Effect of Composition on the Molecular Dynamics of Biodegradable Isotactic Polypropylene/Thermoplastic Starch Blends

Abstract

Polyolefins such as polypropylene are used in an immensely broad range of commodity products and account for the largest volume of synthetic polymers generated worldwide. For this reason, this family of thermoplastics contributes significantly to solid waste both on land and in the ocean. One viable approach to mitigate this growing problem and simultaneously reduce the cost of and dependence on petroleum-based polymers relies on blends wherein an added biopolymer can promote natural biodegradation. Due to their chemical dissimilarity, however, nonpolar polyolefins and polar biopolymers tend to phase-separate, in which case a fundamental, molecular-level understanding of the role of polymer/polymer interfaces on chain mobility in blends differing in composition is needed. In the present study, the molecular dynamics of blends composed of isotactic polypropylene (iPP) and glycerol-plasticized thermoplastic starch (TPS) are investigated by solid-state proton nuclear magnetic resonance and dielectric relaxation spectroscopies. Blends prepared by twin-screw extrusion range in composition from 10 to 70 wt % TPS, and their morphologies and thermal properties are examined by scanning electron microscopy and differential scanning calorimetry, respectively. This comparative analysis establishes the influence of TPS on the molecular dynamics of biphasic iPP/TPS blends relative to the constituent homopolymers.

Poly(l-Lactic Acid)/Pine Wood Bio-Based Composites

“…It is assumed that the long relaxation time T 1L is associated with the rigid amorphous phase in the sample, while the T 1S fraction is related to the more mobile amorphous phase. According to previous NMR studies [ 46 , 61 , 73 , 74 , 75 , 76 ] the broad minimum at a low temperature of about −140 °C (133 K) might be associated with hindered rotations of nonequivalent CH 3 groups. The dielectric spectroscopy analyses indicate that in semicrystalline polymers, among others in PLLA, the secondary relaxation process β was observed below T g , at lower temperatures, ranging between −30 and −150 °C, and represents localized motions of side groups or main polymer chains including thermal motions of carboxyl, hydroxyl or ester functional groups or twisting motions of main polymer chains [ 77 , 78 , 79 ].…”

“…The pine wood used as a filler is mainly composed of cellulose, lignin, hemicellulose, and a small amount of fatty acids and resins, as detailed above. The molecular structure of cellulose indicates a presence of a large number of hydroxyl groups that are responsible for the formation of intramolecular and intermolecular hydrogen bonds [ 73 ]. The cellulose and its derivatives are built from glucose units linked to polymer chains via oxygen atoms creating a glucosidic linkage.…”

A study on melt recycling of bio‐based polypropylene/thermoplastic starch compound

“…Reducing environmental pollution, including soil and water, and reducing greenhouse gas emissions due to the lower need to convert crude oil into the raw material of these plastics, are among the important reasons for the growth and development of synthetic plastics waste recycling industry. Recycling of plastic waste by mechanical‐thermal, biological, energy conversion, and incineration methods are methods of reusing these materials, which at present, mechanical‐thermal recycling of plastics is used more than other solutions 6,7 . Among the various factors, the degradation of the polymer during the process is usually related to the shear forces at high temperatures.…”

“…Therefore, it must first be turned into a quasi‐thermoplastic resin to be able to blend with conventional synthetic polymers. A thermoplastic substance or TPS is produced by mixing natural starch with several different small polar molecules or the same hydroxyl‐ or amide‐rich plasticizers such as water, glycerol, glycol, sorbitol, ethylene bisformamide, formamide, acetamide, urea, amines, citric acid and glucose, at temperatures above the gelatinization temperature of starch, which is usually around 70–90°C 6–8,12–17 …”

Synergistic lignin construction of a long-chain branched polypropylene and its properties

“…Polypropylene (PP), one of the top ve synthetic resins, has been widely used in many elds due to its excellent mechanical and processing properties. [1][2][3][4][5] However, PP with a semi-crystalline linear structure has poor toughness, a low melt strength, and difficulty in thermoforming processing, limiting its use in highvalue-added engineering applications such as in the automobile, construction, and packaging industries. [6][7][8][9] Generally, in order to improve the melt strength of poly-olen, a great deal of effort has been devoted to introducing long-chain branches and hydrogen bonds into the polymer network.…”