Thermomechanical, Crystallization and Melting Behavior of Plasticized Poly(Lactic Acid) Nanocomposites

The incorporation of filler and plasticizer provides effective nucleation and mechanical reinforcement in polymer composites to impart flexibility, toughness, thermal stability and tensile strength of PLA composites that can be used in the development of packaging applications. In this paper, the inclusion of plasticizer and reinforcement of nanofiller in PLA matrix prepared using solvent casting method aims to improve the thermomechanical properties that consequently alter the crystallization and melting behavior of PLA composites. Plasticized PLA with different percentages of TiO2 at 2.0, 3.5, 5.0 and 7.0 % w/w were dispersed in PLA solution using mechanical mixer and ultrasonication technique to introduce a matrix reinforcing nanophase within the composite. The thermomechanical properties and thermal behavior of PLA nanocomposites were characterized using dynamic mechanical analysis (DMA) and differential scanning calorimeter (DSC). DSC cooling curves at low scanning rate of 2.0 K·min-1 proved that the presence of TBC in PLA matrix increased the crystallinity of plasticized PLA nanocomposites that initiated the formation of perfect spherulites. TBC increased the crystallization activity during cooling, which in turn reduced the recrystallization effect on heating, in parallel with DMA results that revealed small peak of cold-crystallization activity on PLA nanocomposites with the addition of plasticizer observed at temperature range of 80 °C to 100 °C. Nanofiller induced nucleation for crystallization of PLA matrix and plasticizer accelerated the overall crystallization process. Considerable adjustments of plasticizer and nanofiller in PLA matrix in having a good balance of stiffness and flexibility are a practical strategy that has a potential in biopolymer medical engineering and in the development of packaging applications.

Numerical Simulation of Fluid Flow Features of Mechanical Mixer with Automatic Variable Frequency Control

For many engineering fields, it is of practical significance to construct and reasonably simplify the solid-liquid two-phase flow model in the cylinder of mechanical mixer. However, the existing studies have not considered how the control technology affects the fluid features in the mixer. From the angle of automatic variable frequency control, this paper carries out a numerical simulation of the fluid flow features in mechanical mixer. Firstly, the authors constructed the system structure for the mixer with automatic variable frequency control, and summarized the basic devices and the number of input/output points of the system. Then, the relationship between the force energy and control frequency of the mixing cylinder was detailed. Afterwards, the Euler-Euler two fluid model was introduced to numerically simulate the solid-liquid two-phase flow in the cylinder of the mixer, which contains both solid particles and liquid, followed by the establishment of control equation, the drag model, and the turbulence model. The proposed model was proved effective through experiments. The research findings provide a reference for the relevant research and the optimal design of the drive module of mixers.

Karakteristik Reologi Komposit Serbuk Cangkang Kemiri dan Poliuretan

AbstrakPenelitian ini bertujuan menentukan karakteristik reologi komposit serbuk cangkang kemiri (SCK) berukuran 45µm<d<75µm dan resin Poliuretan (PU) dengan komposisi bervariasi, yaitu 5%:95%, 10%:90%, 15%:85%. Pencampuran SCK dan PU dilakukan dengan mechanical mixer dengan kecepatan dan lama pengadukan masing-masing 10, 15 dan 20 menit dan 100, 200 dan 250 rpm. Reologi komposit diperoleh dengan pengujian rotational viscometer dan dioptimasi dengan metoda Taguchi. Penelitian menunjukkan viskositas terkecil 218,66 mPa.s, ditemukan pada komposit dengan komposisi 5% 95%, waktu pengadukan 15 menit dan kecepatan pengadukan 100 rpm. Kata kunci: Serbuk cangkang kemiri, Poliuretan, Viskositas, Reologi. Abstract This study aimed to determine the composite rheological characteristics of candlenut shells (SCK) with particle size of 45µm <d <75µm and polyurethane (PU) resins with varying compositions, namely 5%: 95%, 10%: 90%, 15%: 85%. Mixing of SCK and PU is carried out using mechanical mixers with a speed and stirring time of 10, 15 and 20 minutes and 100, 200 and 250 rpm, respectively. Composite rheology was obtained by rotational viscometer testing and optimized by the Taguchi method. The results showed the smallest viscosity of 218.66 mPa.s, found in composites with a composition of 5% 95%, stirring time of 15 minutes and stirring speed of 100 rpm. Keywords: candlenut shell, polyurethane, viscosity, rheology

USAGE OF CANDLE NUT SHELL WITH POWDER SIZE OF D<250 µm AS FILLER STUFF IN EPOXI COMPOSITE RESIN

Recently around 60% of the hazelnut shell has the potential to become wasted material. The purpose of this research is to exploit waste hazelnut shell by examining the mechanical properties of composite from the powder of hazelnut shell. Epoxy resin acts as a matrix mixed with a hazelnut shell powder as a filler with a composition of 20%, 30% and 40% wt. Both materials are mixed using a mechanical mixer with varying speed and stirring times. The resulting composite material is then tested by tensile, impact and hardness testing. The Taguchi method is used to optimize forming process parameters of the epoxy-powder hazelnut shell composite. Research shows that the forming process parameters give different effects for each different mechanical property. Research found out maximum tensile strength of composite material at 30% wt of powder hazelnut shell. Overall, the result of taguchi optimization for the forming process parameters in this study was 43.68 N/mm2 for tensile strength, 0.074 106 J/mm2 for impact strength and 98.57 SHN for hardness.Keywords: .

Processing of Silicas Formed by Slip Casting

In this work suspensions containing natural amorphous silica fibers (NASF), amorphous silica gel and nanometric colloidal amorphous silica were prepared and rheologically analyzed. The suspensions were prepared by varying the volume percentage of solids between 22 and 32%, ammonium polyacrylate (APA), as dispersant, from 0 to 5% and polyvinyl alcohol (PVA), as binder, between 1 and 3.5%. The mixtures were obtained in a propeller mechanical mixer and formed by slip casting. The results of rheological characterization indicated that the suspensions with 30% solids, 4% dispersant and 3% binder were those that showed a stable rheological system and suitable for processing by slip casting.