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of alkali treatment on properties of unidirectional isora fibre reinforced epoxy composites

Abstract

Unidirectional isora fibre reinforced epoxy composites were prepared by compression moulding. Isora is a natural bast fibre separated from Helicteres isora plant by retting process. The effect of alkali treatment on the properties of the fibre was studied by scanning electron microscopy (SEM), IR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Mechanical properties such as tensile strength, Young's modulus, flexural strength, flexural modulus and impact strength of the composites containing untreated and alkali treated fibres have been studied as a function of fibre loading. The optimum fibre loading for tensile properties of the untreated fibre composite was found to be 49% by volume and for flexural properties the loading was optimised at ～45%. Impact strength of the composite increased with increase in fibre loading and remained constant at a fibre loading of 54·5%. Alkali treated fibre composite showed improved thermal and mechanical properties compared to untreated fibre composite. From dynamic mechanical analysis (DMA) studies it was observed that the alkali treated fibre composites have higher E' and low tan δ maximum values compared to untreated fibre composites. From swelling studies in methyl ethyl ketone it was observed that the mole percentage of uptake of the solvent by the treated fibre composites is less than that by the untreated fibre composites. From these results it can be concluded that in composites containing alkalised fibres there is enhanced interfacial adhesion between the fibre and the matrix leading to better properties, compared to untreated fibre composites.     

Properties and phase segregation of crosslinked PCL‐based polyurethanes

Polyurethane (PU) films were prepared from different types of poly(ε‐caprolactone) glycols and hexamethylene diisocyanate without using any other ingredients such as solvent, catalyst, or chain extender. Polymers were stabilized by crosslinking formed as allophanate and/or biuret linkages during the curing process. The effects of different components on the product properties such as chemical structure, microphase segregation, mechanical strength, thermo‐mechanical, thermal properties, and surface hydrophilicities were investigated by FTIR‐ATR, atomic force microscope, mechanical tester, dynamic mechanical analyses, thermogravimetric analyzer, differential scanning calorimetry, and contact angle measurements. Phase separation of hard and soft segments significantly varied depending on the type and molecular weight of diol and triol. Films containing urethane‐urea bonds displayed the maximum phase separation and the highest mechanical strength. Polyols having higher molecular weight increased hydrophilicity while urea bonds caused a reverse effect resulted by bidentate hydrogen bonds. Results showed PUs with various properties can be synthesized via environmentally friendly process without using any solvent or catalyst. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39758.     

Biodegradable hollow microfibres to produce bioactive scaffolds

Biodegradable hollow microfibres containing particles loaded with specific active agents can be potentially employed to produce a special kind of substrate for tissue engineering, able to function as a scaffold and at the same time to act as a drug‐releasing system. Biodegradable hollow microfibres based on poly(lactic acid) were produced by a dry–wet spinning procedure. Drug‐loaded microparticles were prepared by a simple oil‐in‐water emulsion and entrapped inside the fibres. The morphology of both fibres and particles was investigated by scanning electron microscopy. The mechanical and thermal properties of the fibres were investigated by tensile tests and differential scanning calorimetry. In vitro tests were performed to evaluate the release of the drug from the fibres loaded with the particles Copyright © 2004 Society of Chemical Industry     

Preparation of poly(ε‐caprolactone)/poly(ε‐caprolactone‐co‐lactide) (PCL/PLCL) blend filament by melt spinning

Poly(ε‐caprolactone)/poly(ε‐caprolactone‐co‐lactide) (PCL/PLCL) blend filaments with various ratios of PCL and PLCL were prepared by melt spinning. The effect of PLCL content on the physical properties of the blended filament was investigated. The melt spinning of the blend was carried out and the as spun filament was subsequently subjected to drawing and heat setting process. The addition of PLCL caused significant changes in the mechanical properties of the filaments. Crystallinity of blend decreased with the addition of PLCL as observed by X‐ray diffraction (XRD) and differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) revealed that the fracture surface becomes rougher at higher PLCL content. It may be proposed that PCL and PLCL show limited interaction within the blend matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012