An inorganic-organic hybrid material system consisting of (3-glycidyloxypropyl)trimethoxysilane, dimethyldimethoxysilane and zirconium(IV) n-propoxide was prepared by the sol-gel method. The influence of processing parameters including Zr content, UV irradiation and sol ageing on the thermal stability of the resultant thin films was characterised by thermogravimetry. It was demonstrated that the crosslinking of epoxy groups in the structure was the primary reason for variation in the thermal stability of the system. As Zr and/or UV irradiation may be employed to crosslink the epoxy groups in the structure, the thermal stability of the system can be tuned by the optimal combination of these two crosslinking methods. 相似文献
The regularities of branching and thermal destruction processes of polysulfones of different chemical structure at 150–500°С are studied depending on the nature of the reactive medium and blocking method of the terminal groups with the use of a special device for a gas chromatograph allowing one to investigate the branching and thermal destruction of polymers. It is found that the nature of the solvent and deactivator of the terminal hydroxyl groups substantially affects the crosslinking and destruction processes of polysulfones. 相似文献
The polydimethylsiloxane (PDMS) membrane commonly used for separation of biobutanol from fermentation broth fails to meet demand owing to its discontinuous and polluting thermal fabrication. Now, an UV‐induced polymerization strategy is proposed to realize the ultrafast and continuous fabrication of the PDMS membrane. UV‐crosslinking of synthesized methacrylate‐functionalized PDMS (MA‐PDMS) is complete within 30 s. The crosslinking rate is three orders of magnitude larger than the conventional thermal crosslinking. The MA‐PDMS membrane shows a versatile potential for liquid and gas separations, especially featuring an excellent pervaporation performance for n‐butanol. Filler aggregation, the major bottleneck for the development of high‐performance mixed matrix membranes (MMMs), is overcome, because the UV polymerization strategy demonstrates a freezing effect towards fillers in polymer, resulting in an extremely high‐loading silicalite‐1/MA‐PDMS MMM with uniform particle distribution. 相似文献
A hybrid material system consisting of (3-glycidyloxypropyl)trimethoxysilane and dimethyldimethoxysilane as matrix materials and diphenyldimethoxysilane (DPDMS) as both a matrix material and a potential thermal stabiliser by the sol-gel method. A detailed thermogravimetric analysis study of the influence of processing parameters, including DPDMS content, UV irradiation and sol ageing, on the thermal stability of the resultant thin films was presented. FT-IR spectroscopy was used to monitor the changes in the relative amount of epoxy rings in the system during processing. It was demonstrated that the crosslinking of epoxy groups in the structure is the primary reason for changes in the thermal stability of the system. It was also shown that the thermal stability, in terms of 10% mass loss, of the material system could be improved up to 280 °C, by adjusting the preparation conditions, compatible with several subsequent high temperature optoelectronic integration processes. 相似文献
Soft PVC is employed for the manufacturing of a wide range of products with different properties and a relatively low cost. The utilization of soft PVC is restricted by the poor thermal, chemical and mechanical resistance properties. Also, plasticizer migration can modify the properties or can make useless the materials for some applications because of toxicity or a general loss of properties. PVC crosslinking is the most effective way to improve mechanical and transport properties of rigid or flexible PVC at high temperatures, but at the same time the thermal stability of PVC may be significantly reduced. In this work, the crosslinking reaction of plasticized poly(vinyl chloride) (PVC) through difunctional amines was studied. The mechanisms involved in the crosslinking reaction were explained by Fourier transform infrared (FTIR) analysis. The thermal activated crosslinking reaction was studied by cone and plate rheometry, analyzing the evolution of viscoelastic properties of the suspension as a function of time and temperature. The effect of the addition of crosslinking agents on the thermal stability of the polymer was studied by thermogravimetric analysis (TGA), which revealed that crosslinking reactions promote thermal degradation phenomena in the polymer matrix. This is attributed to the formation of HCl and other species promoting polymer degradation during crosslinking, thus leading to higher weight loss during thermal treatment with respect to unmodified PVC plastisols. This was also confirmed by an evident yellowing after crosslinking, especially at higher temperatures. 相似文献
A new method for studying thermal stability and concomitant chemical composition changes on thermal treatment of thin polymeric films is presented. It is applied to the study of thermal properties and modification of properties of polysilane-like materials with variable dimensionality prepared by radio frequency plasma enhanced chemical vapour deposition (CVD). Structure and microphysical properties of these materials, modified by progressive annealing, are examined by fluorimetry, FTIR absorption spectroscopy and XPS. In addition, the role, bonding conditions and structural environments of organic moieties as well as their influence on thermal degradation processes are examined. It is found that plasma polysilanes undergo three consecutive thermal degradation processes: Si-Si bond cleavage, elimination of side groups and final carbide formation. Presence of disorder and crosslinking stabilises the plasmatic material in comparison to classically prepared polysilanes. Nanostructural units in low dimensional polysilanes enable the peak of the luminescence to be adjusted in the spectral range from near UV (360 nm) to red (600 nm). 相似文献
Accelerated thermal and photo-aging of four homopolymers, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and high-impact polystyrene (HIPS), was performed and the impact of subsequent reprocessing conditions on their properties studied. Polymer samples oven-aged at 100 °C for varying periods of time or UV irradiated in a Weather-o-meter (WOM) at λ = 340 nm were reprocessed in a Brabender plasticorder at 190 °C/60 rpm for 10 min. Chemical changes and the evolution of rheological and mechanical properties accompanying the gradual degradation of the individual polymers were monitored and evaluated (DSC, FTIR, colorimetric method, MFI, tensile impact strength). LDPE and HIPS were found to be more susceptible to thermo-oxidation than HDPE and PP, whereas HDPE and PP were affected to a greater extent by UV exposure; the crucial role here is being played by the stabilization of the studied resins. In HDPE the scission and crosslinking reactions competed both in thermo-and photo-degradation. In the case of LDPE, scission prevailed over branching during thermo-oxidation, whereas photo-oxidation of the same sample led predominantly to crosslinking. Abrupt deterioration of the LDPE rheological properties after one week of thermal exposure was suppressed by re-stabilization. The scission reaction was also predominant for PP during thermo-oxidation, and it took place even faster during UV exposure. In the case of HIPS a slight photo-degradation of PS matrix is accompanied by simultaneous crosslinking of the polybutadiene component. 相似文献
HMS-PP in grains was synthesized by the gamma irradiation of PP under a crosslinking atmosphere of acetylene, followed by thermal treatment for radical recombination and thermal treatment for annihilation of the remaining radicals. The UV stability of the material was evaluated in pellet form. The accelerated weathering test of HMS-PP samples were performed under artificial ultra-violet light and in a condensation chamber Comexim (C-UV type) apparatus with UV exposure for 120 and 240 h. The results were compared to those from ageing caused by sunlight and dew under natural exposition. This work investigated changes in mechanical proprieties (elongation and rupture strength), Fourier transform infrared spectroscopy (FTIR), optical microscopy (MO), scanning electron microscopy (SEM) and rheological properties of HMS-PP after the UV ageing. We find that the HMS-PP has more degradation than regular PP and undergoes predominate chain scission in aggressive UV ageing conditions. 相似文献
The effects of three organic colorants on photo-initiated crosslinking and photo-oxidation degradation of polyethylene (PE) samples irradiated by microwave excited (MWE) UV lamp in the melt and the related mechanism have been studied by gel content and thermal extension rate determinations,X-ray photoelectron spectroscopy (XPS),mechanical property tests,UV spectroscopy,and light microscope.The data from the gel content and thermal extension rate determinations of photo-crosslinked polyethylene (XLPE) sam... 相似文献
We present a rapid and highly efficient method to form microstructure of poly(ethylene glycol) (PEG)‐based acrylates by microwave‐induced thermal crosslinking. PEG‐based polymeric microstructures such as polymer microarrays and microwells were fabricated on 3‐(trimethoxysilyl)propyl methacrylate (TMSPMA)‐coated glass slides that were placed on top of a silicon wafer. In comparison to ultraviolet (UV) irradiation curing, microwave‐induced thermal crosslinking could be completed within 10 s, without thermal degradation or oxygen inhibition in the presence of ambient oxygen. Furthermore, the activation of surviving free radical impurities by microwave‐induced heating enabled crosslinking even without an exogenous radical initiator (e.g., 2,2′‐azosisobutyronitrile (AIBN)). This approach can be beneficial for fabricating various PEG‐based microstructures for high‐throughput screening assays, cell‐based biosensors, and biomedical microdevices.
Miniemulsion polymerization is employed to produce high solid content (50%) acrylic/melamine latexes with varied crosslinking capability, for their potential application as waterborne crosslinkable coatings. This synthesis strategy allows the efficient incorporation of a hydrophobic crosslinker, iso‐butylated melamine (iBMF), into polymer particles, and to obtain latexes with different iBMF concentrations and acrylic polymer with varied content of hydroxylic groups (OH–). The involved crosslinking mechanisms and the physical transformations during film thermosetting of acrylic/iBMF nanocomposite are exhaustively investigated by combining thermal, spectroscopic, and thermo‐mechanical analyses. The influence of reactive groups concentration (iBMF and OH– content in the acrylic polymer) on the rate of curing, the crosslinking degree, and consequently onto the sensitive properties of cured films are discussed here. 相似文献