Sirirat Wacharawichanant

Thermo- and Photo-Degradation of LDPE and PP Films Using Metal Oxides as Catalysts

Degradation of LDPE and PP films using the photo sensitive metal oxides or pro-oxidants (e.g. Fe2O3, CuxO, ZnO, and TiO2 at various particle sizes) as the catalysts in both thermo- and photo-oxidation of plastic films with oxygen followed by photolytic process to give free radicals has been studied. Our preliminary study in hexane solution found that the carbonyl index (CI) increased under the shortwave ultraviolet (254nm) significantly greater than under the longer wave (366nm) due to its greater energy and highly absorbed by the pro-oxidants generating more free radical concentration which could then be photolysed into carbonyl compounds. The pro-oxidant blended PE and PP films under ultraviolet (254nm) irradiation showed the carbonyl index elevation at the beginning and then reducing to a constant level similarly in most cases. This probably suggested that the carbonyl primarily formed and degraded into other free radicals. Under shortwave ultraviolet irradiation for 72 hours, the LDPE films containing nano-sized rutile-TiO2 and nano-sized anatase-TiO2 (1%w/w) were able to reduce the film tensile strength by 32% and 55%, respectively. The film containing micron-sized commercial TiO2 lower the film tensile strength only by 7-10%. However, the tensile strength of the TiO2 blended PP films tends to increase possibly because the rate of cross linkage exceeds the rate of scission.

Effects of Compatibilizers on Morphology and Properties of Polyoxymethylene/Polypropylene Blends

The effects of polypropylene-graft-maleic anhydride compatibilizer on the mechanical thermal and morphological properties of polyoxymethylene/polypropylene blends were investigated. Polyoxymethylene/polypropylene blends with and without polypropylene-graft-maleic anhydride compatibilizer were prepared by an internal mixer. The morphology of polyoxymethylene/polypropylene blends clearly demonstrated a two-phase separation of dispersed phase and the matrix phase and the addition of polypropylene-graft-maleic anhydride changed the morphological characteristics of blends. Polyoxymethylene/polypropylene blends showed the decrease of mechanical properties with increasing of polypropylene content. The addition of polypropylene-graft-maleic anhydride improved Young’s modulus and storage modulus of polyoxymethylene/polypropylene blends. The incorporation of polypropylene improved the degradation temperature of polyoxymethylene. GRAPHICAL ABSTRACT

Effect of Clay on the Properties of Polyoxymethylene/Clay Nanocomposites

This work investigated the effect of montmorillonite clay surface modified with 25-30 wt% trimethyl stearyl ammonium (clay) on mechanical, thermal and morphological properties of polyoxymethylene (POM)/clay nanocomposites were investigated. The results showed that POM/clay nanocomposites could maintain or decrease their tensile strength for a certain clay loading range. The Young’s modulus of the nanocomposites increased by adding clay in a range of 0.5-4 wt% while the impact strength showed an increase in a range of 0.5-2 wt%. The percent strain at break of the nanocomposites decreased with increasing filler content. The thermal degradation temperature decreased with an increase of clay content thus the addition of clay did not improve the thermal stability of POM. The microstructure of neat POM and POM/clay nanocomposites was observed that the dispersion of clay was a good in POM matrix at low clay content. The nanocomposites formed the intercalated structure with clay, and the intercalated clay stacks were distributed uniformly in the nanocomposite. The increase of clay content observed increasing of brittleness in POM/clay nanocomposites.

Morphology and properties of poly(styrene-co-acrylonitrile)/poly(methyl methacrylate)/zinc oxide composites

The effect of zinc oxide (ZnO) 250 nm on the mechanical, thermal and morphological properties of the composites of poly(styrene-co-acrylonitrile) (SAN), poly(methyl methacrylate) (PMMA) and ZnO was investigated. The Youngs modulus of 20SAN/PMMA/ZnO and 40SAN/PMMA/ZnO increased at low ZnO content. Increasing content of ZnO up to 0.5–1.0 wt% increased the impact strength of PMMA/SAN blends and then decreased. The addition of ZnO improved the thermal stability of polymer blends. The dielectric constant of 20SAN/PMMA/ZnO and 40SAN/PMMA/ZnO composites increased with increasing ZnO content. The dispersion of ZnO particles was relatively good and uniform throughout the entire polymer matrix.

Acetophenone and Benzophenone Derivatives as Catalysts in Photodegradation of PE and PP Films

Due to their versatile functionalization, acetophenone and benzophenone derivatives as plastic additives were synthesized and blended into PE and PP to study rate of degradation under ultraviolet irradiation by monitoring carbonyl index, tensile strength and weight loss. The photolytic reactions of these ketones in benzene solution showed that acetophenone derivatives, especially 3-nitroacetopheone, underwent rapid degradation under the short-wave ultraviolet (254 nm) rather than in the black light (366 nm) while benzophenone derivatives showed small carbonyl index reduction. However, both groups of ketones, in hexane solution or in PE and PP films, primarily lowered the carbonyl index and rised up again except for the bromo derivatives. At 96 hrs of UV irradiation, the tensile strength of the acetophenone-blended PE film reduced only 20% while the tensile strength of the acetophenone-blended PP film decreased dramatically upto 90% and 95% for the benzophenone-blended PP.

Mechanical and Thermal Properties of Polyoxymethylene Nanocomposites Filled with Different Nanofillers

The effect of the different nanofiller on properties of polyoxymethylene (POM) nanocomposites was investigated. The nanofiller containing CaCO3, Al2O3 and modified clay was used added in POM. The results showed that the Youngs modulus of the nanocomposites increased after adding the nanofiller. The tensile strength and stress at break of the nanocomposites increased by adding CaCO3 nanoparticles in a range of 1–2 wt.%. The addition of CaCO3 enhanced the thermal stability of the POM matrix. The microstructure of neat POM and POM nanocomposites was found that the dispersion of nanofiller particles was relatively good in a low content.

The crystallinity and miscibility of syndiotactic polystyrene blends after mixing with low molar mass liquid crystal or commercial lubricant

The quantities of the crystallinity of syndiotactic polystyrene (SPS) blended with another polymer in the group of poly(α-methyl styrene), poly(n-butyl methacrylate) or poly(cyclohexyl acrylate) with or without the additives were measured by X-ray diffraction and calculated by Ruland’s method. The SPS was synthesized by using metallocene catalyst and modified-methylaluminoxane as cocatalyst. The additive of low molar mass liquid crystal chemical (cyclohexyl-biphenyl-cyclohexane (CBC33)) or lubricant (glycerol monostearate (GMS)) was individually added to the blends of SPS in order to investigate the effects on the crystallinity of the blended SPS. From the experimental results, it was found that the percent crystallinities of the blends decreased with decreasing the percent of SPS in the blend because of the dilution of SPS. The depression of the percent crystallinity was in the order of PaMS > PCHA > PBMA according to the compatibility with SPS. The addition of GMS or CBC33 slightly decreased the percent crystallinity of the pure SPS. The addition of GMS impeded the depression of the SPS crystallinity in the blends, because their percent depression from pure SPS is similar (at around 25%) regardless to the components of the blends. The blends with added CBC33 have the similar depression of crystallinity as the pure blends because of the low concentration of CBC33 and the good compatibility of CBC33 with the SPS.

Prediction of Mechanical Properties of Polymer Materials Using Extreme Gradient Boosting on High Molecular Weight Polymers

The development of a new polymer materials depends on properties and it typically involves synthesizing a lot of compounds that finally becomes a new materials. This process is very expensive and take a long time. Therefore, the accurately prediction of the mechanical properties of polymer materials are required for understanding the rationale behind those predictions would be a valuable knowledge to the material studies. This work proposed the extreme gradient boosting to predict the mechanical properties of polymer materials. The model were developed, learn and the existing mechanical properties dataset. Then, the models were used to predict the mechanical properties for polymer materials. The predicted mechanical properties values were compared with the laboratory experimental results to validate the models. The experiment results have shown that the model could significantly enhance to predict the mechanical properties of polymer materials. In which way, this work could solve the problem of the polymer material and improve the efficiency of prediction obviously. This work evaluated the model with the logarithmic loss function, and the random forest classifier is used to test the model with all the features. Furthermore, this study enhance to reduce both time and cost of polymer material development. Even though, the accuracy of the predictions are not high enough, it has caused the insufficient number of sample in the dataset and the collection of data is widely scattered.

Comparison of Morphology and Mechanical Properties of Polyoxymethylene/Cellulose and Poly(Lactic Acid)/Cellulose Composites

The objective of this study is to fabricate the polyoxymethylene (POM)/microcrystalline cellulose (MCC) and poly(lactic acid) (PLA)/MCC composites, and to compare the effect of MCC on the morphology and mechanical properties of POM and PLA. The polymer composites were prepared by melt mixing in an internal mixer and molded by compression molding. The MCC concentrations were 1, 3, 5, 7, 10, 15 and 10% by weight. From scanning electron microscopy study observes the fracture surface of POM and PLA composites is much rough and the roughness increases with increasing MCC content. This observation indicates MCC induces the ductile fracture characteristic of POM and PLA. The addition of MCC can improve the impact strength of PLA composite and improve Young’s modulus of both POM and PLA composites. While the tensile strength and strain at break decrease after adding MCC. In summary, MCC can enhance the morphology and mechanical properties of PLA composites is better than POM composites.

Mechanical Properties and Phase Morphology of Poly(Lactic Acid)/Acrylonitrile-Butadiene Rubber/Organoclay Nanocomposites Prepared by Melt Blending

This work investigated the mechanical properties and phase morphology of poly(lactic acid) (PLA)/acrylonitrile-butadiene rubber (NBR) blends and nanocomposites, which prepared by melt blending in an internal mixer. The contents of NBR were 5, 10, 15 and 20 wt% and the content of organoclay was 3 phr. The impact test showed that the impact strength of PLA/NBR blends increased with an increase of NBR content and the impact strength of the blends was more than eight times by adding NBR 10 wt% when compared with neat PLA. The tensile test showed that Young’s modulus and tensile strength of PLA/NBR blends and nanocomposites decreased after adding NBR and organoclay. While the strain at break of the NBR blends increased with increasing NBR content. This result is attributed to the rubber phase in NBR in a cause the increment of elongation and elasticity in PLA/NBR blends. The morphology of PLA/NBR blends observed the fractured surface was rougher than that of pure PLA. This observation indicates that the addition of NBR in PLA can change the brittle fracture of PLA to ductile fracture, which has an effect to the strain at break or elongation of PLA. However, the morphology of the PLA/NBR blends were also observed the phase separation of the dispersed NBR phase and PLA matrix phase, and appeared the voids in a polymer matrix. The addition of organoclay had an effect slightly on the morphology of the blends. From X-ray diffraction, results found that PLA/organoclay and PLA/NBR/organoclay nanocomposites showed the intercalated structure, which PLA chains were inserted into the interlayer of clay due to the increase of d-spacing.