Preface

Polypropylene (PP) is one of the most important commodity plastics that was first synthesized by J. Paul Hogan and Robert L. Banks in 1951. After almost seven decades of innovation in science and engineering, PP-based materials have found tremendous applications in automobiles, industrial moldings, consumer packaging, and medical devices. The objective of this book is to provide an overview of the progress in PP from the perspectives of synthesis, structure–property relationship, processing, PP composites, and applications.

In the chapter Versatile Propylene-Based Polyolefins with Tunable Molecular Structure through Tailor-Made Catalysts and Polymerization Process, Dr. Xiong Wang reviews the chemical structure, catalytic systems, and various polymerization processes to synthesize PP.

In the chapter Thermal Conductivity of Polypropylene-Based Materials, Dr. Antonella Patti addresses the growing demand in thermal conductive plastics by providing an overview of the thermal conductivity of PP and methods to enhance the thermal conductivity of PP-based composites.

In the chapter Polypropylene Blends and Composite: Processing-Morphology-Performance Relationship of Injected Pieces, Dr. Alejandra Costantino summarizes the progress and fire retardancy mechanism of PP composite-based nano-fire retardants.

In the chapter Tensile Properties in -Modified Isotactic Polypropylene, Dr. Koh-Hei Nitta prepares spherulitic isotactic PPs by adding -nucleators and investigates the effects the -phase modification on the mechanical properties.

In the last chapter, Effect of Processing and Orientation on Structural and Mechanical Properties of Polypropylene Products, Dr. Luca Fambri illustrates the mechanical and structural properties of oriented i-PP homopolymers by using various characterization methods.

> **Dr. Weiyu Wang** South China University of Technology, Guangzhou, China

> > **Dr. Yiming Zeng** H.B. Fuller Company, United States

**Chapter 1**

*Weiyu Wang*

**1. Introduction**

materials as a resin.

**2. Synthesis and functionalization**

oughly reviewed elsewhere [9, 10].

**1**

Introductory Chapter:

Functionalization

Polypropylene - Synthesis and

First discovered by J. Paul Hogan and Robert L. Banks in 1951, polypropylene (PP) is polymerized from propylene out of crude oil and is the most widely used commodity thermoplastic by volume [1]. Over the past 70 years, significant progress has been achieved to manufacture and commercialize PP (**Figure 1**) [2, 3]. The most recent milestone in the field of polypropylene is from PureCycle Technology, where the waste carpet has been successfully purified into clear, odorless ultrapure recycled polypropylene (UPRP) resin [4]. Through not fully commercialized yet, the innovation opens up a new venue of recycling processed PP into raw

As one of the cheapest plastics with great processability, chemical resistance, and moisture barriers, PP with different tacticity found various downstream applications in textile, automotive, cosmetics, and consumer packaging. In 2016, 26% of

Well-defined polymers with narrow polydispersity and controlled molecular weight are essential to delineate the structure–property relationship of polymeric materials [6]. Using N,N-diethyl hafnium derivative as active transition metal propagation center and ZnEt2 as metal alkyl chain transfer agent, Sita first demonstrated the living coordinative chain transfer polymerization of propene to produce amorphous atactic polypropylene (a-PP) with narrow polydispersity and various molecular weights from 12.6 kDa to 111 kDa [7]. Compared with a-PP, isotactic polypropylene (iPP) is more practical for applications in packaging and automotive parts. Coates designed a pyridylamidohafnium catalyst that produced PP with high iso-selectivity (91%) and living polymerization behavior (**Figure 3**) [8]. The study also confirmed a ligand-monomer interaction as the mechanism of stereo-control. The progress of using coordinative chain transfer polymerization has been thor-

Block copolymers have contributed significantly to thermoplastic elastomers, soft lithography, and drug delivery [11]. Block copolymers containing polypropylene can serve as a compatibilizer to improve the interface interaction between polyolefin and other polar materials. Chen demonstrated an early example of polypropylene-block-poly(methyl methacrylate) (PP-b-PMMA) diblock copolymer using Group IV metal catalyst [12]. By taking advantage of the solubility, the

polymer demand in the world by volume was from PP (**Figure 2**) [5].
