U. S. Ishiaku

New polyester acrylate resins from palm oil for wood coating application

The aim of this study is to investigate the potential use of palm oil and to prepare new UV (ultraviolet) radiation-curable acrylated polyester prepolymers, which could be used in the wood coating industry. Thus, palm oil-based acrylated polyester resins PEPP-1 (from refined, bleached, and deodorized palm oil) and PEPP-2 (from crude palm oil) were synthesized at the Advanced Oleochemical Technology Centre (AOTC) laboratory of Palm Oil Research Institute of Malaysia (PORIM). The performances of these resins with respect to their curing rate and physical-mechanical properties of cured products under UV radiation were studied. It can be concluded that newly synthesized UV radiation-curable polyester acrylated prepolymers (palm oil based), namely PEPP-1 and PEPP-2, can be used as radiation curable coating materials for wood coating applications.

The Flow Behavior of Core Material and Breakthrough Phenomenon in Sandwich Injection Molding: Part II: Influence of Mold Cavity Thickness and Core Cylinder Temperature

Abstract The processing conditions that exert influence on the occurrence of breakthrough during sandwich injection molding were investigated. A spiral flow mold mounted on a twin-barrel injection machine fitted with a single nozzle was used. The effect of mold cavity thickness and the effects of skin material cylinder temperature on skin material viscosity, melt strength, and drawing ratio were considered. Scanning electron microscopy was used to study the morphology of the skin material at the flow front. It was found that the flow length at core expansion region increased and breakthrough phenomenon was delayed as the thickness of the mold cavity increased. When cylinder temperature is increased, the viscosity is lowered and the flow front of the skin material extends with greater ease when pushed by the core material, thus, a greater core volume can be accommodated. As the flow front progresses, the tendency is that the skin material becomes thinner. Polishing and etching followed by SEM examination of the skin material at the flow front revealed that the skin material is oriented perpendicular to the flow direction and the extent of orientation increases with increasing cylinder temperature. This further supported the observation that the deformation ratio and drawing ratio increased with increasing cylinder temperature.

Flow Behavior of Sandwich Injection Molding in Sequential and Simultaneous Injection

Abstract The flow behavior of skin and core materials in co-injection molding was investigated to understand the flow patterns that could lead to core breakthrough in sequential and simultaneous injection molding. A spiral-flow mold was used and the core material was loaded with a black master batch to facilitate the monitoring of the core material. PC/ABS blend was used as the skin material and ABS was the core material. It was revealed irrespective of simultaneous injection time, sandwich injection molding display the four flow regions identified earlier i. e. primary injection region, core advance region, core expansion region and core breakthrough region. The flow length of core expansion region lengthened with increasing simultaneous injection time of skin and core material while the overall injection time decreased. It was also observed that the core became thinner and wider with increasing simultaneous injection time.

The Flow Behavior of Core Material and Breakthrough Phenomenon in Sandwich Injection Molding

Abstract The processing variables that control the occurrence of breakthrough phenomenon in sandwich injection molding were investigated. Particular attention was paid to the conditions that would yield an optimum sandwich molded part. The effects of variation of core volume ratio that would yield optimum core shot size, injection speed and the skin/core viscosity ratio were examined. The flow morphology at the various stages of flow was also explored. The study was conducted with a bar-flow mold mounted on a twin-barrel injection machine fitted with a common nozzle. It was noted that the core material flow distance depends on the core cylinder screw metering position (core shot size). At the stage at which the core material completely penetrated through the skin material (breakthrough), four distinct regions of flow could be identified. The flow distance of the core material is controlled by the injection speed of the core material while the injection speed of the skin material is of little significance. In order to increase the flow distance of the core material, it is effective to increase the core material injection speed albeit limited by an optimum value of screw metering position. It was found that the flow distance of the core material was longer when the core material viscosity was lower than that of the skin material but breakthrough occurred much earlier so core volume is limited. Breakthrough failed to occur when the viscosity of the core material was higher than that of the skin material. It was found that optimum core volume and core distribution occurred when skin/core viscosities were intermediate. The morphology of the skin material leading to breakthrough was also analyzed.

Fatigue behavior of dynamically vulcanized poly(vinyl chloride)/nitrile butadiene rubber thermoplastic elastomers

Abstract Dynamically vulcanized poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR), thermoplastic elastomers (TPEs) were melt mixed at 150°C and 50 rev. min.−1 with a Brabender Plasticorder. Curatives concentration was varied from 0 to 1 phr in order to study the effect of dynamic curing on the plastified formulations. The compounds were characterized with respect to their fatigue life, the strain energy and its exponent, rebound resilience, abrasion resistance, and viscoelastic behavior. Profound enhancement in the fatigue life of the dynamically vulcanized formulations reduced damping and improved rebound resilience. The observed scenario has been attributed to the increase in the degree of curing.

The Effect of Prolonged Thermo-oxidative Ageing on the Mechanical Properties of Dynamically Vulcanized Poly(Vinyl Chloride)/Nitrile Butadiene Rubber Thermoplastic Elastomers

ABSTRACT Plasticized poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR) thermoplastic elastomers (TPEs) were dynamically vulcanized in the melt stage with the incorporation of a semi-efficient vulcanizing system using a Brabender Plasticorder at 150°C and 50 rpm rotor speed. Curative concentration was progressively increased from 0 to 1 part per hundred (phr) NBR in order to study the effect of dynamic curing on the plasticized blend. The mechanical properties investigated include tensile strength, elongation at break (%EB), modulus at 100% elongation (M100), tear strength, and hardness. The effect of thermo-oxidative ageing (TOA) on the mechanical properties was investigated by exposing the PVC/NBR TPEs in an air oven at 100°C for 3, 7, 14, and 21 days. It was found that tensile and tear strength passed through a maximum value, whereas, hardness and M100 increased steadily with the sulfur content and ageing time. On the contrary, the elongation at break reduced gradually with ageing time until it reaches a minimum value. The increase in crosslink density as well as the steady reduction in swelling index with increasing concentration of curatives provided an excellent evidence for the significant increase in crosslink density with ageing time. The changes in physical and mechanical properties of the TPEs is believed to be closely related to some microstructural changes taking place as a result of the formation of new crosslinks due to prolonged thermo-oxidative environment.

Drop Weight Impact Properties of (CO) Injection Molded Short Glass Fiber/Short Carbon Fiber/Polyamide 6 Hybrid Composites

Polyamide 6 (PA 6) composites with short glass fiber (GF)/short carbon fiber (CF) hybrid fiber reinforcement were produced using two types of injection molding techniques, i.e., the conventional and co-injection molding machines. In the latter, sandwich skin-core hybrid composites were produced. The fiber volume fraction for all formulations was fixed at 0.07. The composites were subjected to drop weight impact tests, to determine their impact strength, impact energy, ductility index (DI) and ductility ratio (DR). It was observed that the PA 6 formulation exhibited the highest impact strength and impact energy values whereas carbon fiber/PA 6 (CF/PA 6) exhibited the highest DI and DR values. The carbon fiber skin/glass fiber core/PA 6 (CFS/GFC/PA 6) sandwich skin-core hybrid composites showed the highest impact energy and impact strength values among hybrids. The glass fiber skin/carbon fiber core/PA 6 (GFS/CFC/PA 6) hybrids on the other hand showed the highest DI and DR values among hybrids. Failure mechanisms in the matrix and composites, assessed by scanning electron microscope (SEM), were discussed in relation to the effects of fiber incorporation and its effects on the ductility of the composites, with particular emphasis on the hybrid composites.

Environmental Durability of Natural Fiber Reinforced Unsaturated Polyester Composite

With an industrial increasing interest in sustainable, eco-efficient and green material’s application, natural fiber in polymer composite is guided to develop rapidly, especially kenaf nonwovens in making automotive interior trim parts with its comparative excellent strength and renewability. The objectives of this research are to investigate the environmental degradation behavior on the physical and mechanical properties of kenaf/unsaturated polyester nonwoven composites (KUNC) with special reference to the influence of different geographic natural climate ageing conditions. KUNC was prepared with needle-punched kenaf’s impregnation into unsaturated polyester resin assisted with vacuum oven following by hand lay-up molding. Natural environmental degradation was performed on KUNC by exposing the specimens to Kyoto(Japan), Shanghai(China) and Harbin(China) for a period of 3 months. Weight change and mechanical properties of degraded KUNCs in former three geographic positions in terms of tensile, flexural, impact and fracture toughness were measured instrumentally for ageing effect discussion and comparison. As expected, the aged specimens in those different positions all showed the dropped mechanical properties with weight increasing in varying degrees. Furthermore, the result of degradation level comparison among different positions revealed the positive correlation between increased weight percentages and dropped mechanical properties. In other words, dropped mechanical properties of the degraded composites with increasing weight were attributed to the effect of water, which deteriorates the interfacial properties of composites.Copyright